Persulfate non-radical activation by nano-CuO for efficient removal of chlorinated organic compounds: Reduced graphene oxide-assisted and CuO (0 0 1) 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.