C. L. Proulx, C. Cadieux, D. R. Knaack, D. Fortin, R. R. Goulet
Radium-226 (226Ra) is mobilized following the disturbance of ore bodies containing uranium-238. The availability of radium-226 to aquatic organisms is governed by its aqueous speciation and sorption to mineral substrates. This study evaluated the influence of mineral phases, calcium (Ca) concentration, and organic matter content on the partitioning of 226 Ra over 48 h. Tests were conducted across three nominal 226 Ra activity concentrations (1, 5, and 50 Bq L -1) and four Ca levels (0.9, 7, 35, and 70 mg L -1) representative of freshwater systems both affected and unaffected by metal-mining effluent. Under solution-only conditions, dissolved 226 Ra remained stable, indicating that Ca concentration alone did not influence 226 Ra solubility. The addition of natural sand resulted in rapid removal of dissolved 226 Ra from solution, reaching up to 86% after 48 h depending on 226 Ra and Ca concentrations. Overall, removal decreased significantly with increasing Ca concentration, suggesting that Ca 2+ reduced 226 Ra 2+ adsorption, consistent with competition between 226 Ra 2+ and Ca 2+ for sorption sites. The presence of organic matter in the form of algal cells produced a small but consistent additional removal of 226 Ra (∼6%), indicating that interactions between 226 Ra and organic matter were limited relative to mineral processes. Mineral-specific experiments demonstrated that 226 Ra sorption was strongly mineral-dependent, with extensive sorption onto kaolinite (96% ± 2% within 6h; K d = 49–62 L kg -1) and minimal sorption onto quartz (10% ± 9% at 48h, K d = 0–0.55 L kg -1). These findings demonstrate that 226 Ra partitioning in sandy aquatic environments is governed primarily by the presence of reactive clay minerals rather than quartz or organic matter, and by aqueous Ca concentration. Under the controlled laboratory conditions of this study, these findings provide insight into the factors governing 226 Ra mobility and bioavailability in sandy sediments where clay content and water chemistry strongly influence the fate of 226 Ra.
Aleesha Nabhai, Oliver Charles Wasson, Hongmei Gu, Zhen Cai, Heon E. Park, James Springstead, Qingliu Wu, Jinghao Li
Black liquor, the alkaline effluent of kraft pulping, is one of the largest underutilized sources of technical lignin globally. This chemically valuable aromatic biopolymer is predominantly incinerated for energy recovery, foregoing the considerable chemical value embedded in lignin’s aromatic backbone and reactive functional groups. Conventional lignin isolation via acid precipitation is constrained by high energy demands, equipment corrosion, and acidic waste generation. These limitations collectively undermine the large-scale valorization of lignin. This review examines conventional and emerging approaches for lignin recovery from kraft black liquor, with particular emphasis on ionic liquids and deep eutectic solvents. Beyond extraction, the potential of lignin-derived materials for environmental applications is discussed, highlighting their role in promoting a circular economy. This review discusses lignin precipitation mechanisms and evaluates key barriers, including solvent recovery, scalability, and techno-economic feasibility. Addressing these challenges positions the pulp and paper industry at the forefront of sustainable chemical manufacturing.
The escalating accumulation of electronic waste (e-waste), currently estimated at approximately 45 million tons annually worldwide, causes serious environmental and resource recovery challenges. Printed circuit boards (PCBs), key components of most electronic devices, are particularly valuable due to the presence of precious metals (Au, Ag, Pt, Pd, and Cu), the recovery of which is hindered by the combination of ceramics, polymers, and metals. Metal fraction makes up 25%–30% of total PCB mass, while among all metal elements, copper is present in the highest proportion—most often 60%–70% compared to the metal fraction mass. Copper has recently been designated as a critical raw material by the European Commission. Simultaneously, increasing global demand for copper, alongside limited mining capacity, has led to a growing supply gap. This research responds to both environmental and economic needs by recovering copper from discarded PCBs and converting it into copper oxide (CuO) nanoparticles, a material of high technological relevance—especially in industrial organic synthesis. Mechanical methods were applied to separate polymeric layers from metal-rich components, followed by chemical extraction using ammonium-based salts. Analysis of these extracts showed that copper extraction was more efficient if the polymer/ceramics fraction of PCB is removed by grinding. The present study can report that the PCB types (denoted PCB3) as the coarse fraction leached by (NH 4) 2 C 6 H 6 O 7 and obtaining 29.93 wt% Cu compared to the starting waste mass corresponds to ≈99.8% effective extraction when referenced to a Cu-rich 30 wt% feed. This result is the highest of the published data of ammoniacal-e-waste leaching. Purified extracts were used for CuO nanoparticle synthesis by means of microemulsion synthesis. Characterization by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) confirmed the successful synthesis of CuO nanoparticles. These results point to a practical and eco-friendly hydrometallurgical strategy for copper recovery from electronic waste, followed by CuO nanoparticle production. The method addresses both e-waste pollution and the growing copper shortfall, supporting urban mining initiatives, promoting circular resource use, and complementing green transition goals.
Sameer Neve, Viravid Na Nagara, Zhiming Zhang, Rupali Datta, Dibyendu Sarkar
Converting industrial byproducts into functional adsorbents supports circular and sustainable approaches to water treatment. This study evaluated biochar derived from spent vetiver (Chrysopogon zizanioides) roots, a byproduct of the perfumery essential-oil industry, for the competitive adsorption of copper (Cu), cadmium (Cd), zinc (Zn), and lead (Pb). Vetiver root biochar produced at 500 °C for 60 min exhibited a high surface area of 308.2 m 2 /g and a yield of 53.8%. Batch adsorption experiments were performed in triplicate at a pH of 5.5 ± 0.2, in 0.1 M NaNO 3, at 24 °C ± 2 °C, using 1% (w/v) biochar (10 g/L), with initial metal concentrations of 100 mg/L for each metal, along with a control. After 24 h, removal efficiencies reached 100% for Pb, 99.9% for Cu, 92.6% for Zn, and 77.0% for Cd. Adsorption was rapid, with nearly complete removal of Pb and Cu and approximately 60% removal of Zn and Cd within the first 30 min. High maximum adsorption capacities were achieved particularly for Pb, along with other tested metals, although competition in multi-metal systems influenced adsorption performance. Adsorption edge analysis and surface complexation modeling indicated that chemisorption was the dominant removal mechanism, supporting strong metal retention under the tested extraction conditions. Mild extraction released <3.5% of adsorbed metal, and TCLP/SPLP leachates were below U.S. EPA thresholds. Overall, these findings demonstrate that spent vetiver roots can be converted into high-performance biochar adsorbents, offering a sustainable, value-added strategy for heavy-metal remediation in water treatment systems.
Amjid Khan, Rashid Abbas Khan, Dilawar Hassan, Tauqeer Ahmed Qadri, Bushra Ashiq, Ayesha Sani, Zabta Khan Shinwari, Malik Maaza
The water sector faces an urgent mandate to shift from energy-intensive wastewater treatment toward decentralized, resource-recovering systems that address the global water-energy nexus. Microbial Electrochemical Technologies (METs) have emerged as a transformative engineered solution capable of simultaneously remediating complex pollutant streams while recovering high-value energy carriers. This review provides a comprehensive analysis of the state-of-the-art in METs, explicitly bridging the interface of biochemistry and molecular-scale nanochemistry. We synthesize fundamental extracellular electron transfer (EET) kinetics with recent breakthroughs in green-synthesized nanomaterials, quantum dots, and advanced nanostructured electrode architectures (including carbon nanotubes and 3D graphene composites) engineered to accelerate electrocatalytic remediation. By critically evaluating performance indicators, such as power density, Coulombic efficiency, and nanomaterial-driven pollutant degradation kinetics, this work assesses the feasibility of integrating nano-enhanced METs with existing infrastructure like anaerobic digestion. Furthermore, we address critical barriers to industrial-scale deployment, specifically evaluating the environmental fate, safety risks, and regulatory frameworks governing nanomaterial usage in water reuse. To bridge the gap between laboratory discovery and societal impact, we highlight the pivotal role of “Industry 4.0” tools, including artificial intelligence (AI) and digital twins, in optimizing real-time reactor performance. This review concludes by outlining a strategic roadmap that aligns nano-engineered METs with circular bioeconomy principles, offering a sustainable blueprint for global climate adaptation and resilient water governance.
