茶渣生物炭/g-C_(3)N_(4)复合材料可见光催化还原水中U(Ⅵ)的特性

Visible light photocatalytic reduction of U(Ⅵ)in water by tea waste biochar/g-C_(3)N_(4) composites

以茶渣为原料,三聚氰胺为前驱体,采用高温热聚合法制得茶渣生物炭/石墨相氮化碳(TBC/g-C_(3)N_(4))复合材料。采用SEM,XRD,XPS,UV-Vis DRS,PL和EIS对光催化剂的形貌、结构及光电特性进行表征,研究TBC/g-C_(3)N_(4)复合材料在可见光照射下光催化还原U(Ⅵ)的性能,并探讨TBC/g-C_(3)N_(4)复合材料光催化还原U(Ⅵ)的机理。结果表明:当TBC的质量分数为5%,初始pH值为4,催化剂用量为1 g/L时,可见光照射30 min后TBC/g-C_(3)N_(4)复合材料对U(Ⅵ)的去除率可达99.64%,远高于g-C_(3)N_(4)(58.8%)。TBC/g-C_(3)N_(4)复合材料循环5次后对U(Ⅵ)的去除率仍在80%以上,表现出良好的稳定性。TBC的加入使得g-C_(3)N_(4)禁带宽度从2.63 eV减少为2.14 eV,拓宽可见光吸收范围,促进光生电荷的分离,降低光生电子-空穴对的复合率,从而提升TBC/g-C_(3)N_(4)复合材料的光催化活性。

Tea waste biochar/graphitic carbon nitride(TBC/g-C_(3)N_(4))composites were prepared by high temperature thermal polymerization with tea waste as raw material and melamine as precursor.The morphology,structure and photoelectric characteristics of the photocatalysts were characterized by SEM,XRD,XPS,UV-Vis DRS,PL and EIS.The performance of TBC/g-C_(3)N_(4) composites for photocatalytic reduction of U(Ⅵ)under visible light irradiation was studied,and the mechanism of photocatalytic reduction of U(Ⅵ)by TBC/g-C_(3)N_(4) composites was discussed.The results show that when the mass fraction of TBC is 5%,the initial pH value is 4 and the amount of catalyst is 1 g/L,the removal rate of U(Ⅵ)by TBC/g-C_(3)N_(4) composites is 99.64%after visible light irradiation for 30 min,which is much higher than that of g-C_(3)N_(4)(58.8%).The removal rate of U(Ⅵ)is above 80%after five cycles,which indicates that TBC/g-C_(3)N_(4) composites has an excellent photocatalytic stability.The addition of TBC makes the band gap of g-C_(3)N_(4) reduced from 2.63 eV to 2.14 eV,widens the visible light absorption range,promotes the separation of photogenerated charge,reduces the recombination rate of photogenerated electron-hole pair,and thus enhances the photocatalytic activity of TBC/g-C_(3)N_(4)composites.This study provides a new idea to design and synthesizethe photocatalysts with efficient,low-cost and environmentally-friendly.