Adsorption of UO²⁺₂ Ion onto Tripolyphosphate-crosslinked Magnetic Chitosan Resin

The tripolyphosphate-crosslinked magnetic chitosan resins (TPP-MCR) were prepared at pH＝3, 8 for obtaining resins with different cross-linking degrees. The effects of the pH, the adsorption time and the initial uranium concentration on UO²⁺₂ adsorption onto the TPP-MCR were investigated. The results show that the effects of pH on UO²⁺₂ adsorption differ significantly with the cross-linking degree of the TPP-MCR. The analysis of FTIR indicates that the phosphate groups of the TPP-MCR are the main active sites for UO²⁺₂ adsorption. The adsorption of UO²⁺₂ onto TPP-MCR is endothermic and spontaneous in nature. The adsorption kinetics follows the pseudo second order equation, evidencing chemical adsorption as the rate-limiting step. The adsorption equilibrium data can be described by Langmuir isotherms with the maximum adsorption capacity of 166.7 mg/g at 293 K. The TPP-MCR loaded with UO²⁺₂ can be desorbed by 0.1 mol/L HNO₃ 0.1 mol/L EDTA and reused for several cycles.