Preparation Of Hydrophobic/lipophilic Membranes And Their Oil-water Separation Properties

The marine water pollution levels increase caused by industrial oily waste water and the frequent occurrence of the oil spill,novel and innovative water/oil separation technology has become a global challenging task.Therefore,to find a suitable solution to the oil problem of water pollution,thus purified,recycled oils,can save energy and protect the environment.Membrane separation technology is considered to be the direction of future development,because of its simple operation,low energy consumption,no secondary pollution,obvious separation.This paper aims to develop a hydrophobic/lipophilic membranes,which will be used in the oil-water emulsion separation applications.The experiment is divided into two parts.In the first part,superhydrophobic/superlipophilic oil-water separation fabrics were prepared,nano-sized SiO2 was modified by 3-mercaptopropyl trimethoxysilane(MPTMS)with SH-functionalized.Then,the superhydrophobic coatings were prepared by dip-coating method.The structure and properties of the coated fabrics were characterized,and the separation capability for the oil/water mixture was investigated.Polyvinylidene fluoride(PVDF)film has excellent physical and chemical properties,good thermal stability,resistance to chemical oxidation,strong acid and alkali resistance,strong anti-pollution,which can be prepared in a variety of methods,and the preparation process is simple and easy to be operated,has become an ideal film material.The second part is mainly hydrophobic-lipophilic PVDF membranes with micro/nanoscale structures were prepared by double coagulation bath.First,the effects of the coagulation bath composition and non-solvent system additives on the surface morphology and properties of the membranes were studied.Secondly,the introduction of poly(stearyl methacrylate)(PSMA)which having a long chain alkyl hydrophobic,increasing the composite membranes hydrophobicity by physical blending mode,and in this part of the orthogonal experiment method was designed to study the PVDF/PSMA ratio,temperature of casting solution,phase separation time,temperature of coagulation bath on the effect of the SEE-2 emulsion separation efficiency.Finally,in order to solve the lower flux and the lower mechanical strength of the membranes prepared by the above method.The electrospinning nanofiber membrane was used as the reinforcing support layer,and the composite coating of PVDF/graphene(GE)was used as the separation functional layer.In the solvating process,a novel kind of coral micro-nano structure nanofibrous surface was obtained by using the induced crystallinity of GE.Both the physical mechanical property and the flux of the double-tier composite membrane were improved.Scanning electron microscopy(SEM),Confocal laser scanning microscope(CLSM),Optical contact angle(OCA),X-ray diffraction(XRD),Differential scanning calorimetry(DSC)and Karl Fischer water analyzer(C20),Universal testing machine were used to characterize the structure and performance.The superhydrophobic coating fabric prepared by impregnation-coating method has excellent superhydrophobic and superlipophilic properties and can be used for the separation of oil-water mixtures.For the double coagulation bath membranes making process,the results show that the small molecule alcohols as the first coagulation bath,no dense cortical membrane surface and the cross-section of the membranes composed by spherical particles,and the contact angle is much larger than the contact angle of water as a coagulation bath time.The effect of PVDF/PSMA ratio on the filtrate purity of the SEE-2 is greater,and with the increase of the content of PSMA,the composite membrane flux and efficiency of the separation of emulsions have been improved,M-9 flux up to 230 kg·m-2·h-1,while relatively high separation efficiency was 99.98%.But its physical mechanical properties are poor with tensile breaking strength of 1.6 MPa.The double-tier composite membrane prepared by electrostatic spinning process and surface coating process exhibited a relatively higher physical mechanical property with tensile breaking strength of 2.5 MPa.Furthermore,such high hydrophobic composite membrane may have potential application for the water-in-oil emulsion;and the flux of the membrane is over 150 kg·m-2·h-1 after 10 cycles.The purity of the filtrate oil remained above of 99.90%,which show high separation efficiency and excellent stain resistance.