Construction of low-toxicity cadmium sulfide/nitrogen-doped muti-walled carbon nanotubes for peroxymonosulfate activation: The crucial role of electron transfer.

Cadmium sulfide is widely employed in environmental catalysis due to its excellent catalytic behaviors. However, the inherent toxicity and leaching risk of CdS-based catalyst presents significant challenges for practical applications. This study explored the incorporation of CdS nanowires on the nitrogen-doped multi-wall carbon tubes (N-MWCNTs) substrate to minimize the leaching rate and mitigate the bio-toxicity by regulating the electron transfer process. The low bio-toxicity of CdS/NMWCNT was confirmed by s series of toxicity tests. Additionally, the catalytic performance could be further enhanced with the high conductivity under the interfacial inner-electronic field. Results showed that the TC (20 mg/L) removal efficiency reached 90.31% within 30 min by PMS activation. Moreover, the PMS activation process, unveiled by In-situ Raman, quenching tests, and EPR spectra, demonstrated the improved TC removal efficiency was ascribed to the dominated roles of •OH, SO4•- and O2•-. DFT calculations further conducted the "NMWCNT-CdS-PMS" electron transfer pathway, thus effective activating PMS and protecting the CdS from oxidation. The findings provide a theoretical basis for designing and synthesizing unstable metal catalysts for the removal of emerging organic contaminants from wastewater with PMS activation.