| Trace organic compounds?TOrCs?pose significant harm to water resources and human health due to their physiological activity at trace concentrations,which have received increasing attention.Compared with other membrane separation technologies,forward osmosis?FO?has the characteristics of low energy consumption,high recovery,good anti-fouling performance and a good barrier to TOrCs.It is widely regarded as an effective new technology for treating polluted water.Interfacial polymerization is one of the most effective methods for preparing composite FO membranes at present,but the conventional composite FO membranes produced have the problems of low water flux and large reverse salt flux.Based on the interfacial polymerization method,this paper analyzed various influencing factors in the process of preparing membrane,and added graphene oxide?GO?nanomaterials and polydopamine?PDA?to modify the composite FO membrane to improve its performance and obtain the optimal preparation conditions.On this basis,using the prepared GO/PDA composite FO membrane and commercial HTI-CTA membrane to compare the rejection effect of TOrCs?ibuprofen?in water,explored the influencing of different operating conditions on the performance of the GO/PDA composite FO membrane for rejecting ibuprofen.The main research results were showed as follows:1)The composite FO membranes were fabricated by interfacial polymerization method using polyacrylonitrile?PAN?as the substrate in this study.Then the effects of casting solution composition and interfacial polymerization conditions on the properties of synthetic FO membranes were investigated in detail.Results showed that the optimized casting solution was:the concentration of PAN,N,N-dimethylformamide?DMF?,anhydrous lithium chloride and absolute ethanol in the casting solution were 16%,75%,4%and 5%,respectively.The optimized active layer preparation conditions were following:immersing the base membrane in 2%m-phenylenediamine?MPD?water solution with pH=9 for 120 s,and conducting the interfacial polymerization with 0.1%trimesoyl chloride?TMC?for 60 s to form active layer which was attached to the front surface of membrane,finally 3 min heating treatment at 60?.2)The performance of the composite FO membrane was optimized by adding GO for blending modification and further using PDA for adhesion modification on the surface of the support membrane.Results showed that adding 0.075%GO to the water solution for modification,which contributed to a 26%increase in water flux and above 99.90%rejection rate,meanwhile the anti-fouling property of synthetic FO membrane was also significantly enhanced.The optimum PDA concentration and action time were 2 mg·mL-1 and 40 min respectively.After modification,more and more GO nanosheets were bound to the surface of the composite FO membrane,and the water flux increased by 35%.The rejection rate was still higher than 99.85%,and the anti-fouling capability was further improved.3)The performance of the GO/PDA composite FO membranes were systematically characterized by different instruments.Results showed that the interfacial polymerization active layer with porous network structure and a stacked GO sheet were formed on the surface of the membrane,and the modification of PDA caused more GO to bind on the surface of the membrane.The interfacial polymerization reaction introduced a large amount of amide functional groups,there were abundant oxygen-containing functional groups on the GO nanosheets,and a strong covalent bond could be formed between PDA and GO.With the formation of the interfacial polymerization active layer,the roughness of the composite FO membrane was getting larger and larger,and the hydrophilicity was also getting better and better after modification by GO and PDA.The polyamide composite FO membrane itself had a negative charge.After modification by GO and PDA,the zeta potential on the surface of the membrane was continuously reduced,which made the membrane have more negative charge and improved the stability and anti-fouling property of the composite FO membrane.4)The influencing factors of pH and temperature of feed solution,concentration of draw solution,concentration of TOrCs and membrane fouling on the performance of GO/PDA composite FO membrane for rejecting ibuprofen were investigated.Results showed that the change of the rejection rate of ibuprofen by GO/PDA composite FO membrane was similar to that observed in the commercial HTI-CTA membrane with the change of the operating condition parameters,but the pH and temperature of feed solution and the concentration of draw solution had little influence on the performance of GO/PDA composite FO membrane for rejecting ibuprofen,and the rejection rate of ibuprofen by GO/PDA composite FO membrane was significantly higher than that of CTA membrane. |
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