La2Zr2O7/rGO synthesized by one-step sol-gel method for photocatalytic degradation of tetracycline under visible-light

In this study, La2Zr2O7/rGO (LZO/rGO) composite photocatalyst was prepared by a one-step sol-gel method, which achieved synthesis of LZO and reduction of GO simultaneously. LZO/rGO-3 (dosage of GO: 0.5 g) was well-crystallized and had the specific surface area of 16.5 m2/g which was higher than that of LZO (9.4 m2/g). Moreover, the introduction of rGO improved the surface microstructure and slightly reduced the band gap (LZO/rGO-3: 2.42 eV), expanding the light absorption range. Tetracycline (TC) was chosen as the target contaminant to assess photocatalytic activity in visible-light. The removal rate and constant of reaction rate (kapp) of LZO/rGO-3 was 82.1% and 0.3097 min−1 after 40 min, which was significant higher than that of LZO (57.8% and 0.1741 min−1). In addition, the TC degradation follows pseudo-first-order kinetic and shows the stability after five cycling experiments. The enhanced photocatalytic activity was mainly due to two aspects. Firstly, the improved surface appearance provided more adsorption and reaction sites. Secondly, the rGO as co-catalyst (electron trap) reduced the recombination of electron-hole pairs, and further promoted production of active substances. The photocatalytic mechanism was proposed coupled with analysis of energy structure, active substances and degradation pathways, indicating that h+, 1O2, O2− and H2O2 were the main active substances in TC photocatalytic degradation, and the generation of 1O2 was of vital importance.