Preparation Of Metal-based Core-shell Ozonation Catalyst And Its Application In Advanced Treatment Of High Salt Petrochemical Wastewater

High salt petrochemical wastewater with various refractory organics and high salt concentration,so it needs advanced treatment to realize water reuse.Heterogeneous catalytic ozonation（HCO）is an effective advanced treatments method,the key of which is the design synthesis and preparation of efficient,stable and simple ozonation catalysts.In this paper,Al₂O₃ was used as the supporter,and an environmentally friendly calcium compound was used as the active component.The surface of the supporter was modified by the strong adhesion of polydopamine（PDA）and the covalent grafting of polyethyleneimine（PEI）and PDA to obtain a PEI-PDA shell with abundant and good dispersion surface action groups,and the calcium-based carbon-coated core-shell ozonation catalyst（Ca-C/Al₂O₃）was successfully prepared by impregnation-calcination method.Under the best conditions,Ca-C/Al₂O₃ catalytic ozonation can achieve high COD removal at64.4%.After 20 cycles,the COD removal rate remains at 50%.The carbon shell,calcium sites and nitrogen-doped in Ca-C/Al₂O₃ are beneficial for ozone to generate hydroxyl radical and singlet oxygen,which achieve the efficient organics degradation in high salt petrochemical wastewater.To improve the stabilization of the catalyst,a L-DOPA shell with embedded copper sites was constructed by the self-polymerization reaction of levodopa（L-DOPA）with copper compound as the active component,and L-DOPA was also used as a carbon source to reduce Cu（II）to more reactive Cu（Ⅰ）and copper monomers.An impregnation-surface modification-calcination preparation process was established to successfully prepare carbon-coated copper-based core-shell ozonation catalysts（C/Cu-Al₂O₃）.Under the best conditions,C/Cu-Al₂O₃ catalytic ozonation can achieve high COD removal at62.5%.After 20 cycles,the COD removal rate remains at 53%.The copper active sites and carbon shell provide abundant Lewis acid sites and surface hydroxyl,promoting ozone to generate hydroxyl radical,superoxide radical and singlet oxygen.The efficient degradation of organics in high salt petrochemical wastewater was achieved by both radical and nonradical oxidation pathways.In this study,two novel metal-based core-shell ozonation catalysts with strong catalytic activity and stability were prepared by enhancing the interaction between the supporter and active components through surface modification and forming a carbon shell layer by using the surface modifiers as a carbon source,which realized the efficient removal of COD from high salt petrochemical wastewater.It will provide technical support and theoretical guidance for the design and synthesis of new and efficient ozonation catalysts and advanced treatment of high salt petrochemical wastewater.