Catalytic Wet Peroxide Oxidation Coupled With Membrane Separation For Degradation Of Organic Pollutants

Catalytic wet peroxide oxidation?CWPO?is an effective method for treatment of organic wastewater because of its non-selectivity,wide range of application and environmental friendliness.The catalytic performance of this technology is highly dependent on the catalysts.Compared with homogeneous catalysts,heterogeneous catalysts have gained increasing attention due to they are easy to be recycled and can be used under wide pH range.However,heterogeneous catalysts generally suffer from low catalytic activity.In this work,a CWPO coupled with ceramic tubular membrane separation system was constructed to improve the degradation of organic pollutants by accelerating the mass transfer process of reactants.The main contents are shown as follows:?1?The Fe₂O₃/Al₂O₃ coated tubular ceramic membrane was prepared by sol-gel dip-coating and calcination method.The pore size of the catalytic membrane was controlled to ultrafiltration size by adjusting the PVA concentration and coating times.The properties of obtained catalytic membranes?such as pore size distribution,flux,and hydrophilic of membrane?and composition of catalyst were characterized by Thermo Gravimetric?TG?,X-ray Photoelectron Spectroscopy?XPS?,and X-Ray Diffraction?XRD?.The results showed that smooth functional layer with uniform pore size?around 50 nm?was obtained after 10times of coating with 3 wt.%-PVA.The catalyst uniformly distributed on the surface and channels of the membrane.The catalytic membrane was hydrophilic with contact angle of10.02°.?2?The catalytic performance of the Fe₂O₃/Al₂O₃ catalytic membrane was investigated by phenol degradation.The effects of solution pH,temperature,working pressure and H₂O₂concentration on the catalytic performance were studied.The results showed that Fe₂O₃/Al₂O₃catalytic membrane exhibited good catalytic activity with complete phenol degradation and70%TOC removal within 150 min under 90?C,4 bar pressure,pH 6 and 20 mM H₂O₂.The catalytic membrane exhibited good stability and reusability.The phenol degradation could still reach 96%after 5 recycle.And the iron leaching was only 0.41 mg/L after reaction under the optimized conditions,which is lower than that of EU standard for wastewater discharge?iron ion concentration<2.0 mg/L?.In addition,the electron spin-paramagnetic resonance technique?EPR?showed that the hydroxyl radicals?·OH?generated from H₂O₂ with the catalyst of Fe₂O₃/Al₂O₃ plays a major role in degradation.