Preparation And Properties Of Mixed Matrix Flat Membranes Based On MWCNTS/PVDF

There are many outstanding physical and chemical properties in poly(vinylidene fluoride)(PVDF),therefore,PVDF is regarded as a benign material for the preparation of separation membranes.However,as the matrix material,PVDF has low surface energy and hydrophobic property,these shortcoming lead to be polluted easily,short service life and so on in water treatment fields.The hydrophilicity of PVDF membrane can be improved and it can be applied better by adding the modified multi-walled carbon nanotubes to the casting solution.Firstly,the PVDF flat membranes were prepared via low temperature thermally induced phase separation(L-TIPS).This paper studied the effect of concentration of PVDF,ratio of diluent,additive content and the way of cooling on membrane structure,water flux,rejection,porosity and mechanical properties,etc.Also,it was studied the microstructure of PVDF flat membrane by field emission scanning electron microscopy(SEM),in order to determine the better experimental conditions.Secondly,the paper chose the functionalized hydroxylation multi-walled carbon nanotubes(MWCNTs-OH)as a modifying agent,putting them into the casting solution and microwave ultrasound was performed in order to distributing MWCNTs-OH evenly,therefore,the MWCNTs-OH/PVDF flat sheet membranes were fabricated.It studied the effect of structural parameters of MWCNTs-OH on membrane structure,water flux,rejection,porosity,hydrophilicity,mechanical properties and anti-fouling ability,etc.The study found that with the increase of the content and the tube diameters of MWCNTs-OH,the pure water flux increased firstly and then decreased.The rejection rate of PEG 10000 had been improved to a certain extent;The tensile strength and elongation were significantly improved which were compared with the pristine membrane.The results indicated that the membranes containing MWCNTs-OH in comparison with pristine membrane,their anti-fouling performance was signifi-cantly improved,according to this,the optimum content and tube diameter of MWCNTs-OH were determined.Finally,the paper chose the functionalized carboxyl multi-walled carbon nanotubes(MWCNTs-COOH)as a modifying agent,putting them into the casting solution and microwave ultrasound was performed in order to distributing MWCNTs-COOH evenly,therefore,the MWCNTs-COOH/PVDF flat sheet membranes were prepared.It studied the effect of content and tube diameters of MWCNTs-COOH on membrane structure,water flux,rejection,porosity,hydrophilicity,mechanical properties and anti-fouling ability,etc.The results of experimental showed that with the increase of the content and the tube diameters of MWCNTs-COOH,the pure water flux increased firstly and then decreased.Compared with the pristine membrane,the PEG 10000 rejection rate was obviously improved.The tensile strength and elongation were also significantly improved,but the two would decrease with the increase of content and tube diameters.Anti-fouling test indicated that adding different content and the tube diameters of MWCNTs-COOH into the casting solution,the anti-fouling ability of membrane was improved in comparison with the pristine membrane.Determining the optimal content and tube diameter of MWCNTs-COOH in order to obtain good hydrophilicity,high water flux,excellent anti-fouling perform-ance of the flat sheet membranes.