Efficient Separation of Uranium(VI) by CaCO3-Doped Chitosan with PO4 3- Modification: Adsorption Behaviors and Mechanism Study

The application of chitosan-based materials for the separation of uranium from wastewater was limited due to the lack of active sites. In this work, a chitosan-based composite (CaCO3@aCS/PA) was effectively created by modifying chitosan with CaCO3 and phytic acid to enhance the adsorption performance of chitosan materials. CaCO3@aCS/PA showed no significant changes and no Ca2+ was detected in the solution after stirring for 10 h in a solution with pH > 3, indicating good stability of CaCO3@aCS/PA, which was beneficial for use in adsorption. Moreover, the adsorption capacity and adsorption percentage of CaCO3@aCS/PA for uranium reached 842.0 mg/g (298 K, pH = 4) and 95.4% (C-0 = 10 mg/L, pH = 4) and the adsorption equilibrium time was significantly shortened, indicating that the modification with CaCO3 and phytic acid enhanced the adsorption ability of chitosan for uranium, which was related to the synergistic effect of various active sites (CO32-, PO43-, -OH, and -NH2) on CaCO3@aCS/PA for uranium adsorption.