Synthesis Of Polythiourea Derivatives And Studies On Properties Of Their Microfiltration Membranes

With the rapid growth of population and development of industry,the serious waste and pollution of water resources has become an environmental problem that people have to face.The heavy metal ions pollution in water is a problem that needs to be focused on because the metal ions cannot be naturally degraded,and are very harmful to humans.Currently,the treatment of heavy metal ions in water is mainly by chemical treatment.However,chemical treatment often introduces some new problems,such as excessive additives.Therefore,it is necessary to find a suitable physical method to solve this problem.Membrane water treatment,as an emerging water treatment process,has the advantages of low cost and high separation efficiency,and has been widely used.However,the removal of heavy metal ions in water by membrane water treatment is quite limited.In this study,a polyurea-polythiourea copolymer U-TU-D400 was synthesized with polyetheramine D400,HDI isocyanate,1,1-thiocarbonyl diimidazole.Then it was blended as a modified additive with the cellulose acetate(CA)membrane.Since this copolymer contains such as amino or thiourea group that can interaction with heavy metal ions,it is used as an additive for the modification of the blending in order to obtain a filter membrane that has heavy metal ion adsorption effectFirst of all,the synthesis of polyurea-polythiourea copolymer was carried out,and the structure of the obtained copolymer was characterized by means of FTIR spectroscopy and 1H-NMR spectroscopy.It was proved that this copolymer was successfully synthesized.After that,the pure cellulose acetate membrane and the modified membrane were were prepared by immersion-precipitation phase transformation method,and their structures were characterized.And we investigated the effect of CA and the additive U-TU-D400 concentrations on the structure of the membrane.Studies have shown that the increase of CA content makes the viscosity of the casting solution larger,thus slowing down the diffusion rate of non-solvent in the phase inversion process,resulting in the generation of delayed phase separation.The porosity and pore diameter of the film are made small.The additive U-TU-D400 tends to move toward the surface of the membrane pore during the phase inversion process,and a relatively uniform finger-like pore is formed inside the porous layer of the membrane.After the structures of different membranes were studied,this study focuses on the performance test of the membrane.Firstly,the basic properties such as the flux and rejection of the membranes before and after modification are tested to select a suitable ratio for subsequent analysis.The experimental results show that the membrane with a CA concentration of 14 wt%has a good comprehensive flux and rejection.After that,U-TU-D400 is added to modify the membrane to test the flux and rejection,anti-pollution performance,and mechanical properties of the modified membrane.And the heavy metal ions adsorb performance of the modified membrane were further studied.It was confirmed by experiments that the membrane with U-TU-D400 added had certain adsorption of heavy metal ions in water.The antibacterial properties of the modified membrane were also studied.The results showed that the membrane can partly inhibit the bacteria and alga growth on the membrane surface.