Preparation And Applications Of Functional Inorganic Porous Materials In Environmental Protection

With the rapid development of economic globalization and urbanization,millions of oily sewages and particle matters?PM?are discharged from the offshore oil exploitation,transportation,industrial production,automobile emissions,coal combustion,etc.,which have become one of the most urgent global environmental problems that seriously threaten the water and atmospheric ecological environment as well as republic health and quality of life.Therefore,the preparation of high-efficiency separation materials has attracted tremendous research interest.Till now,the separation and purification technologies,in particular the oil-water separation and air filtration,have been deeply researched and a large number of advanced functional materials have been successfully developedInorganic porous materials are widely applied in heterogeneous catalysis,gas separation and storage,host-guest assembly,etc.because of their large surface area,high porosity,exquisite open-framework structures,and superior chemical/thermal stability,and are finding emerging applications in the energy and environment-related fields.Therefore,the present dissertation is committed to develop the functionalized inorganic porous materials to address the environmental issues of oily wastewater and air pollutions;the superhydrophobic magnetic core-shell dendritic mesoporous organosilica nanoparticles,the antibacterial flexible porous SiO₂-TiO₂ nanofibrous membranes and the anti-biofouling zeolite-coated mesh films have been fabricated,which can achieve high-efficient oil-water separation or PM filtration.These materials provide some ideas for the designed preparation and applications of functional inorganic porous materials in environmental protection.The main achievements are as follows:1.The magnetic core-shell dendritic mesoporous organosilica nanoparticles?Fe₃O₄@DMONs?were fabricated by a step-by-step condensation process.The Fe₃O₄@DMONs exhibited superhydrophobic property and could rapidly and efficiently adsorb dispersed tiny oil droplets from oil-in-water emulsions,and the separation efficiency was higher than 98.06%.After the adsorption process,the dispersed Fe₃O₄@DMONs could be easily collected by using a magnet due to the magnetically responsive property.Compared with the nanoparticles?Fe₃O₄@MONs?without dendritic architecture,Fe₃O₄@DMONs possessed larger adsorption capacities(ranging from 1.37 to 2.04 g g^-1)for various oils.In addition,the Fe₃O₄@DMONs remained stable after five separation-regeneration cycles,giving separation efficiency of higher than 97.90%.Furthermore,Fe₃O₄@DMONs could also realize efficient adsorption of water-soluble dye from oil-in-water emulsions,and the adsorption efficiency was higher than 89.45%.Therefore,Fe₃O₄@DMONs possessed important potentials as candidate for the practical purification of industrial wastewater.2.The flexible porous SiO₂-TiO₂ nanofibrous membranes were fabricated by electrospinning technique,which were further functionalized by embedding Ag nanoparticles into the nanofibers via an impregnation method?Ag@STPNM?.Compared with the reported air filters,Ag@STPNM possessed advantages of high surface polarity,porous structure,low density,high PM removal efficiency and low pressure drop.For example,the removal efficiency and the pressure drop of Ag@STPNM for PM_2.5 reached to 98.84%and 59 Pa,respectively,the basis weight of which was only 3.9 g m^-2.Thanks to the excellent thermal stability,the PM adsorbed on the Ag@STPNM could be cleaned up via a calcination process.The Ag@STPNM could remain filtration performance during five purification-regeneration cycles,as well as the long-time filtration for 12 h,which showed outstanding recyclability and durability.Furthermore,the Ag@STPNM showed obvious antibacterial activity,which could effectively inhibit the growth of bacteria,giving the bacteriostatic rate of 95.8%.Therefore,Ag@STPNM possessed promising potentials as candidate for the practical purification of indoor environment or personal air.3.ZSM-5 zeolite membranes were fabricated on the stainless-steel meshes via secondary hydrothermal growth process,and then functionalized through an Ag⁺ions exchange process?Ag@ZCMF?.The Ag@ZCMF showed superamphiphilicity in air,but became superoleophobic when immersed in water.Based on the special wettability,the Ag@ZCMF could efficiently separate various oil-water mixtures.In addition,the separation efficiency of Ag@ZCMF with optimum secondary growth time of 14 h?Ag@ZCMF-14?was higher than 99%,water flux and intrusion pressure of which were closed to 54720 L m^-2 h^-1 and 4357 Pa,respectively.After ten purification-regeneration cycles,the separation efficiency of Ag@ZCMF-14 kept stable and no obvious attenuation was observed,which exhibited high stability.Furthermore,the loaded Ag⁺ions afforded the membranes excellent anti-biofouling activity,which could achieve resistance to the breeding of both alga and bacteria in the operating environment,therefore avoiding the blockage of the membranes to degrade oil-water separation performance.