Photoreduction of U(VI) from Real Nuclear Wastewater by Sulfur Vacancies Engineered TAPP/CdS Heterojunction under Air without Sacrificial Agents

Photocatalytic technology has been proposed as an effective method for treating uranium-containing wastewater due to its high efficiency, low energy consumption, and environmental friendliness. Herein, a novel sulfur-vacancy-enhanced direct Z-scheme heterojunction photocatalyst was synthesized in situ via the combination of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPP) and cadmium sulfide (CdS) for the photoreduction removal of U(VI) from real uranium mine wastewater. Compared to pristine CdS and TAPP, the optimized TAPP0.01/CdS heterojunction has stronger visible-light absorption, photoreduction ability, and electrochemical performance. Under visible-light irradiation, TAPP0.01/CdS exhibited a superior photoreduction efficiency for U(VI), achieving an ultrahigh removal rate of 99.96% under air without sacrificial agents. Even for the treatment of real uranium mine wastewater under the same conditions, the removal rate for U(VI) remained at 94.41%. Meanwhile, TAPP0.01/CdS demonstrated high selectivity for U(VI) in the presence of multiple cations, maintaining a removal rate of 81.96% after five consecutive cycles. The reduced U(IV) was deposited on the CdS surface in the form of UO2.34. The e– and ·O2– free radicals were the determining factors in the U(VI) photoreduction process. The design of sulfur vacancies engineered direct Z-scheme heterojunction in this work provides a feasible strategy for the efficient recovery of uranium from nuclear wastewater.