Preparation And Properties Of Polyvinyl Alcohol Vapor Permeation Membrane Modified With Hydroxyethyl Cellulose

In modern industrial production and daily life,the requirements for gas humidity are becoming more and more strict,and gas dehumidification technology has become a research hotspot for modern separation technology.The processes of conventional gas dehumidification is complex,exit environmental pollution and recycling problem,such as,desiccant,refrigeration and heating.Membrane dehumidification technology has attracted much attention due to its high selectivity,low energy consumption,simple process and no secondary pollution.The core of this technology is the preparation of high performance dehumidification membranes.Therefore,it is necessary to prepare a gas dehumidifying membrane with strong hydrophilicity,high dehumidification efficiency and good chemical stability.Firstly,a hydroxyethyl cellulose cross-linked modified polyvinyl alcohol(PVA-HEC)plate vapor permeable membrane was prepared by solvent evaporation method.The effects of HEC mass composition on the structure,hydrophilicity,water vapor permeability and air dehumidification performance of PVA-HEC flat membranes were investigated.The results show that with the increase of HEC content,the viscosity of PVA-HEC casting solution,the surface roughness and the hydrophilic property of PVA-HEC membrane all increases.When the HEC content is 5 wt.%,the vapor permeability of the PVA-HEC membrane is up to 103.5 g/(m~2h),and the dehumidification efficiency is up to 72.10%.And the gas dehumidification performance of HEC-PVA membrane is obviously better than that of pure PVA membrane.In order to study the industrialapplication of HEC-PVA membrane in air dehumidification,hollow fiber PVA-HEC/PAN membranes were prepared through polyacrylonitrile(PAN)hollow fiber ultrafiltration membrane used as the base membrane,and PVA-HEC as the hydrophilic separation active layer.The effects of the content of HEC and feed flow on air dehumidification efficiency and dew point temperature were studied.The results show that when the HEC content is 5 wt.%,the gas dehumidification efficiency is up to 84.67%and the dew point temperature is as low as-10?when the feed flow rate is 60 mL/min.Finally,the surface sulfonation modification of PVA-HEC/PAN membrane was carried out by using 5-sulfosalicylic acid(SA).The effects of SA concentration in sulfonated solution on the structure,hydrophilicity,water vapor permeability and membrane dehumidification performance of sulfonated PVA-HEC/PAN vapor permeable membrane were investigated.The results show that with the increase of SA concentration,the hydrophilicity increases,the water contact angle decreases from 26.7°to 15.6°,and the vapor permeability increases from 22.0 g/(m~2h)to 76.2 g/(m~2h).The gas dehumidification efficiency increased from 72.45%to 74.67%at feed rate 60 mL/min,and the dew point temperature was lowered from 18?to-2?.In summary,cross-linking modification of PVA by HEC can increase the vapor permeability and gas dehumidification efficiency;using PVA-HEC as the separation layer on PAN hollow fiber membrane can increase the membrane strength and treatment area;surface sulfonation modification of PVA-HEC/PAN membrane can play a key role in further enhancing the hydrophilicity of the membrane.For the membrane preparation,raw materials are environmentally friendly,low in price and good in separation,which is of promoting significance for promoting industrial production in the new era.