Synthesis, Property Characterization and Photocatalytic Activity of the Ag3PO4/Gd2BiTaO7 Heterojunction Catalyst under Visible Light Irradiation

Abstract

A new type of Gd2BiTaO7 nanocatalyst (GBT) was synthesized by a high-temperature solid-phase method, and a heterojunction photocatalyst, which was composed of GBT and silver phosphate (AP), was prepared by the facile in-situ precipitation method for the first time. The photocatalytic property of GBT or the Ag3PO4/Gd2BiTaO7 heterojunction photocatalyst (AGHP) was reported. The structural properties of GBT and AGHP were characterized by an X-ray diffractometer, scanning electron microscope–X-ray energy dispersive spectra, an X-ray photoelectron spectrograph, a synchrotron-based ultraviolet photoelectron spectroscope, a Fourier transform infrared spectrometer, an UV-Vis diffuse reflectance spectrophotometer and an electron paramagnetic resonance spectrometer. The results displayed that GBT was well crystallized with a stable cubic crystal system and space group Fd3m. The lattice parameter or band gap energy of GBT was found to be a = 10.740051 Å or 2.35 eV, respectively. After visible light irradiation of 30 min, the removal rate of bisphenol A (BPA) reached 99.52%, 95.53% or 37.00% with AGHP as the photocatalyst, with Ag3PO4 and potassium persulfate (AP-PS) as photocatalysts or with N-doped TiO2 (NT) as a photocatalyst, respectively. According to the experimental data, it could be found that the removal rate of BPA with AGHP as a photocatalyst was 2.69 times higher than that with NT as a photocatalyst. AGHP showed higher photocatalytic activity for photocatalytic degradation of BPA under visible light irradiation compared with GBT or AP-PS or NT. The removal rate of total organic carbon (TOC) was 96.21%, 88.10% or 30.55% with AGHP as a photocatalyst, with AP-PS as photocatalysts or with NT as a photocatalyst after visible light irradiation of 30 min. The above results indicated that AGHP possessed the maximal mineralization percentage ratio during the process of degrading BPA compared with GBT or AP-PS or NT. The results indicated that the main oxidation radical was •OH during the process of degrading BPA. The photocatalytic degradation of BPA with AGHP as a photocatalyst conformed to the first-order reaction kinetics. This study provided inspiration for obtaining visible light-responsive heterojunction photocatalysts with high catalytic activity and efficient removal technologies for organic pollutants and toxic pollutants, and as a result, the potential practical applications of visible light-responsive heterojunction photocatalysts were widened. The subsequent research of thin-film plating of the heterojunction catalysts and the construction of complete photoluminescent thin-film catalytic reaction systems, which utilized visible light irradiation, could provide new technologies and perspectives for the pharmaceutical wastewater treatment industry.