Sericite in the remediation of Cd(II)- and Mn(II)-contaminated waters: batch and column studies.

Sericite, a mica-based natural clay was employed in the remediation of waters contaminated with two important heavy metal toxic ions, viz. Cd(II) and Mn(II), under batch and column experimentation. The batch reactor studies were intended to study various physicochemical parameters, viz. effect of sorptive pH, concentration, contact time, and background electrolyte concentrations which helped to deduce the mechanism involved at the solid/solution interface. The percent uptake of Cd(II) and Mn(II) was increased with increasing of the sorptive pH, and almost 100 % of these cations were removed at pH 10. Equilibrium-state sorption data was modeled and fitted well to the Langmuir and Freundlich adsorption isotherms. The kinetic data followed the pseudo-first-order and pseudo-second-order kinetic models. Increasing the background electrolyte concentrations by 100 times caused significant decrease of the uptake of Cd(II) and Mn(II) ions, which inferred that these metal cations were less adsorbed specifically and predominantly attached with relatively weak electrostatic attraction onto the solid surface. Additionally, the fixed-bed column reactor operations were also performed to assess the suitability of sericite in the attenuation of Cd(II) and Mn(II) from aqueous solutions under dynamic conditions. The breakthrough data obtained were successfully utilized to fit into a nonlinear fitting of Thomas equation. The results showed that the naturally and abundantly available sericite could be a potential natural material in the remediation of aquatic environment contaminated with Cd(II) and Mn(II).