C3N5光催化剂制备及其可见光下还原Cr(VI)性能和毒性研究

Preparation of C3N5 photocatalyst and its performance in reduction Cr(VI)under visible light and toxicity study

光催化技术能够通过光的激发使光催化剂中光生电子(e-)发生迁移,光催化剂产生e-速度越快,还原污水中重金属的效率越高.本文采用热聚合法,以3-氨基-1,2,4-三唑和特定的六元氮杂环为原料创新制备了C3N5光催化剂,与传统工艺相比,创新制备的C3N5带隙值降低了0.06~0.17 eV.其中,以3-氨基-1,2,4-三唑、三聚氰酸、巴比妥酸和KBr为原料制备的C3N5光催化剂(CN-7)带隙值降低了0.17eV,在366nm的激发波长下,CN-7在450nm发射峰极低,极大地抑制了光生电子-空穴对的复合效率,拥有比其他C3N5更快的e-迁移速度.CN-7在50W LED灯照射下50 min内还原水中Cr(VI)的效率可达99.3%,经过5次循环实验后,对Cr(Ⅵ)的去除率仍然可达96%,且受干扰离子的影响较小,具有良好的稳定性.通过自由基捕获实验证明了反应体系中的主要活性物种为e-.同时,将小白菜种植在含CN-7的水溶液中考察光催化剂本身的毒性,发现植物的生长指标不受其影响,而生理指标显示其对植物的生长有一定的促进作用.本研究为制备C3N5光催化剂提供了一种新的方法,同时,为印染、电镀等污水处理工艺中高效还原Cr(VI)且不产生二次污染物提供了新的方向.

Photocatalysis technology can transfer photogenerated electrons(e-)in the photocatalyst through light excitation,and the faster the photocatalyst produces e-,the higher the reduction efficiency of heavy metals in wastewater.In this study,the C3N5 photocatalyst was innovatively prepared using 3-amino-1,2,4-triazole and a special six-membered nitrogen heterocycle as raw materials by thermal polymerization method.Compared with the traditional method,the band gap of C3N5 produced by innovative manufacturing was reduced by 0.06~0.17 eV.Among them,the band gap of the C3N5 photocatalyst(CN-7)prepared with 3-amino-1,2,4-triazole,cyanic acid,barbituric acid and KBr as components was reduced by 0.17 eV at the excitation wavelength of 366 nm.The emission peak of CN-7 is extremely low at 450 nm,which greatly inhibits the recombination efficiency of photogenerated electron-hole pairs,and has a faster e-migration rate than other C3N5.The efficiency of Cr(VI)reduction in water by CN-7 under irradiation with 50 W LED lamp for 50 minutes can reach 99.3%,after 5 cycles of experiment,the removal rate of Cr(VI)can still reach 96%,and it is less affected by interfering ions,indicating good stability.Free radical scavenging experiments proved that the main active species in the reaction system was e-.Then,the toxicity of the photocatalyst itself was studied by planting Chinese cabbage in aqueous solution with CN-7.It was found that the growth index of plants was not affected by the photocatalyst,and physiological indicators showed that it had a certain promoting effect on the growth of plants.This study provides a new method for preparing C3N5 photocatalysts and also provides a new direction for the efficient reduction of Cr(VI)without secondary pollutants in wastewater treatment processes such as printing,dyeing and electroplating.