New insights into Co3O4-carbon nanotube membrane for enhanced water purification: Regulated peroxymonosulfate activation mechanism via nanoconfinement

• Published in: Chemosphere (Oxford) 2024-01, Vol.347, p.140698-140698, Article 140698
• Main Authors: Ma, Huanran, Feng, Guoqing, Zhang, Xiao, Song, Chengwen, Xu, Ruisong, Shi, Yawei, Wang, Pengcheng, Xu, Zhouhang, Wang, Guanlong, Fan, Xinfei, Pan, Zonglin
• Format: Article
• Language: English
• Subjects: adsorption; Carbon nanotube membrane; carbon nanotubes; catalytic activity; electron transfer; energy; mass transfer; Nanoconfinement effect; Peroxymonosulfate activation; reactive oxygen species; sulfamethoxazole; Sulfamethoxazole removal; Theoretical calculation; toxicity; water purification
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2023.140698

Co-based peroxymonosulfate (PMS) activation system with fascinating catalytic performance has become a promising technology for water purification, but it always suffers from insufficient mass transfer, less exposed active sites and toxic metal leaching. In this work, a carbon nanotube membrane confining Co3O4 inside (Co3O4-in-CNT) was prepared and was coupled with PMS activation (catalytic membrane process) for sulfamethoxazole (SMX) removal. Compared with counterpart with surface-loaded Co3O4 (Co3O4-out-CNT), the Co3O4-in-CNT catalytic membrane process exhibited enhanced SMX removal (99.5% vs. 89.1%) within residence time of 2.89 s, reduced Co leaching (20 vs. 147 μg L−1) and more interestingly, the nonradical-to-radical mechanism transformation (from 1O2 and electron transfer to SO4•− and •OH). These phenomena were ascribed to the nanoconfinement effect in CNT, which enhanced mass transfer (2.80 × 10−4 vs. 5.98 × 10−5 m s−1), accelerated Co3+/Co2+ cycling (73.4% vs. 65.0%) and showed higher adsorption energy for PMS (cleavage of O–O bond). Finally, based on the generated abundant reactive oxygen species (ROS), the seven degradation pathways of SMX were formed in system. [Display omitted] •A novel flow-through confined cobalt-based PMS activation system was constructed.•The Co3O4-in-CNT catalytic membrane process showed a superfast SMX removal.•Nonradical-to-radical-dominated mechanism was regulated via nanoconfinement effect.•The redox potential played a key role in high selectivity for SMX removal.•The degradation pathways of SMX were deduced by theoretical calculations and HPLC-MS.