PTFE Conductive Microporous Membrane EVMD Process Research And Its Electrocatalytic Applications

Electrochemical membrane separation coupling technology plays an increasingly significant role in the field of water treatment,but the shortcomings of the absence of flexible of traditional conductive membrane makes its development be restricted.Carbon nanotubes and graphene as the advanced conductive materials have broad application prospects.In this paper,a biaxial stretching polytetrafluoroethylene(PTFE)membrane was employed as the base membrane of the conductive membrane,and either multi-walled carbon nanotubes(MWCNTs)or a mixture of MWCNTs/graphenes as a conductive substrate.PTFE conductive microporous membrane was applied to electric field assisted vacuum membrane distillation(EVMD)experiment and electro-catalytic degradation of dye.Firstly,PTFE/MWCNTs conductive microporous membranes were prepared by vacuum filtration,in which using MWCNTs as the conductive substrate,and the effects of per unit area loading mass(PUALM)on the membrane properties were investigated.The results showed that with the increasing of PUALM,the conductivity of the membrane increased gradually and N2 gas flux decreased gradually.When the PUALM was lOg/m2,the conductivity was 0.12 ± 0.01(Ω/sq)-1,the N2 gas flux was 59.24 ±5.0m3/m2h,which showing both good conductivity and separation performance.The hydrophobicity of PTFE conductive membranes would be significantly increased with graphene doped into conductive substrate,and when the ratio of graphenes to MWCNTs was 2:1,the water contact angle could be up to 134.3 ± 0.76°.Secondly,the conductive membrane was applied to the EVMD process to alleviate membrane fouling,in which humic acid(HA)was used as the organic pollutant,and sodium chloride(NaCl)as electrolytes and inorganic pollutant,and the conductive membrane as the cathode surrounded by stainless steel mesh as the anode.The experimental results revealed that EVMD can effectively inhibit the membrane fouling through the repulsive force of the electric field and other electrochemical effects.There would be achieved better anti-pollution effect with the electric field strength of 1.Ov/cm,and the relative flux increasing from 36.38%to 71.98%.When conductive membrane fouled by HA was cleaned by electrochemical method,the MD flux could be recovered effectively,and the flux recovery effect would increase with the increase of electric field intensity and cleaning time.The initial flux could increase from 8.5L/m2h to 11.75 L/m2h fixing field intensity and cleaning time at 1.0 v/cm and 8h,respectively.Finaly,when a conductive membrane was used as an anode for electro-catalytic degradation of a dye,and NaCl as electrolytes and a stainless steel mesh as a cathode,and nano-TiO2 was employed as electro-catalyst.The results showed that the degradation efficiency of dye increased with the increase of PUALM,the catalytic time,the intensity of the electric field and the addition of nano-Tio2,and decreased with increase of dye concentration.When the PUALM was 20g/m2,the decolorization rate of the dye was even up to 100%.PTFE conductive membrane possessed excellent catalytic stability,in which the decolorization rate was still up to 90.05%after repeated use 6 times.