Design and implementation of control system for electroplating wastewater treatment by photovoltaic energy sinusoidal alternating current coagulation technology

Abstract

A novel photovoltaic energy-sinusoidal alternating current coagulation (PE-SACC) system was proposed for the removal of heavy metal ions (HMs) in electroplating wastewater. A response surface methodology was used to study the combined effect of two factors on removal efficiency (Re) and energy consumption (EEC), and the optimal process parameters were obtained. The morphology, surface element content, crystal structure, and chemical composition of the flocs generated during the electrocoagulation (EC) process were characterized using SEM, EDS, XRD, FTIR, and XPS techniques. The intra-particle diffusion model was used to describe the adsorption behavior of HMs (Cu2+, Zn2+ and Ni2+) by flocs. Finally, the removal mechanism of HMs by SACC technology and its application in actual wastewater treatment were discussed in detail. The results revealed that when c0(Ni2+) = c0(Zn2+) = c0(Cu2+) = 50 mg·dm−3, cCl− = 100 mg·dm−3, pH0 = 10, j = 1.3 A·m−2, t = 85 min, the Re(Cu2+), Re(Zn2+) and Re(Ni2+) were 99.3%, 99.1%, and 98.4%, respectively, and the EEC was 0.105 kWh·m−3. Compared with the traditional direct current coagulation (DCC), EEC, electrode consumption, and sludge production in SACC mode were reduced by 37.1%, 62.2%, and 66.6%, respectively. The PE-SACC system achieved ultra-low cost treatment of heavy metal electroplating wastewater. The adsorption process included surface adsorption, pore adsorption, and adsorption equilibrium. The mechanisms for the removal of HMs included cathode reduction, alkaline precipitation, and adsorption. In the actual wastewater treatment process, the removal efficiency of HMs could still be maintained above 99%, and the effluent met the national discharge standard (GB 31574–2015). This study presented an economically and environmentally sustainable approach for the evolution and industrial utilization of novel electrocoagulation technologies.