| Phenol and aniline as two typical industrial chemicals,the discharge of dilute aqueous solution will cause serious ecological damage.Therefore,separating and recycling them not only has economic value,but also has environmental benefits.Furfural as a platform compound is derived from biomass hydrolysis.Timely separation of it from hydrolysate can effectively increase the yield.Pervaporation technology has great potential in the separation and recovery of high boiling point organic matters because of its economic,environmental protection and easy amplification.Poly(ether block amide)(PEBA-2533)has excellent separation performance for pervaporation of phenol and aniline.It is of great significance to study the swelling property and mass transfer characteristics for the selection of membrane materials and the adjustment of membrane structure.In this paper,the diffusion characteristics of component molecules inside PEBA-2533 membrane and membrane swelling property in phenol,aniline and furfural solution were studied by Materials studio(MS)software.PEBA-2533 membrane was used to separate the furfural in dilute aqueous solution by pervaporation.Molecular dynamics(MD)simulation was adopted to study the feed-membrane surface affinity and transport behavior of furfural molecules when a PEBA-2533membrane was employed.The furfural molecules exhibited a stronger interaction with the PEBA-2533 membrane than the water molecules.Transport behavior analysis indicated that the self-diffusion selectivity in the membrane increased with an increase in feed furfural concentration and the cavity size of the membrane was crucial for the separation of larger molecules.Additionally,the fractional free volume,fractional accessible volume,and fractional cavity volume(FCV)of the PEBA-2533 membrane were analyzed to reveal the variation in membrane structure.The invariant peak position of the FCV illustrated that the swollen volume was mainly distributed between the polymer chains.Interestingly,the water flux was more sensitive to the variation in membrane thickness than the furfural flux.The permeate furfural concentration increased with an increase in membrane thickness and a membrane selectivity damping model was proposed to explain this phenomenon.The MD technique showed great potential as an approach to characterize the performance of the PEBA-2533 membrane during the pervaporation process.In order to study the difference of membrane swelling degree and adsorption concentration in phenol,aniline and furfural solution,three kinds of solution models were constructed and the molecular dynamics simulation was carried out.It is found that the greater the non-bond interaction energy and the more the number of hydrogen bonds between the high boiling point organic matter and the water molecules is,the greater the swelling degree of PEBA-2533 in the solution is.It revealed that the swelling degree of PEBA-2533 in organic solution is closely related to the ability of organic compounds to form hydrogen bonds.The variance of the dispersion component parameter,the polar component parameter and the hydrogen bonding component parameter between the organic molecules and the water molecules were calculated to measure the affinity between them.The greater the affinity is,the greater the membrane swelling degree is.In addition,the aggregation of phenol molecules is most serious in the membrane,followed by aniline,and furfural is uniformly dispersed in the membrane.It is suggested that the membrane swelling degree will be greater if the molecules are easier to reunite.Interestingly,the concentration of organic matter in the membrane is not related to the swelling degree.The analysis of feed-membrane surface affinity revealed that the larger the concentration of organic matter on the membrane surface,the greater the concentration of organic matter in the corresponding membrane.To sum up,MD technology has great potential in the analysis of membrane performance in pervaporation process. |
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