Evaluation of Adsorption Potential of Reed Bed Substrates for Chromium(III) Removal from Tannery Effluent: A Batch Study

The adsorption capacity of riverbed sand, sawdust, vermiculite and soil for Cr(III) ions from tannery effluent has been investigated in detail in order to evaluate their possible application as filter material in reed bed treatment system. The adsorption isotherm was determined along with the effect of contact time, initial Cr concentration and pH on the efficiency of Cr removal. It was concluded that the maximum adsorption of Cr (> 90 per cent) was achieved by vermiculite and soil within 24 h. The equilibrium isotherm data for vermiculite was found to follow the Freundlich and Langmuir equations and a separation factor was used to judge the favourable adsorption. Vermiculite exhibited a higher adsorption capacity (Xm =100 mg g(-1)), followed by sand, sawdust and soil (Xm=20 mg g(-1)). The Cr retention capacity of adsorbents at different pH was calculated on the basis of the distribution coefficient (Kd) and the highest Kd value was achieved by vermiculite (61.1) at pH 5.0.