Activated carbon/persulfate-driven in-situ remediation of naphthalene-polluted groundwater: Insights into active sites, passivation-activation mechanisms and practical applications

Carbonaceous material-activated persulfate (PS) has shown great potential for in-situ groundwater remediation. Herein, original coconut shells were treated via a multistep process to obtain activated carbon denoted as AC700, which was used to efficiently activate PS for the degradation of naphthalene (NAP). Compared with other carbonaceous materials, the AC700 showed an excellent activation performance, high reusability, and easy recovery by secondary pyrolysis. More importantly, the main functional active sites of AC700 and its corresponding activation mechanism were comprehensively revealed. The activation ability of AC700 was related to its electron exchange capacity of functional groups and electrical conductivity of graphite-like structure. In the AC700/PS system, the coexistence of free radical and non-free radical pathways produced multi-active species that synergistically degraded NAP. Encouragingly, the AC700/PS system exhibited excellent anti-interference ability and satisfactory activation stability in spiked natural groundwater. This study will further facilitate the development of the metal-free catalyst/PS system as a new technological strategy for in-situ remediation of groundwater.