Experimental investigation on adsorption of U(VI) by chitosan-biochar composite

Chitosan-biochar (CTS-AC) composites were prepared by using chitosan (CTS) and biochar (AC) as raw materials. The effect of initial U(VI) concentration, reaction time, initial pH, reaction temperature and interference ion on the adsorption of U(VI) by CTS-AC was investigated, and the adsorption behavior of U(VI) by CTS-AC was characterized by FT-IR, XRD, SEM-EDS and specific surface area analysis(BET). The results show that the optimum conditions for the adsorption of U(VI) by CTS-AC are pH = 4, dosage of CTS-AC 0.8-1 g/L and adsorption time 240 min. Under these conditions, the maximum adsorption rate can reach 94.85%. The isothermal thermodynamic data of the adsorption of U(VI) by CTS-AC accord with the Langmuir model, and the adsorption kinetics is in accordance with the quasi-second-order kinetic model. The inhibiting effect of high concentration of Cu²⁺ on the adsorption of U(VI) by CTS-AC is obvious. The results of FT-IR, XRD and EDS show that adding CTS dose not change the original structure of AC, but the pore size and the binding sites increase. The adsorption mechanisms are coordination and ion exchange. (authors)