Montmorillonite helps BiOCl photodegradation of antibiotics

Abstract

Constructing efficient photocatalysts for the degradation of antibiotics was highly challenging. The support carrier played an active role in the reactivity, adsorption and lifetime of the catalyst. Herein, BiOCl/Mt photocatalysts were successfully prepared on a large scale by mixing natural iron-rich montmorillonite (Mt), bismuth nitrate, ethylene glycol (EG) and deionized water at room temperature. The optimal mass ratio of BiOCl/Mt was 1 : 1, and it could degrade 95.9% tetracycline hydrochloride (TCH) within 60 minutes. Compared with that of pure BiOCl, the degradation rate and kinetic constant were increased by 39% and 3.4 times, respectively. This was due to the fact that BiOCl/Mt has a smaller band gap and more positive valence potential than pure BiOCl, indicating a higher utilization efficiency of light and a stronger oxidation capability of holes (h⁺). The leading role of holes in TCH degradation was confirmed by free radical trapping experiments. In addition, the potential intermediates were identified by liquid chromatography-mass spectrometry, and ECOSAR software predicted that more than half of the products were less toxic than TCH molecules. This study demonstrated that iron-rich Mt not only was a carrier but also participated in the photocatalytic reaction as a p-type semiconductor and formed a p–n heterojunction with n-type semiconductor BiOCl, which significantly improved the photocatalytic ability of BiOCl/Mt.