Study On The Influence Of Polymer Plasticization On Mass Transfer Behavior Of PVC-based PIM

Polymer inclusion membranes(PIM)has become a hot area of research in liquid membranes because of its good stability and high selectivity of mass transfer behavior.In this paper,two plasticizers of polymethyl methacrylate(PMMA)and styrene maleic anhydride copolymer(SMA)were doped,and modified to prepare,the polymer doped modified PD-PIM and PN-PIM with polyvinyl chloride(PVC)as the substrate were prepared.The structural characteristics of modified PIM doped with polymer were investigated.The effects of the modification of polymer plasticizer on the transmission behavior of PIM were investigated with metal In(?),small molecule organic phenol and p-nitrophenol(PNP)as the objects of mass transfer.The main research contents were as follows:(1)The compatibility between PMMA,SMA and PVC was studied by solubility parameter method and mixture enthalpy method.By means of IR,SEM,XRD,mechanical properties and other analytical techniques,the physical and chemical properties of the binary blend membranes of PMMA/SMA and PVC prepared with tetrahydrofuran(THF)as co-solvent were investigated,and the blending compatibility between PMMA/SMA and PVC was analyzed.The results showed that the blending of PVC and PMMA/SMA belonged to a partially compatible system,and the critical blending mass ratios were 80:20 and 85:15,respectively.Compared with SMA,the hydrogen bonding and dipole interaction between PMMA and PVC are more significant.The mechanical properties of the binary blend membranes were better than that of PVC membrane within PMMA20% and SMA15%.These two kinds of binary blend membranes all showed a "Sea Island" surface structure,and there were third heterogeneous phases in the PVC/SMA blending membranes.With the increase of PMMA and SMA content,the "islands" area and discontinuous phases increases gradually.(2)A series of PMMA plasticized PVC/di(2-ethylhexyl)phosphoric acid(D2EHPA)polymer inclusion membranes were prepared.The microstructure,interaction,crystallization behavior and mechanical properties of each component in PMD-PIM were analyzed and characterized.The mass transfer behavior of PMD-PIM was investigated using In(?)as the mass transfer target.The results show that the interaction between D2 EHPA and PMMA is strong,and the surface morphology of the series of PMD-PIM membranes is quite different from that of PVC/PMMA binary blend membranes without carrier.A dense distribution of convex structure appeared on the surface of membrane,and its number and radius increased with the increase of PMMA.Compared with the unplasticized PD-PIM,the mass transfer ability of PMD-PIM to In(?)is greatly enhanced and has good stability.The permeability coefficient at the best mass transfer condition is 17.44 ?m/s,and the concentration of PMD-PIM to In(?)is 6.5 times in 122 h.After PMMA plasticization,the mass transfer mechanism of PD-PIM to In(?)was changed from the jumping mechanism of the fixed site to the carrier diffusion mechanism,and the speed control step was changed from chemical complex control to diffusion control.(3)A series of polymer inclusion membranes(PMN-PIM)using PMMA polymer plasticized PVC/N,N-di(1-methyl heptane)acetamide(N503)as the carrier were prepared.The effects of PMMA plasticization on the structure and mass transfer properties of PIM were investigated with phenol and p-nitrophenol(PNP)as mass transfer targets.The research shows that the plasticizing ability of N503 to PMMA is stronger than that of PVC.The island part on the surface of the original PVC/PMMA binary blend membranes evolves into a circular convex structure due to the plasticization of N503 to PMMA.Compared with the unplasticized PN-PIM,the introduction of PMMA did not change the mass transfer mechanism of PN-PIM to phenol,but the mass transfer capacity of PMNPIM to phenol was greatly improved,and it had good stability.The permeability coefficient remained unchanged in the six cycles of continuous mass transfer processes,and the removal rate of the solution containing up to 200mg/L of phenol reached the national emission standard 1mg/L.Compared with phenol,the transmission rate of PNP on the PN-PIM and PMN-PIM with N503 as the carrier is faster.The transmission rate of these two kinds of membranes conforms to the first order kinetic equation.The transmission rate is controlled by the diffusion step in the membrane.The enrichment multiplier of the phenol is 3.2 times in 120h;the enrichment factor of PNP is 6.5 times in 208 h.(4)PSN-PIM was prepared using SMA plasticized PN-PIM,and the morphology and structure of PSN-PIM for the mass transfer behavior of two phenols were investigated.The study shows that the mass transfer of PSN-PIM to phenol is a fixed site jump mechanism,and the mass transfer of PSN-PIM to PNP is the carrier diffusion mechanism;the control stage of the transmission rate of phenol through PSN-PIM is mainly chemical reaction process,while PNP control stage through PSN-PIM is still mainly membrane diffusion process.The 6 cycle transmission experiment of PSN-PIM to phenol showed that PSN-PIM had good stability.