Search Results (408)

The precise synthesis of non-precious metal single-atom electrocatalysts is crucial for enhancing the yield of highly active reactive oxygen species (ROSs). Conventional oxidation methods, such as Fenton or NaClO processes, suffer from poor efficiency, high energy demand, and secondary pollution. In contrast, heterogeneous electro-Fenton systems based on cascade oxygen reduction reactions (ORRs), which require low operational voltage and cause pollutant degradation through both direct electron transfer and ROS generation, have emerged as a promising alternative. Recent studies showed that carbon cathodes decorated with atomically dispersed transition metals can effectively integrate the excellent conductivity of carbon supports with the tunable surface chemistry of metal centers. However, the electronic structure of active sites intrinsically hinders the simultaneous achievement of high activity and selectivity in cascade ORRs. This review summarizes the advances, specifically from 2020 to 2025, in understanding the mechanism of cascade ORRs and the synthesis of transition metal-based single-atom catalysts in cathode electrocatalysis for efficient wastewater treatment, and discusses the key factors affecting treatment performance. While employing atomically engineered cathodes is a promising approach for energy-efficient wastewater treatment, future efforts should overcome the barriers in active site control and long-term stability of the catalysts to fully exploit their potential in addressing water pollution challenges. Full article

The discharge of oily wastewater threatens the ecosystem and human health, and the efficient treatment of oily wastewater is confronted with problems of high mass transfer resistance at the oil-water-solid multiphase interface, significant light shielding effect, and easy deactivation of photocatalysts. Although traditional physical separation methods avoid secondary pollution by chemicals and can effectively separate floating oil and dispersed oil, they are ineffective in removing emulsified oil with small particle sizes. To address these complex challenges, photocatalytic technology and photocatalysis-based improved technologies have emerged, offering significant application prospects in degrading organic pollutants in oily wastewater as an environmentally friendly oxidation technology. In this paper, the degradation mechanism, kinetic mechanism, and limitations of conventional photocatalysis technology are briefly discussed. Subsequently, the surface interface modulation functions of metal doping and heterojunction energy band engineering, along with their applications in enhancing the light absorption range and carrier separation efficiency, are reviewed. Focus on typical studies on the separation and degradation of aqueous and oily phases using photocatalytic membrane technology, and illustrate the advantages and mechanisms of photocatalysts loaded on the membranes. Finally, other new approaches and converging technologies in the field are outlined, and the challenges and prospects for the future treatment of oily wastewater are presented. Full article

The contamination of water bodies by industrial dyes poses a significant environmental challenge on a global scale. Conventional wastewater treatment methods often suffer from limitations related to high cost, limited efficiency, and potential secondary environmental impacts. Recent advances in photocatalytic technologies have highlighted the potential of metal sulfide-based photocatalysts, particularly those synthesized through environmentally friendly, plant-mediated approaches, as promising alternatives for efficient and sustainable dye degradation. However, despite their promising potential, metal sulfide photocatalysts often suffer from limitations such as photocorrosion, low stability under irradiation, and rapid recombination of charge carriers, which restrict their long-term applicability. In light of these challenges, this review provides a comprehensive examination of the physicochemical characteristics, synthetic strategies, and photocatalytic applications of metal sulfides. Particular emphasis is placed on green synthesis routes employing plant-derived extracts, which offer environmentally benign and sustainable alternatives to conventional methods. Moreover, the review elucidates various modification approaches, most notably, the formation of heterostructures, as viable strategies to enhance photocatalytic efficiency and mitigate the aforementioned drawbacks. The green synthesis of metal sulfides, aligned with the principles of green chemistry, offers a promising route toward the development of sustainable and environmentally friendly water treatment technologies. Full article

Iopamidol (IPM), as a typical recalcitrant emerging pollutant and precursor of iodinated disinfection by-products (I-DBPs), is unsuccessfully removed by conventional wastewater treatment processes. This study comprehensively evaluated the ozone/peracetic acid (O₃/PAA) process for IPM degradation, focusing on degradation kinetics, environmental impacts, transformation products, ecotoxicity, disinfection byproducts (DBPs), and microbial inactivation. The O₃/PAA system synergistically activates PAA via O₃ to generate hydroxyl radicals (^•OH) and organic radicals (CH₃COO^• and CH₃CO(O)O^•), achieving an IPM degradation rate constant of 0.10 min⁻¹, which was significantly higher than individual O₃ or PAA treatments. The degradation efficiency of IPM in the O₃/PAA system exhibited a positive correlation with solution pH, achieving a maximum degradation rate constant of 0.23 min⁻¹ under alkaline conditions (pH 9.0). Furthermore, the process demonstrated strong resistance to interference from coexisting anions, maintaining robust IPM removal efficiency in the presence of common aqueous matrix constituents. Furthermore, quenching experiments revealed ^•OH dominated IPM degradation in O₃/PAA system, while the direct oxidation by O₃ and R-O^• played secondary roles. Additionally, based on transformation products (TPs) identification and ECOSAR predictions, the primary degradation pathways were elucidated and the potential ecotoxicity of TPs was systematically assessed. DBPs analysis after chlorination revealed that the O₃/PAA (2.5:3) system achieved the lowest total DBPs concentration (99.88 μg/L), representing a 71.5% reduction compared to PAA alone. Amongst, dichloroacetamide (DCAM) dominated the DBPs profile, comprising > 60% of total species. Furthermore, the O₃/PAA process achieved rapid 5–6 log reductions of E. coli. and S. aureus within 3 min. These results highlight the dual advantages of O₃/PAA in effective disinfection and byproduct control, supporting its application in sustainable wastewater treatment. Full article

In wet flue gas desulfurization and denitrification processes, nitrite accumulation inhibits denitrification efficiency and induces secondary pollution due to its acidic disproportionation. This study developed a Mn-modified ZSM-5 zeolite catalyst, achieving efficient resource conversion of nitrite in nitrogen-containing wastewater through an O₃ + Mn/ZSM-5 catalytic system. Mn/ZSM-5 catalysts with varying SiO₂/Al₂O₃ ratios (prepared by wet impregnation) were characterized by BET, XRD, and XPS. Experimental results demonstrated that Mn/ZSM-5 (SiO₂/Al₂O₃ = 400) exhibited a larger specific surface area, enhanced adsorption capacity, abundant surface Mn³⁺/Mn⁴⁺ species, hydroxyl oxygen species, and chemisorbed oxygen, leading to superior oxidation capability and catalytic activity. Under the optimized conditions of reaction temperature = 40 °C, initial pH = 4, Mn/ZSM-5 dosage = 1 g/L, and O₃ concentration = 100 ppm, the $\mathrm{N}{\mathrm{O}}_2^{-}$ oxidation efficiency reached 94.33%. Repeated tests confirmed that the Mn/ZSM-5 catalyst exhibited excellent stability and wide operational adaptability. The synergistic effect between Mn species and the zeolite support significantly improved ozone utilization efficiency. The O₃ + Mn/ZSM-5 system required less ozone while maintaining high oxidation efficiency, demonstrating better cost-effectiveness. Mechanism studies revealed that the conversion pathway of $\mathrm{N}{\mathrm{O}}_2^{-}$ followed a dual-path catalytic mechanism combining direct ozonation and free radical chain reactions. Practical spray tests confirmed that coupling the Mn/ZSM-5 system with ozone oxidation flue gas denitrification achieved over 95% removal of liquid-phase $\mathrm{N}{\mathrm{O}}_2^{-}$ byproducts without compromising the synergistic removal efficiency of NO_x/SO₂. This study provided an efficient catalytic solution for industrial wastewater treatment and the resource utilization of flue gas denitrification byproducts. Full article

Honey processing is closely linked to water pollution due to the lack of a specific wastewater treatment. This study proposes a sustainable and innovative solution based on two sequential bioprocesses using a real effluent from an Argentine honey-exporting facility. In the initial stage, the honey wastewater was enriched with a non-Saccharomyces yeast (Candida ethanolica), isolated from the same effluent. Treatment with this yeast in a bioreactor nearly doubled the total sugar removal efficiency compared to the control (native flora). Subsequent clarification with diatomaceous earth reduced the optical density (91.6%) and COD (30.9%). In the second stage, secondary sewage effluent was added to the clarified effluent and inoculated with Chlorella vulgaris under different culture conditions. The best microalgae performance was observed under high light intensity and high inoculum concentration, achieving a fivefold increase in cell density, a specific growth rate of 0.752 d⁻¹, and a doubling time of 0.921 d. Although total sugar removal in this stage remained below 28%, cumulative COD removal reached 90% after nine days under both lighting conditions. This study presents the first integrated treatment approach for honey industry effluents using a native yeast–microalgae system, incorporating in situ effluent recycling and the potential for dual waste valorization. Full article

Fenton oxidation can contribute to meeting effluent standards for COD in actual wastewater treatment plant effluents. However, Fenton oxidation is prone to produce iron sludge waste. The application of heterogeneous Fenton-like systems based on Fenton iron mud carbon in wastewater treatment plants is essential for Fenton iron mud reduction and recycling. In this study, a Fenton iron mud carbon catalyst/Ferrate salts/H₂O₂ (FSC/Fe(VI)/H₂O₂) system was developed to remove chemical oxygen demand (COD) from secondary effluents at the pilot scale. The results showed that the FSC/Fe(VI)/H₂O₂ system exhibited excellent COD removal performance with a removal rate of 57% under slightly neutral conditions in laboratory experiments. In addition, the effluent COD was stabilized below 40 mg·L⁻¹ for 65 days at the pilot scale. Fe(IV) and ¹O₂ were confirmed to be the main active species in the degradation process through electron paramagnetic resonance (EPR) and quenching experiments. C=O, O-C=O, N sites and Fe⁰ were responsible for the generation of Fe(IV) and ¹O₂ in the FSC/Fe(VI)/H₂O₂ system. Furthermore, the cost per ton of water treated by the pilot-scale FSC/Fe(VI)/H₂O₂ system was calculated to be only 0.6209 USD/t, further confirming the application potential of the FSC/Fe(VI)/H₂O₂ system. This study promotes the engineering application of heterogeneous Fenton-like systems for water treatment. Full article

Swine wastewater (SW) has a high chemical oxygen demand (COD) content and is difficult to degrade; an effective strategy to address this issue is through biodegradation, which poses negligible secondary pollution risks and ensures cost-efficiency. The objectives of this study were to isolate an effective COD-degrading strain of SW, characterize (at the molecular level) its transformation of SW, and apply it to practical production. A strain of Corynebacterium xerosis H1 was isolated and had a 27.93% ± 0.68% (mean ± SD) degradation rate of COD in SW. This strain precipitated growth in liquids, which has the advantage of not needing to be immobilized, unlike other wastewater-degrading bacteria. Based on analysis by Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), this bacterium removed nitrogen-containing compounds in SW, with proteins and lipids decreasing from 41 to 10% and lignins increasing from 51 to 82%. Furthermore, the enhancement of the sequencing batch reactor (SBR) with strain H1 improved COD removal in effluent, with reductions in the fluorescence intensity of aromatic protein I, aromatic protein II, humic-like acids, and fulvic acid regions. In addition, based on 16S rRNA gene sequencing analysis, SBR_H1 successfully colonized some H1 bacteria and had a higher abundance of functional microbiota than SBR_C. This study confirms that Corynebacterium xerosis H1, as a carrier-free efficient strain, can be directly applied to swine wastewater treatment, reducing carrier costs and the risk of secondary pollution. The discovery of this strain enriches the microbial resource pool for SW COD degradation and provides a new scheme with both economic and environmental friendliness for large-scale treatment. Full article

Microplastics (MPs) have emerged as a critical environmental challenge in China’s aquatic ecosystems, driven by rapid industrialization and population growth. This review synthesizes recent findings on the abundance, morphology, and polymer types of MPs in China’s freshwater systems (rivers, lakes, reservoirs) and coastal marine environments. Spatial analysis reveals significant variability in MP abundance, ranging from 0.1 items/L in Tibet’s Lalu Wetland to 30.8 items/L in Beijing’s Qinghe River, with polypropylene (PP) and polyethylene (PE) dominating polymer profiles. Coastal regions exhibit distinct contamination patterns, with the Yellow Sea (5.3 ± 2.0 items/L) and the South China Sea (180 ± 80 items/m³) showing the highest MP loads, primarily as fibers and fragments. Fluvial transport, atmospheric deposition, and coastal anthropogenic activities (e.g., fisheries, tourism) are identified as major pathways for marine MP influx. Secondary MPs from degraded plastics and primary MPs from industrial/domestic effluents pose synergistic risks through the adsorption of heavy metals and organic pollutants. Human exposure routes—ingestion, inhalation, and dermal contact—are linked to inflammatory, metabolic, and carcinogenic health outcomes. Policy interventions, including bans on microbeads and non-degradable plastics, demonstrate progress in pollution mitigation. This work underscores the urgency of integrated source control, advanced wastewater treatment, and transboundary monitoring to address MP contamination in aquatic ecosystems. Full article

Heavy metal pollution, especially from Pb(II) and Cd(II), poses significant risks due to its persistence and bioaccumulation potential. Traditional removal methods face challenges like high costs and secondary pollution. This study developed a novel three-dimensional porous adsorbent XBS, derived from xanthate-modified Phanerochaete sordida YK-624 (a white-rot fungus), for the rapid and efficient removal of Pb(II) and Cd(II) from wastewater. Characterization showed that XBS has a sponge-like structure with abundant functional groups, significantly enhancing its adsorption capacity and kinetics. XBS achieved 96% Pb(II) and 32% Cd(II) removal within 1 min at a 0.25 g/L dose, reaching over 95% of the maximum adsorption capacity within 30 min for Pb(II) and 240 min for Cd(II). The maximum capacities were 224.72 mg/g for Pb(II) and 82.99 mg/g for Cd(II). Kinetic and thermodynamic analyses indicated a chemisorption-driven process, which was both endothermic and spontaneous. XBS exhibited high selectivity for Pb(II) over Cd(II) and other metals (Tl(I), Cu(II)), attributed to stronger covalent interactions with sulfur- and nitrogen-containing groups. Mechanistic analyses (XRD, FTIR, and XPS) revealed that removal occurs via ion exchange, complexation, and precipitation, forming stable compounds like PbS/CdS and PbCO₃/CdCO₃. Given its cost-effectiveness, scalability, and high efficiency, XBS represents a promising adsorbent for heavy metal remediation, particularly in Pb(II)-contaminated wastewater treatment applications. Full article

Sawdust is receiving increasing attention as a promising green adsorbent. However, due to its powder nature, it is difficult to recover after adsorbing heavy metals and may even cause secondary pollution. To solve this problem, a novel sawdust/foamed geopolymer (SFG) adsorbent was prepared by using sawdust as a raw material, geopolymer as a binder, and hydrogen peroxide as a foaming agent. This study discussed the effect of SFG dosage, solution temperature, solution pH, contact time, and initial Cu²⁺ solution concentration on the adsorption capacity and removal rate. The results showed that a desirable SFG adsorbent with the SFG dosage of 0.5 g, temperature of 25 °C, pH of 5, contact time of 720 min, and initial Cu²⁺ solution concentrations of 90 mg/L is recommended, of which the adsorption capacity is 31.5 mg/g with the removal rate being 92.76%. In addition, the adsorption performance of the SFG adsorbent is superior to that of pure sawdust and similar to that of the foamed geopolymer adsorbent, and it has the characteristics of higher strength, lower cost, and more environmental friendliness. This study indicated that the SFG adsorbents are feasible as adsorbents; meanwhile, this work can provide a scientific reference for the development of new bio-composite adsorbent materials, especially in the field of the treatment of heavy metal ions in wastewater. Full article

A cellulose-based material with high adsorption capacity and surface area was developed by selecting appropriate copolymer monomers for structural design. This material was used for selective dye adsorption in wastewater treatment. The copolymer was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) to investigate its microstructure, structure, thermal stability, and thermal decomposition. We explored the factors affecting dye adsorption, including dye type, adsorption reaction time, initial dye concentration, copolymer dosage, temperature, and the acidity or alkalinity of the reaction environment. The results showed that as the adsorption reaction time increased, the amount of adsorbed Rhodamine B dye gradually increased, and the initial stage (0–20 min) increased rapidly. When the initial dye concentration was 15 mg/L, the adsorption capacity (q_e) was at its maximum (3.67 mg/g). In addition, when the amount of copolymer used was 5 mg/10 mL, the adsorption capacity (q_e) was the highest (12.37 mg/g). High-temperature conditions were favorable for adsorption, with the maximum adsorption capacity (q_e) at 35 °C (13.48 mg/g). The prepared copolymer exhibited significant adsorption performance in acidic environments (pH = 3). The polymer adsorbed with dye was degraded by UV irradiation, avoiding secondary pollution caused by recycling. Full article

Water regeneration in PVC production is a key issue to consider, given the high freshwater consumption rate of the process. This research evaluates the inherent safety of poly(vinyl chloride) (PVC) production via suspension polymerization by implementing mass and energy integration strategies in combination with wastewater regeneration under a zero-liquid-discharge (ZLD) approach. The impact of these integrations on process safety was examined by considering the risks associated with the handling of hazardous materials and critical operations, as well as the reduction in waste generation. To this end, the Inherent Safety Index (ISI) methodology was employed, which quantifies hazards based on factors such as toxicity and flammability, enabling the identification of risks arising from system condition changes due to the implementation of sustainable water treatment technologies. Although the ISI methodology has been applied to various chemical processes, there are few documented cases of its specific application in PVC plants that adopt circular production strategies and water resource sustainability. Therefore, in this study, ISI was used to thoroughly evaluate each stage of the process, providing a comprehensive picture of the safety risks associated with the use of sustainable technologies. The assessment was carried out using simulation software, computer-aided process engineering (CAPE) methodologies, and information obtained from safety repositories and expert publications. Specifically, the Chemical Safety Index score was 22 points, with the highest risk associated with flammability, which scored 4 points, followed by toxicity (5 points), explosiveness (2 points), and chemical interactions, with 4 points attributed to vinyl chloride monomer (VCM). In the toxicity sub-index, both VCM and PVC received 5 points, while substances such as sodium hydroxide (NaOH) and sodium chloride (NaCl) scored 4 points. In the heat of reaction sub-index, the main reaction scored 3 points due to its high heat of reaction (−1600 kJ/kg), while the secondary reactions from PVA biodegradation scored 0 points for the anoxic reaction (−156.5 kJ/kg) and 3 points for the aerobic reaction (−2304 kJ/kg), significantly increasing the total index. The Process Safety Index scored 15 points, with the highest risk found in the inventory of hazardous substances within the inside battery limits (ISBL) of the plant, where a flow rate of 3241.75 t/h was reported (5 points). The safe equipment sub-index received 4 points due to the presence of boilers, burners, compressors, and reactors. The process structure scored 3 points, temperature 2, and pressure 1, reflecting the criticality of certain operating conditions. Despite sustainability improvements, the process still presented significant chemical and operational risks. However, the implementation of control strategies and safety measures could optimize the process, balancing sustainability and safety without compromising system viability. Full article

A 3D-printed device was designed and printed by a stereolithographic technique (SLA) and coated with a highly selective solid phase extraction resin for on-site diclofenac extraction from wastewater, avoiding the transport and treatment of large volumes of samples in the laboratory. The best results in terms of chemical and mechanical resistance were obtained with Rigid 10K resin. The “stick-and-cure” impregnation technique was used to coat the 3D-printed device with Oasis^® HLB resin. The coated 3D-printed device can be reused up to eight times without losing extraction efficiency. The eluent and derivatization reagent volumes were optimized by a multivariate design. The proposed method allowed for the extraction and determination of diclofenac by PTV-GC-MS, achieving methodological detection and quantification limits of 0.019 and 0.055 μg L⁻¹, respectively, with a preconcentration factor of 46. The analysis time was 23 min per sample. To validate the proposed methodology, addition/recovery tests were carried out in different wastewater samples, obtaining recoveries above 90%. The methodology was applied at the wastewater treatment plant (WWTP) of Calvià (Mallorca, Spain), finding diclofenac in concentrations of 15.39 ± 0.07 μg L⁻¹ at the input of the primary decantation process, 4.48 ± 0.03 μg L⁻¹ at the output of the secondary decantation, and 0.099 ± 0.001 μg L⁻¹ at the output of the tertiary treatment, demonstrating the feasibility of the on-site extraction method in monitoring diclofenac over a wide concentration range. Finally, a greenness index of 0.58 for the proposed on-site sample preparation was achieved according to the AGREEprep metrics, making it an eco-friendly alternative for diclofenac monitoring. Full article

Excess phosphorus (P) and nitrogen (N) in wastewater contribute to eutrophication, driving the need for low–cost and sustainable recovery technologies. This study presents a novel adsorbent synthesized from spent coffee grounds biochar (CB) chemically modified with Mn²⁺/Zn²⁺/Fe³⁺ (oxy)hydroxide nanoparticles (CB–M) for simultaneous removal of phosphate and ammonium. Batch adsorption experiments using both synthetic solution and municipal wastewater were conducted to evaluate the material’s adsorption performance and practical applicability. Kinetic, isotherm, thermodynamic, and sequential extraction analyses revealed that CB–M achieved maximum phosphate adsorption capacities ranging from 42.6 to 72.0 mg PO₄³⁻·g⁻¹ across temperatures of 20–33 °C, reducing effluent phosphate concentrations to below 0.01 mg·L⁻¹. Ammonium removal was moderate, with capacities ranging between 2.8 and 2.95 mg NH₄⁺·g⁻¹. Thermodynamic analysis indicated that phosphate adsorption was spontaneous and endothermic, dominated by inner–sphere complexation, while ammonium uptake occurred primarily through weaker, reversible ion exchange mechanisms. Sequential extraction showed over 70% of adsorbed phosphate was associated with Fe-Mn-Zn phases, indicating the potential for use as a slow–release fertilizer. The CB–M retained structural integrity and exhibited partial desorption, supporting its reusability for nutrient recovery. Compared to other biochars, CB–M demonstrated superior phosphate selectivity at a neutral–pH, avoided the use of hazardous metals, and transformed coffee waste into a multifunctional material for wastewater treatment and soil amendment. These findings underscore the potential of CB–M as a circular economy solution for nutrient recovery without introducing secondary contamination. Full article