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Research On Forward Osmosis Membranes With Turing Structures

Posted on:2021-03-05Degree:MasterType:Thesis
Country:ChinaCandidate:S Q ZhangFull Text:PDF
GTID:2491306548984879Subject:Chemical Engineering
Abstract/Summary:PDF Full Text Request
Forward osmosis(FO)technology has received widespread attention in water treatment field owing to its inherent characteristics of low energy consumption,low pollution,and low cost,which alleviated the stress caused by scarcity of water resource and energy crisis.In this study,the support layer and active layer of FO membrane were regulated and optimized,and the preparation of Turing structure composite membrane was explored to achieve the important indexs of high water flux(Jv)and low reverse solute flux(Js)of FO membrane.NaCl of different concentration used as draw solution(DS),the properties of composite films with different PVP concentrations and thickness of support layer were studied under the two modes of active layer facing feed solution(AL-FS)and active layer facing draw solution(AL-DS).The results showed that the overall performance of TFC-PVP3.5 membrane was the best in AL-DS mode,with Jv of 55 L·m-2·h-1,Js of9.828 g·m-2·h-1,and R reached 98.9%,when the concentration of PVP was 3.5 wt%,the thickness of AL was 30μm,and 4 mol·L-1 NaCl was used as the DS.The SEM images of TFC-PVP3.5 membrane revealed that the surface of the composite membrane showed uniform pore structure and the cross surface presented dense sponge-like structure.The uniformly distributed based layer provided favorable sites for the loading of polyamide.The roughness(Ra)of TFC-PVP3.5 membrane was as low as 11.2 nm,which laid the solid foundation for the modification of AL.On the basis of TFC-PVP3.5,the effects of interfacial polymerization(IP)temperature,concentration,and different types of hydrophilic macromolecules(polyvinyl alcohol,polyacrylamide,and polyvinyl pyrrolidone)on the performance of membrane were furthered investigated.The results showed that the performance of TFC-PVP(3:1)membrane was the best in AL-DS mode,with Jv of 75 L·m-2·h-1 and Jsof 6.201 g·m-2·h-1,when the IP temperature was 20°C,the mass ratio of PVP to PZ was3:1,and 4 mol·L-1 NaCl was used as DS.The Jv of TFC-PVP(3:1)was 36%higher than that of TFC-PVP3.5.In the morphologies of SEM and AFM,the relatively regular stripe-like Turing structures can be seen clearly in the AL.2D DOSY NMR showed that the difference between the diffusion rates of PZ and TMC was in the range of 10-100,which reached the conditions for the formation of Turing structure.2.5 mol·L-1 MgCl2 used as DS for simulated desalination test,the Jv of TFC-PVP(3:1)reached 25 L·m-2·h-1and Jvdecreased to 12 L·m-2·h-1 after stable operation within5 h.After continuous deionized water cleaning of the TFC-PVP(3:1)membrane for 1h,Jv gradually recovered to the original level of 25 L·m-2·h-1.Compared those of published literatures,the Js/Jv value of TFC-PVP(3:1)was as low as 0.02 g/L and the performance of Jv,Js,and R reached the best.
Keywords/Search Tags:Forward osmosis membrane, Support layer, Active layer, Turing structure, Water flux, Reverse solute flux
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