Preparation And Application Of High Performance Nanofiltration Membrane Based On Porous Functional Materials

As a burgeoning membrane-based technology,nanofiltration(NF)is a promising candidate owning to the environmental friendliness,high efficiency and low-energy process,rendering it an ideal wastewater treatment technology.However,the dense crosslinking structures among polymeric NF membrane result in the low permeance,which means higher membrane areas and greater capital investment.Therefore,it is imperative to further develop a high permeance and high rejection NF membrane.Firstly,a NH2-MCM-41/polyimide(PI)mixed matrix membrane(MMM)was prepared.MCM-41 was modified by APTES to obtain NH2-MCM-41,and doped into PI to prepare NH2-MCM-41/PI mixed substrate membrane.NH2-MCM-41 can be chemically crosslinked with PI to improve the compatibility between the two phases,and its mesoporous properties provide additional transport channels for solvents and greatly reduce the transport resistance.In addition,-NH2 as a hydrophilic group is also beneficial to increase the transport of polar molecules(water and alcohols).Furthermore,the effect of different doping amount on the performance of the NF membrane was evaluated:the 5 wt%NH2-MCM-41/PI MMM shows the best performance:compared with pure PI membrane,the permeances in water,ethanol and isopropanol systems were increased by 102%,78%and 131%,respectively,while the rejection rate remained basically stable.During the long test period of 50 h,the NH2-MCM-41/PI mixed matrix membrane showed excellent stability.Secondly,a tubular COF-300 nanofiltration membrane was prepared.The ceramic substrate was firstly modified,and then the continuous and uniform COF-300 nanofiltration membrane was prepared by an in-situ solvothermal synthesis method.The grafted aldehyde group and TAPM can form coordination bonds,which successfully strengthens the adhesion between the substrate and the membrane,and promotes the nucleation and growth of COF-300 on the substrate to a large extent.The nanofiltration performance of tubular COF-300 membrane was tested in five different dye aqueous solutions,among which the highest water permeance was 83.66 L m-2 h-1 bar-1,and the lowest was 51.26 L m-2 h-1 bar-1,much higher than the commonly used polymeric nano filtration membranes(10-20 L m-2 h-1 bar-1).Meanwhile,it can effectively intercept rose red,methyl blue,congo red and chrome black T dyes.In addition,the stability test was carried out in chrome black T aqueous solution for a long time.The tubular COF-300 membrane displays a permeance of about 80 L m-2 h-1 bar-1 for 90 h,and the rejection rate was more than 98%.