Preparation and Characterization of Two Modified Laterite Soils for Arsenic Removal in Aqueous Solutions: Efficiency and Kinetic Modelling

Abstract

Consumption of arsenic-contaminated water is the cause of major problems such as melanosis, hyperkeratosis and cancer. To mitigate this pollution, this study was carried out using analytical methods to prepare chemically treated laterite (TL) and chemically doped laterite with ferrihydrite (DL). The adsorbents were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluorescence (XRF) and the Brunauer Emmett Teller (BET) method. The specific surface area, bulk density and pH at zero charge point ( pHPZC) of TL and DL ranged from 81.306 to 40.099 m2/g, from 1.67 to 2.27 and from 5.41 to 8.02, respectively. The SiO2/(Fe2O3 + Al2O3) ratio was 0.31 for TL and 0.20 for LD, showing that the materials prepared were still classified as laterite adsorbents. Experimental results from batch experiments on the removal of arsenic species (As (III)) and arsenic (As (V)) using two adsorbents showed the strong influence of operating conditions such as pH, initial concentration, adsorbent dose and contact time. The isotherm modelling concluded that the removal of arsenic species was occurred by multilayer adsorption on the heterogenous surfaces of laterites. For the removal of As(V), the maximum adsorption capacity was 7.36 and 9.79 mg/g for TL and DL, respectively, while for the removal of As (III), the adsorption capacity for TL and DL was 5.17 and 7.89 mg/g, respectively. The kinetic study of the adsorption of As(V) or As(III) on modified laterites concluded that the process was described by the pseudo-second-order model, with a chemisorption process to be explored.