Research On Fabrication And Properties Of Surfaces With Super-Wettability Used For Oil-Water Separation

Oceans of oil-water mixtures are created due to continuous discharge of oily industrial wastewater and domestic sewage,and frequent occurrence of marine oil spillage.Therefore,it is of significant practical meanings and application values to develop oil-water separation technology.Recently,oil-water separation materials with super-wettable surfaces have shown great application potential.However,there still are some common problems,such as poor environmental friendliness of fabrication process,high cost and lack of performance stability,which pose nontrivial hurdle for practical oil-water separation.In this thesis,oil-water separation mesh and oil adsorption foam with super-wettable surfaces are created by atmospheric pressure cold plasma jet(APCPJ)and template method,respectively.Then the separation of various oil-water mixtures is realized by the as-prepared materials with super-wettable surfaces.The work completed herein offers new insights on the fabrication of surfaces with super-wettability and the treatment of oil-water pollutions.The main research content and results of the thesis are as follows:(1)Traditional methods to prepare superhydrophilic polymeric mesh for oil-water separation generally face some undesired shortcomings,such as poor environmental friendliness,complicated process and low efficiency.Here He-APCPJ is employed to hydrophilize polymeric mesh,which is then used for the separation of light oil-water mixtures.Results show that He-APCPJ exposure can impart polymeric mesh surface superhydrophilicity and underwater superoelophobicity by plasma induced etching effect and hydrophilic groups introduction.This as-prepared polymeric mesh with superhydrophilic surface can be used for the gravity-driven,water filtrated separation of light oil-water mixtures with the separation efficiency above 97.7%.(2)Nitrogen APCPJ(N-APCPJ)is employed to functionalize Al mesh with reversible super-wettability for separation of heavy oil-water mixture and light oil-water mixture.On the basis of plasma characteristics analysis,N-APCPJ is used to conduct the hydrophilization of superhydrophobic Al surface,and the aging behavior of the obtained superhydrophilic surface is also studied.Results indicate that N-APCPJ can change the surface wettability from superhydrophobicity to superhydrophilicity by altering the surface chemistry while having little effect on its surface morphology.The as-prepared superhydrophilic surface can recover the original superhydrophobicity after aging under certain conditions.The surface micro-structures can retard the aging process,while high temperature and high relative humidity favor the wettability recovery.Consequently,reversible and repeatable super-wettability transition of superhydrophobic Al mesh is achieved by combination of N-APCPJ treatment and high temperature aging.Separations of heavy oil-water mixture(oil filtrated)and light oil-water mixture(water filtrated)are thereafter realized.(3)Most of the existing oil adsorbents with superhydrophobic surface involve the use of strong acid and base solutions,and their performance stability is always poor.To address this problems herein,poly(vinylidene fluoride)(PVDF),table salt and multi-walled carbon nanotube(MWCNT)are selected as raw materials,and sacrificial template method is proposed to prepare superhydrophobic porous PVDF-MWCNT foam without using any organic solvent.Then a series of oil adsorption testings by the as-prepared foam are performed.Results demonstrate that the PVDF-MWCNT foam can realize oil-water separation by selective oil adsorption,and the foam's oil adsorption capacity for various oily liquids is 300%-1200%.The foam possesses excellent UV resistance,acid and alkali corrosion resistance and reusability.Additionally,by combining vacuum pump assistance,the foam can be used for contunious clean-up and collection of large scale oil spills under complex conditions.