Passivating Effect of Wastewater on Iron Electrocoagulation Treatment Efficiency

Abstract

Iron electrocoagulation (Fe-EC) is a cost-effective water/wastewater treatment method that has demonstrated effectiveness in the remediation of many forms of polluted water. This technique utilizes a Fe sacrificial anode to produce coagulant in-situ, hence offering several advantages over conventional iron-based chemical coagulation procedures. However, the occurrence of solid precipitation on the electrodes during operation results in a passivating effect that has been reported to reduce treatment effectiveness and increase energy consumption. The objective of this investigation was to evaluate the passivation effect of oily wastewater (OW) and chicken slaughterhouse wastewater (CSW) on Fe anode, specifically in relation to the Faradaic efficiency (FE), using initial pH (4, 7, and 9) and applied current intensity (0.1, 0.2, and 0.4 A) as variables. The study also sought to assess the potential passivating impact of the wastewaters on the efficacy of Fe-EC in the removal of chemical oxygen demand (COD) from the wastewaters. The results revealed that the mean passivating effect was 13.4%, 7.67%, and 22.7% for OW and 22.3%, 17.13%, and 12.3% for CSW at 0.1 A, 0.2 A, and 0.4 A, respectively. FE ranged from 0.77 to 0.92 and 0.78 to 0.88 for OW and CSW, respectively. The initial pH of the wastewater was observed to significantly influence the FE at the given applied currents. While the mean COD removal from both wastewaters was greater than 83%, there was a lack of correlation between the FE and COD removal. This finding suggests that the mass of the coagulant is one of several potential COD removal factors. Further research includes electroanalytical studies of Fe corrosion in various wastewaters.