Chromium Removal from Real Tannery Wastewater by Electrocoagulation Assisted with Prickly Pear (Opuntia spp.) Cladode Powder

Abstract

This study investigated the performance of electrocoagulation (EC) coupled with prickly pear cladode powder (PPP) for removing chromium from real chrome-tanning wastewater. Experiments were performed in a batch stirred electrocoagulation cell equipped with two aluminum-based electrodes. The effects of treatment time, current density, initial pH and PPP dosage were examined, with the experiments performed in triplicate using the same wastewater sample. The wastewater initially contained 3.60 g L^-1 of chromium (3,600 mg L^-1). Optimum conditions were found to be an initial pH of 7.02, a PPP dosage of 20.00 g and a current density of 200 A m^-2. Under these conditions, a treatment time of approximately 200 minutes reduced the chromium concentration to 2.00 mg L^-1, corresponding to a removal efficiency of around 99.90 %. Compared with EC alone, the EC/PPP process improved chromium removal performance while reducing energy consumption. The specific energy consumption was 3.00 kWh m^-3 for EC and 1.50 kWh m^-3 for EC/PPP, representing a 50.00 % reduction in energy usage. These results demonstrate that adding prickly pear cladode powder enhances chromium removal and substantially decreases the electrocoagulation process's energy requirements, highlighting the EC/PPP process's potential for treating highly concentrated chrome-tanning wastewater.