Bioadhesion-inspired Fabrication Of Pervaporation Composite Membranes And Intensification Of Esterification

Most pervaporation members for industrial use were composite membranes, and the structural stability of the composite membrane was closely related to the service life. It is very important both in theory and practicality to develop the composite with high structural stability and separation performance. In the present work, the pervaporation separation of the water and ethanol mixture was chosen as the investigation object and the goals were to increase the interfacial interaction between the separation layer and the support layer, and enhance the structural stability of composite membrane. Inspired by the bioadhesion phenomena, a new method of fabricating composite membrane was found by introducing bioadhesives into it. Furthermore, the interfacial interaction was analyzed and adjusted basing on the bioadhesion principle, and the composite membranes with high structural stability and separation performance were fabricated.Firstly, the GCCS/CP/PAN composite membrane with three layers structure was fabricated by introducing CP bioadhesive as the intermediate layer. T-peel test veri?ed the interfacial adhesion strength of CS/PAN membrane was considerably increased by the introduction of CP. Contact angle measurement results suggested that CP was helpful to enhance the hydrophilic nature of PAN support layer and resulted in a better compatibility with CS separation layer. With the presence of the CP intermediate layer, the separation selectivity of CS/PAN membrane was greatly increased. Basing on this, GCGE/PAN and GCHA/HM-PAN composite membranes with two layers structure were fabricated. GE and HA bioadhesives could firmly adhere onto the support layers and displayed extremely high hydrophilicity, which acted as the separation layer of composite membrane directly. Comparing the pervaporation performance of GCCS/CP/PAN, GCGE/PAN and GCHA/HM-PAN membranes, the GCHA/HM-PAN membrane showed the best separation efficiency. Using the hydrophilically modified-PAN (HM-PAN) as the support layer, when the HA concentration was 0.8 wt.%, and the cross-linking degree was 0.3, the GA(0.3)HA(0.8)/HM-PAN membrane displayed the permeation flux of 1.634 kg/(m2 h) and the separation factor of 233 for 90 wt.% aqueous ethanol solution at 353 K with a flow rate of 60 L/h. Secondly, molecular dynamics simulation was employed to reveal the relationship of membrane materials, microstructure and separation performance from molecular level, and explored the interfacial adhesion principle of CS/CP/PAN, GE/PAN and HA/HM-PAN composite membranes. Interfacial energies were composed of hydrogen bond, van der Waals force and electrostatic force, and the dominant forces at the interfaces of three kinds of composite membranes were different. Electrostatic force, van der Waals force and hydrogen bond played a dominant role at the interface of CS/CP/PAN, GE/PAN and HA/HM-PAN composite membranes, respectively. Meanwhile, the HA/HM-PAN membrane showed the strongest interfacial interaction, which could further inhibit the polymer chains mobility and decrease the swelling of the separation layer, leading to an improved selectivity.Finally, the effects of GCCS/CP/PAN, GCGE/PAN and GCHA/HM-PAN composite membranes on the chemical balance motion of esterification between lactic acid and ethanol were investigated. Pervaporation-assisted esteri?cation results suggested that the incorporation of pervaporation process to preferentially remove water from the reaction mixture, broke the limit of initial chemical balance, and the yield of ethyl lactate was substantially enhanced by 28.2%. Furthermore, the optimum thchnological parameter for coupling process was confirmed, and the yield of ethyl lactate reached to 94.9% after 8 h.