Biochar encapsulated metal nanoflowers for high efficient degradation of metronidazole via peroxymonosulfate activation

• Published in: Separation and purification technology 2024-01, Vol.328, p.125081, Article 125081
• Main Authors: Xu, Weicheng, Liang, Jinzhi, Li, Jianghong, Pillai, Suresh C., Liang, Fawen, Li, Meng, Xiao, Kaibang, Li, Jiesen, Wang, Yu, Jiang, Xueding, Liu, Zhang, Beiyuan, Jingzi, Wang, Hailong
• Format: Article
• Language: English
• Subjects: Bimetallic NZVI/Cu0; Biochar; Degradation mechanisms; Metronidazole; Peroxymonosulfate activation
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2023.125081

Three-dimensional flower-like bimetallic shell/core NZVI/Cu0/biochar heterostructures were synthesized as an effective and green PMS activator for MNZ removal. [Display omitted] •Flower-like bimetallic NZVI/Cu0/biochar composites are prepared.•The hierarchical structures with exposed Fe active sites promote high efficient PMS activation.•The electron transfer between shell/core NZVI/Cu0 maintains low valence of Fe layer.•The biochar inhibits metal ion release and improves the stability of the composite.•Bimetal core/shell structures can easily break down the O-O bond in PMS to generate SO4•− radicals. A three-dimensional (3D) flower-like zero-valent bimetallic shell/core iron/copper/biochar composite (NZVI/Cu0/BC) was synthesized for the purpose of removing antibiotic metronidazole (MNZ) through the activation of peroxymonosulfate (PMS). Under optimal conditions, complete removal of MNZ (10 mg/L) was achieved within 6 min. The study quantitatively investigated the contribution of different participants in the complex system, including carbon composites, Fe and Cu species, and radicals and nonradicals. Based on the characterization and analysis data, possible activation mechanisms were proposed, which involved the oxygenated functional groups of BC and the bimetallic structure feature of NZVI/Cu0 accelerating the generation of 1O2 and other oxidation species. Additionally, the synergistic effect of Cu-Fe-BC facilitated the redox cycle of Cu2+/Cu+ and Fe3+/Fe2+, thereby promoting radical in the NZVI/Cu0/BC-3/PMS system. Notably, NZVI/Cu0/BC-3 has the advantages of wide pH usable range as well as broad-spectrum adaptability towards various organic pollutant and various water environments. Density functional theory (DFT) results indicated that the adsorption energy of PMS onto NZVI/Cu0/BC was more negative compared to their individual adsorption energies, and the O-O bond in the structure of PMS molecules became weaker after adsorption, resulting in improved efficiency of PMS activation. Liquid chromatograph combined with mass spectrometry (LC-MS) measurement and DFT calculation suggested three main degradation pathways of MNZ, and the toxicities of their intermediates were evaluated.