Performance evaluation of modified calcined bauxite in the sorptive removal of arsenic(III) from aqueous environment

This research was aimed at evaluating the effectiveness of the adsorbent, modified calcined bauxite (MCB), in removing As(III) from aqueous environment by completely mixed batch reactor (CMBR) and continuous flow fixed bed studies. It was observed that an adsorbent dose of 5 g l−1 could effectively remove 99.2% and 93.4% of As(III), from initial concentrations of 1 and 2 mg l−1, respectively. The sorption kinetics was found to follow pseudo-second-order model. Freundlich isotherm model was well fitted to the experimental equilibrium data rendering a maximum adsorption capacity of 1.362 mg g−1. The sorption process was found unaffected by temperature variations. The removal of As(III) was observed almost consistent over a pH range of 2–8, producing effluent within pH range of 6–7.5. It appears that the mechanism of arsenic removal is dependent on pH, surface charge of the adsorbent and nature of the As(III) speciation. The fixed bed study performed in a 20 mm diameter column at a feed flow rate of 8 ml min−1, demonstrated that an adsorbent bed depth of 10 cm could effectively treat 428 bed volumes of As(III) spiked influent water with 1 mg l−1 concentration, before the attainment of breakthrough. Logit method was used to evaluate the column parameters, adsorption rate constant and adsorption capacity co-efficient.