Modeling and fixed bed column adsorption of As(III) on laterite soil

The performance of a fixed bed column for the removal of As(III) from aquatic environment was studied. Laterite soil was used as the adsorbent material. The column with 2-cm diameter, different bed heights such as 10 cm, 20 cm and 30 cm could treat 1.3 l, 7.9 l and 14.88 l, respectively, of As(III) bearing (conc. 0.5 mg/l) water at a flow rate of 7.75 ml/min. Bohart and Adams sorption model was employed for the determination of different parameters like height of exchange zone, adsorption rate, time required for exchange zone to move, and the adsorption capacity. Effect of flow rate and initial concentration was studied. The adsorption capacity and the adsorption rate constant of the adsorbent laterite soil for 0.5 mg/l of As(III) were found to be 108.02 mg/l and 0.6523 l/(mg h), respectively. The column was designed by the bed depth service time (BDST) model. Column design parameters were also tested with varying flow rate and initial As(III) concentration of the influent. Freundlich isotherm model was used to compare the theoretical and experimental breakthrough profile in the dynamic process. The bed saturation obtained was 53–71%. Regeneration of the exhausted column was possible with 1 M NaOH.