Removal of arsenic(III) from groundwater using low-cost industrial by-products - Blast furnace slag

Abstract

Blast furnace slag (BFS), a steel industrial by-product, was tested for the removal of As(III), which is a highly toxic, mobile and predominant species in anoxic groundwater. Batch adsorption experiments were performed to determine the feasibility of BFS as an adsorbent for removing As(III) from groundwater as As(III) concentration and the pH of water were varied. The maximum As(III) adsorption capacity by BFS was 1.40 mg As(III)/g of BFS at 1 mg/L As(III) initial concentration, at 25 degrees C, which was calculated using the Langmuir isotherm. The homogeneous surface diffusion model (HSDM) was successfully applied to predict the sorptive removal of As(III) onto the BFS. Kinetic studies indicated that the film diffusion as well as surface diffusion of As in the BFS was involved. It was found that the film diffusion coefficient (k(f)) was 5.27 x 10(-5) to 4.06 x 10(-6) m/s and surface diffusion coefficient (D-s) was 2.31 X 10(-14) to 7.13 X 10(-14) m(2)/S for the initial As(III) concentrations of 0.1 to 100 mg/L. Oxidation of As(III) to As(V) and its adsorption/precipitation onto BFS is involved during the As(III) removal mechanism. It was also found that H4SiO40, PO43-, NO3-, SO42- and HCO3- are potential interferences in the As(III) adsorption reaction. Results suggest that 99.9% As(III) at 1 mg/L can be removed by 10 g/L BFS, which can be used as a permeable reactive barrier (PRB) material to remove As(III) from groundwater. Details of As(III) adsorption and coprecipitation systems and interferences of As(III) molecular interactions were also studied.