Plating Wastewater Research Articles

Electrocatalysis coupled super-stable mineralization for the efficient treatment of phosphorus containing plating wastewater

The automotive, electronics, and aerospace sectors use electroless nickel plating (ENP) technology for surface treatment. Hypophosphite, a widely used reducing agent in ENP, generates large volumes of hypophosphate (H2PO2-) and nickel ions (Ni2+) in its wastewater which poses potential risks to human health. However, it is a highly challenging task to remove and recycle the H2PO2- and Ni2+ from such wastewater. In this study, a novel electrocatalysis coupled super-stable mineralization process was developed for the treatment of phosphorus-containing ENP wastewater. The electrocatalytic system, utilizing commercial lead dioxide and stainless steel as the anode and cathode, separately, achieved remarkable results in simultaneously removing H2PO2- and recycling valuable Ni2+ ions from ENP wastewater, with a 99.1 % oxidation efficiency for H2PO2- and a high recovery rate of 99.8 % for nickel. In order to meet industrial emission standards, layered double hydroxide (CaAl-LDH) and its calcined derivatives (CaAl-900) were employed as super-stable mineralizers for the further treatment of total phosphorus (TP) and residual Ni2+ in the wastewater. The mechanism underlying the enhanced treatment of ENP wastewater was elucidated through free radical quenching experiments, revealed superoxide radicals (·O2–) as the primary active species. It is noteworthy that the successful treatment of actual ENP wastewater was achieved, meeting standard discharge requirements. This study provides novel insights for achieving resource-efficient wastewater treatment and promoting environmentally friendly electroplating industries.

Synthesis and properties of multi-porous multi-doped nano-Na3V2(PO4)3@C materials from electroless nickel plating wastewater

Synthesis and properties of multi-porous multi-doped nano-Na3V2(PO4)3@C materials from electroless nickel plating wastewater

Synthetic Cu(III) from copper plating wastewater for onsite decomplexation of Cu(II)- and Ni(II)-organic complexes

Synthetic Cu(III) from copper plating wastewater for onsite decomplexation of Cu(II)- and Ni(II)-organic complexes

Treatment of heavy metal in the plating wastewater by electrocoagulation

Abstract This present paper evaluated a batch electrocoagulation (EC) scale containing two flat aluminium plate electrodes to treat total Cr, Zn2+ in real plating wastewater taken from CX Technology company. Response Surface Methodology (RSM) and Design-Expert 12 software were applied to optimize the operating conditions with three main factors including current density, pH, and retention time. The control experiments using FeSO4 10% were performed to compare with the electrocoagulation method. The best treatment efficiency occurred at a current density of 16.93 A/m2, pH 9, and a 31-minute reaction. The conductivity did not significantly affect to the total Cr and Zn2+ removal but reduced energy consumption. The jar-test experiment result was obvious the optimal factors of the coagulation-flocculation encompassing pH 10 and 3 ml/L FeSO4 10 %. The treatment efficiency of total Cr and Zn2+ were 97.22±0.3 % and 99.53± 0.006 %, higher than others. The generated sludge in the electrocoagulation method was 2,031± 0.91 g/L, equal to 51.7 % sludge of the coagulation-flocculation method. The treatment cost by electrocoagulation was less than others.

Supported liquid membrane with selective stripping for separative recovery of copper and zinc from plating wastewater

For separation and recovery of different but chemically similar metal from dilute wastewater with reduced process complexity and cost, a supported liquid membrane (SLM) system that utilizes a single carrier together with strip dispersion for selective stripping of coextracted metal ions was proposed to enable concurrent separation and recovery. This study aims to investigate the effectiveness of the proposed SLM system for separative recovery of copper and zinc from real plating wastewater. Solvent extraction experiments were conducted to understand the effect of feed pH and carrier concentration on organic phase migration to the aqueous phase. The effect of stirring speed on the SLM transport rate was studied using synthetic feed. Combined with the insights from our previous study, appropriate settings were identified and applied to the SLM system. The SLM system could recover 83.7% copper with 91.0% purity and 85.5% Zn with 99.3% purity from the plating wastewater in 30 h. The findings indicate the feasibility of using SLM with selective stripping for the concurrent separation and recovery of copper and zinc from a dilute aqueous waste stream predominantly containing these two metals.

High-efficiency phosphorus recovery from hypophosphite and phosphite-containing wastewater via a new electrodialysis enrichment and hydrothermal oxidation coupling process

Hypophosphite is an ideal reducing agent used in industries such as electroplating. However, the presence of high concentrations of hypophosphite and phosphite in industrial wastewater necessitates the consumption of large amounts of strong oxidants to oxidize hypophosphite to phosphate for subsequent removal by precipitation. This study introduces an innovative application of green hydrothermal process for the oxidation treatment of inorganic materials, combined with the ion enrichment advantages of electrodialysis. This novel coupling process achieves efficient enrichment and rapid oxidation of high-concentration hypophosphite and phosphite with minimal chemical consumption and more economical operating costs, yielding high-quality phosphate resources. Under electrodialysis conditions with a particle electrode dosage of 3 %, a voltage of 20 V, and a residence time of 10 h, the total phosphorus in the middle chamber was reduced from 2801.17 mg/L to 119.05 mg/L, achieving an anodic enrichment rate of 95.75 %. Under hydrothermal conditions of 400 °C for 15 min, with an H2O2 doping ratio of 7 % and a Ca(OH)2 doping ratio of 35 g/L, the peak oxidation rates of H2PO2− and HPO32− reached 99.38 %, and 99.39 % of phosphorus was transferred from the liquid phase to the solid phase in recyclable forms such as Ca5(PO4)3OH, Ca3(PO4)2, and FePO4. H2O2 enhances the hydrothermal oxidation process by increasing the concentration of free radicals. Ca(OH)2 acted as a catalyst to enhance •OH generation during the hydrothermal reaction, provided Ca2+ required for phosphorus recycling, and increased the pH to obtain crystalline products with a high Ca/P molar ratio. Compared to conventional advanced oxidation processes, the electrodialysis and hydrothermal coupling process offers a clean alternative for treating high-concentration hypophosphite and phosphite in plating wastewaters, achieving a cost saving of 22.99 %.

Efficient simultaneous removal of nickel, phosphorus and COD from electroless nickel plating wastewater by three dimensional electrodialytic system

The simultaneous removal of nickel (Ni), phosphorus (P) and chemical oxygen demand (COD) from electroless Ni plating (ENP) wastewater by a three-dimensional electrodialysis (3D ED) system with graphite as the third electrode was investigated in this study. Compared to conventional two-dimensional electrodialysis (2D ED) system a significantly higher removal efficiency of complexed Ni, P and COD was achieved. The optimal process conditions were determined as dilution factor of 20, voltage of 20 V, treatment time of 10 h and particle electrode addition of 3 %, with removal rates of 95.8 %, 97.7 %, and 91.8 % for Ni2+, total phosphorus (TP) and COD, respectively. The decomplexed Ni2+ was recovered in the form of Ni(OH)2. Additionally, the mechanisms of enhanced ENP wastewater treatment was discussed and analyzed through SEM-EDS and XPS on solid and liquid products prior to and after treatment. This study provides crucial theoretical and practical support for the application of electrochemical technology in the treatment of ENP wastewater. It also offers new insights for achieving resource-efficient wastewater treatment and environmentally friendly electroplating industries.

Performance and oxidation mechanism of VUV photo–Fenton in simultaneous removal of Ni-EDTA and hypophosphite: decomplexation, low-valent phosphorous oxidation and DFT calculation

The photo–Fenton process offers a promising alternative for the oxidation of complex heavy metals. However, the potential influence of coexisting substrates may be overlooked. The •OH radicals generated in the photo–Fenton process ensure superior oxidation ability. In this study, we used a vacuum ultraviolet (VUV) light-assisted photo–Fenton (VPF) process to explore its performance in the synergistic oxidation of Ni-ethylenediaminetetraacetic acid (EDTA) and coexisting hypophosphite, typical pollutants in electroless nickel plating (ENP) wastewater. Based on electron spin resonance (ESR) and DMSO-probing results, •OH was the predominant reactive oxygen species, and VPF possessed the highest •OH concentration compared to other photochemical processes under identical conditions (pH, Fe, H2O2). Enhanced •OH generation in VPF was attributed to various photochemical reactions, including photo–Fenton, UV/H2O2, and VUV/H2O. Consequently, VPF exhibited efficient Ni-EDTA decomplexation and hypophosphite oxidation. Notably, the evolution and rate-limiting steps during hypophosphite oxidation were demonstrated by experimental results and density functional theory calculations. Hypophosphite was initially oxidized to phosphite, which subsequently oxidized to phosphate. The oxidation of phosphite could be considered the rate-limiting step as it exhibits higher energy barriers than hypophosphite oxidation. Adequate •OH generation in the VPF process could overcome this energy barrier, indicating its potential for application in pollutant removal and resource recovery from ENP wastewater.

Expression of Concern: Removal of copper, nickel and chromium mixtures from metal plating wastewater by adsorption with modified carbon foam. (Chemosphere, Volume 166, January 2017, Pages 203–211)

Expression of Concern: Removal of copper, nickel and chromium mixtures from metal plating wastewater by adsorption with modified carbon foam. (Chemosphere, Volume 166, January 2017, Pages 203–211)

High-pressure batch reverse osmosis (RO) for zero liquid discharge (ZLD) in a Cr(III) electroplating process

A batch RO system was designed and built for high-pressure (120 bar) operation. The system was developed for a ZLD application involving treatment of metal plating wastewater from a Cr(III) electroplating process at a major industrial plant. Hybrid semi-batch/batch operation enabled a compact design to be achieved. To maximize water recovery without exceeding a set peak pressure, a method for controlling the switch point between semi-batch and batch phases was developed. The system was tested with feed representative of rinse water from the electroplating process. A range of feed concentrations (at 10–20× dilution of the plating bath), feed flows (0.21–0.46 m3/h), water fluxes (6–14 LMH) and water recoveries (87–95.7 %) were investigated. The system successfully recovered Cr(III) and restored its concentration to that of the electrolyte bath, thus meeting the requirements for reuse in the electroplating process. Rejection of most species was >99.8 %, sufficient for reuse of the permeate as rinse. However, rejection of boric acid was only 69–80 % such that a second RO pass may be needed to remove boric acid. Specific Energy Consumption was <2.25 kWh per m3 of treated rinse water, representing a 50-fold saving compared to the current method of treatment and disposal at the industrial plant.

Optimizing Cr(VI) Reduction in Plastic Chromium Plating Wastewater: Particle Size, Irradiation, Titanium Dose

The preservation of the aquatic environment and water systems has been a fundamental objective that has led great scientists and researchers to seek new alternatives or techniques that allow the decontamination of water sources. The plastic chromium plating industries have been identified as important sources of contamination since their residues are characterized by having considerable amounts of hexavalent chromium Cr (VI), which alters the stability of water resources and can affect effluents on the surface and the subsoil. Given this problem, the need to improve the usual methods and techniques for wastewater treatment with more effective solutions, such as photocatalysis, which presents significant advantages over the inefficiency of traditional methods, is recognized. However, given the limited availability of research in the country that addresses the removal of hexavalent chromium from the wastewater of these industries, this work focuses on optimizing the process by varying conditions of variables such as particle size, catalyst dose, and irradiation time. The optimization of the photocatalysis process was evaluated using the Box-Behnken experimental design. The results show that contaminant removal occurred when the particle size was 0.177 mm. This particle size showed the highest photocatalytic activity, with 100% removal at 45 minutes. These findings represent a significant step towards solving the problem of contamination in this business sector by this pollutant and contribute to preserving our water resources. Doi: 10.28991/ESJ-2024-08-01-02 Full Text: PDF

Selective Recovery of Palladium from Plating Wastewater Using Chitosan Nanofiber Hydrogels

Selective Recovery of Palladium from Plating Wastewater Using Chitosan Nanofiber Hydrogels

Copper recovery from treatment of simulated copper-iron wastewater using fluidized-bed homogeneous crystallization technology

Electroless plating wastewater contains highly soluble Cu-EDTA complex which poses challenges for copper recovery using conventional methods. These complexes are destroyed first using Fenton process producing treated solutions with iron concentrations that may interfere copper recovery. The purpose of this study was to confirm the influence of trace amount of iron on copper removal, crystallization, and copper salt recovery using fluidized-bed homogeneous crystallization (FBHC) process. By varying several parameters like pH, initial copper and iron concentrations, and metal and precipitant inlet flowrate and molar ratio, the optimized conditions include pHe of 6.5–7.0, inlet flowrate of 15 mL min−1, and MR of 1.5. The effects of variable copper (3.15–9.44 mM) and iron concentrations (0.36–1.08 mM) were examined. The addition of iron had no significant impact on copper removal mainly due to its minimal presence in the solution, but a trend of decreasing, then increasing, copper crystallization ratio was observed at higher iron concentrations. The study recorded copper removal and crystallization rates from 88% to 96% and 75% to 95%, respectively, with varying iron concentrations. Characterization analyses of precipitates confirmed predominant presence of malachite and azurite. The FBHC's ability to obtain high purity spheroidal solid salts enables resource recovery and catalyzes strategies for circular economy practices.

Assessment of the suitability of adsorption water treatment as a concentration process for resource recovery and wastewater treatment

Electroplating plants dispose of the diluted plating solution (DPS) as plating wastewater due to its reduced plating efficiency. Solid waste produced by various industries is discarded in landfills, leading to the generation of landfill leachate (LL). Employing suitable wastewater treatments is crucial for either recovering valuable resources from wastewater or ensuring that its discharge aligns with wastewater discharge standards. In this study, we examined the feasibility of an adsorption water treatment (AWT) process for recovering valuable resources from DPS and efficiently treating LL. The AWT process using DPS and LL demonstrated that the influence of feed quality (composition and concentration) on water treatment capacity was insignificant, with a water recovery of up to 50 %. In addition, the AWT process demonstrated its ability to efficiently concentrate DPS without the need for pre-treatment, resulting in a notable 12.1 % increase in the plating efficiency of the DPS. This made it reusable for electroplating, and it was realized with a low specific energy consumption (SEC) of 1.63 kWh/m3 by utilizing waste heat in electroplating plants. Furthermore, the freshwater produced by the AWT process, including simple pre- and post-treatments, met 26 water quality parameters of the landfill leachate discharge standard.

Highly efficient ZnO/WO3 nanocomposites towards photocatalytic gold recovery from industrial cyanide-based gold plating wastewater

Discharging the gold-contained wastewater is an economic loss. In this work, a set of ZnO/WO3 was facile synthesized by hydrothermal method in order to recover gold from the industrial cyanide-based gold plating wastewater by photocatalytic process. Effect of ZnO contents coupled with WO3 was first explored. Then, effects of operating condition including initial pH of wastewater, type of hole scavenger, concentration of the best hole scavenger and photocatalyst dose were explored. A series of experimental results demonstrated that the ZnO/WO3 nanocomposite with 5 wt% ZnO (Z5.0/WO3) depicted the highest photocatalytic activity for gold recovery due to the synergetic effect of oxygen vacancies, a well-constructed ZnO/WO3 heterostructure and an appropriate band position alignment with respect to the redox potentials of [Au(CN)2]− and hole scavengers. Via this ZnO/WO3 nanocomposite, approximately 99.5% of gold ions was recovered within 5 h using light intensity of 3.57 mW/cm2, catalyst dose of 2.0 g/L, ethanol concentration of 20 vol% and initial pH of wastewater of 11.2. In addition, high stability and reusability were observed with the best nanocomposite even at the 5th reuse. This work provides the guidance and pave the way for designing the ZnO/WO3 nanocomposite for precious metal recovery from a real industrial wastewater.

Electrochemical Removal of Metal-Organic Complexes in Metal Plating Wastewater: A Comparative Study of Cu-EDTA and Ni-EDTA Removal Mechanisms.

Cu and Ni complexes with ethylenediaminetetraacetic acid (Cu/Ni-EDTA), which are commonly present in metal plating industry wastewaters, pose a serious threat to both the environment and human health due to their high toxicity and low biodegradability. In this study, the treatment of solutions containing either or both Cu-EDTA and Ni-EDTA using an electrochemical process is investigated under both oxidizing and reducing electrolysis conditions. Our results indicate that Cu-EDTA is decomplexed as a result of the cathodic reduction of Cu(II) with subsequent electrodeposition of Cu(0) at the cathode when the cathode potential is more negative than the reduction potential of Cu-EDTA to Cu(0). In contrast, the very negative reduction potential of Ni-EDTA to Ni(0) renders the direct reduction of EDTA-complexed Ni(II) at the cathode unimportant. The removal of Ni during the electrolysis process mainly occurs via anodic oxidation of EDTA in Ni-EDTA, with the resulting formation of low-molecular-weight organic acids and the release of Ni2+, which is subsequently deposited as Ni0 on the cathode. A kinetic model incorporating the key reactions occurring in the electrolysis process has been developed, which satisfactorily describes EDTA, Cu, Ni, and TOC removal. Overall, this study improves our understanding of the mechanism of removal of heavy metals from solution during the electrochemical advanced oxidation of metal plating wastewaters.

Ultra-high selective recovery of Cu2+ and Ni2+ by a combination of photocatalysis and adsorption from electroless plating wastewater

Ultra-high selective recovery of Cu2+ and Ni2+ by a combination of photocatalysis and adsorption from electroless plating wastewater

Rapid photocatalytic gold recovery from industrial cyanide-based gold plating wastewater via TiO2/WO3 nanocomposites: Role of mixed hole scavengers and operating conditions

A rapid photocatalytic gold recovery from the industrial cyanide-based gold plating wastewater was carried out via TiO2/WO3 nanocomposites synthesized by hydrothermal method. Effects of different weight ratios of TiO2 and WO3 in nanocomposites, types of hole scavenger (Na2S2O3, C2H5OH, Na2S2O3/C2H5OH), concentrations of Na2S2O3 (0–100 mM) and photocatalyst loading (1–4 g/L) were examined. The preliminary results demonstrated that the employed wet chemical process induced a well formation of TiO2/WO3 nanocomposites with better textural properties as well as a more negative band position than the pristine WO3. The presence of mixed hole scavengers of Na2S2O3 and C2H5OH played a crucial role on the photocatalytic gold recovery from the cyanide-based gold plating wastewater. A more stable form of gold cyanide ([Au(CN)2]-) was altered to a less stable form ([Au(S2O3)2]3-) by the addition of Na2S2O3. At the end, approximately 85.9 % and 98.2 % of gold were respectively recovered within 180 and 300 min via the T6/WO3 nanocomposite in the presence of 10 mM Na2S2O3 and 20 vol% C2H5OH at photocatalyst loading of 2 g/L and light intensity of 3.20 mW/cm2. The photocatalytic gold recovery was significantly improved via the 1st reused T6/WO3 nanocomposite, in which 99.9 % of gold was recovered within 180 min. The obtained results can pave the way for the design of novel TiO2/WO3 nanocomposites for gold recovery as well as the strategy of waste management for the practical operation.

Molecular mechanisms of pyrophosphate-mediated selective adsorption of Ni(II) by polyamine-grafted chitosan–wood flour composite from alkaline plating wastewater: EXAFS investigation and theoretical calculations

The efficient removal of complexed heavy metals (HMs) from alkaline electroless plating wastewater is still challenging. A polyamine-grafted chitosan–wood flour-based composite (ACS-AWF) was optimally synthesized. Its adsorption behavior toward Ni(II) in simulated pyrophosphate (PP, the main complextant)–Ni plating wastewater and underlying mechanisms were examined. PP considerably promoted Ni(II) adsorption by up to 108.1%, and the enhancement tolerated excess PP or other substances. Ni(II) adsorption by ACS-AWF was 1.38–∼10 times that of several commercial HM-favored resins in the same complexed system. According to the liquid solute species tracking, solid chemical characterizations (eg. synchrotron radiation X-ray adsorption spectroscopy), and theoretical calculations, it was found that Ni(II), primarily as NiP2O72−, could be captured by charge-assistant coordination with the surface polyamine. Then, the coadsorption of PP altered the interface properties via both electrostatic shielding and bridging effect, enhancing Ni(II)–amine coordination efficiency. A dinuclear multilayer coordination structure [-amine–Ni–PP–Ni–amine-] was proposed as the dominant Ni(II) binding mode in the presence of PP. Ni(II) and PP could be sequentially desorbed from ACS-AWF using gradient elution with ＞95.5% Ni(II) purity. ACS-AWF was then stably reused in five cycles (capacity loss ＜10%). These results may guide adsorbent design and application in HM purification and recycling from complexed wastewater.

Approaches to Enhancing Cathodic Nickel Recovery from Ni-EDTA Containing Synthetic Wastewaters

Ethylenediaminetetraacetic acid (EDTA) is widely employed as a chelating agent in the electroless nickel plating industry to form stable metal–organic complexes (e.g., Ni-EDTA). These metal–organic complexes cannot be removed from plating wastewaters by traditional treatments in a cost-effective way. While electrochemical advanced oxidation processes (EAOPs) have been utilized for the efficient degradation of Ni-EDTA at the anode, challenges remain in the simultaneous and effective recovery of nickel at the cathode. In this study, we investigate the efficacy of five cathode materials [i.e., carbon felt (CF), titanium plate, graphite plate (GP), copper plate, and stainless-steel plate] with respect to Ni recovery. The highest Ni removal efficiency of 81.6 ± 0.1% was achieved with the carbon felt cathode which was 30% higher than that of the titanium cathode (52.1 ± 1.4%) with the improvement in performance attributed to the higher rate of mass transport of Ni ions (CF: 4.3 ± 0.4 × 10–4 s–1 vs Ti: 1.8 ± 0.2 × 10–4 s–1) toward the nanowire structure of carbon felt and to the large surface area of the carbon felt cathode compared with the other cathodes. While the chemical composition of the deposits was independent of the cathodic material or structure, the morphology of deposition varied with the cathode material. The accumulated Ni on the carbon felt surface was successfully recovered either as a nickel salt solution by acid leaching or as high purity NiO by calcinating the Ni-loaded carbon felt cathode at over 800 °C. The performance of the regenerated carbon felt after acid leaching was comparable to that of the fresh cathode even after 10 cycles of use and regeneration via acid leaching with this result confirming the stability and reusability of the carbon felt material.