Preparation And Characterization Of GO-Polyamide Nanocomposite Forward Osmosis Membranes

Forward osmosis(FO), deserved many focuses and researches, is an osmotically driven membrane technology, and it has many applications with broad prospect. In order to improve the permeability performance and antifouling performance, Support membranes and forward osmosis membranes were modified by blending with GO in this paper. The membranes were preparated by phase inversion and interfacial polymerization. With the help of cross-flow testing platform and forward osmosis testing platform, the water flux and reverse solute diffusion flux of the modified membranes were investigated.The results showed as follows:(1) By means of process conditions and operation performance, the inorganic nanoparticles modified membranes had been studied. The results showed that the modified membranes of PES/GO and PES/GO/TiO2 were been typical finger-like pore structure, and the mean pore size was increased, the fluid resistance was decreased, the static angle was smaller, the hydrophilicity improved, the thermal stability improved, and the surface roughness was smaller than the pure membranes, mechanical strength also improved. At the same time, the pure water flux, rejection rate and antifouling ability of the modified membranes greatly improved. With the improvement of the GO blending, the pure water flux of the support membranes first increased and then reduced. When the GO blending reached 0.5%, the pure water flux reached its peak of 265 LMH, which was up to 55% higher than pristine membranes. Compared to pure membranes, the rejection rates of BSA and SA improved at different degree. The ultrafiltration membrane loading GO and nano-TiO2(0.8%GO+0.2%nano-TiO2) had the optimal performance in permeability. The pure water flux of the membrane with 0.8%GO+0.2%nano-TiO2 reached 260 LMH, up to 52.1% higher than pristine ultrafiltration membrane. During the 180min’s filtration tests of BSA and SA solution, the stable flux reached 67.8 and 68.0LMH respectively, and both of the rejections were more than 99%.(2) The operation processing and polymerization methods of FO membranes were emphatically studied. The results showed that GO-blending thin film nanocomposite forward osmosis membranes had obvious shape of “peak and valley”, as a result, the surface roughness was bigger than the pure membranes, and the thermal stability improved. With the help of GO, the pure water flux and reverse solute diffusion flux increased greatly. GO-blending thin film nanocomposite forward osmosis membranes first increased and then reduced with the GO blending increasing. Compared to the pure TFC membranes, the water flux of the TFC0.5 membrane was improved by 133% and 108% respectively under different FO/PRO modes. But the reverse solute diffusion flux of all the membranes became serious in view of the salt blending effect. It could be seen that by the research of the physical influencing factors of GO-blending thin film nanocomposite forward osmosis membranes, the water flux of PRO was bigger and the reverse solute diffusion flux was more serious compared to FO mode. From the perspective of velocity, the cross-flow velocity was smaller; the water flux was also smaller and reverse solute diffusion flux was smaller. From the perspective of driving force of osmotic pressure, the water flux increased and the reverse solute diffusion flux also increased with the concentration of draw solution increasing. When the draw solution was NaCl and Glucose solution, the water flux of NaCl was bigger. It could be seen that by the research of the chemical influencing factors of GO-blending thin film nanocomposite forward osmosis membranes, the more the number of interfacial polymerization was, the more the water flux increased, and the more the reverse solute diffusion flux decreased. From the perspective of the double interfacial polymerization, the water flux and reverse solute diffusion flux were decreased greatly compared to the simple interfacial polymerization.(3) The antifouling of FO membranes were emphatically studied. The results showed that whatever the pollutants consisted of organic systems, or inorganic systems, or organic systems & inorganic systems, attenuation rate of the water flux of TFC0.3 was smaller, and the final stable water flux was bigger compared to the pure TFC membranes. At the same time, by mixed nano-TiO2, combined pollution reduced, and the water flux became stable from the perspective of the organic pollutants between BSA and SA.