Abstract

Adsorption of Cr(III) ions from aqueous solutions using a micaceous polymineral (MPM) from Kenya was studied using batch experiments as function of contact time, adsorbent dosage, Cr(III) concentration, pH and temperature. Chromium adsorption was found to be a fast process taking place in less than 20 min to reach equilibrium. Near complete removal of the metal was realized at Cr(III) concentrations of 200 mg/L, using 0.15 g/mladsorbent doses at pH range of 4 to 6 and 25 to 40°C. Equilibrium and kinetics analysis indicated that Cr(III) adsorption onto MPM progresses through an inner-sphere surface complexation of the hydrolysis products of Cr(III) with surface sites in the adsorbentmineral. The adsorption process could be described by the Lagergren pseudo-second order kinetics model and the adsorption equilibrium was found to conform to H–type according to Giles classification of adsorption isotherms. The adsorption data couldtherefore be validated by Langmuir model. The adsorption capacity of 7.9 mg/g showing that this low-cost material could be used for the scavenging Cr (III) from aqueous streams.

Key words: Chromium(III) adsorption, Giles classification of isotherms, Lagergren kinetics models, Langmuir isotherm, Micaceous adsorbent mineral.