[Adsorption mechanism of chromium cation by floc-type biosorbent ZL 5-2]

Biosorption of Cr(VI) by the novel biosorbent ZL5-2 produced by Agrobacterium sp. was studied and infrared spectra of native, absorbing and desorbing ZL 5-2 were compared. The initial pH was important for biosorption. The optimum effect on Cr(VI) biosorption was acquired within initial pH 0.5 to approximately 1.5, then with the pH increasing, the effect on Cr6+ biosorption was reduced. The biosorption for Cr(VI) was a quick process,only within 10 min 65.4% Cr(VI) is biosorbed, and the biosorption rate was over 90% after 60 min, then all the Cr(VI) was biosorbed after 80 min. The biosorption were fitted with Langmuir and Freundlich isotherm adsorption equations. The absorbed Cr(VI) could be recovered by desorption and the desorption rate reached 13.696% to approximately 67.9%. Progress of biosorption was reversible adsorption and irreversible adsorption simultaneously through infrared spectra analysis, however the reversible adsorption was more important in the biosorption and the adsorption belongs to physics adsorption.