Preparation And Characterization Of Solvent-resistant Organosilica Nanofiltration Membrane

Organic solvents are widely used in petroleum,petrochemical,pharmaceutical,printing,textile and other industrial fields,and the usage of organic solvents is increasing year by year.Environmental pollution and safety issues caused by organic solvents cannot be ignored,so how to reuse organic solvents more safely and effectively is particularly important.Organic solvent nanofiltration is a new type of green,energy-saving and environmentally friendly membrane separation technology,where the key is solvent resistant nanofiltration membrane.The influence of membrane microstructure and the change of bridging group’s properties were systematically investigated on organic solvent nanofiltration membrane.Organically bridged silica nanofiltration membranes were prepared by sol-gel technique,using 1,2-bis(triethoxysilyl)ethane(BTESE)as the silica precursor.The influence of sol synthesis conditions on BTESE particles were systematically investigated for organic solvent nanofiltration.The pore structure and physicochemical properties of the membranes were characterized by dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FT-IR),thermogravimetric analysis(TGA),nitrogen adsorption-desorption isotherm measurement and field emission scanning electron microscopy(FE-SEM).The influence of operating variables such as operating pressure and feed temperature on the membrane separation performance were systematically investigated.The experimental results showed that BTESE membrane exhibited good RB5 rejection and DMF flux,and DMF permeability remained stable.In the 720 min stability experiment,the BTESE membrane showed good solvent resistance,which remained at 1.05±0.1 kg·m-2·h-1 and 99%,respectively.A promising new ethenylene–bridged organosilica membrane has been developed for organic solvent nanofiltration.BTESEthy membrane was prepared by a sol-gel method through an acid-base two-step catalytic reaction.The effect of ethenylene groups on the pore microstructure and surface properties of the membrane were investigated.The network structure formation and solvent transfer mechanism of BTESEthy organic solvent nanofiltration membrane were discussed.Due to the introduction of polarizable and rigid ethenylene bridges in the silica networks,the membrane exhibited an improved DMF affinity and superior hydrothermal stability.The research on the transfer mechanism shows that the acid-base two-step catalysis will cause the membrane network structure to rearrange and become looser.Organically bridged silica membranes were prepared by sol-gel technique,using 1,4-bis(triethoxysilyl)benzene(BTESB)and 1,6-bis(triethoxysilyl)hexane as the silica precursors.The effect of the flexibility and rigidity of the bridging group and the long-term stability on organic solvent nanofiltration membranes were investigated.The results show that the long flexible carbon chain bridging groups are easy to bend,which lead to the collapse of the pore structure.The pore size distribution exceeds the range of the nanofiltration membrane.Due to the introduction of polarizable and rigid benzene ring bridges in the silica networks,which increased its effective pore size and had a good affinity for DMF,the BTESB membrane exhibited high permeability.In the 100-hour continuous experiment with cleaning operation,the initial flux of BTESB membrane decreased by only 13.4%.After simple cleaning,the flux recovered to 96.2% of the initial flux,showing excellent solvent stability.