Research Of Degradation Of Phenolic Wastewater By Copper Based Catalyst

Treatment of concentrated phenolate wastewater is one of hotspots in the field of industrial water treatment.In the recent years,advanced oxidation progresses（AOPs）on the basis of persulfate（PS）have attracted more attention in the remediation of hazardous organic pollutants.Compared with Fenton and Fenton-like reaction systems,PS has a higher oxidation ability and shows little dependence on pH conditions,which make it more appropriate for the treatment of alkaline phenolate wastewater.However,given that PS is very stable and-O-O-in PS is not easily to be activated and transformed into oxidative radicals under ambient conditions,catalysts that can effective activate PS are always required in applications.In this study,the kinetics and mechanisms involved in the removal of phenol by PS catalyzed by two homogeneous catalyst CuO and Cu₂（NO₃）（OH）₃ under alkaline conditions will be investigated.In the CuO/PS oxidation system,we investigated the removal efficiency and mechanism involved in the removal of phenol.Our results indicate that CuO/PS exhibits a high removal efficiency in the removal of phenol under alkaline conditions.A complete removal of 1.1 m M phenol can be achieved within 5 min at an initial pH11.0 and in the presence of 4.2 m M PS and 1 g L^-1CuO.In addition,CuO shows a high reusability and stability,and after 12 rounds of repeated uses of CuO,the removal efficiency of phenol can still reach 98%.Moreover,CuO/PS can effectively remove 2-chlorophenol,2,6-dichlorophenol,2,4,6-trichlorophenol and various organic dyes,suggesting the wide applicability of CuO/PS in the remediation of organics.No oxidative radical detected in the EPR results further indicates that PS activation follows a non-radical pathway that effectively removes phenol in solution.In this process,-O-O-in PS firstly forms a cyclic ring with Cu-O-Cu in CuO,followed by an activation of phenol anions to phenol radicals by-O-O-in the cyclic ring.A large number of phenol radicals are then polymerized to form water-insoluble polyphenylene oxides.Although phenol is not mineralized into CO₂ and H₂O,the higher value of polyphenylene oxide than that of phenolate waste suggests that this process is a green oxidation technology,turning waste into treasure.We also investigated the removal efficiency and mechanism involved in the removal of phenol by Cu₂（NO₃）（OH）₃/PS.The results show that Cu₂（NO₃）（OH）₃/PS exhibits high removal efficiencies in the removal of phenol in a wide range of pH from weak acid to base（pH 5.0-10.0）.A complete removal of 100 mg L^-11 phenol can be achieved within 240 min at initial pH 8.0,1 g L^-11 PS and 1 g L^-11 Cu₂（NO₃）（OH）₃.Scavenger experiments and EPR results suggest that the primary oxidative species in the Cu₂（NO₃）（OH）₃/PS system are SO₄^·-and ¹O₂.Therefore,Cu₂（NO₃）（OH）₃/PS system is a new kind of oxidation system,exhibiting different mechanisms from the CuO/PS oxidation system.This study provides new insight into the non-radical mechanism involved in the removal of phenol by PS activated by CuO under alkaline conditions,which enriches our understanding on PS activation by transition metals and provides theoretical guidance for the remediation of alkaline phenolate wastewater.Moreover,this study has important implications for selective oxidation of organics in wastewater in future work.