Doped Polydimethylsiloxane Membranes: Fabrication And Pervaporation Desulfurization Performance

As energy and environmental issues are being paid more and more attention,increasingly stringent restrictions on the sulfur content of gasoline have been made inmany countries and regions. With the advantages of low energy consumption andenvironment-benignity, membrane pervaporation separation process is obviouslyhighlighted with promising prospects, compared with many other gasolinedesulfurization methods.Polydimethylsiloxane （PDMS） is considered an excellent material forpervaporation desulfurization of gasoline, and multiple modification means becomethe focus of attention. This paper designed and prepared three kinds of additives forpolydimethylsiloxane to optimize the micro-structure of the membrane, in order toimprove its permeation flux and enrichment factor.First, the reversible Ï€-complexation of transition metal cerium and thiophene wasintroduced, and cerium loaded titanium dioxide nanospheres were added to thePDMS membrane. The effects of nanospheres content were studied. Operatingconditions were as follows: the liquid flow rate was40L·h^-1, the thiophene contentin octane was1312ppm, the operating temperature was25oC. When the content ofTiO₂-Ce nanoparticles reached7.5%, the permeate flux of the hybrid membrane was3.00kg·m^-2·h^-1with the enrichment factor of4.34.Subsequently, inspired by the adhesion function of protein with metal ions within,porous titanium dioxide-dopamine particles with an average pore size of46.1nmwere prepared using calcium carbonate nanoparticles as templates. In theabove-mentioned operating conditions, when the content of TiO₂-DA nanoparticlesincreased from0%to7%, the permeate flux increased to6.61kg·m^-2·h^-1, which wasa maximum value. The enrichment factor varied in the range of4.34to4.82for allinvestigated particles contents.Finally, a surfactant mixture of non-ionic surfactant Tween-80and Span-80, withdifferent HLB values, were prepared and added to polydimethylsiloxane as anadditive, which could improve the hydrophilicity of polydimethyl siloxanesignificantly, proved by the decrease of water contact angle from98oto37o. When the mass ratio of Tween-80and Span-80was3:7, and the mass ratio of the additive topolydimethylsiloxane was0.7:2, the flux was9.25kg·m^-2·h^-1with the correspondingenrichment factor of4.05.