Photovoltaic electrocoagulation process for remediation of chromium plating wastewaters

Abstract

The proposed photovoltaic electrocoagulation (PV-EC) process combines the autonomous and environmentally friendly photovoltaic (PV) solar energy with the capability of iron electrocoagulation (EC) to effectively reduce both trivalent and hexavalent chromium ions from electroplating effluents. The PV array can be connected directly to the EC reactor without batteries increasing, in this way, the system sustainability and eliminating the environmental threat of improper battery disposal. The PV-EC system is made versatile according to the instantaneous solar irradiation by adjusting the wastewater flow rate to the current intensity supplied by the PV array. The experiments were conducted in Kavala Institute of Technology (latitude 40° 55′, longitude 24° 22′, and altitude 138 m above the sea level). All operating parameters affecting the efficiency of the proposed process, such as wastewater conductivity, pH, flow rate, current density, electroprocessing time, and solar irradiance, were studied and optimal conditions were investigated. The experimental results showed that by applying a current density of 20 mA cm2, the chromium concentration in the treated electroplating wastewater was effectively reduced from its initial value of 96 mg L−1 to less than the permissible limit amounting to a removal percentage of over 99%. The corresponding electrical energy consumption was 8.4 kWh per m3 of treated wastewater. The proposed process is appropriate for removal of chromium from industrial effluents and especially for small applications in remote and isolated locations with lack of electric grid.