超薄g-C_3N_4在可见光下协同PDS降解双氯芬酸钠的机理研究

Mechanism of synergistic degradation of sodium diclofenac with PDS and ultrathin g-C_3N_4 under visible light

运用一步热聚合法成功制备出二维超薄g-C_3N_4(UCN)纳米片,通过透射电子显微镜、比表面测定仪、紫外可见漫反射光谱、荧光光谱对UCN的形貌及光学性能进行表征,并利用g-C_3N_4对水相中的双氯芬酸钠(DCF)进行了光催化降解实验.结果表明,UCN具有二维超薄纳米片结构,且具有较高的比表面积、较强的可见光吸收能力及空穴-电子转移能力.UCN的光催化活性优于块状g-C_3N_4,过硫酸盐(PDS)的加入对双氯芬酸钠的降解有促进作用,UCN/PDS体系中对双氯芬酸钠降解起主导作用的活性物种为O【math203z】,经过150 min的反应,双氯芬酸钠的矿化率达到78%.双氯芬酸钠在UCN/PDS体系下的光催化降解符合一级动力学规律和Langmuir-Hinshelwood模型,DCF的光催化降解在偏酸和偏碱性的情况下具有较快的反应速率.DCF在河水中的反应速率是超纯水中的3.4倍.循环实验表明,UCN具有很好的光催化稳定性.

Two-dimensional ultra-thin g-C3N4 （UCN） nanosheets were successfully prepared by one-step thermal polymerization. The morphology and optical properties of UCN were characterized by using transmission electron microscopy, specific surface analyzer, UV-Vis diffuse reflectance spectroscopy, and fluorescence spectroscopy. The characterization results indicate that UCN was a two-dimensional ultra-thin uanosheet structure, and possessed a higher specific surface area, strong visible light absorption capacity, as well as hole electron transfer ability. The g-C3N4 was used for the photocatalytic degradation of sodium diclofenac in aqueous phase. Results show that the photoeatalytic performance of UCN was higher than that of bulk g-C3N4, and the addition of PDS could promote the degradation of DCF. The predominant active species of DCF degradation was O~＇- in the UCN/PDS system. After 150 minutes of light irradiation, the mineralization rate of DCF reached 78%. The photocatalytic degradation of DCF in the UCN/PDS system was in accordance with the first-order kinetics and the Langmuir-Hinshelwood reaction kinetic model. Photoeatalytie degradation of DCF demonstrates a faster reaction rate under partial acidity and alkaline conditions. The reaction rate of DCF in river water is 3.4 times higher than that in ultrapure water. Results of the cycle experiments reveal that UCN has good photocatalytic stability.