Kinetic and isotherm studies on adsorption of arsenic using silica based catalytic media

This study investigates the removal of arsenic (both As (III) and As (V)) from drinking water using a silica based catalytic media (DMI-65). In this study, BET, FTIR, XRD, SEM and XRF were used to characterize the adsorbent before and after contact with As (III) and As (V). Batch experiments were performed to evaluate the adsorption kinetics at different pH (5, 6, 7 and 8.5). The kinetic study showed that a contact time of 6 h was needed to reach equilibrium and the experimental data were best fitted to the pseudo second-order kinetic model for both As (III) and As (V). Several batch tests were conducted with different concentration of arsenic at different pH conditions (5, 6, 7 and 8.5). During the adsorption test, the maximum adsorption of As (III) occurred at pH 5, while As (V) adsorption reached its maximum at pH 8.5. The adsorption data showed a good fit to Langmuir isotherm models and the maximum adsorption capacity of the silica based catalytic media for As (III) and As (V) were estimated to be 0.318 mg/g and 0.237 mg/g respectively.