Biosorption of hexavalent chromium by chemically modified seaweed, Cystoseira indica

The sorption of hexavalent chromium by marine brown algae Cystoseira indica, which was chemically-modified by cross-linking with epichlorohydrin (CB1, CB2), or oxidized by potassium permanganate (CB3), or only washed by distilled water (RB) was studied with variation in the parameters of contact time, pH, initial metal ion concentration and solid/liquid ratio. They were used for equilibrium sorption uptake studies with Cr(VI). The results indicate that biosorption equilibriums were rapidly established in about 2 h. The Cr(VI) adsorption was strictly pH dependent, and maximum removal of Cr(VI) on biosorbents were observed at pH 3.0. The maximum Chromium uptakes were 22.7, 24.2, 20.1 and 17.8 mg g−1, respectively, for CB1, CB2, CB3 and RB. The order of maximum Cr(VI) uptakes for various biomasses was CB2 > CB1 > CB3 > RB. A comparison of different isotherm models revealed that the Dubinin–Radushkevich (D–R) isotherm model fitted the experimental data best based on R^2, qmax and standard error (S.E.) values and the mean energy of the sorption values indicated that biosorption of Cr(VI) by C. indica may be an ion exchange reaction.