# Construction of novel Bi2S3@Zn-Co-cLDHs heterojunction for enhanced photocatalytic degradation of levofloxacin with persulfate activation under visible light: mechanism and degradation pathway

## TL;DR

Researchers created a new photocatalyst that efficiently breaks down a drug called levofloxacin under visible light, using a combination of materials and persulfate activation.

## Contribution

The novel Bi2S3@Zn-Co-cLDHs heterojunction was developed for enhanced visible-light photocatalytic degradation of levofloxacin.

## Key findings

- Bi2S3@ZC-cLDHs showed higher photocatalytic efficiency than individual components for levofloxacin degradation.
- Persulfate activation increased degradation efficiency from 74.8% to 90.1% under visible light.
- LC-MS analysis revealed the degradation pathway and identified low-impact photoproducts.

## Abstract

This study effectively synthesized the novel Bi2S3@Zn-Co calcined layered double hydroxides heterojunction (Bi2S3@ZC-cLDHs) via co-precipitation and thermal methods. ZC-LDHs built with a Zn2+/Co2+ molar ratio of 3 : 1, after calcination at 600 °C, yielded a blend of ZnO and ZnCo2O4 oxide, uniformly distributed on Bi2S3 rods. Bi2S3@ZC-cLDHs heterostructures exhibited superior photocatalytic efficiency for levofloxacin (LF) degradation compared to Bi2S3 and ZC-cLDHs under same catalytic conditions. The enhanced photodegradation efficiency results from the increased surface area and the establishment of a heterojunction at the interface of Bi2S3 rods and ZC-cLDHs. In addition, the photocatalytic degradation efficiency of LF enhanced from 74.8% to 90.1% with the addition of persulfate (PS) as an activating under visible light, utilizing a catalyst loading of Bi2S3@ZC-cLDHs at 1.0 g L−1, initial concentration of 20 ppm, PS loading of 0.25 g L−1, and light exposure duration of 90 minutes. The Z-scheme established the photocatalytic mechanism for the degradation of LF using Bi2S3@ZC-cLDHs with PS activation. Radical trapping tests demonstrated that O2˙− and h+ were the significant active species. The combination of PS and catalyst had a synergistic effect, wherein S2O82− interacted with electrons to create SO4˙− during the photocatalytic process. The analysis using LC-MS provided a thorough understanding of possible photocatalytic breakdown path of LF; the photoproducts were small-sized molecules with little impact on the environment.

This study effectively synthesized the novel Bi2S3@Zn-Co calcined layered double hydroxides heterojunction (Bi2S3@ZC-cLDHs) via co-precipitation and thermal methods.