| In recent years,a large amount of oily wastewaters with complex components has been produced from various industrial processes.Traditional techniques are applicable for treating floating oil and dispersed oil,however,they are not effective for physiochemically stable emulsion.Membrane separation technique has shown promising potential due to its advantages such as high separation efficiency,small footprint and continuous operation.Nevertheless,conventional membranes often suffer from membrane fouling and insufficient rejection for dissolved organic pollutants in oily wastewater.To address these issues,this work will provide a novel insight of electro-enhanced membrane separation for oily wastewater treatment.The main research contents,results and conclusion are shown as follows:(1)Preparation and characterization of copper metallic membranes.Porous copper metallic membrane was prepared via dry-pressing and atmosphere-sintering technique.The effects of sintering temperature on membrane morphology,structure,and properties were investigated.Compared with most reported ceramic membranes,copper metallic membranes provided superior mechanical stability and ductility,overcoming the critical brittleness bottleneck of traditional inorganic membranes.In addition,copper metallic membranes showed higher conductivity,which provided the feasibility for the electro-enhanced separation.(2)Electro-enhanced membrane separation performance and fouling mechanism for oily wastewater.By applying electric-field with copper membrane as electrode,membrane separation performance under various electrochemical conditions was systematically studied for treating emulsion wastewater.The effects of bias voltage type,negative bias voltage intensity and ionic strength on membrane separation performance and anti-fouling property were explored.The results showed that membrane could reject small-size oil droplets under negative polarization.Due to an electrostatic repulsion mechanism,membrane permeability and rejection were improved with mitigated membrane fouling.At low ionic strength,the redistribution of negatively charged surfactant caused by electric field reduced the interfacial tension at oil-water interface,avoiding oil coalescence.However,at high ionic strength,the dominant fouling mechanism converted from cake filtration to complete blocking model.This could be ascribed to that further increasing of the salt concentration could form competitive adsorption with surfactant on the oil-water interface,increasing interfacial tension and reducing the stability of droplets.(3)Preparation and performance of nanosheet decorated copper membranes for dissolved organic pollutants degradation via electro-Fenton process.Porous copper metallic hollow fiber membrane was prepared via dry-wetting spinning and atmospheresintering technique and followed by anodic oxidation for the construction of nanosheet decorated copper oxide.Then the degradation performance for phenol was studied via electroFenton process.The results showed that dense and regular nanosheets could be obtained by adjusting the oxidation time,oxidation current intensity and surfactant concentration.Compared to unmodified copper membrane,mineralization efficiency increased from 5% to60% and current efficiency increased from 3% to 8.6% in the treatment of phenol wastewater(20 ppm),cofirming the feasibility of phenol degradation.Electro-enhanced fouling control and electro-Fenton degradation strategies can effectively treat emulsified oily wastewater with dissolved organic pollutants,breaking the permeabilityselectivity trade-off and improving antifouling performance.This work provided a new insight for efficient treatment of oily wastewater.Meanwhile,this is of great significance for the development for electro-enhanced function and more applications of porous metallic membranes. |
