Catalytic strategies for sustainable and efficient textile processing: a review

1 Introduction

The textile industry is one of the largest and most economically important manufacturing industries in the world, providing critical items for apparel, healthcare, transportation, building and many industrial applications (Abtew et al., 2025). But rising industrialization, urbanization, population growth and the advent of fast fashion have dramatically boosted the manufacturing of textiles leading to excessive consumption of water, energy and chemicals with substantial environmental repercussions. The production of textiles by traditional methods is one of the most resource-intensive industrial sectors because of the water- and chemical-intensive wet-processing activities like desizing, scouring, bleaching, dying, printing, washing and finishing (Faiza et al., 2025). The development of clean technologies of production and sustainable processing of textile products has become a priority around the world.

The use of water is one of the major environmental issues related to textile production (Rahaman and Hossain Khan, 2025). For dying, washing, rinsing and finishing processes large amounts of fresh water are needed. The global textile sector uses around 79 billion m³ of freshwater annually, placing it among the leading industrial consumers of water (European Parliament, 2021; Ella Kärkkäinen, 2024). At the same time, the textile industry produces large amounts of wastewater with residual dyes, salts, surfactants, acids, alkalis, heavy metals and other dangerous organic compounds. This wastewater has a high mineral content resulting in low biodegradability (biodegradability index (BI) ≤ 0.4) (Al-Momani et al., 2002). Therefore, bio-treatment is limited (Paździor et al., 2019). Textile wastewater has wide ranges of chemical oxygen demand (COD): 150–12,000 (mg/L), biochemical oxygen demand (BOD): 80–6000 (mg/L) (Wang et al., 2022), and total organic carbon (TOC): 50–40,000 (mg/L) (Paździor et al., 2019). A number of other factors make textile wastewater especially difficult to purify, not the least of which is the fact that the chemical composition of the effluent fluctuates according to the production conditions. The settings. The composition of the textile garment imposes mainly the settings of textile processing. Textile dyeing and finishing operations are estimated to be responsible for over 20% of the world’s industrial wastewater pollution, underscoring the need for environmentally sustainable processing solutions (Leal Filho et al., 2022). Besides water consumption, textile manufacturing involves an enormous amount of thermal and electrical energy for pretreatment, bleaching, dying, drying and finishing operations, which are usually carried out at high temperatures for lengthy durations (Hasanbeigi and Zuberi, 2022; Catarino et al., 2025). A lot of textile companies still rely on fossil fuels, and the sector is a big source of greenhouse gas emissions (UNEP, 2025). The textile and garment business accounts for about 8%–10% of the world’s carbon emissions, which highlights the need for low carbon production, according to recent research (Leal Filho et al., 2022). It also says that the textile production process involves over 8,000 commercial chemicals including alkalis, acids, oxidizing agents, surfactants, dye-fixing compounds, flame retardants, antimicrobial agents and synthetic dyes (Bailey et al., 2022). The inefficient use of these chemicals increases pollution in wastewater and risk to the environment, which in turn causes tighter regulations and sustainability initiatives such as the United Nations Sustainable Development Goals (SDGs), the European Green Deal and the EU Strategy for Sustainable and Circular Textiles.

Catalysis has been recognized as one of the promising approaches to improve the efficiency of textile processing and to mitigate the environmental implications. Catalysts minimize the activation energy, so reactions can occur under less severe conditions, meaning lower chemical consumption, lower energy demand and faster processing times (Amari et al., 2021). Recent advances in heterogeneous catalysts, photocatalysts and improved oxidation catalysts have shown considerable potential for the entire textile value chain. The catalytic systems have been successfully applied in enzymatic desizing, bio-scouring, low temperature bleaching, enhanced dye fixing, functional textile finishing and effective degradation of dye pollutants in textile effluent. In addition, developments in catalyst regeneration, immobilised enzymes, magnetic separation and recyclable catalytic materials have improved the stability, reusability and economic feasibility of the catalysts enabling the transition to circular textile manufacturing (Pormazar and Dalvand, 2025). While several evaluations have focused on catalytic dye degradation or remediation of textile wastewater, there are few complete reviews on catalytic applications throughout the full textile value chain. Earlier research has concentrated on end-of-pipe pollution management, while attaching little importance to the catalytic advances for cleaner textile production, catalyst renewal and resource recovery.

This review presents a comprehensive overview of catalytic solutions for sustainable and efficient textile processing from textile pretreatment, dying, finishing, wastewater remediation, catalyst regeneration and recyclable catalytic systems. This review combines cleaner production with environmental remediation and resource recovery to provide a holistic picture and pave the road and propose future research directions for translation of catalytic breakthroughs from lab investigations to large scale industrial textile manufacturing.

2 Catalysis in sustainable textile manufacturing

The negative influence on the environment due to the excess use of water, high energy usage and emissions of hazardous chemical substances has increased the interest of the textile sector all over the world. Conventional textile processing techniques have used strong chemicals and high-energy reactions, such as pretreatment, dying, and finishing. Catalysis is a process of accelerating the speed of a chemical reaction by using a chemical compound referred to as a catalyst which is not consumed during the process. Catalysis provides an innovative technique that can be used to attain the “Green Chemistry” in textiles.

2.1 Classification of catalysts used in textile industry

Catalysts used in the textile industry are mainly categorized into three groups: Biocatalysts (Enzymes), Homogeneous Catalysis, and Heterogeneous Catalysis. They are important in wet processing of textiles, improving efficiency, saving energy and handling effluent wastewater (Figure 1).

2.1.1 Homogeneous catalysts

Homogeneous catalysts are widely used in the textile sector, especially in the treatment of effluents from high concentration dying and printing by AOPs and CWAO. Fenton oxidation is the reaction between ferrous ions (Fe²⁺) and hydrogen peroxide (H₂O₂) in acidic conditions (pH 3–4) to form hydroxyl radicals (•OH) which degrade organic contaminants (Lei et al., 2000; Pascale et al., 2026). Copper salts (especially copper nitrates) have been shown to be very effective catalysts to increase the removal rates of COD and total organic carbon (TOC) during wet-air oxidation. Double-component catalysts such as copper/iron salt pairs (e.g., Cu1Fe1) have better activity and cost efficiency making use of concurrent free-radical reactions and Fe(III) polymer coagulation. Homogeneous Fenton processes are noted for high performance, achieving significant reductions in BOD₅, COD, and turbidity, and enabling complete decolorization of textile effluents.

2.1.2 Heterogeneous catalysts

A heterogeneous catalyst system is considered to be a better option in view of the possibility of separation from the reaction medium and catalyst reuse along with reduced metal leaching. In heterogeneous catalytic systems, solid materials like metal-containing polymers or iron powder are used for dye degradation using UV light exposure or batch reactor (Tsaih and Chen, 2003). Cu-Fe bimetallic grafted polytetrafluoroethylene (PTFE) fiber complexes have been engineered as heterogeneous Fenton catalysts, enabling the reuse of treated dying effluents for subsequent dying cycles (Punzi et al., 2012; Li et al., 2013). The heterogeneous photo-Fenton system with iron powder may retain good performance for numerous batches and achieve complete decolorization for over 20 cycles, with much reduced release of iron ions compared to homogeneous systems. These catalysts are useful for the treatment of synthetic textile effluent containing azo dyes, giving a feasible way for water recycling in the industry.

2.1.3 Enzymes

Enzymes are efficient, specific and eco-friendly catalysts. They work under very mild reaction conditions lowering the energy cost and pollutants (Verma et al., 2021; Farhan et al., 2025). They are very significant in several processes of wet processing of textiles such desizing, scouring, bleaching and finishing (Verma et al., 2021; Farhan et al., 2025). Desizing is done by amylases while degradation of hydrogen peroxide and lignin is often done by peroxidases and catalases. Catalase is used specifically after peroxide bleaching to break down any remaining hydrogen peroxide to water and oxygen. This is important for the dying processes that follow. Enzymes are favoured by the industry since they are biodegradable, non-toxic and provide a huge potential to build innovative and high efficiency textile processes.

2.1.4 Nanocatalysts

Nanocatalysts, in particular metallic nanoparticles and nanocomposite, have attracted much attention for their dual role in antimicrobial textile finishing and textile wastewater treatment. The extremely high surface area to volume ratio offers a more considerable number of active sites which leads to a large increase in the catalytic activity in reduction processes (Rahman et al., 2022). Among the numerous nanocatalysts created, nitrogen-doped composites have been found to be effective in degrading hazardous textile dyes, such as N-Ti-melamine-capped Ag₂S and N-doped TiO₂-capped Ag₂S (Rahman et al., 2022). These compounds can rapidly decolorize dyes such as Remazol Blue RR and Levafix Amber RR in combination with reducing agents such as NaBH₄. Additionally, the capacity of these catalysts to maintain their catalytic activity for repeated usage demonstrates their stability, reusability and significant possibility for sustainable treatment of textile effluent.

2.1.5 Photocatalysts

Photocatalysis has emerged as a potential and eco-friendly method for treatment of textile wastewater, as it uses light energy for degradation of recalcitrant organic contaminants (Punzi et al., 2012; Li et al., 2013). TiO2 and ZnO have been most researched among the numerous photocatalytic materials because of their outstanding chemical stability, strong oxidative potential, and high photocatalytic activity (Rahman et al., 2022). These semiconductors when irradiated with UV or solar light generate highly reactive oxygen species which attack and degrade complex and non-biodegradable dye molecules to simpler and less toxic compounds which are readily attacked by biological processes. Therefore, photocatalysis is a very promising process for the remediation of recalcitrant contaminants that cannot be efficiently removed by conventional wastewater treatment processes. Photocatalysis, as an advanced oxidation process, provides a sustainable and energy efficient approach for the remediation of dye laden textile effluents. Furthermore, its ability to function under solar irradiation increases its potential as a cost-effective and environmentally sustainable technology for future wastewater treatment applications (Bikerchalen et al., 2025).

2.1.6 Advanced oxidation processes

Because they generate extremely reactive radicals that may degrade complex, persistent organic contaminants, advanced oxidation processes (AOPs) have emerged as one of the most dependable methods of treating textile wastewater (Rocha et al., 2024; Pascale et al., 2026). Particularly for textile effluents that have persistent, non-biodegradable chemicals that are difficult to remove by standard treatment procedures. Ozonation, in particular, can be made even more effective when paired with inorganic catalysts like zinc sulfate. These catalysts increase the production of reactive species, accelerate the decolorization and disintegration of complex azo dyes, and reduce the overall treatment time (Saddique et al., 2024). Consequently, catalytic AOPs have become a popular choice for treating textile effluent. Besides the high performance in removal of pollutants, these processes provide the operational flexibility to be modified as the criteria for environmental discharges become stricter. According to Pascale et al. (2026), catalytic advanced oxidation processes (AOPs) are presented as a practical and sustainable solution for the management of modern wastewater due to their combination of effectiveness and adaptability (Pascale et al., 2026). The major catalytic systems used in AOPs and their primary functions are summarized in Table 1.

TABLE 1. Catalytic system with their primary functions.

3 Catalytic strategies across the textile value chain

3.1 Catalytic pretreatment

Pretreatment can be considered as one of the critical stages in the textile industry since it is a process of cleansing natural impurities, processing chemicals, and contaminants from raw fibers prior to dying and finishing. Proper pretreatment leads to uniform dying, increased quality of textile material and effective functioning of finishing techniques (Catarino et al., 2025). Conventional pretreatment of textiles includes three major steps desizing, scouring and bleaching (Figure 2). Such processes were traditionally conducted using highly concentrated sodium hydroxide (NaOH), hydrogen peroxide, stabilizers and temperature above 100 °C for achieving the required effect (Bouwhuis, 2011; Kreuz et al., 2024). Though highly efficient, those processes consume considerable amount of water and energy, produce wastewater with high COD and potentially can decrease quality of cellulose fibers due to hard conditions of pretreatment (Ibrahim et al., 2021; Catarino et al., 2025). Environmental concerns, along with strict regulations, have thus motivated the need for catalytic pre-treatment technology. Biocatalysts and metal-organic catalysts are considered to be the sustainable option due to their high efficiency at relatively milder conditions of temperature, neutral pH value, and atmospheric pressure while minimizing environmental impacts (Table 2) (Saddique et al., 2024).

TABLE 2. Comparison of conventional and catalytic pretreatment.

3.1.1 Enzymatic desizing: mechanism and performance

Desizing is the first stage in the preparation of textile production and it removes the sizing chemicals which are added to the warp yarns during weaving. In wet processing, the sizing material is most typically starch and it is important to remove it totally from future processing.

3.1.1.1 Role of amylase enzymes

Amylases are the preferred enzyme for this purpose, as they easily break down the α-(1→4) glycosidic linkages of starch into smaller, water-soluble sugars like maltose and (Abedi et al., 2024). The uniqueness of amylases over traditional desizing methods which are based on acids or oxidants is the specificity towards starch, without affecting the cellulose structure of cotton fibers. In this process, starch is selectively attacked and removed, without affecting the strength, quality and structural integrity of the fabric (Đorđević et al., 2025).

3.1.1.2 Process efficiency

Enzymatic desizing is normally conducted at moderate temperatures (generally between 30 °C and 70 °C) and at near neutral pH, so it requires substantially less energy than the current methods (Rehman et al., 2023). More contemporary integrated one-step pretreatment systems have been developed where amylase is combined with other enzymes such as amyloglucosidase. Starch is entirely hydrolysed to glucose in these systems, which is used as substrate for enzymatic production of hydrogen peroxide in the bleaching (Eren et al., 2009). The combination of these procedures allows integrated approaches which helps in reducing processing time, chemical consumption and total operational expenses.

3.1.2 Bio-scouring: an eco-friendly alternative to conventional scouring

Scouring is a process to remove non-cellulosic components including pectins, waxes, proteins and mineral impurities from cotton fibers to improve their wettability and absorbency. Conventional scouring uses concentrated sodium hydroxide at high temperatures, which often degrades the fibers and results in highly alkaline wastewater (Raafi et al., 2023).

3.1.2.1 Action of pectinases and cutinases

Bio-scouring is an alternative and there is no harsh alkali but particular enzymes such as pectinases and cutinases. Pectinases act on the pectin of the primary cell wall by means of β-elimination reactions, and cutinases act on the waxy cuticle that covers the surface of the fiber (Degani, 2021). These enzymes act synergistically to remove hydrophobic impurities and enhance cotton fibers’ hydrophilicity in much milder conditions than traditional methods.

3.1.2.2 Performance comparison

In fact the enzymatic bio-scouring is generally performed around 50 °C and the rinsing is done around 30 °C (Raafi et al., 2023) which is a significantly milder process compared to the alkaline scouring. Numerous studies have demonstrated that the absorbency and wettability of bio-scoured cotton fabric are comparable to that of conventionally scoured fabric. Secondly, enzymatic treatment usually results in lower fabric weight loss, and better softness and overall preservation of fiber quality (Roy Choudhury, 2014; Kumar et al., 2021).

3.1.3 Catalytic bleaching through hydrogen peroxide activation

Bleaching is used to remove the natural pigments in cotton to get the required degree of whiteness before dying. Hydrogen peroxide (H₂O₂) is the preferred bleaching agent because it is efficient and decomposes into environmentally benign products. However, traditional peroxide bleaching is generally efficacious at temperatures of 90 °C–100 °C and in severely alkaline circumstances (pH > 10).

3.1.3.1 Metal-organic catalysts

Another approach is catalytic bleaching, where metal-organic complexes can activate hydrogen peroxide at much milder conditions. One of the best catalysts produced for this purpose is a manganese complex, MnTACN (manganese trimethyl-triazacyclononane), which catalyzes the creation of extremely reactive oxygen species. This allows efficient bleaching of cotton at temperatures as low as 30 °C (Hage and Lienke, 2006). Fabrics bleached using MnTACN are as white as fabrics bleached by conventional high temperature bleaching but at a fraction of the energy cost.

3.1.3.2 Glucose oxidase-based bleaching

Another interesting catalytic technique is the in situ production of hydrogen peroxide with glucose oxidase. In integrated pretreatments, the glucose obtained in enzymatic desizing is oxidized by glucose oxidase to generate hydrogen peroxide needed for bleaching (Farooq et al., 2013). Reported concentrations of hydrogen peroxide in studies have been in the region of 765 mg/L, sufficient for efficient bleaching, without the requirement for external peroxide addition (Eren et al., 2009). After bleaching, catalase is used to decompose any leftover hydrogen peroxide so that it does not interfere with the subsequent dying process and the overall efficiency is improved (Kreuz et al., 2024).

3.1.4 Advantages of low-temperature catalytic bleaching

Low-temperature catalytic bleaching has clear advantages for the environment and the material in comparison with the conventional high-temperature treatments. Table 3 summarizes representative catalytic systems together with their conversion efficiencies, energy savings, water and chemical savings, catalyst reusability, and reported economic benefits.

TABLE 3. Quantitative comparison of conventional and catalytic textile processing technologies.

3.1.4.1 Reduced energy consumption

High temperatures required for traditional peroxide bleaching are a significant contributor to energy use and greenhouse gas emissions. In contrast, bleaching catalyzed by systems such as MnTACN operates at 30 °C–50 °C, with lower energy requirements, lower operational costs, and better sustainability of textile processing (Bouwhuis, 2011).

3.1.4.2 Improved fabric quality

Cellulose fibers were damaged by the treatment with strong alkaline and high temperature to form oxycellulose. Catalytic bleaching prevents much of this damage by simply working under gentler circumstances. Indeed, research suggests that cold bleaching and enzymatic polishing can raise the tear strengths of warp and weft by about 14% and 28%, respectively, over conventional bleaching (Hossain et al., 2025), improvements that contribute directly to improved fabric durability and product quality.

3.1.4.3 Sustainability and industrial significance

Besides the strength of the fiber, catalytic pretreatment technologies offer genuine environmental, economic, and operational advantages over conventional processes.

3.1.4.4 Environmental benefits

Biocatalytic pretreatment has been shown to reduce COD in textile wastewater by approximately 38.3% when compared with conventional methods (Bouwhuis, 2011). Integrated one-bath systems that combine desizing, bleaching and dying also do away with several intermediate washing steps, which adds up to a considerable water savings (Eren et al., 2009). Because of their biodegradability and potential to substitute many synthetic chemicals, the employment of enzymes further reduces the pollutant load arriving at wastewater treatment plants (Catarino et al., 2025).

3.2 Catalytic dying

Conventional textile dying is among the most resource-intensive and polluting sectors of industry, mainly due to its high dependence on freshwater, non-renewable energy, and synthetic chemicals (Ibrahim et al., 2021; Catarino et al., 2025). One of the primary challenges is that reactive dyes, widely used for cotton and other cellulosic fibers need considerable quantities of electrolytes (salts) and alkali for proper fixing (Chowdhury et al., 2024). However, despite these additions, fixation rates are generally less than optimal, resulting in significant dye wastage and release of highly pigmented, salt-rich wastewater that is difficult and costly to treat (Catarino et al., 2025; Chowdhury, 2025). Conventional vs. Catalytic dying is compared in greater details in Table 4.

TABLE 4. Comparison between conventional and catalytic dying.

Catalysts have been identified as an important solution to these problems, allowing the dye-fiber reaction to occur at lower temperatures and without the use of excessive chemical auxiliaries (Chowdhury et al., 2024; Kreuz et al., 2024). The catalytic dying systems, either molecular or biological enzymes, lead to a greener production by reducing the activation energy required for fixation as well as enhancing the specificity of dye uptake (Roy Choudhury, 2014; Anju Kushwaha et al., 2024).

3.2.1 Catalytic mechanisms in dye fixation

The main goal of catalytic dye fixation is to strengthen the interaction between dye molecules and textile fibers, achieving higher fixation rates while cutting down on the chemicals required. In conventional reactive dying, large amounts of salt are needed to overcome the electrostatic repulsion between negatively charged reactive dyes and cellulose fibers. Catalytic dying offers a more sustainable path forward, promoting selective chemical interactions that strengthen dye–fiber bonding without relying so heavily on salt (Chowdhury et al., 2024). A range of catalytic systems has been explored to this end, including surfactants, mordants, crosslinking agents, and metal-organic catalysts.

Among these, micellar catalysis has drawn considerable interest as an environmentally friendly dying technique. Here, surfactant molecules spontaneously form micelles that encapsulate dye molecules and carry them closer to the fiber surface. By raising the local concentration of dye near the fibers, micelles improve dye–fiber interactions and boost fixation efficiency, all while significantly cutting water and salt use during dying (Chowdhury et al., 2024). Certain metal complexes and organic catalysts work in a similar way, activating the reactive functional groups of dyes and enabling efficient fixation under milder pH and temperature conditions than conventional alkali-based dying requires (Bouwhuis, 2011; Farhan et al., 2025).

3.2.2 Nano-assisted dying

Recent advances in nanotechnology have opened up further possibilities for catalytic dying, improving both dying performance and fabric functionality. Nano-assisted dying uses nanoparticles either as catalysts themselves or as supports for catalysts, enhancing dye adsorption, boosting color strength, and improving dye uptake (Rahman et al., 2022; Chowdhury, 2025). Among the nanomaterials studied so far, silver (Ag) and titanium dioxide (TiO₂) nanoparticles stand out for their high surface area and strong catalytic properties (Rahman et al., 2022). N-doped Ti-melamine-capped Ag₂S nanocomposite, for example, have demonstrated excellent catalytic activity, enhancing textile dye reduction and improving how efficiently dye-containing wastewater can be treated (Rahman et al., 2022). Their high surface area encourages greater contact between dye molecules and textile fibers, which translates into higher color strength (K/S values) and improved dye uptake (Tochetto et al., 2022). Beyond better coloration, these nanomaterials also bring valuable functional properties to the table, such as antimicrobial activity, UV protection, and greater durability, making the resulting textile products more functional and commercially appealing (Chowdhury, 2025). In contrast to enzymatic systems, nanocatalysts generally exhibit higher operational stability and reusability, although concerns regarding synthesis cost and nanoparticle recovery remain.

3.2.3 Enzyme-assisted dying

One of the most promising uses of white biotechnology in the textile industry is enzyme-assisted dying, given to its great selectivity, environmental compatibility, and energy efficiency (Shahid et al., 2016; Tochetto et al., 2022). Of the enzymes utilized, laccases have received much attention as they are able to catalyse the oxidative polymerisation of color precursors directly on textile fibers (Sun and Tang, 2013; Tochetto et al., 2022). Laccases from fungal species such as Pleurotus, Trametes, and Cerrena oxidize compounds such as gallic acid, producing colored polymers that form directly on the fiber surface (Sun and Tang, 2013; Tochetto et al., 2022). The in situ dying procedure provides appealing hues, including gray tones on wool and silk fabrics, without the use of traditional synthetic dyes (Sun and Tang, 2013). Enzyme-assisted dying not only imparts color but also improves the functional performance of textiles such as ultraviolet protection, antioxidant activity, and deodorizing properties. The benefits are mainly related to the generation of oxidation products rich in aromatic structures and phenolic hydroxyl groups, which are responsible for both the development of color and the functionality of the fabric (Sun and Tang, 2013).

The catalytic performance of laccases is strongly influenced by reaction conditions, particularly pH and the redox potential of the enzyme–substrate system. Under optimized conditions, laccases predominantly oxidize phenolic precursors to reactive radicals that undergo polymerization, forming stable colored polymers on the fiber surface. However, variations in pH, redox potential, and substrate characteristics can shift the reaction towards degradation rather than polymer formation, thereby affecting color development and dye fixation. Compared with conventional dyeing, laccase-assisted systems generally operate under milder conditions with lower chemical requirements while providing comparable color yield (K/S) for suitable substrates. Nevertheless, careful optimization of reaction conditions remains essential to achieve consistent dyeing performance and facilitate industrial application.

In addition, enzymes like as amylases, pectinases and celluloses can be used to integrated pretreatment and dying processes for desizing, scouring and dying in one bath. This one-bath process reduces textile finishing, and dramatically cuts back water and chemical consumption as well as processing time and energy requirements. At the same time the fabric quality is maintained at a high level and enzyme assisted processing offers an efficient and environmentally friendly alternative to standard textile dying procedures (Tochetto et al., 2022; Kreuz et al., 2024). While enzymatic catalysts provide excellent selectivity and operate under mild conditions, their industrial application can be limited by enzyme stability and reusability compared with inorganic catalytic systems.

3.2.4 Plasma-assisted catalytic dying

Plasma-assisted catalysis, by integrating physical surface alteration and catalytic dying, has appeared as a viable way to improve dye fixing. The plasma technology is a clean and dry treatment and it modifies the fiber surface by adding polar functional groups and slightly increasing surface roughness without additional chemicals (Chowdhury, 2025). These surface modification lead to increase the wettability of the fiber and provide more active sites for dye adsorption, which results in higher dye uptake and better fixing in future dying process (Chowdhury et al., 2024). Thus, plasma-treated fabrics often result in darker tints, improved fastness to washing and greater dye use with less dye and catalyst (Chowdhury, 2025). Besides better dying performance, the synergy of plasma technology and catalytic dying reduces the consumption of water and chemicals, minimizes waste creation and promotes more sustainable textile manufacturing methods (Hossain et al., 2025).

3.2.5 Low-salt and salt-free dying

One of the important environmental benefits of catalytic dying is its potential to significantly reduce or even eliminate the need for electrolytes in reactive dying (Chowdhury et al., 2024). In traditional cotton dying, a large quantity of sodium chloride or sodium sulfate, up to 100 g/L, is added to overcome the electrostatic repulsion between negatively charged reactive dye molecules and cellulose fibers, enhancing the absorption of the dyes (Chowdhury et al., 2024). However, this salt outflow considerably increases the salinity and total dissolved solids (TDS) of the textile effluent, which complicates the treatment and raises the overall environmental load of the operation.

Catalytic dying overcomes this challenge by facilitating dye migration and fixation through alternative mechanisms, including micellar catalysis, catalytic activation, and the application of specific crosslinking agents, instead of relying on high salt concentrations for dye exhaustion (Chowdhury et al., 2024). As a consequence, low salt or even salt free dying is a viable alternative, which reduces the consumption of chemicals, saltiness of the effluent and eases its treatment. Besides the environmental benefits, this strategy can also lower production costs by reducing the consumption of raw materials and reducing wastewater treatment needs. These advantages make catalytic dying a possible route for the development of more sustainable textile production (Bansal, 2022; Ghosh et al., 2025).

3.2.6 Benefits and industrial significance

Growing industrial interest in catalytic dying is motivated by the possibility of improving both environmental sustainability and process efficiency. Catalytic systems are generally softer than traditional dying processes, which need temperatures of ∼95 °C–100 °C. Catalytic systems are usually operated at temperatures between 30 °C and 70 °C and at atmospheric pressure (Bouwhuis, 2011; Kreuz et al., 2024). The dying performance is satisfactory and these circumstances considerably decrease the energy usage and the released greenhouse gases (Roy Choudhury, 2014). Despite the promising laboratory-scale performance of catalytic technologies, several challenges remain for their large-scale implementation. Catalyst manufacturing costs, long-term stability and replacement frequency, reactor design, regulatory compliance, and process integration must be carefully addressed through techno-economic assessments before widespread industrial commercialization can be achieved.

Some other advantages of catalytic textile processing have been reported. Fewer washing steps and lower operating temperatures result in reduced water and energy usage (Bouwhuis, 2011; Kumar et al., 2021). Compared with conventional dying, catalytic systems generally offer higher dye fixation efficiency, lower chemical consumption, and improved environmental performance. However, their large-scale implementation depends on catalyst stability, recyclability, and cost-effectiveness, which remain important considerations for industrial adoption. Catalytic procedures also yield a less polluted effluent. Some studies reported COD reductions of ∼38% in catalytic bleaching systems with MnTACN catalysts (Bouwhuis, 2011). Furthermore, the mild reaction conditions maintain the mechanical strength of textile fibers, leading to better longevity of the fabric and lower damage compared to standard chemical treatments (Hossain et al., 2025). Sustainable catalytic dying technologies have been proved to be economically viable in terms of processing costs and have shown good color fastness and fabric performance, indicating their feasibility for large-scale industrial application (Hossain et al., 2025). Although catalytic dyeing offers significant environmental and operational advantages, large-scale implementation still requires improvements in catalyst durability, recovery, and cost-effectiveness. Compared with enzymatic systems, inorganic and nanocatalysts generally provide greater operational stability, whereas enzymes offer higher selectivity under milder reaction conditions.

3.3 Catalytic textile finishing

Textile finishing is a crucial component of fabric production that improves the performance, durability, and functionality of textiles beyond their initial appearance. Traditional finishing procedures sometimes rely on the use of synthetic chemical additives to impart desired attributes such as wrinkle resistance, antibacterial activity and water repellency. These treatments are widely used but many have limited durability, often require repeated chemical application and can give rise to environmental and health concerns due to the hazardous nature of the chemicals involved. These challenges have increased the interest for catalytic textile finishing as more sustainable and efficient alternative. Catalytic finishing is a way of applying functional catalysts on the textile surface, so that the fabrics can actively catalyze certain chemical reactions without consuming the catalysts during their use. Accordingly, catalytic textiles can offer strong and often self-regenerating functionalities that are hard to realize with conventional passive finishes. These include self-cleaning ability, antimicrobial activity, ultraviolet (UV) protection, super hydrophobicity and increased wrinkle resistance. In view of these advantages, catalytic finishing has attracted much attention in the face of the increasing demand for hygienic, multifunctional and low maintenance textiles. These materials are increasingly being used in healthcare applications, sportswear, outdoor clothing and in the fast-growing field of smart textiles (Mollick et al., 2023; Mahmoud and Kianfar, 2024). Despite these promising developments, the industrial adoption of catalytic finishing remains dependent on coating durability, catalyst stability after repeated washing, manufacturing cost, and compatibility with existing textile production lines.

3.3.1 Methods for catalyst immobilization on textile surfaces

The performance of a catalytic textile is highly dependent on the uniformity and stability of the catalyst fixed on the fiber surface. To do that, researchers have developed a variety of fabricating techniques to ensure a strong attachment of the catalyst without sacrificing the fabric’s flexibility, softness and comfort. The sol-gel method is one of the most popular techniques for depositing metal oxide nanoparticles such as titanium dioxide (TiO 2) and zinc oxide (ZnO) onto cotton, polyester and mixed fabrics. The process gives homogenous nanostructured coatings with high chemical stability and good adhesion to textile fibers, thereby making it a suitable method for durable catalytic finishes (Maity et al., 2020; Aalipourmohammadi et al., 2021).

Another widely used approach is the layer-by-layer (LbL) self-assembly technique, in which oppositely charged components are deposited sequentially to form well-defined multilayer coatings. This gives excellent control over coating thickness, composition and surface functionality. For instance, TiO₂/g-C₃N₄ composite coatings fabricated by LbL assembly have demonstrated enhanced photocatalytic performance, due to the intimate contact between the two semiconductors promoting greater charge separation and helping to suppress electron-hole recombination (Wang et al., 2019).

Other advanced surface modification techniques including sonochemical deposition and plasma-assisted coating have also attracted much attention. Plasma pretreatment enables to increase the surface energy of textile fibers and to create active functional groups, improving thus the dispersion and adhesion of the catalyst. This strategy has been effectively employed to immobilize TiO2/Ag/ZnO heterojunctions on textile surfaces to improve the photocatalytic efficiency and antibacterial performance (Samal et al., 2010; Kashif et al., 2024). In-situ synthesis has also become an attractive option for constructing more complex catalytic textiles. Here, catalysts like metal-organic frameworks (MOFs) are directly produced on the fabric surface, leading to impressively durable coatings with huge surface areas and significant catalytic activity (Liu et al., 2026). While catalytic pretreatment, dying, and wastewater treatment improve process efficiency and reduce environmental impacts, catalytic finishing further enhances textile functionality by imparting self-cleaning, antimicrobial, UV-protective, and other value-added properties.

3.4 Catalytic materials and their functional applications

3.4.1 Self-cleaning textiles

Self-cleaning is one of the most investigated applications in catalytic textile finishing. Its main dependence is on photocatalysis, where light energy is used by semiconductor catalysts to decompose organic pollutants that build up on the surface of textiles. Among the photocatalysts studied so far, titanium dioxide (TiO₂) has been the most investigated, particularly its anatase phase. Under ultraviolet (UV) light, TiO₂ generates electron-hole pairs which react with oxygen and water to produce highly reactive oxygen species, namely, hydroxyl (•OH) and superoxide (•O₂ ⁻) radicals. These species then convert organic contaminants to environmentally friendly byproducts like carbon dioxide and water (Maity et al., 2020; Mahmoud and Kianfar, 2024). The strong photocatalytic capability of TiO₂ has been proven in many studies, for example, TiO₂-coated fabrics have shown to degrade about 96% of methyl orange in only 3 h of UV exposure (Mushtaq et al., 2024).

Another extensively studied photocatalyst is zinc oxide (ZnO) because to its low cost, high catalytic activity, and ability to produce diverse nanostructures including nanoflowers and nanorods that give substantial reactive surface area (Verbič et al., 2019; Mollick et al., 2023). More recently, heterojunction photocatalysts have attracted much attention because of their improved performance under visible light. For example, the composite systems TiO2/Ag/ZnO have improved photocatalytic activity because of more effective charge separation. In these materials, silver nanoparticles operate as an electron sink by the Schottky barrier effect which slows down the recombination of electron-hole pairs and increases the lifetime of charge carriers. This has resulted in degradation efficiencies of about 93% for methyl red under visible light, indicating the promise of these composite catalysts for practical self-cleaning textile applications (Görgülüer et al., 2021; Kashif et al., 2024). Overall, TiO₂- and ZnO-based photocatalysts exhibit consistently high degradation efficiencies (>90%) under optimized conditions, while heterojunction systems generally provide improved visible-light activity and better catalyst stability.

3.4.2 Antibacterial finishes

Catalytic antibacterial coatings are particularly relevant for healthcare textiles, protective clothing and sportswear, where microbial contamination can jeopardise hygiene and product performance. Silver nanoparticles are regarded as one of the most efficient antibacterial agents due to their capability to release Ag⁺ ions that destroy bacterial cell membranes, inhibit enzyme function, and damage genetic material. The combination of silver nanoparticles with semiconductor photocatalysts such as TiO two or ZnO results in synergistic interactions, which improve both the antibacterial and photocatalytic activity (El-Hamshary et al., 2021; Görgülüer et al., 2021). For example, the TiO 2 -coated cotton fabrics made based on the corona pretreatment showed the total suppression of both Staphylococcus aureus and Escherichia coli (Aalipourmohammadi et al., 2021). More recently, heterojunctions based on graphitic carbon nitride (g-C₃N₄) have attracted significant attention due to their ability to utilize visible light. Composite photocatalysts including pg-C3N4/ZnO may create reactive oxygen species under sunlight, and hence exhibit the antibacterial activity around 3.6 times higher than that of single catalyst components (Guo et al., 2025). These visible-light-responsive polymers offer great potential for next-generation antimicrobial textiles with enhanced performance under natural lighting circumstances (Glažar et al., 2023).

3.4.3 UV-protective finishes

The long-term exposure to ultraviolet (UV) radiation can cause degradation of textile materials and increase the risk of skin damage to the wearer. The use of photocatalytic nanoparticles in textile coatings has been shown as a promising technique to improve UV protection. Among the available materials, titanium dioxide (TiO2) and zinc oxide (ZnO) are the most common because they effectively absorb and scatter UV radiation in the UVA and UVB range, thereby diminishing the quantity of UV light that actually passes through the fabric (Ibrahim et al., 2021; Prasad et al., 2024). Due to their nanoscale size and large surface area they have an advantage over bulk materials in UV-shielding performance. ZnO based coatings are particularly attractive since they can provide more than one protection function at the same time. In addition to strong UV protection, ZnO also possesses intrinsic antibacterial qualities, making these coatings suitable for medical textiles, sporting and outdoor protective clothing where cleanliness and UV resistance are of importance (Verbič et al., 2019; Buşilă et al., 2022).

3.4.4 Super hydrophobic surfaces

Super hydrophobic textile finishes give passive self-cleaning properties by preventing water wetting of the fabric surface. This phenomenon is known as the Lotus Effect and is characterized by water contact angles of above 150°, meaning that water droplets roll off the surface taking dust and dirt with them. Generally, super hydrophobicity is obtained by combination of photocatalytic nanostructures and hydrophobic surface modifiers such as polydimethylsiloxane (PDMS) or silane compounds (Afzal et al., 2014). For example, multilayered TiO₂@g-C₃N₄ coatings coated with PDMS showed water contact angles up to 157.9° and good photocatalytic degradation efficiency (Shi et al., 2024). Similarly, MOF-functionalized textiles have showed multifunctional behavior, integrating super hydrophobicity with photocatalytic activity and pollutant adsorption, thereby representing interesting prospects for advanced smart textile applications (Liu et al., 2026).

3.4.5 Wrinkle-resistant finishing

The mechanical performance of cotton fabrics can also be improved by catalytic finishing to improve their wrinkle resistance. Typical wrinkle-resistant coatings include cross-linking agents such as 1,2,3,4-butanetetracarboxylic acid (BTCA) and dimethylol-dihydroxyethyleneurea (DMDHEU). The integration of TiO₂ nanoparticles into these finishing systems leads to better crosslinking into the cellulose structure resulting in better wrinkle recovery at a lower catalyst level. Good wrinkle resistance has been obtained at relatively low concentrations of TiO₂ of about 0.1%–0.2%, which helps to keep the softness and mechanical strength of the fabric and also improves the crease recovery. Overall, while photocatalytic and nanocatalysis finishing systems exhibit excellent multifunctional performance, their long-term stability, recyclability, and scalability require further validation before widespread industrial implementation. Table 5 shows the comparison between standard textile processing methods and catalytic approaches for sustainable textile manufacture. Together, these catalytic approaches demonstrate how different technologies complement one another across successive stages of textile manufacturing, supporting a more sustainable and resource-efficient production process.

TABLE 5. Conventional textile processing methods and catalytic alternatives for sustainable textile manufacturing.

Overall, catalytic textile processing offers a lower environmental footprint than conventional methods by reducing water and energy consumption, chemical usage, and pollutant generation. These improvements contribute to lower COD and BOD loads, reduced greenhouse gas emissions, and more sustainable resource utilization, highlighting the potential of catalytic technologies to support environmentally responsible textile manufacturing.

4 Catalysis for textile wastewater treatment

4.1 Heterogeneous catalysis

The textile effluent comprises high color, COD and TOC levels and substantial quantities of synthetic dyes, surfactants, salts, auxiliaries and refractory organic compounds. Such contaminants are poorly biodegradable and persistent in water (Pormazar and Dalvand, 2025). Traditional biological restoration methods are therefore not successful. Thus, heterogeneous catalytic advanced oxidation processes (AOPs) are efficient alternatives because of the generation of highly reactive oxygen species (ROS), mainly hydroxyl (•OH) and sulfate (SO₄•^-) radicals that rapidly oxidize complex molecules of aromatic dyes to less hazardous products and finally CO₂ and H₂O (Kallawar and Bhanvase, 2023; Khan et al., 2024).

Fe-based catalysts are one of the most explored heterogeneous catalysts due to its inexpensive cost, nature-friendly property and high Fenton-like catalytic activity. Iron oxides (Fe₃O₄, α-Fe₂O₃, α-FeOOH), zero-valent iron and Fe-based catalysts can efficiently activate H₂O₂ or persulfate via reversible Fe²⁺/Fe³⁺ redox cycling and generate ROS without the iron sludge that is intrinsic to homogeneous Fenton reactions. In addition, the Fe catalysts can be easily recovered and reused numerous times due to their magnetic property (Kallawar and Bhanvase, 2023; Akinyemi et al., 2024). The Fe-Y zeolite catalyst was employed for treatment of a Black B azo dye synthetic wastewater, which resulted in total decolorization and TOC removal more than 80%, with significant enhancement in the performance under sunshine exposure. Another Fe-based strategy was the application of Fe₃O₄–Mn₃O₄ heterogeneous electro-Fenton catalyst for textile wastewater treatment (Phong, 2018).

Copper (Cu)-based catalysts such as CuO, Cu₂O and composite forms of copper are highly interesting due to the redox behavior of Cu⁺/Cu²⁺ which facilitates the rapid activation of hydrogen peroxide and peroxymonosulfate (PMS) to produce high radical generation in a wide pH range in comparison to the Fe-based catalysts. Moreover, Mn (manganese)-based catalysts (MnO₂, Mn3O4, and Mn₂O₃) have a remarkable ability to activate PMS across the several oxidation states of Mn and showed excellent catalytic stability and little metal leaching throughout their successive application (Akinyemi et al., 2024; Khan et al., 2024).

Also, porous zeolites are commonly utilized in heterogeneous catalysis due to their high surface area, ion-exchange capacity and well-defined pore structure. Metal laden zeolites aid in simultaneous distribution of catalytic active sites, prevention of metal leaching and adsorption of dye molecules. In the same way, activated carbon supported catalysts combine adsorption and catalytic oxidation. Activated carbon has a variety of surface functional groups and a porous structure that concentrates pollutants around catalytic sites and supports Fe, Cu and Mn-based nanoparticles (Ingrassia et al., 2023; Gadore et al., 2024). AC-based catalysts combine adsorption and oxidative catalysis. Fe₃O₄ catalyst on biochar (Fe₃O₄/CBc) showed more than 99.4% efficiency in the methyl orange decomposition under optimal H2O2 addition and acidic pH conditions, whereas activated carbon-assisted Fenton oxidation of biologically pre-treated textile wastewater resulted in a COD reduction efficiency from 64% (Fenton only) to 83%–88%, due to the addition of reed and activated carbon. The Fe₃O₄ nanoparticles coated on granular activated carbon as a three-dimensional cathode for the heterogeneous electro-Fenton process achieved 98.97% dye removal and 66.66% COD removal and maintained 98.56% of its initial efficiency after six reuse cycles, indicating excellent stability (Kadıoğlu et al., 2025).

The use of heterogeneous catalytic devices for the treatment of the textile effluent is very efficient. The azo, anthraquinone and triphenylmethane chromophores are swiftly broken and the dyes are immediately decolorized. Moreover, the lowering of COD is also attributed to the oxidation of intermediates. A total mineralization process is difficult to realize, but more than 80% of COD removal and significant TOC removal were obtained in optimal heterogeneous catalysis systems such as the photoreaction of Fenton process and persulfate activation systems (Kallawar and Bhanvase, 2023). Compared with homogeneous catalysts, heterogeneous catalytic systems generally demonstrate superior catalyst recovery, reusability, and operational stability, making them more suitable for continuous industrial wastewater treatment despite the higher initial material cost.

4.2 Photocatalysis

Photocatalysis has been considered as an environmentally friendly catalytic method for textile wastewater treatment. It employs semiconductor materials to transform solar or artificial light into chemical energy for pollutant destruction (Acharya and Parida, 2020; Manikandan et al., 2021; Garg et al., 2023). Semiconductor photocatalysis uses the absorption of light to create electron–hole pairs that are responsible for redox reactions at the surface of the catalyst, thereby generating reactive oxygen species (ROS) that can mineralize dyes and organic pollutants without requiring additional chemical dosing (Chen et al., 2025). Figure 3 Showing the semiconductor photocatalysts (TiO₂, ZnO, BiVO₄, g-C₃N₄, and MOFs) along with their electronic structure, optical properties, and mechanisms for generating reactive oxygen species (ROS). The Table 6 reveals that heterogeneous catalysts, photocatalysts, electro-Fenton catalysts and immobilised biocatalysts show consistently high degrading efficiencies (usually above 90%) and good stability across several regeneration cycles.

TABLE 6. Performance comparison of catalytic technologies.

4.2.1 TiO₂

TiO₂ is still the benchmark photocatalyst since the landmark discovery of photo electrochemical water splitting on TiO2 electrode by Bahadori et al. (2025), due to its low cost, chemical stability and strong oxidizing capacity, while its comparatively wide band gap limits its intrinsic activity mostly in the UV region (Acharya and Parida, 2020). To overcome this limitation, the coupling of TiO₂ with g-C₃N₄ in an all-solid-state Z-scheme heterojunction spatially separates the oxidation and reduction processes to the valence band of TiO₂ and the conduction band of g-C 3 N 4, respectively, which greatly reduces electron–hole recombination and substantially improves photocatalytic activity under visible-light irradiation (Liu et al., 2016; Garg et al., 2023).

4.2.2 ZnO

ZnO, like TiO₂, is a first-generation single-component photocatalyst, but it suffers from similar high electron–hole recombination rates and inefficient visible-light absorption, leading to the development of semiconductor heterojunction systems coupling two or more components to achieve synergistic adsorption and charge-carrier migration such as g-C₃N₄–Co₃O₄ Z-scheme junctions with green-synthesized ZnO, which have been shown to efficiently degrade methylene blue in aqueous solution (Tamiru Mengistu et al., 2023).

4.2.3 BiVO₄

BiVO₄ has an inherently smaller band gap for direct visible light response. Mo-doped BiVO₄ photocatalyst decorated with metal-oxide cocatalysts (Ag₂O_x, CoO_x and CuO_x) achieved 80.2% degradation efficiency of Orange II dye after 5 h visible-light irradiation. The 2 wt% CuO_x-loaded sample simultaneously achieved 97% inactivation of Escherichia coli and 99% inactivation of S. aureus, demonstrating the dual utility of BiVO₄ for pollutant degradation and microbial disinfection (Manikandan et al., 2021).

4.2.4 g-C₃N₄

g-C₃N₄ is a metal-free, visible-light-active polymeric semiconductor that is typically synthesized by condensation of nitrogen-rich precursors such as melamine, urea, or cyanamide; it is chemically stable even in strongly acidic media but is limited by a comparatively low bandgap, fast electron–hole recombination, and weak electrical conductivity (Nemiwal et al., 2021). For example, the band gap of porous g-C₃N₄ nanosheets can be reduced from 2.98 to 2.66 eV via non-metal doping strategies such as phosphorus doping, leading to improved photo-excitation of electrons and holes, whereas the charge separation and visible-light utilization can be further boosted by forming heterojunction with TiO₂, ZnO, or BiOI (Tamiru Mengistu et al., 2023).

4.2.5 MOFs

MOFs and new composites show significant temperature-dependent photocatalytic effects; increasing reaction temperature from about 20 °C to 50 °C in g-C3N4@CdO/ZnO photocatalysts sped up dye degradation by enabling molecular collisions and surface reactions, MOFs generally have higher hydrogen evolution rates at higher temperatures owing to thermally activated surface sites, and BiVO4-based systems have ideal operating temperature ranges for degradation of pollutants, while Zn-based photo thermal composites are also highly temperature-dependent in charge-transport and adsorption dynamics (Chen et al., 2025). Among the reported photocatalysts, TiO₂ remains the benchmark owing to its stability and low cost, whereas g-C₃N₄-, BiVO₄-, and MOF-based composites provide improved visible-light utilization. However, their practical application depends on balancing photocatalytic efficiency with catalyst durability, synthesis cost, and scalability.

4.2.6 Reactions mechanisms and ROS generation

In the general photocatalytic mechanism, photoexcited electrons reduce dissolved O₂ to the superoxide radical anion (O₂•^-), photogenerated holes oxidize surface hydroxide/water to hydroxyl radical (•OH), and electron or energy transfer to O₂ can additionally generate singlet oxygen (¹O₂), all together representing the dominant ROS responsible for pollutant mineralization (Wang et al., 2025). This pathway was corroborated by direct experimental evidence of a TiO₂–Fe₂O₃ nanocomposite, where radical trapping experiments confirmed the formation of both •OH and O₂•^-, and •OH was found to be actively involved in the oxidation of polyunsaturated membrane phospholipids and bacterial cell death in conjunction with pollutant degradation, and photogenerated organic products (aldehydes, ketones, carboxylic acids) were confirmed by FTIR/DRIFT analysis (Manikandan et al., 2021).

4.3 Advance oxidation catalysis

AOPs are currently one of the most efficient treatment technologies due to their ability to generate highly reactive oxygen species (ROS), primarily hydroxyl (•OH) and sulfate (SO₄•^-) radicals, which are strong oxidizing reagents capable of degrading persistent dyes, surfactants and other refractory organic pollutants into harmless products (Manikandan et al., 2021; Chen et al., 2025). In comparison with the biological conventional treatment, the AOPs present faster kinetics of reactions, higher mineralization rates and a more pronounced effect on non-degradable compounds (Acharya and Parida, 2020). They can be considered as suitable technologies for polishing textile wastewater and water reuse. Figure 4 shows the schematic depiction of the comparison between heterogeneous catalysts, AOP catalysts, and photo catalysts for treating textile wastewater based on their mechanism of reactions, ROS formation, and degradation pathways.

4.3.1 Fenton and photo-Fenton catalysis

The classical Fenton process is based on the redox reaction of hydroperoxide (H₂O₂) with Fe²⁺ ions, producing •OH, a highly reactive, nonselective and very powerful radical species with high oxidation potential (E0 = 2.80 V), which is involved in the degradation of organic pollutants by AOP methods (Liu et al., 2016). In photo-Fenton systems, UV/visible light causes the breakdown of Fe³⁺ to Fe²⁺ ions, which prolongs radical generation for lengthy reaction periods. Solar-assisted Fenton treatment for the elimination of Rhodamine B-containing wastewater has been reported as an affordable and ecologically beneficial process for the removal of contaminants (Behera et al., 2024). From a mechanistic standpoint, recent investigations have shown that the electronic structure of active sites is the critical factor to influence the catalytic pathway in Fenton-like systems. This implies that FeOCl-based catalysts with externally coordinated moiety can be switchable between radical and non-radical oxidation pathways by adjusting the electronic density around the Fe center, which provides an approach to govern selective/non-selective degradation (Garg et al., 2023).

4.3.2 Persulfate activation and sulfate radical catalysis

Other probable oxidizing agents include peroxydisulfate and peroxymonosulfate which can be activated thermally, photolytically and catalytically to create SO₄•⁻. SO₄ ^•− is a radical form that is said to have better stability than •OH. Persulfate-based AOPs using heterogeneous catalysts to activate sulfate radicals from PDS and PMS under light irradiation have been extensively investigated for water treatment, and optimization is mainly focused on photocatalyst design, photoelectricity coupling and indirect activation by homogeneous Fe(III) or Cu(II) ions (Acharya and Parida, 2020). Activation of persulfate and peroxydisulfate by g-C₃N₄ has been proved to guarantee, as evidence. •OH generation in spite of the decreased reductive capability of g-C₃N₄ itself. The Cu-doped Bi₂WO₆ showed a synergistic impact between visible LED irradiation and sulfate radical–Fenton reactions for a typical visible-light system, which could achieve 89.27% norfloxacin elimination and still retain high efficiency after five cycles with little Cu leaching. Radical quenching experiments and electron paramagnetic resonance (EPR) studies confirmed the simultaneous production of sulfate and hydroxyl radicals. A three-dimensional electro-activated persulfate system with magnetic resin particle electrodes was used to demonstrate non-radical mechanisms. The system achieved simultaneous removal of antibiotics, antibiotic-resistant bacteria and resistance genes through a singlet oxygen dominated pathway without detectable •OH or SO₄•⁻. Radicals (Tamiru Mengistu et al., 2023).

4.3.3 Electro-fenton catalysis

The system of electrolysis has proved to be very effective in treating a wide range of hazardous industrial contaminants, persistent pesticides, synthetic dyes and pharmaceuticals, through the sustained production of H₂O₂ via cathodic O₂ reduction and Fe²⁺ catalysis, without the need for the continuous addition of external oxidants (Liu et al., 2016). Recently developed cathode engineering strategies involved trimetallic Fe-Co-Mo cathodes for efficient non-radical degradation in heterogeneous photo-electro-Fenton systems and sulfur-vacancy-engineered MoS₂/Fe₃P cathodes to promote non-radical pathways in Fenton-like reactions in the presence of real water matrices. Furthermore, it has been demonstrated that three-dimensional particle electrode-persulfate connection has the potential to significantly enhance micropollutants removal (Nemiwal et al., 2021).

Although degradation efficiencies vary depending on catalyst type, pollutant characteristics, and operating conditions, heterogeneous photocatalysts generally offer better reusability and long-term stability, whereas enzymatic catalysts provide higher selectivity under milder reaction conditions.

5 Regeneration and circular catalytic system

Catalyst regeneration and reuse ability is one of the primary characteristics affecting the sustainability and practical viability of catalytic technology for textile wastewater treatment (Anekwe and Isa, 2025). Heterogeneous catalysts, photocatalysts, and biocatalysts have great catalytic potential, but their catalytic ability is gradually decreased because of catalyst deactivation caused by surface fouling, poisoning, particle aggregation, structure disintegration, blocking of active sites, and metal leaching in cyclic reactions (Zheng et al., 2024; Anekwe and Isa, 2025). Hence, enhancing catalyst stability and lowering the catalyst loss has been a key target in the current investigations (Chae et al., 2024).

After usage, many regeneration procedures have been devised for the recovery of catalyst activity (Zheng et al., 2024). Thermal regeneration is the removal of accumulated organic pollutants by calcination at high temperatures while chemical regeneration uses acids, alkalis, oxidizing agents or reducing agents to restore active catalytic sites (Zheng et al., 2024). Electrochemical regeneration is a in situ method which regenerates the redox state of catalyst surfaces with minimal chemical consumption, whereas photo regeneration uses light irradiation to degrade adsorbed intermediates on semiconductor photocatalysts without the need for any other reagents (Anekwe and Isa, 2025). Also of great interest is magnetic separation since the magnetic catalysts can be recovered swiftly by an external magnetic field so as to skip filtration and make catalyst recycling easier (Zhu et al., 2024). Thermal regeneration is effective in restoring catalytic activity but generally involves calcination at 400 °C–800 °C leading to high energy consumption, increased greenhouse gas emissions and possible structural damage including pore collapse, particle sintering and loss of active sites after repeated regeneration cycles (Zheng et al., 2024). By comparison, chemical regeneration is carried out under milder conditions and takes less energy, but it involves the use of acids, alkalis, oxidants or organic solvents which may yield secondary liquid waste that needs further treatment. Thus, the environmental benefits of regeneration rely on the trade-off between catalyst recovery, energy demand, chemical usage and trash creation.

Circular catalytic systems are developing as a possible way to translate the textile industry from the linear “take–make–dispose” model to a more sustainable, regenerative and resource-efficient system. As opposed to conventional catalytic processes that are primarily concerned with the degradation of pollutants, circular catalytic systems are concerned with catalyst renewal, resource recovery, waste valorisation, and recycling of materials. Together, these measures result in more efficient use of resources and less environmental impacts (Suen et al., 2023; Vidal-Ayuso et al., 2026). Such a comprehensive strategy is in line with the principles of the circular economy, which aims at the constant use of materials, longevity of catalysts, reducing dependence on primary resources and minimising waste.

The environmental impact of regenerating old catalysts is often lower than manufacturing new ones from LCA perspective because to the reduction of virgin raw materials, catalyst synthesis, transportation, and disposal. Techno-economic analysis also shows that regeneration is usually cheaper than completely replacing the catalyst, as the synthesis of the catalyst (including preparation of precursors, fabrication, drying and calcination) is a major part of the production costs. However, these environmental and economic benefits are eventually compromised with the erosion of the catalyst performance, following repeated regeneration, due to irreversible structural degradation, metal leaching and active site deactivation. Therefore, the regeneration efficiency should not be the only criterion to evaluate the regeneration of catalysts but a holistic framework including the cumulative energy consumption, greenhouse gas emission, resource utilisation, regeneration costs and the overall catalytic lifetime should be considered. The combination of LCA and TEA in future studies will allow to find the best replacement point, where the production of a new catalyst is more advantageous from an environmental and an economic point of view than further regeneration cycles. Recent works show promising advances in enhancing the recyclability of catalysts through the use of magnetic and immobilized catalytic systems (Chandra et al., 2026). Fe₃O₄-coated granular activated carbon electrodes showed 98.56% degradation efficiency after six successive reuse cycles in a heterogeneous electro-Fenton process, suggesting high structural stability and recyclability (Pormazar and Dalvand, 2025). Likewise, laccase immobilized on Fe₃O₄@SiO₂ nanoparticles exhibited 109.7% activity recovery with excellent reusability in photothermal degradation of textile color (Zhu et al., 2022). In another study, laccase immobilized on magnetic metal-organic frameworks (Fe₃O₄-NH₂@MIL-101(Cr)) efficiently decolorized Reactive Black 5 and Alizarin Red S for five regeneration cycles, indicating the potential of immobilized biocatalysts in sustainable wastewater treatment (Amari et al., 2021). In general, many heterogeneous and photocatalytic catalysts reported in recent studies retain about 80–90 %of their initial catalytic activity after 5–8 regeneration cycles. Irreversible deactivation, structural deterioration and leaching of the catalyst after this stage commonly lead to gradual decrease in performance and increase the expense of operation (Kallawar and Bhanvase, 2023; Akinyemi et al., 2024).

6 Future prospective

Future research should focus on developing efficient, cost-effective, and environmentally sustainable catalysts with high stability and long-term reusability for industrial textile applications. Greater attention should be given to visible-light-responsive photocatalysts, multifunctional catalytic systems, and green synthesis approaches using renewable and sustainable materials. In addition, emerging technologies such as artificial intelligence (AI), machine learning (ML), and high-throughput computational screening offer promising opportunities to accelerate catalyst development and optimize process conditions. Further research should also emphasize pilot-scale demonstrations, continuous-flow catalytic reactors, life cycle assessment, techno-economic analysis, and the integration of catalytic technologies within circular textile manufacturing. Addressing these challenges will help bridge the gap between laboratory research and industrial implementation, paving the way for more resource-efficient, commercially viable, and sustainable textile manufacturing.

7 Conclusion

Catalysis is now a key instrument to promote sustainability and resource efficiency in textile production. It boosts performance in textile production and wastewater treatment, lowering the use of water, energy and chemicals. Catalytic methods including heterogeneous catalysis, photocatalysis, and advanced oxidation processes not only enhance the dye fixation but also enable the effective destruction of persistent contaminants in textile effluents. In recent years, the development of catalytic materials such as regenerable catalysts, immobilized enzymes, magnetic catalysts, and recyclable catalytic systems has improved catalyst stability, operating efficiency, and resource recovery. These advancements in concert foster cleaner production, enable circular manufacturing techniques and reduce environmental impacts. Catalysis is therefore playing an ever-growing role in the drive to make the textile industry more sustainable, efficient and ecologically friendly.

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Footnotes

Edited by: Jianhua Zhang, Victoria University, Australia

Reviewed by: Chi-Wing Tsang, Technological and Higher Education Institute of Hong Kong, China

Vishwajit Chavda, Kyungpook National University, Republic of Korea