TREATMENT OF ELECTROPLATING EFFLUENT EMPLOYING MEMBRANE AND ELECTROCHEMICAL PROCESSES

Abstract

With increasing population and urbanization, the fast-moving lifestyle needs more vehicles and electronic gadgets in our daily routine. More industries have been set up to fulfil this demand and require plenty of water. The industries such as electroplating, automobile, electronic semiconductor etc., generate a considerable amount of effluents. These effluents contain hazardous heavy metals, which leads to potential risks to the surrounding environment. The life form of the terrestrial and aquatic ecosystem is severely affected by heavy metals; finally, all the way through the food chain creates a health risk to humans residing in the affected area. To regulate these effluents' quality at the standard's permissible limits to release into nearby water bodies. Various measures and practices have been employed, like chemical precipitation, adsorption, coagulation-flocculation, ion exchange etc. The comprehensive determination of the study is to assess the electrocoagulation (EC) and nanofiltration (NF) processes for heavy metals removal in electroplating industry effluent and further proceed with a hybrid approach with EC-NF and EC-CDI (Capacity Deionisation) systems to reach the permissible limit suggested by govt regulatory body for discharge in the natural water bodies. Highly concentrated metal sludge presents a viable option for recovering metals from the waste effluent. The present study efficiently removes heavy metals from the effluent by deploying a combined EC-NF and EC-CDI hybrid approach for water reuse from the electroplating wastewater with environmental resilience. The suggested hybrid system also minimized the drawbacks of the NF and EC process for heavy metals removal, as indicated in the previous and present studies. The preliminary research aimed to improve the process for removing copper, nickel, and zinc from an aqueous solution through nanofiltration (NF) and electrocoagulation (EC), using response surface methodology (RSM). The experiment design was based on central composite design (CCD). The variables analysed were feed concentration, temperature, pH, and pressure for NF and time, solution pH, feed concentration, and current for EC. The results were analysed statistically through analysis of variance (ANOVA) in the RSM models. For the NF membrane, the rejection of Zn, Ni, and Cu was observed as 98.64%, 90.54%, and 99.79% respectively; while the removal of these through the EC process was observed as 99.81%, 99.99%, and 99.98%, respectively with synthetic aqueous solution. The study results suggest an advantage of using NF and EC processes compared to conventional precipitation and adsorption methods. Additionally, the EC process was found to be more efficient in removing the metals compared to NF. After a preliminary study, the electroplating effluent was treated using nanofiltration (NF) and electrocoagulation (EC) processes simultaneously. Response surface methodology (RSM) based central composite design (CCD) was employed to identify the parametric effects of different input factors to improve the treatment process of electroplating (EP) effluent conditions. The operating parameters for NF were pH, temperature, and pressure, and for EC, they were current, time, and pH. Both techniques have shown a significantly higher removal efficiency of metal ions. At optimum conditions, NF process removes 98.09, 99.39, 99.37, 94.82, and 91.58 percentage of Cr, Cu, Fe, Mn, Ni, and Zn, respectively. Similarly, in EC process, the removal efficiency of 96.34, 99.99, 96, 98.16, and 98.09 percentage of Cr, Cu, Mn, Ni and Zn, respectively, is observed. Even so, according to the standard recommended effluent discharge parameters, the Cr cannot be mitigated individually. Following EC treatment, the NF and EC processes were coup led to achieve the recommended parameter for Cr effluent discharge permissible limits. According to the findings, hybrid strategies effectively deal with electroplating effluent, and both methods combined overcome each technique's shortcomings. The present study's initial experimentations were conducted to explore the affinity preference of Cr and Fe to activate carbon and graphene electrodes of Capacitive Deionization (CDI) in EC-treated effluent. Results show the removal % through electro-sorption is higher for Fe than for the Cr ions in the EC-treated effluent. The removal efficiency of the CDI unit at optimum conditions reaches 10.05 and 22.48 % for Cr and Fe, respectively. The conditions for optimization are as follows, voltage 1.3(V), Flow rate 400 (ml/hr) and time 90(min.). This experimental study provides the fundamental aspects of metal ions removal from electroplating industrial effluent. The results further can be beneficial for an in-depth and detailed study CDI system for metal ions removal.