A comparative study on Pb²⁺ removal efficiencies of fired clay soils of different particle size distributions

Abstract

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 S_3F, S_2F and S_1F 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.