Experimental and theoretical study on the photocatalytic degradation of brilliant green dye by N-doped Zn2GeO4

• Published in: Chemical engineering science Vol. 281; p. 119154
• Main Authors: Liu, Jiaoqin, Guo, Chengjie, Lu, Yanrong, Liu, Hao, Jia, Mengye, Zhang, Jingjing, Jin, Riya, Qiao, Yina, Ma, Rui, Wu, Zhibo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.11.2023
• Subjects: Brilliant green; N-doped Zn2GeO4; Reaction mechanisms; Theoretical calculations; N-doped Zn2GeO4; Reaction mechanisms; Theoretical calculations; Brilliant green
• ISSN: 0009-2509; 1873-4405
• DOI: 10.1016/j.ces.2023.119154

[Display omitted] •N-doped Zn2GeO4 showed excellent photocatalytic activity under UV irradiation.•Catalyst addition amounts and initial concentrations had effects on BG degradation.•N was doped into the crystal interstitial site with the most probable Zn-N-Ge mode.•DFT calculations revealed the locations that were vulnerable to attack by ∙OH/O2∙-.•Five possible pathways were given, the toxicity of some products requires attention. In this study, experimental and theoretical insights on the photocatalytic degradation of BG in an N-doped Zn2GeO4/UV irradiation system were explored. Kinetic experiments, degradation mechanisms analysis, and toxicity evaluation of intermediates were involved. The catalytic performance of N-doped Zn2GeO4 was optimum when the molar ratio of CO(NH2)2 and GeO2 is 1: 1. BG was almost 100% degraded within 10 min. Catalyst dosage and initial concentration had effects on the photodegradation of BG. Materials Studio calculations indicated that the nitrogen atoms are interstitially doped into Zn2GeO4 in the form of Zn–N–Ge. The N 2 s orbital contributes more than the N 2p orbital to the PDOS of N-doped Zn2GeO4, suggesting the difficult recombination of e- and h+. According to mass spectrometry analysis, de-ethylation, hydroxylation, condensation, carboxylation, and ring-opening were the main photocatalytic degradation pathways of BG. ∙OHs and O2∙-s played important roles in the Hg lamp/N-doped Zn2GeO4 reaction system, while h+ was existed in this system using quenching experiments. The 2FED2HOMO and (FED2HOMO + FED2LUMO) values implied the locations vulnerable to attack by free radicals of BG, which validated the reasonableness of the LC-MS/MS analysis result. Toxicity evaluations by the ECOSAR program suggested that photocatalytic degradation can exacerbate the aquatic toxicity of BG in the initial stage.