ABSTRACT
The mutagenic and carcinogenic effects of Cr(VI) on biological systems are well known (Güell et al., 2008). It gives serious damage to lungs, kidney, liver and the gastric system (Al-Ohtman et al., 2012; Sahu et al., 2008). Therefore, the limit for discharge of Cr(VI) into the surface waters is defined as 0.1 mg L−1 (Ozcan et al., 2010). Contrary to Cr(VI) species or chromates, Cr(III) is less toxic and very insoluble at neutral to alkaline pH. Therefore, chemical precipitation is the most often preferred method for the treatment of wastewaters with a high Cr(VI) concentration. During the process, Cr(VI) is reduced to Cr(III) first, followed by the adjustment of pH which is needed to form insoluble Cr(OH)3 as a precipitate (Lin and Huang, 2008; SenGupta, 2002). However, for the removal of Cr(VI) at trace levels, chemical precipitation is not very effective due to the low reduction efficiency of Cr(VI) to Cr(III) (Edwards, 1995; Sag˘ and Kutsal, 1995).
