Reclamation of Cr(VI) rich water and wastewater by wollastonite

Abstract

Chromium exists in two forms mainly Cr(III) and Cr(VI) and out of the two forms the later one is highly toxic and is documented as high priority pollutant. It has attracted the attention of the scientific workers worldwide. The present work was addressed to the use of clay mineral, wollastonite in order to provide an economically viable treatment of Cr(VI) containing aqueous solutions and industrial effluents. The removal of chromium is found to be concentration dependent. The removal increased from 47.4 to 69.5% by decreasing the concentration from 2.0 × 10-4 to 0.5 × 10-4 M at pH 2.5, 0.01 M NaClO4 ionic strength, 100 μm adsorbent particle diameter and 30 °C temperature. Rate of uptake of Cr(VI) was found to be 3.0 × 10-2 min-1 under optimum conditions and the process is governed by first order kinetic equation. The process of Cr(VI) removal from aqueous solutions and wastewater involves intraparticle diffusion and the coefficient of intraparticle diffusion, D, was found to be 3.5 × 10-4 cm2 s-1 under favourable conditions. Thermodynamic parameters for the process of removal have also been calculated to understand the process better. © 2006 Elsevier B.V. All rights reserved.