| In recent years,Forward Osmosis(FO)membrane separation technology has been attracted more and more attention because of its advantages such as low energy consumption and low emission.Firstly,a high performance cellulose acetate membrane was prepared in this paper.Secondly,four kinds of metal organic frameworks(MOFs)materials with porous structure and the highly hydrophilic Graphene oxide(GO)materials were synthesized.And then the MIL-101(Cr)was implanted into the surface of the graphene oxide to synthesize the MIL-101(Cr)/GO composite with both porous and hydrophilic properties that based on this two materials can be surface modified.Then they were used as blend additives to improve the forward osmosis membranes performance.In this paper,high performance forward osmosis membrane was prepared by using cellulose acetate(CA)as membrane material,polyester screen as membrane support lattice,N,-methylpyrrolidone(NMP)and acetone as solvent,polyethylene glycol(PEG)as pore additive.The effects of various process parameters to the membranes performance were systematically studied and the optimum parameters were obtained.At the same time,the performance and structure of the film were also characterized.The best membrane parameters are as follows: the CA content was 12wt%,the best pore-form additive is PEG-400 which content was 3wt%,the blending temperature is 45?,the coagulation bath temperature is25?.At this point the water flux of the membrane was 50.9L/m2·h,reverse salt flux was3.6g/m2·h.From the scanning electron microscope,it was observed that the membrane had a typical asymmetric structure,and the finger-pore structure in support layer is well developed.On the basis of the above experiments,cellulose acetate/metal organic framework forward osmosis membrane was prepared.ZIF-8,MIL-53(Fe),MIL-100(Fe)and MIL-101(Cr)were prepared by hydrothermal(solvent)method(or mechanical stirring method)They were characterized by FTIR,XRD and SEM respectively.The results showed that four kinds of nanomaterials were synthesized successfully.The effect of various factors on the membrane properties were studied systematically by using MOFs as modified additives and the optimum process parameters were obtained.The best membrane parameters are as follows: the type of MOF was MIL-101(Cr)which content was 0.2wt%,the best blending temperature was 60?and the heat treatment temperature was 60?.At this point the water flux of the membrane was 63.7L/m2·h,reverse salt flux was 2.2g/m2·h.From the scanning electron microscope,it was observed that the surface of the membrane had obvious nanoparticle deposits,and the membrane pores of the support layer were more dense than the unmodified film.On the basis of high performance CA forward osmosis membrane membrane,cellulose acetate/graphene oxide film was prepared.GO was prepared by modified Hummers method.It was characterized by FTIR,XRD and SEM respectively.The results showed that GO was synthesized successfully.The effect of various factors on the membrane performance were studied systematically by using GO as a modified additive and the optimum process parameters were obtained.The best membrane parameters are as follows: the addition content of GO was 0.5wt%,the best blending temperature was 50? and the heat treatment temperature was 70?.At this point the water flux of the membrane was 65.2L/m2·h,reverse salt flux was 1.5g/m2·h.From the scanning electron microscope,it was observed that the membrane surface roughness and surface cracks of unmodified membrane were significantly improved after doping GO,and the nano-GO particles were attached to the inner pore of the membrane and the wrinkled surface of GO also increased the area of the positive permeable membrane,so that the water flux was improved.In this paper,cellulose acetate/composite forward osmosis membrane was also prepared.The MIL-101(Cr)/GO composites were synthesized by hydrothermal method.It was characterized by FTIR,XRD and SEM respectively.The results showed that composite was synthesized successfully.The effect of various factors on the membrane performance were studied systematically by using composite as a modified additive and the optimum process parameters were obtained.The best membrane parameters are as follows: the addition content of MIL-101(Cr)/GO composites was 0.3wt%,the best blending temperature was 50? and the heat treatment temperature was 60?.At this point the water flux of the membrane was74.5L/m2·h,reverse salt flux was 1.2g/m2·h.From the scanning electron microscope,it was observed that the surface and support layer of composite forward osmosis membrane had internal nanoparticles attached.Compared with the unmodified membrane,the surface roughness of the film was significantly increased and the support layer was more dense.Finally,the four kinds of self-made cellulose acetate FO membrane and HTI-CTAcommercial film were studied by desalination.In this experiment,seawater was used a feed solution(FS)and the glucose solution of 2mol/L was used as driving solution(DS),the changes of water flux and salt removal rate of different kinds of FO membrane were tested by the forward osmosis device.As far as the water flux,the four kinds of self-made forward osmosis membranes were obviously higher than that of the HTI commercial membrane.However,in terms of stability,there was a certain gap between the self-made film and HTI film.The water flux of the modified membranes was better than that of the blank membrane.In the performance of the three modified films,composite blending membrane was the best.In terms of the salt rejection rate,there was a certain gap between the self-made membrane and the HTI membrane too.During the testing process,the HTI film could be maintained at about 99.9%,while the self-made film taked a certain amount of time to reach a stable state,and was significantly lower than that of the HTI film.The results showed that the salt rejection rate of the blend film was better than that of the blank film,and the performance of the MIL-101/GO film was better than that of the other two kinds of blending membranes. |
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