Treatment of electroplating industry wastewater: a review on the various techniques

Transition metal phosphide/ molybdenum disulfide heterostructures towards advanced electrochemical energy storage: recent progress and challenges

Transition metal phosphide @ molybdenum disulfide (TMP@MoS2) heterostructures, consisting of TMP as the core main catalytic body and MoS2 as the outer shell, can solve the three major problems in the field of renewable energy storage and catalysis, such as lack of resources, cost factors, and low cycling stability. The heterostructures synergistically combine the excellent conductivity and electrochemical performance of transition metal phosphides with the structural robustness and catalytic activity of molybdenum disulfide, which holds great promise for clean energy. This review addresses the advantages of TMP@MoS2 materials and their synthesis methods-e.g., hydrothermal routes and chemical vapor deposition regarding scalability and cost. Their electrochemical energy storage and catalytic functions e.g., hydrogen and oxygen evolution reactions (HER and OER) are also extensively explored. Their potential within battery and supercapacitor technologies is also assessed against leading performance metrics. Challenges toward industry-scale scalability, longevity, and environmental sustainability are also addressed, as are optimization and large-scale deployment strategies.

Removal of Cu(II) and Cr(VI) from electroplating wastewater by magnetic Fe3O4@SiO2-UiO-66-EDTA: Adsorption behavior and mechanism

The heavy metals discharged from electroplating wastewater, represented as copper and chromium ions, is harmful to aquatic lives and human beings, and will break the ecological balance. In this work, magnetic hybrid porous structure adsorbent of Fe3O4@SiO2-UiO-66-EDTA is prepared for recycling copper and chromium ions. The adsorbent exhibits a maximum adsorption capacity of 212.10 mg/g for Cu(II) and 118.10 mg/g for Cr(VI). Notably, it shows excellent regenerability of 80.89% after 10 cycles. The adsorption of Cu(II) and Cr(VI) on Fe3O4@SiO2-UiO-66-EDTA follows the pseudo-second-order model, where chemical adsorption is dominant and it occurs spontaneously and exothermally. Based on XRD, FTIR, XPS, and DFT calculations, the adsorption mechanisms are driven by electrostatic attraction, chelation, and redox reactions. This work provides a novel and promising strategy for designing highly efficient adsorbents, paving the way for more effective treatments of electroplating wastewater contaminated with Cu(II) and Cr(VI).

Iron oxide-MXene-based composite for the removal of copper ions from wastewater

The present work primarily aims to evaluate the adsorption properties of MXene and its nanocomposite, Fe3O4@MXene, for removing heavy metal ions from industrial wastewater. Two-dimensional (2D) MXene nanosheets were combined with Fe3O4 nanoparticles through a hydrothermal synthesis process to create the Fe3O4@MXene nanocomposite. Characterization revealed that Fe3O4 nanoparticles self-assembled onto MXene sheets, forming a structure that enhanced the 2D structure of MXene, with nanoparticles uniformly distributed throughout the nanosheet network. Performance experiments demonstrated that Fe3O4@MXene nanocomposite significantly outperformed pristine MXene in adsorbing heavy metal ions from wastewater. Notably, Fe3O4@MXene nanocomposite achieved an 83% removal efficiency for Cu ions, highlighting its potential as a highly efficient adsorbent in industrial wastewater treatment. This work underscores the viability of Fe3O4@MXene for heavy metal remediation, marking an important step toward practical environmental applications of MXene-based materials.

Appraisal of potential toxic elements pollution, sources apportionment, and health risks in groundwater from a coastal area of SE China

Groundwater is a vital natural resource, but the presence of potentially toxic elements (PTEs) poses significant risks to both groundwater safety and human health. This study collected 120 groundwater samples from a coastal area in southeastern China during wet and dry seasons to assess PTE levels, identify their sources, and evaluate pollution and health risks. Results showed that Mn, Zn, and Al had the highest average concentrations in both seasons, with Mn, Cd, and Zn frequently exceeding safe limits. PTE levels were higher during the wet season. Natural background levels (NBLs) were determined, revealing that most elements met quality standards except for Mn and Cd. Four PTE sources were identified using principal component analysis and the APCS-MLR model: industrial emissions (25.5% dry, 23.8% wet), geological background (21.2% dry, 19% wet), natural sources (27.2% dry, 16.2% wet), and mining activities (20.8% dry, 23.4% wet). Heavy metal pollution was significant (moderate to heavy: 72.73% dry, 45.76% wet), but ecological risks were low (low risk: 92.73% dry, 66.10% wet). Health risk assessments and Monte Carlo simulations indicated low carcinogenic and non-carcinogenic risks, slightly higher in children than adults. Risks were more severe in the southwestern part of the study area. These findings support local groundwater management efforts.

Sustainable pollution removal and resources recovery from electroplating wastewater by coagulation, advanced oxidation coupling with bioaugmentation

Electroplating wastewater contains high concentrations of dissolved organic matter, heavy metal ions (HMs), refractory organic compounds (ROC), and the complicated composition of effluents. Bioaugmentation presents an efficient strategy for eliminating pollution and recycling resources from electroplating effluent. In this study, simultaneous removal of pollution and sustainable resources recovery from electroplating wastewater were conducted by polyferric sulfate (PFS)-based coagulation, ultraviolet (UV)-activated persulfate (PS) (UV-APS)-based advanced oxidation coupling with bioaugmentation. To reduce carbon emissions and achieve carbon neutrality, genetically engineered Vibrio natriegens with an aerobic sulfate reduction pathway (GeVin) was introduced to remove sulfate, organics, and HMs, which further promoted generation of metal sulfides. The results of coagulation by PFS eliminated 34.68% of chemical oxygen demand (COD), 38.56% of ammonia nitrogen (NH4-N), 36.30% of ROC, and 16.67% of HMs. The rest of refractory contaminants in the effluent of coagulation were oxidatively degraded by UV-APS to improve biodegradability index. The bioaugmentation using immobilized GeVin (IMGevin) coupled with membrane bioreactor (MBR) (IMGevin-MBR) significantly removed 98.25% of COD, 96.23% of NH4-N, 99.42% of biochemical oxygen demand (BOD), 97.85% of sulfate, and 97.68% of HMs. Mechanism analysis indicated that sulfate derived from PFS-based coagulation and UV-APS provided more electron acceptors to generate H2S metabolized by GeVin, contributing to HMs removal via sulfate reduction pathway. Furthermore, IMGeVin-MBR decreased startup phase, hydraulic retention time (HRT), increased the microbial activity, functional microbial community and abundances of genes related to sulfate metabolism, resulting in improvement of systemic stability. Meanwhile, IMGeVin-MBR decreased the total treatment cost, sludge yields, and greenhouse gas (GHG) emissions for treatment of electroplating wastewater. In conclusion, this study provides a sustainable pollution removal and resources recovery strategy for treating electroplating wastewater.

Typical heavy metals in wastewater treatment plants in Nanjing, China: perspective of abundance, removal, and microbial response

Heavy metals (HMs) are hazardous contaminants with persistence and bioaccumulation, attracting widespread attention. Wastewater treatment plants (WWTPs) play vital roles in the pollution control of sewage, closely related to human health and the biological environment. Therefore, eight HMs in three typical WWTPs of Nanjing were determined in this study. The results revealed that Cr, Ni, Cu, and Zn were high-level HMs in all WWTPs. Notably, the highest contents of high-level HMs were found in electroplating WWTP (EWWTP) influent among three WWTPs, probably causing their higher removal (19.34-55.32%) during their primary treatment. In contrast, most HMs could be removed in the secondary treatment stage of municipal WWTP (MWWTP) and industrial WWTP (IWWTP) with the highest removal of As (72.00-85.81%). Analogously, nutrients were mainly removed during the secondary stage, with superior performance in MWWTP. A decrease in HMs removal was observed in the tertiary treatment of MWWTP and IWWTP compared to the secondary stage, while higher HMs removal (0.51-29.15%) was found in EWWTP except Hg. The highest content of HMs in sludge was Zn and Cr, which was more abundant in EWWTP than other WWTPs. The results of Illumina Miseq sequencing demonstrated the inhibition of microbial richness and diversity of EWWTP and IWWTP by industrial wastewater. Besides, alterations of microbial community structure and components were also observed owing to various influent sources. More similarity was found between EWWTP and MWWTP, in which the abundance of dominant genera, including Saccharimonadales (7.60-9.56%), Raineyella (5.06-7.38%), and Thauera (2.48-4.45%) was much higher than IWWTP.

Review on the impact of heavy metals from industrial wastewater effluent and removal technologies

The incidence of water pollution in developing countries is high due to the lack of regulatory policies and laws that protect water bodies from anthropogenic activities and industrial wastewater. Industrial wastewater contains significant amounts of heavy metals that are detrimental to human health, aquatic organisms, and the ecosystem. The focus of this review was to evaluate the sources and treatment methods of wastewater, with an emphasis on technologies, advantages, disadvantages, and innovation. It was observed that conventional methods of wastewater treatment (such as flotation, coagulation/flocculation, and adsorption) had shown promising results but posed certain limitations, such as the generation of high volumes of sludge, relatively low removal rates, inefficiency in treating low metal concentrations, and sensitivity to varying pH. Recent technologies like nanotechnology, photocatalysis, and electrochemical coagulation have significant advantages over conventional methods for removing heavy metals, including higher removal rates, improved energy efficiency, and greater selectivity for specific contaminants. However, the high costs associated with these advanced methods remain a major drawback. Therefore, we recommend that future developments in wastewater treatment technology focus on reducing both costs and waste generation.

Shopping around: Comparing Cd(II) sorption performance of disparate functional groups-modified microcrystalline cellulose composites

The structure-function relationship of functionalized microcrystalline cellulose (MCC) composites as adsorbents remains unclear. Herein, the orange peel-derived MCC (i.e., OP-OH-H-25) was treated by different functional agents to prepare adsorbents for cadmium (Cd(II)) removal. Mercaptoacetic acid and orthophosphoric acid did not apparently impact MCC's surface site types and contents. Alternatively, they efficiently purified OP-OH-H-25 and generated OP-OH-SH and OP-OH-P samples with increased cellulose amounts. In contrast, the glycine modification produced OP-OH-NH2 with fewer sulfhydryl/carboxyl functional groups and more amide/amino sites. The pH-dependent Cd(II) removal trends by the MCC-related materials showed three successive stages with disparate sorption modes. The Cd(II) sorption kinetics processes on OP-OH-SH, OP-OH-P, and OP-OH-NH2 reached equilibrium after 0.25 h, faster than 0.5 h on OP-OH-H-25. The maximum Cd(II) sorption capacities of MCC-related adsorbents were OP-OH-P (151.81 mg/g) > OP-OH-SH (150.80 mg/g) > OP-OH-H-25 (124.90 mg/g) > > OP-OH-NH2 (55.23 mg/g). OP-OH-P exhibited the strongest Cd(II) sorption ability under the interference of mixed aquatic components. The intrinsic Cd(II) sorption mechanisms were identified as inner-sphere complexation and cation-π bond interaction. Overall, the select priority of modifying agents is orthophosphoric acid > mercaptoacetic acid > > glycine when preparing functionalized MCC adsorbents for purifying Cd(II)-polluted water systems.

A Robust High-Pressure RO Technology to Overcome the Barriers to Full Circularity in Cr(III) Electroplating Operations

Electroplating is a widely used technology for anticorrosion materials and decorative coatings. In view of the transition to a circular economy, the current electroplating wastewater treatment disposing of heavy metal sludge and wastewater severely lacks sustainability. Authors recently reported the successful recycling of electroplating agents using hybrid semibatch/batch reverse osmosis technology (hybrid RO). Despite promising results, technology assessment to treat new, second-generation electrolytes, enhance boric acid recovery, close the water loops, and evaluate process robustness is still needed. This study investigates the viability of a high-pressure (120 bar) hybrid RO system, working with the DuPont XUS180808 membrane, to reclaim valuable second-generation plating components and water from electroplating rinses. The pilot-scale system showcased resilience in processing artificial electroplating wastewaters of variable concentration, achieving water recoveries of ≤87.7%, increasing chromium and sulfate to electrolyte levels (>6 g/L and >80 g/L), with low energy consumptions (≤2.7 kWh/m3), underlining its potential as a circular treatment in the chromium electroplating industry. A second-pass RO treatment strategy was explored, addressing residual boric acid in the permeate and leveraging solubility interactions to enhance its rejection, enabling water reuse. Based on these findings, an RO designed for industrial application was proposed for future scale-up and evaluation within a real-world production environment.

Efficient gold-cyanide recovery from activated carbon by electrocoagulation technology

Mexico is the 9th largest world gold producer with 1016 tonnes in reserves as of 2024. 41 % losses of gold with an average consumption of 40 g/t, is due to the escape of fine AC particles because they do not have the scope to prevent the loss of particles below 0.40 mm. The recovery of gold in Mexico is becoming more important. Given the low quantities of this metal present in the mineral ore and the difficulty of its extraction due to its encapsulation in its mineralogy, recoveries are low. Adsorption processes with activated carbon (AC) in the mining-metallurgy industry include phases that diminish the particle durability, coupled with its nature as organic matter, which tends to deteriorate and disintegrate in the adsorption systems. In this study, Electrocoagulation (EC) technology is shown as a better option to increase the efficient recovery of gold impregnated in extremely fine AC particles, without the use of chemical reagents in the metallurgical systems, by recovering the fine particles loaded with gold, EC tests were done on a batch pilot scale, on AC particles of 0.106 mm and 0.053 mm, using iron and aluminum electrodes with the best variables determined, they were interpolated at an industrial level. The trend that has been noticed is that smaller particles stick together to generate larger particles that contain aluminum hydroxide species. This means that using EC to recover incredibly fine AC particles is viable. Finally, the EC system with aluminum (Al) and iron (Fe) electrodes shows AC recoveries with gold were greater than 96 % and 88 % respectively. This study is a green technology for the effective recovery of gold, and cyanide in activated carbon thereby in increasing gold productivity in Mexico and the global market.

New insights into the remediation of chromium-contaminated industrial electroplating wastewater by an innovative nano-modified biochar derived from spent mushroom substrate: Mechanisms, batch study, stability and application

To enhance the adsorption and detoxification capabilities of hexavalent chromium (Cr(VI)) using agricultural spent mushroom substrate (SMS), this study pioneered the preparation of biochar (NBC) from Lentinus edodes spent substrate. Subsequently, nano iron sulfide (FeS) particles were integrated onto NBC with carboxymethyl cellulose (CMC) as a stabilizer, resulting in a novel composite biosorption material, nFeS-BC. The adsorption and reduction potential of both NBC and nFeS-BC against Cr(VI) were evaluated through batch experiments, which identified pH as a critical factor influencing adsorption efficiency. Remarkably, nFeS-BC exhibited a superior maximum adsorption capacity (qmax) of 99.57 mg g-1 and a reduction efficiency of 68.65%, outperforming NBC by 277.73% and 211.76% under optimized conditions, respectively. Characterization techniques including Scanning Electron Microscopy-Energy Dispersive X-Ray (SEM-EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and X-ray Photoelectron Spectroscopy (XPS) elucidated the removal mechanisms, predominantly attributed to ion exchange, electrostatic attraction, functional group interaction, and redox reaction. The carbon-oxygen functional groups and nano particles were crucial in the adsorption and reduction processes. Compared with NBC, the incorporation of FeS particles increased the specific surface area and pore volume of nFeS-BC by 130.86% and 183.77%, respectively. nFeS-BC owned a shelf-life of up to ∼3 months of use and exhibited excellent performance in the processing of actual electroplating wastewater with q of 16.71 mg g-1 under 0.1 g L-1 dosage. These findings underscore the potential of nFeS-BC as an efficient material for Cr(VI) removal, presenting a novel adsorbent for the sustainable detoxification of contaminated water resources and the potential for using agricultural waste materials in environmental remediation.

Highly efficient recovery of Zn (II) from zinc-containing wastewater by tourmaline tailings geopolymers to in-situ construct nanoscale ZnS for the photodegradation of tetracycline hydrochloride

While treating zinc-containing wastewater, recovering zinc for reuse as a secondary resource has significant environmental and economic benefits. Herein, based on the alkali-activated tourmaline tailings geopolymers (TTG) after adsorption of zinc ions (Zn (II)), a series of new composites with in-situ construction ZnS nanoparticles on TTG (ZnS/TTG) were synthesized, and used as photocatalysts for the photodegradation of tetracycline hydrochloride (TCH) in solution. Specifically, ZnS nanoparticles were uniformly and stably distributed in the layered structure of TTG, interweaving with each other to generate an interfacial electric field, which could induce more photocarrier generation. Meanwhile, TTG acted as an electron acceptor to accelerate the electron transfer at the interface, thus enhancing the photodegradation activity for TCH. The active radical quenching experiments combined with the ESR indicated that the active species produced during the photocatalytic degradation of TCH by ZnS/TTG composites were •O2- and photogenerated h+. When the initial concentration of Zn (II) was 60 mg/L, the synthesized 60-ZnS/TTG composites (0.5 g/L) reached 91.53% degradation efficiency of TCH (10 mg/L) at pH = 6. Furthermore, the possible pathways and mechanism of 60-ZnS/TTG composites photodegraded TCH were revealed with the aid of degraded intermediates. This report not only proposed valuable references for reusing heavy metal ions and removing TCH from wastewater, but also provided promising ideas for realizing the conversion of used adsorbents into high-efficiency photocatalysts.

Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst

Catalysts for the selective catalytic reduction (NOX SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NOX SCR shows various SCR efficiencies. In the current work, an SCR catalyst developed from the sludge produced with Fe/C micro-electrolysis Fenton technology (MEF) in wastewater treatment was investigated, taking into account various sludge compositions, Fe/C ratios, and contaminant contents. It was found that, at about 300 °C, the NOX removal rate could reach 100% and there was a wide decomposition temperature zone. The effect of individual components of electroplating sludge, i.e., P, Fe and Ni, on NOX degradation performance of the obtained solids was investigated. It was found that the best effect was achieved when the Fe/P was 8/3 wt%, and variations in the Ni content had a limited effect on the NOX degradation performance. When the Fe/C was 1:2 and the Fe/C/P was 1:2:0.4, the electroplating sludge formed after treatment with Fe/C MEF provided the best NOX removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NOX. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P effectively reduces the catalytic reaction temperature, and the formation of phosphate promotes the generation of adsorbed oxygen, which in turn contributes to improvements in catalytic efficiency. Therefore, our work suggests that controlling the composition in the sludge is an efficient way to modulate SCR catalysis, providing a bridge from contaminant-bearing waste to efficient catalyst.

Waste-treating-waste: Effective heavy metals removal from electroplating wastewater by ladle slag

Ladle slag, a by-product of steelmaking, presents a valuable strategy for waste reduction and valorization in wastewater treatment. This work demonstrates the successful simultaneous removal of Al(III), B(III), Ba(II), Cr(III), Mg(II), Sr(II), Pb(II), and Zn(II), from electroplating wastewater by ladle slag. First, Cr(III) and Pb(II) removals were evaluated in single synthetic systems by analyzing the influence of pH, temperature, and ladle slag dosage. Competitive removal was observed in binary batch experiments of Cr(III) - Pb(II), achieving 88% and 96% removal, respectively, with fast kinetics following a pseudo-second-order model. The findings of XRD, SEM, EDX, and FTIR of the slag after removal helped to elucidate the synergic removal mechanism involving ladle slag dissolution, precipitation, ion exchange, and adsorption in a tight relationship with the solution pH. Lastly, ladle slag was tested in real electroplating wastewater with the aforementioned ions at concentrations ranging from <1 to 1700 mg/L. The removal was performed in two steps, the first attained the following efficiencies: 73% for Al(III), 88% for B(III), 98% for Ba(II), 80% for Cr(III), 82% for Mg(II), 99% for Pb(II), 88% for Sr(II), and 88% for Zn(II). Visual MINTEQ simulation was utilized to identify the different species of ions present during the removal process. Furthermore, the leaching tests indicated a minimal environmental risk of secondary pollution in its application. The results promote an effective and sustainable approach to wastewater treatment within the circular economy.

Anaerobic cyanides oxidation with bimetallic modulation of biological toxicity and activity for nitrite reduction

Cyanide is a typical toxic reducing agent prevailing in wastewater with a well-defined chemical mechanism, whereas its exploitation as an electron donor by microorganisms is currently understudied. Given that conventional denitrification requires additional electron donors, the cyanide and nitrogen can be eliminated simultaneously if the reducing HCN/CN- and its complexes are used as inorganic electron donors. Hence, this paper proposes anaerobic cyanides oxidation for nitrite reduction, whereby the biological toxicity and activity of cyanides are modulated by bimetallics. Performance tests illustrated that low toxicity equivalents of iron-copper composite cyanides provided higher denitrification loads with the release of cyanide ions and electrons from the complex structure by the bimetal. Both isotopic labeling and Density Functional Theory (DFT) demonstrated that CN--N supplied electrons for nitrite reduction. The superposition of chemical processes reduces the biotoxicity and enhances the biological activity of cyanides in the CN-/Fe3+/Cu2+/NO2- coexistence system, including complex detoxification of CN- by Fe3+, CN- release by Cu2+ from [Fe(CN)6]3-, and NO release by nitrite substitution of -CN groups. Cyanide is the smallest structural unit of C/N-containing compounds and serves as a probe to extend the electron-donating principle of anaerobic cyanides oxidation to more electron-donor microbial utilization.

Addressing preliminary challenges in upscaling the recovery of lithium from spent lithium ion batteries by the electrochemical method: a review

The paramount importance of lithium (Li) nowadays and the mounting volume of untreated spent LIB have imposed pressure on innovators to tackle the near-term issue of Li resource depletion through recycling. The trajectory of research dedicated to recycling has skyrocketed in this decade, reflecting the global commitment to addressing the issues surrounding Li resources. Although metallurgical methods, such as pyro- and hydrometallurgy, are presently prevalent in Li recycling, they exhibit unsustainable operational characteristics including elevated temperatures, the utilization of substantial quantities of expensive chemicals, and the generation of emissions containing toxic gases such as Cl2, SO2, and NOx. Therefore, the alternative electrochemical method has gained growing attention, as it involves a more straightforward operation leveraging ion-selective features and employing water as the main reagent, which is seen as more environmentally benign. Despite this, intensive efforts are still required to advance the electrochemical method toward commercialisation. This review highlights the key points in the electrochemical method that demand attention, including the feasibility of a large-scale setup, consideration of the substantial volume of electrolyte consumption, the design of membranes with the desired features, a suitable layout of the membrane, and the absence of techno-economic assessments for the electrochemical method. The perspectives presented herein provide a crucial understanding of the challenges of advancing the technological readiness level of the electrochemical method.

Sorption capacity of Eichhornia crassipes (Mart.) Solms for zinc removal from electroplating industry wastewater

Various industrial operations in the dye, fertilizer, pesticide, battery, mining, and chemical industries have been associated with releasing heavy metals in wastewater, such as lead, zinc, copper, arsenic, cadmium, chromium, nickel, and mercury. These metals are dangerous to aquatic life as well as to humans, who may consume them directly or indirectly. Therefore, before being released into open water and land resources, it is necessary to minimize the concentration of toxic ions below the discharge limit. This study used Eichhornia crassipes (Mart.) Solms to remove zinc from wastewater from the electroplating industry in a constructed wetland. Experimental investigations were conducted for removing zinc ions from electroplating industry wastewater using various process parameters such as nutrient dosages, dilution ratios, potential of hydrogen ions, biomasses, and contact times. The outcome of this study revealed that the maximum zinc removal percentage in electroplating industrial wastewater was found for the optimum nutrient dosages of 60 g, dilution ratios of 10, potential hydrogen ion levels of 8, and biomass amounts of 100 g. The maximum zinc removal by Eichhornia crassipes (Mart.) Solms was found to be 88.3 ± 0.6 and 93.4 ± 0.4% at the optimum parameter values for the electroplating industry wastewater and the aqueous solution, respectively, against the optimum contact time of 22 days. This study suggests using this phytoremediation technology to remove all pollutants from industrial wastewater in general, not just wastewater from the electroplating industry.

Competitive heavy metal adsorption on pinecone shells: Mathematical modelling of fixed-bed column and surface interaction insights

Pinecone shells are assessed as a cost-effective biosorbent for the removal of metal ions Pb(II), Cu(II), Cd(II), Ni(II), and Cr(VI) in a fixed-bed column. Influent concentration, bed height, and flowrate are studied to improve efficiency. The breakthrough data is well fitted by the Sips adsorption model, suggesting a surface complexation mechanism, with maximum adsorption capacities of 11.1 mg/g for Cu(II) and 66 mg/g for Pb(II). In multimetal solutions, the uptake sequence at breakthrough and saturation is Pb(II) > Cu(II) > Cd(II). Characterization via FTIR and XRD reveals carboxyl and hydroxyl functional groups interacting with metal ions. Ca(II) does not compete with Pb(II), Cu(II), and Cd(II) adsorption, highlighting the ability of pinecone to adsorb heavy metals via surface complexation. Its application in the treatment of industrial effluents containing Cu(II), Ni(II), and Cr(VI) is explored. The study investigates bed media regeneration via eluting adsorbed metal ions with hydrochloric acid solutions. The potential of pinecone shells as an efficient biosorbent for removing toxic metal ions from industrial wastewater is emphasized. These findings enhance our understanding of the adsorption mechanism and underscore the fixed-bed column system's applicability in real-world scenarios, addressing environmental concerns related to heavy metal contamination of industrial effluents.

Physicochemical assessment of industrial effluents of Kala Sanghian drain, Punjab, India

The discharge of industrial effluents has a significant impact on the Water Quality Index (WQI) of the water bodies and is a major source of contamination of groundwater. The present study investigated the physicochemical characteristics and scrutinized the pollution potential of the tannery, textile, and electroplating effluents uploading into the Kala Sanghian drain, located in Jalandhar, Punjab, India. In this study, 12 samples were collected from the four sites (leather complex drain (LD), leather complex outlet (LO), focal point drain (FD), and Bulandpur drain (BD)) of Kala Sanghian drain in the dry season. The result showed that the drain under consideration is very much contaminated and the water is not suitable for irrigation and agricultural purposes. Rather it has a bad impact on the health of local people, the physiology of aquatic organisms, and the soil quality of agricultural land nearby. The present study confirmed the water quality index was more than 100, indicating a highly contaminated drain and water is unfit for any use. The correlation analysis shows that there exists a positive correlation between TDS and temperature (r = 0.994), DO and pH (r = 0.808), BOD and temperature (r = 0.987), BOD and TDS (r = 0.978), EC and temperature (r = 0.963), EC and TDS (r = 0.954), and EC and BOD (r = 0.956). The principal component analysis (PCA) confirms that PC1 alone has more than 89% of the variance with high positive loading for TDS, temperature, EC, and BOD. The hierarchical cluster analysis (HCA) reflected two clusters where cluster 1 consists of pH, DO, temperature, and BOD of water while cluster 2 consists of TDS and EC of water. The PCA and HCA study of the data set confirms the high degree contribution of anthropogenic activities through the application of chemicals in agriculture, disposal of municipal waste, and industrial effluents in the deterioration of water quality. The results of the study will help to enhance the sustainable action plan for the management of industrial effluents in the studied area.

Utilization of biochar for remediation of heavy metals in aqueous environments: A review and bibliometric analysis

Biochar usage for removing heavy metals from aqueous environments has emerged as a promising research area with significant environmental and economic benefits. Using the PICO approach, the research question aimed to explore using biochar to remove heavy metals from aqueous media. We merged the data from Scopus and the Web of Science Core Collection databases to acquire a comprehensive perspective of the subject. The PRISMA guidelines were applied to establish the search parameters, identify the appropriate articles, and collect the bibliographic information from the publications between 2010 and 2022. The bibliometric analysis showed that biochar-based heavy metal remediation is a research field with increasing scholarly attention. The removal of Cr(VI), Pb(II), Cd(II), and Cu(II) was the most studied among the heavy metals. We identified five main clusters centered on adsorption, water treatment, adsorption models, analytical techniques, and hydrothermal carbonization by performing keyword co-occurrence analysis. Trending topics include biochar reusability, modification, acid mine drainage (AMD), wastewater treatment, and hydrochar. The reutilization of heavy metal-loaded spent biochar includes transforming it into electrodes for supercapacitors or stable catalyst materials. This study provides a comprehensive overview of biochar-based heavy metal remediation in aquatic environments and highlights knowledge gaps and future research directions.

Biological Iron Removal and Recovery from Water and Wastewater

Iron is a common contaminant in source water and wastewater. The mining and metallurgical industries in particular can produce and discharge large quantities of wastewater with high iron concentrations. Due to the harmful effects of iron on organisms and infrastructure, efficient technologies for iron removal from water and wastewater are needed. On the other hand, iron is a valuable commodity for a wide range of applications. Microorganisms can facilitate iron removal and recovery through aerobic and anaerobic processes. The most commonly utilized microbes include iron oxidizers that facilitate iron precipitation as jarosites, schwertmannite, ferrihydrite, goethite, and scorodite, and sulfate reducers which produce hydrogen sulfide that precipitates iron as sulfides. Biological iron removal has been explored in various suspended cell and biofilm-based bioreactors that can be configured in parallel or series and integrated with precipitation and settling units for an effective flow sheet. This chapter reviews principles for biological iron removal and recovery, the microorganisms involved, reactor types, patents and examples of laboratory- and pilot-scale studies, and full-scale implementations of the technology.

Analysis of soil pollution characteristics and influencing factors based on ten electroplating enterprises

The electroplating industry encompasses various processes and plating types that contribute to environmental pollution, which has led to growing public concern. To investigate related soil pollution in China, the study selected 10 sites with diverse industrial characteristics distributed across China and collected 1052 soil samples to determine the presence of industrial priority pollutants (PP) based on production process and pollutant toxicity. The factors influencing site pollution as well as proposed pollution prevention and control approaches were then evaluated. The results indicate the presence of significant pollution in the electroplating industry, with ten constituents surpassing the risk screening values (RSV). The identified PP consist of Cr(VI), zinc (Zn), nickel (Ni), total chromium (Cr), and petroleum hydrocarbons (C10-C40). PP contamination was primarily observed in production areas, liquid storage facilities, and solid zones. The vertical distribution of metal pollutants decreased with soil depth, whereas the reverse was true for petroleum hydrocarbons (C10-C40). Increase in site production time was strongly correlated with soil pollution, but strengthening anti-seepage measures in key areas can effectively reduce the soil exceedance standard ratio. This study serves as a foundation for conceptualizing site repair technology in the electroplating industry and offers a reference and methodology for pollution and source control in this and related sectors.

High-performance nanofiltration concentrate treatment by a five-chamber bioelectrochemical system

A combination of bioelectrochemical systems and electrodialysis has been considered an effective strategy for removing salts from the nanofiltration (NF) concentrate of electroplating wastewater; however, the recovery efficiency of multivalent metals is low. Herein, a new process based on microbial electrolysis desalination and chemical-production cell with five chambers (MEDCC-FC) has been proposed for the simultaneous desalination and recovery of the multivalent metals from NF concentrate. The MEDCC-FC was found to be significantly superior to the MEDCC with the monovalent selective cation exchange membrane (MEDCC-MSCEM) and MEDCC with the cation exchange membrane (MEDCC-CEM), in terms of the elevated desalination efficiency, multivalent metal recovery efficiency, current density, and coulombic efficiency, and decreased energy consumption and membrane fouling. Within 12 h, the MEDCC-FC provided the desirable outcome, indicated by a maximum current density of 6.88 ± 0.06 A/m2, desalination efficiency of 88 ± 10%, metals recovery efficiency of >58%, and total energy consumption of 1.17 ± 0.11 kWh for the per kg total dissolved solids removal. Mechanistic studies revealed that the integration of CEM and MSCEM in the MEDCC-FC promoted the separation and recovery of multivalent metal. These findings revealed that the proposed MEDCC-FC was promising in treating NF concentrate of electroplating wastewater towards advantages of effectiveness, economic viability, and flexibility.

Electrodialysis as a potential technology for 4-nitrophenol abatement from wastewater

4-Nitrophenol is a widely used emerging pollutant in various industries, including the production of agrochemicals, drugs, and synthetic dyes. Due to its potential environmental harmful effects, there is a need to study its reuse and removal from wastewater. This study used electrodialysis technology to separate 4-nitrophenol ions using a four-compartment stack. The effects of supporting electrolyte concentration, pH, voltages, and current density on the performance of electrodialysis for separating 4-nitrophenol were investigated. A high extraction percentage of 77% was achieved with low energy consumption (107 kWh kg-1) when high 4-nitrophenol flows and transport numbers were reached.

Electrochemical treatment of electroplating wastewater using synthesized GO/TiO2 nanotube electrode

The graphene oxide (GO) deposited TiO₂ nanotube (GO/TiO₂) electrode on a titania plate was prepared using a simple anodization method. The morphological and structural properties of TiO₂ and GO/TiO₂ electrodes have been studied using field emission scanning electron microscopy energy dispersive spectroscopy (FESEM-EDS), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Raman spectroscopy, Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS). FESEM-EDS analysis confirmed that the 13.56% wt of GO nanoparticles was formed over the TiO₂ substrate, with the thickness of the wall to be ∼300 nm. The crystallite size of GO/TiO₂, i.e., 19.53 nm, was confirmed by XRD analysis. Analysis of the UV-DRS spectrum showed the bandgap of the synthesized GO/TIO₂ nanotube electrode to be 3.052 eV. Box-Behnken design (BBD) under response surface methodology (RSM) was used to design the experiments. The effect of operating input parameters like pH, current (i), and degradation time (t) on % COD degradation (X₁) and energy consumed (X₂) were also examined. At optimum process parameters, the value of X₁ and X₂ were 57.61% and 15.00 kWh/m³, respectively. Possible intermediates were identified based on the GC-MS data analysis. Scavenger tests showed that •OH radical plays a major role in electroplating effluents degradation. Based on the results, the EO process using GO/TiO₂ electrodes could be considered a promising technique for electroplating effluent degradation due to high degradation efficiency.

A comparative study for the removal of reactive red 49 (RR49) and reactive yellow 15 (RY15) using a novel electrode by electrocoagulation technique

The present work deals with the investigation of the efficiency of the electrocoagulation (EC) technique in the removal of two different reactive dyes as a simple, durable, and cost-effective technique for wastewater treatment. The difference in structure between Reactive Red 49 (RR49) and Reactive Yellow 15 (RY15) is explored during the treatment process through the use of a novel design of electrodes. The optimum conditions obtained were 80 and 60 mg/L of initial dye concentrations, pH of 5.9 and 4 for RR49 and RY15, respectively, 0.5 g of NaCl electrolyte, and 900 and 500 rpm of stirring rate for RR49 and RY17 dyes respectively, which led to the highest percent removal (98.5%) for both dyes. The suitable temperatures were 20 and 30 °C for RR49 and RY15, respectively. The thermodynamic parameters were designated, and it was a spontaneous process for both dyes. The removal process was designated to pseudo- second-order for the RR49 dye and pseudo- first-order for the RY15 dye and fitted to the Langmuir model. Analysis of Variance (ANOVA) was presented to assess the variation of the outcomes attained from each factor.

Circular Economy Approach in Treatment of Galvanic Wastewater Employing Membrane Processes

According to the idea of sustainable development, humanity should make every effort to care for the natural environment along with economic development. Decreasing water resources in the world makes it necessary to take action to reduce the consumption of this resource. This article presents the results of research conducted to improve the use of recyclable materials in line with the circular economy model. The research focused on the development of a technological solution for the recovery of raw materials from galvanic wastewater. The concept of a galvanic wastewater treatment system presented in the article includes wastewater pre-treatment in the ultrafiltration (UF) process and water recovery in the reverse osmosis (RO) process. In addition, the purpose of the work was to manage post-filtration waste (RO retentate) containing high concentrations of zinc in the process of galvanizing metal details. The obtained results indicate that it is possible to reduce the amount of sewage from the galvanizing industry by reusing the recovered water as technical water in the process line. The carried-out model tests of galvanizing confirmed the possibility of using RO retentate for the production of metal parts. The achieved results are a proposal to solve the problem of reducing the impact of galvanic wastewater on the environment and to improve the profitability of existing galvanizing technologies by reducing the consumption of water and raw materials.

Production and characterization of a bioflocculant produced by Proteus mirabilis AB 932526.1 and its application in wastewater treatment and dye removal

Microbial flocculants affect the aggregation of suspended solutes in solutions, thus, they are a viable alternative to inorganic and organic synthetic flocculants which are associated with deleterious health problems. Moreover, a potential solution for wastewater treatment. The study aimed to produce and characterize a bioflocculant from Proteus mirabilis AB 932526.1 and apply it in domestic wastewater treatment and dye removal. The bioflocculant was extracted using butanol and chloroform (5:2 v/v). Carbohydrates, proteins, and uronic acid were identified using phenol-sulphuric acid, Bradford, and Carbazole essays. The morphology, crystallinity and elemental composition of the purified bioflocculant were determined using a Scanning electron microscope (SEM), X-ray diffraction analysis and SEM energy dispersive elemental detector (SEM-EDX). The antimicrobial properties and dye removal efficiencies were evaluated. About 3.8 g/L yields of the purified bioflocculant were attained. Chemical composition analysis revealed the presence of 65 % carbohydrates, 10 % proteins, and 24 % uronic acids. The bioflocculant displayed an amorphous and crystalline structure. Bioflocculant further shows some remarkable properties as they can be able to inhibit the growth of both Gram-positive and Gram-negative microorganisms. The removal efficiencies of 85 % (COD), 82 % (BOD), and 81 % (SO4 2−) in domestic wastewater were achieved. Moreover, the high removal efficiency of staining dyes such as methylene blue (71 %), carbol fuchsin (81 %), safranin (83 %), methylene orange (90 %), and Congo red (90 %) were found. The produced bioflocculant can imply industrial applicability.

Optimization of Cr (VI) removal from aqueous solution with activated carbon derived from Eichhornia crassipes under response surface methodology

Tannery industries' effluent contains a high concentration of Cr (VI) which has the potential to affect the environment and public health. Therefore, this study aimed to investigate the optimization of Cr (VI) adsorption by activated carbon (AC) derived from Eichhornia crassipes from an aqueous solution. The adsorbent was activated with dilute sulfuric acid followed by thermal activation. AC was characterized using proximate analysis, SEM, FTIR, X-ray diffraction, and the BET method. The Cr (VI) removal optimization process was performed using a central composite design under the response surface methodology. The proximate analysis showed that the moisture content, volatile matter, ash content, and fixed carbon of the activated carbon were 5.6%, 18.2%, 14.4%, and 61.8% respectively. The surface areas of the Eichhornia crassipes before activation, after activation, and after adsorption were 60.6 g/m², 794.2 g/m², and 412.6 g/m² respectively. A highly porous structure with heterogeneous and irregular shapes was observed in the SEM micrograph. In the FTIR analysis, different peaks are indicated with various functional groups. The intensity of XRD peaks decreased as 2 theta values increased, which indicates the presence of an amorphous carbon arrangement. The point of zero charge (pH_pzc) of the activated carbon was found to be 5.20. A maximum Cr (VI) removal of 98.4% was achieved at pH 5, contact time 90 min, adsorbent dose 2 g, and initial Cr (VI) concentration of 2.25 mg/L. Statistically significant interactions (P < 0.05) were observed between the initial Cr (VI) concentration and adsorbent dose as well as the initial Cr (VI) concentration and contact time. Langmuir adsorption isotherm fitted the experimental data best, with an R² value of 0.99. The separation constant (RL) indicates that the adsorption process is favorable. The kinetic experimental data were best fitted with the pseudo-second-order model with an R² value of 0.99 whereas the adsorption rate is controlled by intraparticle and extragranular diffusion processes. Generally, the AC has the potential to be a strong adsorbent candidate for wastewater treatment at the industrial level.

Investigation of Electrochemical Assisted Deposition of Sol-Gel Silica Films for Long-Lasting Superhydrophobicity

Current methods for the protection of metal surfaces utilize harsh chemical processes, such as organic paint or electro-plating, which are not environment-friendly and require extensive waste treatments. In this study, a two-step approach consisting of electrochemical assisted deposition (EAD) of an aqueous silane solution and a dip coating of a low surface energy silane for obtaining a superhydrophobic self-cleaning surface for the enhanced protection of copper substrate is presented. A porous and hierarchical micro-nanostructured silica basecoat (sol-gel) was first formed by EAD of a methyltriethoxysilane (MTES) precursor solution on a copper substrate. Then, a superhydrophobic top-coat (E-MTES/PFOTS) was prepared with 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (PFOTS) for low surface energy. The superhydrophobic coating exhibited anti-stain properties against milk, cola, and oil, with contact angles of 151°, 151.5°, and 129°, respectively. The EAD deposition potential and duration were effective in controlling the microscopic morphology, surface roughness, and coating thickness. The E-MTES/PFOTS coatings exhibited chemical stability against acids, bases, and abrasion resistance by sandpaper. The proposed 2-layer coating system exhibited strong chemical bonding at the two interfaces and provided a brush-like surface morphology with long-lasting superhydrophobicity. The developed method would provide an environment-friendly and expedient process for uniform protective coatings on complex surfaces.

Saline Wastewater: Characteristics and Treatment Technologies

The discharge of saline wastewater has significantly increased due to rapid urbanization and industrialization [...].