| Water pollution is still the main challenge of the world today.Membrane separation technology has attracted more and more attention in the field of water purification due to its advantages of high efficiency,low energy consumption,simple operation and continuous operation.With the rapid development of economy and society,the composition of pollutants in wastewater becomes more and more complex.Therefore,it is urgent to develop a kind of water purification membrane with wide adaptability,low cost and eco-friendly,which can remove a variety of pollutants in water.Geopolymer nanoparticles（GPs）have many advantages,such as hydrophilicity,adsorption and the ability to construct microchannels.The surface roughness,hydrophilicity and mechanical properties of the composite membrane can be improved by adding GPs.In this study,three kinds of ultrafiltration membranes with different structures were prepared based on GPs.They were biomimetic heterogeneous multilayer（GPs-SA/CS）,mixed cellulose composite membrane（GPs-PVA/MCE）with geopolymer particles and polyvinyl alcohol as active layer,pore filled geopolymer particles chitosan/dopamine/glass fiber membrane（GPs-CS/PDA/GF）,and three kinds of ultrafiltration membranes were applied to oil emulsion,dyestuff and heavy oil in water.Removal of metal ions and other pollutants.The main results are as follows:（1）Inspired by the hierarchical structure and function of wood,a layer-by-layer assembly method was used to prepare multilayer films with heterogeneous structure.Geopolymer particles（GPs）with an average particle size of 1.36μm were prepared by suspension solidification method and doped into sodium alginate（SA）matrix to construct a“xylem”layer with numerous microchannels.Chitosan（CS）was used to construct a dense“phloem”layer.The biomimetic multilayers（GPs-SA/CS）showed obvious heterogeneous multilayer structure with water flux of 53.88 L·m-2·h-1·MPa-1.The results showed that the removal efficiency of the 50 nm polystyrene microspheres was 98.30±0.88%,the removal rate of crystal violet（CV）was 99.38±0.52%,the removal rate of Pb（II）was 99.41±0.50%,the removal rate of Cu（II）was 97.77±0.49%,and the removal rate of oil in water emulsion was 99.30±0.50%.In addition,the bionic membrane showed good stability in the use of oil-bearing emulsion for 7 consecutive days.（2）A multifunctional geopolymer particle polyvinyl alcohol/mixed cellulose ultrafiltration membrane（GPs-PVA/MCE）was prepared by assembling geopolymer nanoparticles（GPs）modified with polyvinyl alcohol（PVA）on the surface of mixed cellulose（MCE）by vacuum filtration.When the average particle size of GPs is 208 nm and the addition amount is 0.15 g,the performance of the composite membrane is the best,and the water flux is 11293 L·m-2·h-1·MPa-1.The multi-functional composite membrane showed excellent removal performance for different pollutants:100%of 50 nm polystyrene microspheres and 99.87%of emulsified oil in water could be removed by channel interception;100%of cationic dyes in water could be removed by adsorption;Compared with the original MCE membrane,the treatment capacity of the composite membrane was increased by 528.54%,25.78%and 90.96%respectively.Especially after continuous processing of oil-bearing emulsion,the flux of the composite membrane decreased only 21.70%after 1 h,much lower than that of the MCE film.The formation of active layer（GPs-PVA）on the base film increased the hydrophilicity of the composite membrane,so the antifouling performance was significantly improved.（3）On the basis of not changing the original thickness of glass fiber membrane（GF）,chitosan modified geopolymer nanoparticles dispersion（GPs-CS）was dynamically assembled in GF membrane,and then packed with polydopamine（PDA）to obtain“hole filled”adsorption ultrafiltration bifunctional membrane（GPs-CS/PDA/GF）.The addition of GPs-CS can effectively adjust the pore structure and hydrophilicity of the composite membrane,so that it has high throughput and ensures the performance of pollutant removal.The composite membrane is super hydrophilic and super oleophobic,and the removal rate of different types of oil in water is more than 99.50%.The adsorption capacity of GPs-CS can remove heavy metal ions and dyes in emulsion oil at the same time:the removal rates of6 mg·L-1 Pb（Ⅱ）,5 mg·L-1 crystal violet and 4 g·L-1 n-hexadecane in water are 100%,93.52%and 99.73%respectively.Compared with the multiple composite films reported in the literature,the advantages are obvious.After soaking in deionized water for 35 days,the removal rate of n-hexadecane in water can still reach 99.31%;After soaking in extreme acid-base conditions for one day,the removal rate is still above 99.30%,which proves that it has good stability and good application prospects. |
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