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

Abstract

Laterite soil, an abundant locally available natural adsorbent, has been evaluated for As(V) removal from aqueous solutions in column mode operation. The column studies were conducted using columns of 10, 20, 30 cm bed depth with 2 cm internal diameter. Initial As(V) concentration was 0.5 mg/L and flow rate was 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 of the laterite soil for 0.5 mg/L of As(V) was found to be 62.32 mg/L, and the adsorption rate constant was 1.0911 L/mg h for the minimum bed depth of 8.47 cm. The column was designed by the BDST model. Freundlich isotherm model was used to compare the theoretical and experimental breakthrough profile in the dynamic process. The bed saturation obtained was 36–80%. Regeneration of the exhausted column was possible with 1M NaOH.

Keywords:

• As(V) adsorption
• laterite soil
• column studies
• breakthrough curve
• BDST model
• desorption studies

Acknowledgements

The authors are thankful to Prof. B. Biswanathan, IIT, Madras, India, for his kind help in BET analysis and for helpful discussions, and to the Department of Science and Technology, New Delhi for financial support.