Evaluation of the adsorptive properties of locally available alumino-silicate clay in As(III) and As(V) remediation from groundwater

This study evaluates the adsorptive properties of locally available alumino-silicate clay in removal of As(III) and As(V) from groundwater. Physicochemical properties of the clay were characterized using x-ray diffraction (XRD), x-ray fluorescence (XRF), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) techniques. Batch adsorption experiments were conducted to evaluate the effectiveness of the alumino-silicate clay in the removal of As(III) and As(V) under various conditions of contact time, adsorbent dosage, initial adsorbate concentration and initial pH. The results showed that adsorption of As(III) by alumino-silicate clay is not affected by the change in pH while adsorption of As(V) was optimum at acidic pH and remained almost constant as pH increases to 12. Maximum As(III) and As(V) adsorption capacities were 2.65 and 2.9 mg/g, respectively at 0.7 g/100mL adsorbent dosage, initial adsorbate concentration of 5 mg/L and contact time of 60 min. The kinetics study showed that the data for As(III) fitted better to pseudo second-order while the adsorption data for As(V) fitted better to pseudo first-order suggesting that As(III) was through chemisorption while adsorption of As(V) was physiosoption. The adsorption isotherm data showed a better fit to Freundlich adsorption isotherm indicating that the surface of the clay is heterogeneous in nature. The presence of co-existing anions inhibits the adsorption of As(III) and As(V) by the clay. Th...
Source: Physics and Chemistry of the Earth, Parts ABC - Category: Science Source Type: research