Synergistic removal of U(VI) from aqueous solution by TAC material: Adsorption behavior and mechanism

The adsorption and recovery of uranium from wastewater is of positive significance to the development of nuclear industry and environmental remediation. The ternary polymer (PZS-co-TA) was prepared from hexachlorocyclotriphosphazene (HCCP), 4,4-sulfonyldiphenol (BPS) and tannic acid (TA) under ultrasonic. TAC was then obtained after carbonization under high temperature from PZS-co-TA. The structure and performance of TAC were analyzed using SEM, EDS, FT-IR, XRD, Raman, BET and TG. The adsorption capacity of TAC for uranium under different static adsorption conditions was investigated. The adsorption process was more consistent with pseudo-second-order model. The maximum adsorption capacity calculated by non-linear Langmuir model was 492.5 mg/g at pH 5.5. The thermodynamic values suggested that the adsorption process was spontaneous and endothermic. Moreover, after five cycles of adsorption-desorption tests, TAC remained effective at adsorbing uranium, implying the introducing of TA to the precursor (PZS-co-TA) could enhance the adsorption capacity for uranium.