Zinc-assisted pyrolysis for optimal graphitization of carbon nanotubes for boosted Fenton-like catalysis

Carbon-based materials are extensively utilized as catalysts in peroxymonosulfate-based advanced oxidation processes (PMS-AOPs). However, their basal active sites often exhibit inferior intrinsic activity, necessitating the development of facile modification techniques to enhance their catalytic efficacy in water purification. This study introduces a facile Zn-assisted pyrolysis strategy designed to increase the graphitization degree of carbon nanotubes (CNTs), thereby improving their PMS activation capabilities. The Zn-modified CNTs exhibited a pseudo-first-order rate constant ( k obs ) of 0.2065   min -1 , which is 7.9-fold and 59.0-fold higher than that of the thermally treated CNTs (0.015   min -1 ) and pristine CNTs (0.0035   min -1 ), respectively. Mechanistic studies revealed that the graphitization advancement led to an augmented contribution of the direct electron transfer (ETP) pathway for pollutant degradation, in conjunction with the contribution from singlet oxygen ( 1 O 2 ). Such pathway alteration can be owing to the increased electrical conductivity due to the presence of a highly conjugated π-electron system. Additionally, the practical application of the modified CNTs was rigorously evaluated under continuous treatment scenarios and in the presence of diverse anions such as Cl - , NO 3 - , HCO 3 - , and SO 4 2- . The insights gained from this study are pivotal for the optimization of carbon-based catalysts for environmental remediation purposes.