A comparative study on Pb2+ removal efficiencies of fired clay soils of different particle size distributions
Batch adsorption studies were carried out to evaluate the Pb2+ adsorption capacities of three different fired clay soils with different particle size distributions. Adsorption efficiency was observed to increase with an increase in clay content. Adsorption efficiencies of the fired clay soils were also influenced by the firing temperature, the solution’s acidity, initial Pb2+ concentration, shaking time and adsorbent dose. Adsorption of Pb2+ by the clay soils was observed to increase linearly from pH 1 to 5 and then remained nearly constant at higher pH values. The adsorption of Pb2+ was observed to increase sharply with Pb2+ for the lower initial concentrations (5 to 10 mg/L), while a modest increase in Pb2+ adsorption was found from 10 to about 50 mg/L, a concentration at which maximum removal was attained. The Langmuir and Freundlich adsorption models were applied to the adsorption data and the Langmuir model represented the adsorption process better than the Freundlich model, with correlation coefficients (R2) ranging from 0.97 to 0.99. The adsorption capacities (qm) calculated from Langmuir for the adsorption of Pb2+ by S3F, S2F and S1F were found to be 17.3, 15.9, and 11.2 mg/g, respectively.
Key words: Adsorption, fired clay soils, isotherm, adsorption kinetics, sand, silt, particle size.