Search Results (55)

Ozonation and ozone-based advanced oxidation processes, including ozone/hydrogen peroxide and ozone/ultraviolet irradiation, have been extensively studied for their efficacy in treating wastewater across various industries. While sectors such as pulp and paper, textile, food and beverage, microelectronics, and municipal wastewater have successfully implemented ozone at full scale, others have yet to fully embrace these technologies’ effectiveness. This review article examines recent publications from the past two decades, exploring novel applications of ozone-based technologies in treating wastewater from diverse sectors, including food and beverage, agriculture, aquaculture, textile, pulp and paper, oil and gas, medical and pharmaceutical manufacturing, pesticides, cosmetics, cigarettes, latex, cork manufacturing, semiconductors, and electroplating industries. The review underscores ozone’s broad applicability in degrading recalcitrant synthetic and natural organics, thereby reducing toxicity and enhancing biodegradability in industrial effluents. Additionally, ozone-based treatments prove highly effective in disinfecting pathogenic microorganisms present in these effluents. Continued research and application of these ozonation and ozone-based advanced oxidation processes hold promise for addressing environmental challenges and advancing sustainable wastewater management practices globally. Full article

Soil contamination with potentially toxic elements (PTEs) not only poses potential ecological risks (RI) but also leads to human health risks (HI) through the uptake of potentially toxic elements by crops. However, most studies primarily focus on potentially toxic element contamination in either soil or crops, often neglecting the intrinsic connections between soil and crop contamination risks. In reality, some regions may exhibit severe soil PTE exceedances, yet the PTE levels in crops may not necessarily exceed regulatory limits, resulting in human health risks that are not uniformly high. This study investigated a typical area with severe soil PTE pollution caused by wastewater from electroplating, smelting, and ore beneficiation industries, and conducted risk assessments on soil and crops. The research aims to elucidate the differences in soil and crop PTE contamination risks and the correlations between PTE concentrations in soil and crops. Results showed that Cd was the most severe PTE contaminant in the soil in the study area, with an average concentration of 1.11 mg/kg and a maximum concentration of 7.30 mg/kg. However, the average concentrations of eight PTEs in crops were all below the standard limits for cereal crops specified in the Food Safety National Standard for Pollutant Limits in Foods (GB 2726-2022). Cd was identified as the most severe PTE contaminant in the soil, resulting in the highest RI (836) in the MY sub-region of the study area. However, Cr in crops contributed the most to health risk (63.5%), leading to the highest HI (7.1) in sub-region MY. Despite Cd being the most severely polluting PTE in soil, its contribution to human health risk through crops was relatively low, ranging from 2.82% to 9.90%. This discrepancy in pollution risks indicates that a PTE causing severe soil contamination may not necessarily result in significant human health risks via crop uptake. Correlation and regression analyses revealed that soil PTEs had the greatest impact on Cd levels in crops. Soil Ni, Cd, Cu, As, and Zn exhibited different synergistic or antagonistic effects on crop PTE uptake. Notably, soil Cd content showed a highly significant positive regression relationship with Cd, Cr, and Ni concentrations in crops. Overall, the influence of soil PTEs on crop PTEs varied significantly, and the spatial differentiation characteristics of PTEs in soil and crops differed. For PTEs with high spatial differentiation, localized and precise management measures should be implemented. Conversely, for PTEs with low spatial differentiation, unified risk management and control measures can be adopted. Full article

Hydrothermal conversion is an effective strategy to transform heavy metals in electroplating sludge into catalytic materials and use them to treat electroplating wastewater. This study presents a one-step hydrothermal method for converting Sn-bearing sludge, containing 23.41% Sn, 52.12% Fe, and other impurities, into Fe/S rods using a NaOH/Na₂S solution. The resulting Fe/S rods, with a diameter of 50–100 nm and length of 0.5–2.5 μm, showed excellent performance in wastewater treatment. In the presence of 50 mg/L EDTA, the Fe/S rods removed 22.9% of Ni, 30.2% of Cu, and 41.5% of Zn. When activated with PMS, the removal efficiencies increased significantly to 68.9%, 90.9%, and 91.6% for Ni, Cu, and Zn, respectively. The optimal rod dosage (1 g/L) achieved removal efficiencies of 94.2%, 78.5%, and 99.7% for Cu, Ni, and Zn, while increasing PMS dosage led to nearly 100% removal within 60 min. Additionally, the process allowed for the complete recycling of the alkaline solution, with regenerated rods showing similar performance to the original ones in wastewater treatment. This method offers an efficient and sustainable approach to sludge resource utilization and heavy metal removal from wastewater. Full article

Electroplating sludge, a hazardous waste generated from the electroplating industry, contains significant quantities of heavy metals such as Cu, Cr, and Ni. Improper disposal of these metals poses severe environmental and health risks. This study proposes a comprehensive resource recovery process for Cu, Ni, and Cr from electroplating sludge, involving leaching, solvent extraction, stripping, and precipitation. The extraction efficiency of three extractants (P507, LIX984, and M5640) was evaluated, with M5640 demonstrating superior performance in Cu recovery (near 100%) at pH 3.0–4.0. Multi-stage extraction and stripping experiments further optimized metal recovery, achieving high efficiencies for Cu, Cr, and Ni. The recovered metals were precipitated as CuCO₃, CrPO₄, and Ni(OH)₂, with wastewater discharge meeting environmental discharge standards. This study not only enriches the technical approaches for the selective recovery of high-value metals from electroplating sludge with complex components, but also closely aligns with the laws, regulations, and policies of the Chinese government regarding environmental governance. It serves as a driving force for promoting the construction of “waste-free cities” and the establishment of a closed-loop circular economy industrial chain. Full article

The rapid detoxification and mineralization of Cr(VI) in aqueous environments hold critical importance for emergency response and resource recovery yet remain technically challenging. Herein, we report the synthesis of FeS₂/ZVI composites through ethanol-assisted wet ball-milling and their application in Cr(VI) removal under microwave (MW) irradiation. This study systematically investigates the effects of MW irradiation on the removal efficiency of Cr(VI) using FeS₂/ZVI composites, with particular focus on key parameters including composite dosage, initial pH, MW temperature, and Cr(VI) concentration. Notably, 1 g/L FeS₂/ZVI composites achieved near-complete removal (>99%) of 50 mg/L Cr(VI) within 7 min at a MW irradiation temperature of 333 K, which exhibited 5.9-fold and 13.1-fold superior performance compared to pure pyrite and ZVI, respectively. Additionally, there is a 96.1% reduction in reaction time in comparison to non-MW irradiation system. In real electroplating wastewater samples, Cr(VI) concentration was reduced from 38.93 to 0.42 mg L⁻¹ by MW irradiation-assisted treatment, validating its potential for practical applications in industrial Cr(VI) pollution control. The activation energy determined by fitting the Arrhenius equation showed a 39.7% reduction for the MW-assisted FeS₂/ZVI system (16.0 kJ mol⁻¹) compared to conventional thermal heating (from 25.6 kJ mol⁻¹), indicating that MW irradiation induced catalytic enhancement of FeS₂/ZVI, thereby lowering the energy barrier for Cr(VI) reduction. Moreover, MW irradiation-assisted processes facilitated the mineralization of reduced Cr(III) to stable spinel FeCr₂O₄. These findings collectively establish a synergistic mechanism between MW activation and FeS₂/ZVI composites, offering innovative pathways for efficient Cr(VI) detoxification and resource recovery from high-strength industrial wastewaters. Full article

Spatiotemporal analysis of heavy metal pollution and risks in soils from a shut-down electroplating plant was carried out. Two batch samples were tested in December 2020 and August 2022, obtained from different sampling positions and depths. The results show that Cu, Pb, As, and Ni were the main pollutants, and their spatial distribution characteristics in December 2020 and August 2022 were similar. The pollution depth of Cu, Pb, As, and Ni was mainly concentrated within 1.0 m from the ground. In the horizontal direction, the four kinds of pollutants had some relatively concentrated pollution areas and many dispersed pollution points. In December 2020, Cu contamination was heavy, and the comprehensive ecological risk was slight. In August 2022, Cu contamination was heavy, Pb contamination was moderate, and the comprehensive ecological risk was moderate as well. Both As and Ni posed carcinogenic risks in both samples. Cu, Pb, As, and Ni migrated very slowly under the action of rainfall infiltration. Soil pollution was primarily attributed to wastewater discharge, while dispersed pollution sites were mainly caused by the landfilling of production waste. The research findings hold significant implications for heavy metal pollution control and risk prevention in the soil of electroplating enterprises. Full article

The dominant treatment process for removing heavy metals from industrial wastewater is chemical neutralisation precipitation using lime milk as a precipitation agent, resulting in a highly voluminous hydroxide sludge with a low heavy metal concentration. These sludges are predominantly landfilled, and the metals are lost to the circular economy. At the same time, metals are urgently needed as raw materials. A new approach is represented by the low-pressure, low-energy Specific Product-Oriented Precipitation process (SPOP). This approach, however, requires the adjustment of various reaction parameters for optimal operation. This study presents the impacts of the stirring rate during the reaction and the Fe concentration in the solution on the recovery of Cu from Cu-enriched electroplating wastewater. Three different recovery options are described: Option (1), the formation of CuO; Option (2), the generation of brochantite, a Cu-hydroxysulphate; and Option (3), the incorporation of Cu into ferrite. Tenorite (CuO) is precipitated at 40 °C reaction temperature at a low stirring rate of 100–200 rpm. At an accelerated stirring rate of 400–500 rpm, brochantite (Cu₄(OH)₆SO₄) is formed. With high Fe concentrations and a molar ratio of Cu:Fe of 1:2, Cu-ferrite (CuFe₂O₄) is the precipitation product. In any case, the achieved recovery rates in the treated wastewater are better than 99.9%. Full article

Bis-N,N-(3-triethoxysilylpropyl)thiosemicarbazide 3 was obtained by the condensation of 3-aminopropyltriethoxysilane 1 with thiosemicarbazide 2. Ethyl ether N-[3-(triethoxysilyl)propyl]-b-alanine 5 was obtained by the interaction of an equimolar amount of aminopropyltriethoxysilane 1 and ethyl acrylate 4 (aza-Michael reaction). Synthesized functional organosilanes 3 and 5 were successfully immobilized on the surface of natural zeolite Z (Chankanai deposit, Kazakhstan). Compounds and materials have been studied by NMR and IR Fourier spectroscopy and X-ray diffraction analysis. The elemental composition and morphology of modified zeolites Z3 and Z5 were studied using SEM-EDX analysis. The modification of zeolite by organosilanes 3 and 5 leads to changes in the surface structure of the material: with the enlargement of particles and agglomerates, the surface becomes more homogeneous and less porous. This indicates a high degree of zeolite coverage by the modifier layer. The study of the sorption characteristics of the initial Z and modified zeolites (Z3 and Z5) showed a high sorption capacity relative to Ag(I) and Co(II) (static sorption capacity, SSC = 35.85–23.92 mg/g), whereas the SSC values for Z were SSC = 20.63 and 16.64 mg/g. The adsorption of Ag(I) and Co(II) ions was studied in solutions prepared using Co(NO₃)₂·6H₂O, AgNO₃ and distilled water. The choice of the initial concentration of metal ions, as well as the pH of the solutions, corresponded to the composition of wastewater from real electroplating production. Zeolites Z3 and Z5 can be used in various sectors of industry, in ecology and for medical purposes as inexpensive and effective adsorbents (enterosorbents) of heavy and noble metals. Full article

In this study, sodium polyacrylate (PAAS) and ultrafiltration membranes were used to extract and separate Cu²⁺ and Ni²⁺ ions from electroplating wastewater. The effects of pH, the P/M ratio (mass ratio of sodium polyacrylate to metal ions), tartaric acid, and sodium citrate on the complexation of Cu²⁺ and Ni²⁺ by sodium polyacrylate were investigated. The retention of Cu²⁺ and Ni²⁺ by PAAS in single metal solutions with a P/M ratio = 4 and pH = 5 differed by 45.36%. When the complexation system of PAAS with a single metal contained tartaric acid and sodium citrate, the retention of PAAS for Cu²⁺ and Ni²⁺ increased to 80.36% and 58.84%. PAAS retention for Ni²⁺ decreased, but retention for Cu²⁺ remained the same. All the results indicated that there was competition between tartaric acid, sodium citrate, and PAAS for the adsorption of Cu²⁺ and Ni²⁺. Some of the Ni²⁺ complexed with PAAS were detached from PAAS complexed by tartaric acid and sodium citrate and permeated through the membrane pores, while the Cu²⁺ complexed with PAAS was not complexed by tartaric acid and sodium citrate and could not permeate through the membrane pores. Therefore, this study helps to provide a theoretical basis for the separation of Cu²⁺ and Ni²⁺ in electroplating wastewater. Full article

Catalysts for the selective catalytic reduction (NO_X SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NO_X 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 NO_X 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 NO_X 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 NO_X 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 NO_X removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NO_X. 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. Full article

Electroplating is a key process in many industrial fields such as automotive, electronics and decorative applications; this process makes it possible to provide new properties to substrates materials such as corrosion resistance, hardness and aesthetic value. Nonetheless, electroplating is considered one of the most non-sustainable industries related to the manufacturing sector, from both an environmental and a social point of view. With the approaching deadlines set by the United Nations for the 2030 Agenda, electroplating companies have started a trend of innovating their production processes with a focus on sustainability, acting on several fronts: performing simulations to predict criticalities and optimize working procedures, reducing the material used and recovering it from processing water. The purpose of this communication is to highlight the state of the art of sustainable practices peculiar to the electroplating industry, critically analyzing ongoing challenges to achieve and exceed the targets set by regulatory agencies. Both atomistic and multiphysics simulations will be analyzed as powerful tools to design both new sustainable formulations and items; then, the problem of metal dispersion will be discussed, evaluating different industrial approaches; finally, the focus will be shifted towards the general procedures to recover metal from wastewater. Full article

Large volumes of wastewater containing toxic contaminants (e.g., heavy metal ions, organic dyes, etc.) are produced from industrial processes including electroplating, mining, petroleum exploitation, metal smelting, etc., and proper treatment prior to their discharge is mandatory in order to alleviate the impacts on aquatic ecosystems. Adsorption is one of the most effective and practical methods for removing toxic substances from wastewater due to its simplicity, flexibility, and economics. Recently, hierarchical oxide composites with diverse morphologies at the micro/nanometer scale, and the combination advantages of oxides and composite components have been received wide concern in the field of adsorption due to their multi-level structures, easy functionalization characteristic resulting in their large transport passages, high surface areas, full exposure of active sites, and good stability. This review summarizes the recent progress on their typical preparation methods, mainly including the hydrothermal/solvothermal method, coprecipitation method, template method, polymerization method, etc., in the field of selective adsorption and competitive adsorption of hazardous substances from wastewater. Their formation processes and different selective adsorption mechanisms, mainly including molecular/ion imprinting technology, surface charge effect, hard-soft acid-base theory, synergistic effect, and special functionalization, were critically reviewed. The key to hierarchical oxide composites research in the future is the development of facile, repeatable, efficient, and scale preparation methods and their dynamic adsorption with excellent cyclic regeneration adsorption performance instead of static adsorption for actual wastewater. This review is beneficial to broaden a new horizon for rational design and preparation of hierarchical oxide materials with selective adsorption of hazardous substances for wastewater treatment. Full article

Chitosan is a promising adsorbent for removing a wide range of pollutants from wastewater. However, its practical application is hindered by instability in acidic environments, which significantly impairs its adsorption capacity and limits its utilization in water purification. While cross-linking can enhance the acid stability of chitosan, current solvent-based methods are often costly and environmentally unfriendly. In this study, a solvent-free mechanochemical process was developed using high-energy ball milling to cross-link chitosan with various polyanionic linkers, including dextran sulfate (DS), poly[4-styrenesulfonic acid-co-maleic acid] (PSSM), and tripolyphosphate (TPP). The mechanochemically cross-linked (MCCL) chitosan products exhibited superior adsorption capacity and stability in acidic solutions compared to pristine chitosan. Chitosan cross-linked with DS (Cht-DS) showed the highest Reactive Red 2 (RR2) adsorption capacity, reaching 1559 mg·g⁻¹ at pH 3, followed by Cht-PSSM (1352 mg·g⁻¹) and Cht-TPP (1074 mg·g⁻¹). The stability of MCCL chitosan was visually confirmed by the negligible mass loss of Cht-DS and Cht-PSSM tablets in pH 3 solution, unlike the complete dissolution of the pristine chitosan tablet. The MCCL significantly increased the microhardness of chitosan, with the order Cht-DS > Cht-PSSM > Cht-TPP, consistent with the RR2 adsorption capacity. When tested on simulated rinsing wastewater from chromium electroplating, Cht-DS effectively removed Cr(VI) (98.75% removal) and three per- and polyfluoroalkyl substances (87.40–95.87% removal), following pseudo-second-order adsorption kinetics. This study demonstrates the potential of the cost-effective and scalable MCCL approach to produce chitosan-based adsorbents with enhanced stability, mechanical strength, and adsorption performance for treating highly acidic industrial wastewater containing a mixture of toxic pollutants. Full article

Concerning environmental safety and mitigating the risk of water pollution, the electroplating industry, historically reliant on the use of elevated concentrations of heavy metals to achieve high-quality products, faces a crucial challenge in monitoring wastewater enriched with these metals, notorious for their adverse effects on ecosystems and human health. Chromium, in both oxidation states Cr (III) and Cr (VI), emerges as a prominently employed metal, yielding noteworthy outcomes throughout the galvanisation process. This research showcases the prototype of an automatic in situ sensor tailored to industry sustainability efforts to facilitate real-time monitoring and efficient water management. This custom sensor, characterized by sensitivity, reliability, and user-friendliness, utilizes UV-Vis colorimetric principle to detect Cr in both oxidation forms ranging from grams per litre (g/L) to parts per million (ppm). This is made possible by the unique vibrant colours induced by chromium ions, enabling the precise measurement of analyte concentrations. Thanks to 3D printing, this sensor system interacts with customized parts, designed and validated through simulation processes, for filtering out particulate that may interfere with the analysis. The outcome represents a synergistic blend of technology and environmental responsibility, aligning industrial processes with the goal of safeguarding water resources and ecosystems. Full article

Manganese oxides reportedly exhibit pronounced adsorption capacities for numerous heavy-metal ions owing to their unique structural properties. Herein, a biogenic manganese oxide (BMO) composite was developed and used to remove Ni ions from Ni²⁺-containing electroplating wastewater. The formation of BMO and the micro-/nanoscale fine microstructure were characterized via scanning/high-resolution transmission electron microscopies and X-ray diffraction assays. Under the optimized conditions, with an adsorption temperature of 50 °C, pH 6, the BMO composite showed a 100% removal efficiency within a rapid equilibrium reaction time of 20 min towards an initial Ni²⁺ concentration of 10 mg L⁻¹ and a remarkable removal capacity of 416.2 mg g⁻¹ towards an initial Ni²⁺ concentration of 600 mg L⁻¹ in Ni-electroplating wastewater. The pseudo-second-order equation was applicable to sorption data at low initial Ni²⁺ concentrations of 10–50 mg L⁻¹ over the time course. Moreover, Freundlich isotherm models fitted the biosorption equilibrium data well. Fourier-transform infrared spectroscopic analysis validated that the removal capacity of the BMO composite was closely associated with structural groups. In five continuous cycles of adsorption/desorption, the BMO composite exhibited high Ni²⁺ removal and recovery capacities, thereby showing an efficient and continuous performance potential in treating Ni²⁺-containing industrial wastewater. Full article