Persulfate non-radical activation by nano-CuO for efficient removal of chlorinated organic compounds: Reduced graphene oxide-assisted and CuO (001) facet-dependent

Non-radical activation of persulfate by CuO to degrade chlorinated organic pollutants has been studied. Currently, reduced graphene oxide modified spindle-like CuO (CuO/rGO, no preferential exposed crystal facet) and CuO with preferential exposed crystal facet (0 0 1) (sheet-like CuO) has been prepared to improve the performance of persulfate activation. Results showed that CuO/rGO-persulfate system and sheet-like CuO-persulfate system exhibited much better 2,4,6-trichlorophenol (TCP) removal rate than spindle-like CuO-persulfate system. The formation of Cu-O-C bond between CuO and rGO enhanced the persulfate activation by CuO. On the other hand, CuO showed crystal facet effect on persulfate activation, and the crystal facet (0 0 1) of CuO (all exposed atoms were Cu) were proved to be efficient for persulfate non-radical activation, revealing that Cu atom on surface was active site for persulfate activation. Furthermore, the pollutants selective removal by CuO/rGO-persulfate system has been found. 4-chloroaniline was most easily degraded, followed by 2,4,6-trichlorophenol, 2,4-dichlorophenol and 4-chlorophenol, under acidic, neutral and weak basic condition (pH 3-9). What's more, pollutants with benzene ring was more reactive than that with double bond of carbon in the system.