Mesoporous sulfur-doped g-C3N4@attapulgite composite as an advanced photocatalyst for efficiently uranium(VI) recovery from aqueous solutions

Photocatalytic reduction of uranium(VI) via g-C 3 N 4 is a promising and efficient method for the recovery of radioactive uranium contamination from wastewater. In this work, the mesoporous sulfur-doped g-C 3 N 4 @attapulgite composite was first synthesized via a two-step hydrothermal-roasting method with (NH 4 ) 2 S 2 O 8 as the sulfur source and attapulgite as the supporter, respectively. As expected, the recovery efficiency of uranium(VI) using S-doped g-C 3 N 4 was 1.80 times higher than that of g-C 3 N 4 . Additionally, compared to S-doped g-C 3 N 4 , the mesoporous S-doped g-C 3 N 4 @attapulgite composite exhibited further improved photocatalytic efficiency and stability. The experimental results further showed the uranium(VI) was quickly eliminated within 20 min by mesoporous S-doped g-C 3 N 4 @attapulgite, and the recovery rate of which remained at 88.4 % even after seven cycles. According to the XPS results and trapping experiments, the excellent uranium(VI) recovery and stability can be attributed to the adsorption capacity of attapulgite and the e - reduction from sulfur doping g-C 3 N 4 , respectively. This result contributes to understanding the enhanced photocatalytic reduction mechanism of uranium(VI) and to achieving the high-efficiency recovery of uranium from wastewater using the mesoporous S-doped g-C 3 N 4 @attapulgite composite.