Fabrication of a novel Ag2S-ZnS/ZIF-8 hollow heterojunction by in-situ formation of Ag2S and ZnS on ZIF-8 with enhanced tetracycline degradation performance

Abstract

Currently, antibiotics are extensively utilized in the pharmaceutical industry to assist humans and animals in combating various infectious diseases. The extensive use of various antibiotics enhances the quality of life. However, it can also have negative effects on the environment and human health, including water pollution and the rise of antibiotic-resistant microorganisms. To date, antibiotics have been detected in rivers, groundwater, and even drinking water. There is an urgent need to design and develop advanced materials for the remediation of antibiotics present in our environment. In this paper, we successfully synthesized a novel Ag2S-ZnS/ZIF-8 hollow heterojunction via facile sulphuration and solvothermal methods. This heterojunction was employed as a catalyst for the degradation of tetracycline (TC) in water under UV and visible light irradiation. The physicochemical properties of the as-synthesized catalysts were thoroughly analyzed using XRD, EDS, SEM, BET, XPS, TEM, ESR, UV–vis techniques. The results demonstrate that Ag2S-ZnS/ZIF-8 displays enhanced photocatalytic activity for TC degradation no matter under visible or UV light irradiation. After 10 min of UV light irradiation, its photocatalytic degradation efficiency was achieved 92.74 %. Additionally, Ag2S-ZnS/ZIF-8 was able to degrade 92.14 % of TC (visible light, with 35 min). The corresponding kinetic rate constant of Ag2S-ZnS/ZIF-8 is 0.145 min−1 (UV light) and 0.043 min−1 (visible light), respectively. Furthermore, Ag2S-ZnS/ZIF-8 also shown excellent stability for the degradation of TC in the presence of visible light. This is a result of its high specific surface area, superior photocurrent and efficient separation of photo-generated electrons-hole pairs. Apart from this, the photocatalytic degradation mechanism of TC over Ag2S-ZnS/ZIF-8 is discussed in detail.