Removal of Arsenic from Simulated Groundwater using Calcined Shale as the Adsorbent

Well water intended for human consumption in the Akouédo area (Ivory Coast) contained arsenic at a concentration average above 0.01 mg/L, WHO guideline value. The shale was used as an adsorbent for the removal of arsenic from these waters. This shale was collected in Lomo Nord in Ivory Coast, washed then dried at a temperature of 60°C and finally calcined in an oven at several temperatures: 200°C, 300°C, 400°C, 500°C, 600°C and 700°C. X-ray diffraction, Fourier transform infrared spectroscopy (FTIR) and thermal analysis (TGA-DSC) were used to characterize the fraction of uncalcined and calcined shale powder. Batch mode tests were performed with water containing arsenic in order to study the influence of contact time, initial concentration and pH on the adsorption of arsenic on calcined shale. The results showed that shale calcined at 300°C could remove 99.41% of arsenic in water. The treated water meets the World Health Organization (WHO) standard for drinking water. Regarding the kinetic data, 0.034 mg/g of arsenic was adsorbed on the calcined shale within 7 hours. At pH 8, the maximum reduction rate was estimated up to 96%. The pseudo-second order model is the most appropriate of all the models applied to describe the kinetic data. This study shows that slate shale calcined at 300°C could be used as a low cost adsorbent to remove arsenic from Akouédo well water for consumption.