Removal of chromium from tannery industry wastewater using iron-based electrocoagulation process: experimental; kinetics; isotherm and economical studies

Abstract

Chromium is a hazardous compound from industrial processes, known for its toxicity, mutagenicity, teratogenicity, and carcinogenicity. Chemical methods are efficient but cost-effective alternatives with reduced sludge are sought. Electro-coagulation, utilizing low-cost iron plate electrodes, was explored for factual tannery wastewater treatment in this manuscript. Operating parameters such as initial chromium concentration, voltage, electrode number, operating time, agitation speed and current density has been studied to evaluate the treatment effeciency. Under optimal conditions (15 V, 0.4 mA/cm2, 200 rpm, 330 ppm chromium, 8 iron electrodes with a total surface area of 0.1188 m2, 3 h), chromium elimination was 98.76%. Iron anode consumption, power use, and operating cost were 0.99 gm/L, 0.0143 kW-h/L, and 160 EGP/kg of chromium eliminated, respectively. Kinetics studies were pursued first-order reaction (97.99% correlation), and Langmuir isotherms exhibited strong conformity (Langmuir R2: 99.99%). A predictive correlation for chromium elimination (R2: 97.97%) was developed via statistical regression. At HARBY TANNERY factory in Egypt, industrial sewage treatment achieved a final chromium disposal rate of 98.8% under optimized conditions.