The Preparation And Separation Of Silicalite-1/PDMS And PIM-1 Based Organic Solvent Membranes

Organic solvent nanofiltration(OSN)is an extension of nanofiltration to applications in organic solvents,which is a novel efficient and green unit process to separate mixtures down to a molecular level.This study chooses two kinds of polymer materials,PDMS with strong thermal and chemical stability and polymer of intrinsic microporosity PIM-1.The study aims to improve the solvent stability and separation performance of polymers in OSN by respectively filling the Silicalite-1 zeolite molecular sieve into PDMS and modifying the PIM-1 composite film with ultraviolet irradiation.First,Silicalite-1 was prepared by hydrothermal synthesis method and modified with silane coupling agent VTES(vinyl triethoxy silane).By filling the VTES modified Silicalite-1 into PDMS/PVDF composite membrane,we studied the influence of molecular sieve amount and modifying agent on the membrane swelling degree and separation performance.Results showed that Silicalite-1 effectively improved PDMS swelling,the optimal amount was 10%,swelling degree of PDMS hybrid membrane in ethyl acetate,toluene,methylene chloride and tetrahydrofuran decreased by 13%,23%,16%and 41%.With the increase of VTES modified Silicalite-1 amount,ethanol flux of PDMS hybrid membrane showed a slight decrease,while a significant higher selectivity was achieved,the molecular cut off(MWCO)decreased from 799.5 to 324 g/mol.When filling amount was 5%,the rejection to methyl orange of the hybrid membrane was 95.8%,the ethanol flux was 0.77 L/m2hMpa.The PIM-1/PVDF composite membranes were prepared using dip-coating method.By modifying PIM-1 with ultraviolet(UV)irradiation,we studied the UV effect on the membrane solvent stability and separation performance.After UV irradiation,PIM-1 polymer showed decreases in both the pore size and the fractional free volume(FFV).And the swelling resistance of the PIM-1 were significantly improved,the SD(%)of UV-4h-PIM-1 membrane in toluene,ethanol,methyl alcohol and n-hexane decreased by 80%,40%,17%and 25%,respectively.Moreover,better retentions to different dyes without sacrificing solvent fluxes were obtained in the UV-irradiated PIM-1/PVDF composite membranes which showed the potential for OSN applications.UV 8h resulted in a monotonously decrease in the molecular weight cut-off(MWCO)from 600 to 324 g/mol while the ethanol flux maintained at about 5.6 L/m2hMpa.