In the ZnO/MMT composite catalyst, the high dispersion of ZnO on the MMT surface enhances the interaction between the oxide and the carrier, accelerates the spatial separation of photo generated carriers, and improves the degradation efficiency of tetracycline hydrochloride.

Abstract

Efficient degradation of antibiotics is an effective means to control environmental pollution. In this study, a series of ZnO/MMT composite photocatalysts were prepared by an impregnation method using montmorillonite (MMT) as the precursor. The structure and physicochemical properties of the photocatalysts were characterized by the different characterization technologies, such as X-ray diffraction (XRD), scanning electron microscope mapping (SEM-Mapping), Fourier transform infrared spectroscopy (FTIR), UV–vis absorption spectra, N₂ adsorption–desorption isotherm, X-ray photoelectron spectroscope (XPS), ultraviolet photoelectron spectroscopy (UPS), electrochemical impedance spectroscopy (EIS), and so on. The photocatalytic degradation performance and mechanism for tetracycline hydrochloride were studied. The results show that the spectral response performances of the as-prepared samples are improved by a composite process. Among them, ZnO₂₀/MMT-300 has the largest degradation efficiency (91.61%) and the best catalytic activity, and its maximum apparent rate constant is 3.590 × 10⁻³ L·mg⁻¹·min⁻¹. The analysis of photocatalytic mechanism and energy band structure shows that the main active substance of the system is h⁺, and the photocatalytic degradation process follows the type II heterojunction photocatalytic reaction mechanism. This study provides ideas for the design and construction of high-efficiency photocatalytic composites, and provides a reference for the photocatalytic degradation of other organic pollutants.