Study On Polyacrylonitrile (PAN) Ultrafiltration Membrane Modification By Atmospheric Dielectric Barrier Discharge Plasma

Atmospheric dielectric barrier discharge (DBD) is a novel type of plasma technique which can generate atmospheric pressure glow discharge (APGD), possessing wide industry application prospect. In this work, poly(acrylonitrile)(PAN) ultrafiltration (UF) membrane as matrix, the atmospheric pressure DBD plasma was used to explore preparation of pervaporation composite membranes, studied hydrophilic modification of ultrafiltration membrane and environment stimuli.The asymmetric PAN ultrafiltration membranes were used as substrate membranes, and the macromonomer poly(ethylene glycol) methacrylate (PEG526OHMA) was used as the monomer to develop the pervaporation composite membranes for aromatics permeation by double-plasma grafting strategy. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle measurement (WCA) and scanning electron microscopy (SEM) were utilized to characterize the morphology and chemical structure of the composite membrane. The effects of the monomer temperature and input voltage on the degree of grafting (DG) and pervaporation performance of composite membrane were systematically investigated. Toluene/n-heptane mixtures (1:4in mass) system at80℃as feed was experimented by pervaporation experiments. The results showed that, atmospheric DBD plasma technique can fabricate the composite membrane. At the input voltage of70V and monomer temperature of30℃, the DG of the composite membrane reached a maximum value of1.2mg/cm2, meanwhile, for toluene/n-heptane system, the separation factor αtoluene/n-heptane up to4.8, the permeate flux up to2.8kg/m2-h, the composite membrane show a excellent stability.The PAN UF was enhanced hydrophilcity using acrylic acid (AA) as the grafted monomer by postirradiation grafting. The chemical structure of the modified membrane was characterized by ATR-FTIR, WCA and SEM. The influences of the DG.with pure water and1000mg/L bovine serum albumin (BSA) solution, was studied on UF performance and anti-fouling performance. The results showed at the input voltage of25V, plasma treatment time of120s and AA concentration of2%, the modified membranes exhibited desirable fouling release property with highest and stable cleaning efficiency.The weak polyelectrolyte2-dimethylamino ethyl methacrylate (DMAEMA) was grafted onto the surface of the PAN UF membrane to enhance anti-fouling performance. The chemical structure of the modified membrane was characterized by ATR-FTIR, WCA, SEM. The results showed that the influences of pH and NaCl concentration in the feed solution on the amount of protein adsorption and UF performance. The experiments showed that the stimuli-responsive properties of the DMAEMA grafted PAN membrane changed significantly with the high pH and NaCl concentration.