Heterojunction photocatalyst FeS/g-CN for activating sulfites to degrade tetracycline: A stable degradation system based on heterogeneous processes.

The UV/sulfite system is a promising source of •SO and/or •OH, but its application is largely limited by the use of UV light due to its high cost and high energy consumption. Graphite carbon nitride (g-CN), as a new photocatalytic material, has better visible light absorption capacity and narrower band gap than g-CN, which is expected to activate sulfite under visible light to solve this problem. Herein, a novel FeS/CN heterojunction material based on g-CN was constructed by hydrothermal in-situ synthesis method and successfully activated sulfite, which was confirmed by tetracycline degradation experiments in water. Under optimized conditions, the degradation rate of TC in 1 h reached 96%. The experimental results revealed that the FeS/CN heterostructure enhances the absorption of visible light and inhibits the recombination of carriers, enabling more electrons and holes to be utilized. Holes play a major role in the degradation reaction, promote the sulfite chain reaction, and effectively regulate the cycle of Fe and Fe in the solution. Iron ion leaching is negligible and the degradation reaction remains stable at pH 5-9.