Carbon attrition during continuous electrolysis in carbon bed based three-phase three-dimensional electrode reactor: Treatment of recalcitrant chemical industry wastewater

Abstract

The performance of a carbon bed based three-dimensional electrode reactor (TDR) in terms of chemical oxygen demand (COD) removal from recalcitrant chemical industry wastewater was assessed. The pH and temperature changes in the TDR during electrolysis were correlated with COD removal efficiency. The carbon weight loss and particle size reduction due to erosion of carbon particles during electrolysis was also examined. Two cases of experiments were performed; ‘case I’ employed a high surface area Indcarb-60 GAC, whereas a low surface area carbon (GAC-10) was used for ‘case II’. The other experimental variables are, initial COD concentration, hydraulic retention time (HRT) and the duration of electrolysis. The experimental results showed that TDR could remove COD efficiently (49±7%). The apparent Faradic efficiency and specific electrical energy consumption were estimated to be 3.42% and 6.59kWhkg−1 COD for case I and 0.78% and 28.65kWhkg−1 COD for case II. Use of high surface area carbon in TDR is inferred to be beneficial. However, the GAC particles in TDR were found to undergo slow attrition during electrolysis. It is inferred that carbon attrition may prove to be a major setback for scale up attempts as it can lead to gradual loss in liquid holding capacity of carbon bed due to stratification and filling of voids in the carbon bed with carbon fine dust.