Structural design of hierarchical porous biomass carbon with a built-in electric field for efficient peroxymonosulfate activation

Biomass-derived carbon materials have excellent adsorption capacity and cost-effectiveness, and the electron interactions between multiphase composite materials improve the efficiency of water pollutant removal by advanced oxidation processes (AOPs). Herein, a multistage biochar catalyst in which metallic cobalt-embedded carbon tubes are prepared uniformly on the surface of kapok tubes is designed and fabricated. The closely connected structure grown in situ accelerates electron migration and forms a directional transfer electric field. The N-doped carbon nanotube encapsulated Co nanoparticles growth on the kapok biochar/PMS (Co-N-KBC/ PMS) system removes tetracycline hydrochloride (TCH) at a rate 11.8 times higher than that of KBC/PMS. Free radicals (SO4 center dot-, center dot OH, and center dot O-2(-)) and non-free radicals (O-1(2)) are generated in conjunction with electron transfer during PMS activation. The cobalt sites and C=O groups are possible active sites. Density-functional theory (DFT) calculations verify the built-in electric field from N-KBC to the Co surface, which accelerates electron transfer and improves TCH removal. The results reveal an effective strategy to activate PMS and address environmental remediation by utilizing carbon materials derived from biomass.