Chromium adsorption and Cr(VI) reduction to trivalent chromium in aqueous solutions by soya cake

Chromium as Cr(VI) is a industrially produced pollutant. Hexavalent chromium can be reduced to the trivalent state using various reductive agents or it can be removed from solution by surface-active adsorbents. In this study, both of these methods were evaluated using soya cake. A high efficiency for reduction of Cr(VI) to trivalent chromium was observed at pH < 1. Increasing the temperature, also increased the yield. Experimentally, the optimum time and soya cake mass were 5 It and 0.7 g, respectively. In the second treatment method, a high efficiency for adsorption of chromium was also observed at pH < 1. The favorable temperature for adsorption was found to be 20 degreesC. Experimentally, the best time was 1h and with increasing soya cake mass up to 30g, the adsorption efficiency was increased. Dissolution of LiCl in the experimental solutions, increased the efficiency of adsorption, however, this effect was not observed in the case of KCl. Langmuir isotherm constants, Q and b, for ground soybeans, were found to be 2.8 x 10(-4) mg/mg and 0.623, respectively. Freundlich isotherm constants, K-f and n, were found to be 1.4 x 10(-4) and 4.99, respectively, (C) 2002 Elsevier Science B.V. All rights reserved.