Photocatalytic degradation of ammonia nitrogen using a Z-type nano-TiO2/LaMnO3 heterojunction

Abstract

In this experiment, a novel heterostructured nano-TiO₂/LaMnO₃ composite photocatalyst was prepared by the sol–gel method, and the crystalline shape, morphology and photoresponse of the samples were analysed by combining XRD, FI-IR, SEM, TEM, BET, XPS, UV-Vis and PL characterization techniques, and the effects of different composite ratios, catalyst dosage, ammonia–nitrogen aqueous concentration and pH on the photocatalysis of the photocatalytic degradation of ammonia–nitrogen were investigated by combining with kinetic simulations. The results showed that T/LMO has a polyhedral shape with a microporous structure, a particle size of about 30 μm, and a band gap of 2.82 eV. After irradiation with a 25 W, 254 nm UV lamp for 3 h, T/LMO (1 : 2) could exhibit a 61.15% degradation rate in 100 mL NH₄Cl solution with a mass concentration of 75 mg L⁻¹ and pH 5, the degradation rate was still 52.5% after three times of recycling, the degradation products were mainly non-toxic nitrate nitrogen and nitrogen gas, and it was also experimentally demonstrated that ˙O₂⁻ and ˙OH are active radicals that play an important role in the photocatalytic degradation process. Finally, the experimental results were verified in conjunction with the results of photoelectrochemical tests, demonstrating that the binary composite T/LMO is a Z-type heterojunction structure. With good performance of photocatalytic degradation of ammonia nitrogen, reduced electron–hole pair complexation, and an increased photogenerated carrier migration rate, this study provides some theoretical knowledge and experimental evidence for the practical application of novel photocatalysts in the removal of ammonia nitrogen from wastewater.