Remediation of arsenic contaminated groundwater by electrocoagulation: Process optimization using response surface methodology

Abstract

Elevated arsenic in groundwater is a serious health hazard and needs attention. In this study, electrocoagulation was investigated in an effort to find the optimum condition for samples having a mixture of As3+ and As5+. A two-level full factorial design was used to investigate the effects of three independent process variables on the response variable (arsenic removal efficiency), namely (i) pH (6.5–8.5), (ii) As (III) = (100–400) ppb, and (iii) treatment time (2–9) min. Three factors (As3+ concentration, As5+ concentration, and treatment time) were used to design centre composite design (CCD) experiments, and the effect of each variable on arsenic removal efficiency was studied using response surface methodology (RSM) with a fixed current density (CD) of 10 A/m2 and an initial pH of 7.4. Arsenic removal from the samples was confirmed by Raman spectroscopy, which showed the multiple peaks of iron and arsenic compounds in the sludge sample. Arsenic removal was also indicated by the amorphous structure of flocs of iron oxide/hydroxide, observed in scanning electron microscopy (SEM) images of sludge and evidenced from X-ray diffraction studies.