Photocatalytic degradation of antibiotics in water by pollution-free photocatalytic films with a three-dimensional layered structure and the reaction mechanism study

Although powdered photocatalysts has shown high degradation efficiency in photocatalytic reactions, their practical applications are limited by the poor recovery of powder. To improve its recycling performance, a three-dimensional layered photocatalytic fiber membrane was newly designed through electrospinning and coating process. The composition of the photocatalytic membrane was polyacrylonitrile (PAN), polydopamine (PDA) and Tb doping graphitized carbon nitride/ZnIn 2 S 4 (Tb-g-C 3 N 4 /ZnIn 2 S 4 ) from bottom to top. The photocatalytic performance of the prepared composite membranes was investigated under simulating sunlight. Compared to the prepared PAN@Tb-g-C 3 N 4 (PT), PAN@PDA/Tb-g-C 3 N 4 (PPT) and monolithic PAN@PDA/Tb-g-C 3 N 4 /ZnIn 2 S 4 (PPTZ), the PPTZ displayed the highest photocatalytic ability. The degradation rates of PPTZ for tylosin (TYL) and tetracycline (TC) were approximately 2.1 and 2.5 times than that of other samples. The superior photocatalytic activity of the PPTZ sample resulted from the formation of a heterostructure among Tb-g-C 3 N 4 , ZnIn 2 S 4 and PDA, which significantly inhibited the recombination of photogenerated carriers. PDA could act as an electron transfer medium so that electrons were transferred from the Tb-g-C 3 N 4 to the ZnIn 2 S 4 and PDA, which could be found in the study of its electron density with density functional theory (DFT). According to the free radical trapping analysis, the order of importance of the redox species was O 2 − > h +  >  OH. Moreover, the toxicity of the material was investigated to ensure that the material would not cause secondary pollution in practical applications.