Preparation of PVA-PFSA-Si pervaporative hybrid membrane and its dehydration performance

The dehydration performance and sorption behavior of PVA/silica hybrid pervaporative membrane

A polyvinyl alcohol (PVA)/SiO2 organic-inorganic hybrid membrane was fabricated, using PVA as the basic material, SiO2 nanoparticles as the inorganic material, γ-(2,3)-glycidoxy propyl trimethoxysilane (GPTMS) and 3-aminopropyl triethoxysilane (APTEOS) as the second modified agents. The dehydration performance of PVA-SiO2/polyacrylonitrile (PAN) composite membrane to ethyl acetate (EA)/H2O, EA/ethanol (EtOH)/H2O and EA/EtOH/acetic acid (HAc)/H2O solutions was investigated. After modification of the second coupling agent of APTEOS or GPTMS, PVA-SiO2/PAN composite membrane had the better dehydration performance to these aqueous solutions. When dehydrating PVA-SiO2/PAN composite membrane modified by GPTMS (M5 membrane) in EA/H2O binary solution (98/2, wt%) at 40°C, the separation factor and the total permeation flux were 5245 and 293.9 g m−2 h−1, respectively. The preparation method of PVA/SiO2 membrane through adding the second coupling agent was simple, it had good dehydration performance and has excellent application prospects. The sorption behavior of PVA/SiO2 hybrid membrane was systematically studied, providing sufficient data for studying the separation mechanism of pervaporative membrane. The degree of swelling (DS) and the sorption selectivity of the membrane in different feed compositions and temperatures were measured to determine the static sorption of membrane. Dynamic sorption more clearly reflects the sorption and swelling processes of the membrane, and the dynamic sorption curves of the membrane in EA aqueous solutions were obtained. The sorption behavior of membrane to permeate components was studied by ATR-FTIR. Changes in the characteristic peaks for the permeate components and membrane indicated the sorption behavior of the membrane.

Raw cellulose/polyvinyl alcohol blending separators prepared by phase inversion for high-performance supercapacitors

The development of a biodegradable cellulose-based separator with excellent performance has been of great research significance and application potential for the green development of supercapacitors. Herein, the regenerated porous cellulose/Polyvinyl alcohol films (CP-10, CP-15, CP-20, CP-25) with different mass ratio were successfully fabricated by a simple blending and phase inversion process. Their electrochemical properties as separators in assembled supercapacitor were evaluated. Fourier transform infrared spectroscopy and x-ray diffraction analysis indicate that intermolecular and intramolecular hydrogen bonding existed between cellulose and polyvinyl alcohol of the CP films. Compared with other CP films, the CP-20 film shows higher mechanical strength (28.02 MPa), better wettability (79.06°), higher porosity (59.69%) and electrolyte uptake (281.26 wt%). These properties of CP-20 are expected to show better electrochemical performance as separator. Indeed, the electrochemical tests, including electrochemical impedance spectroscopy, cyclic voltammetry, galvanostatic charge discharge, demonstrate that the SC-20 capacitor (with CP-20 as separator) shows the lowest equivalent series resistance of 0.57 Ω, the highest areal capacitance of 1.98 F cm^-2 at 10 mV s^-1, specific capacitance of 134.41 F g^-1 and charge-discharge efficiency of 98.62% at 1 A g^-1 among the four capacitors with CP films as separators. Comparing the assembled SC-40 and SC-30 with two commercial separators (TF4040 and MPF30AC) and SC-PVA with Polyvinyl alcohol (PVA) separator, the CV and GCD curves of SC-20 maintain the quasi rectangular and symmetrical triangular profiles respectively at different scan rates in potential window of 0-1 V. SC-20 exhibits the highest value of 28.24 Wh kg^-1 at 0.5 A g^-1 with a power density of 0.26 kW kg^-1, and 13.41 Wh kg^-1 at 10 A g^-1 with a power density of 6.04 kW kg^-1. SC-20 also shows the lowest voltage drop and the highest areal and specific capacitance. Moreover, SC-20 maintains the highest value of 86.81% after 4000 cycles compared to 21.18% of SC-40, 75.07% of SC-30, and 6.66% of SC-PVA, showing a superior rate capability of a supercapacitor. These results indicate that CP films can be served as promising separators for supercapacitors.