Investigating the potential of arsenic removal from water by ferric ions using response surface methodology

Abstract

Contamination of surface and groundwater water reservoirs with arsenic (As) oxyanions has raised global concerns for humans as well as ecosystem. Therefore, there is an urgent need to improve existing treatment systems with the capability of decreasing concentration of toxic As species to a safe level. In this regard, the optimization of process parameters of conventional C/F/S treatment systems may provide feasible solutions to ensure public health safety. Herein, the removal response of As oxyanions were investigated using ferric chloride (FC) in context of single, binary, and ternary systems. Moreover, response surface methodology (RSM) and Fourier transform infrared spectroscopic (FTIR) analysis was conducted to identify the optimum process conditions. The results of single system with varying pH conditions indicated that the ideal pH range for the removal of As(III, V) using FC was (8-9) and (5-6), respectively. Furthermore, binary system showed higher removal on As(III, V) in case of humic acid when compared with phosphate ions during chemical coagulation process, probably because of the existence of more reactive functional groups. The RSM study indicated that the solution containing higher concentration of phosphate and humic acid needs a higher concentration of FC to achieve higher As(III, V) removal in ternary environment. The As removal response model was successfully developed and validated in the presence of humic acid and phosphate. Moreover, RSM was found useful in determining optimum As removal conditions by FC coagulation. In binary and ternary systems, the FTIR analysis revealed the combined impact of reduction, complexation, and charge neutralization as dominant As removal mechanism from complex water environment. Overall, the current study's findings will be useful in providing new insights on the removal, mobility, and fate of toxic As oxyanions in multicomponent environment.