Study On The Preparation, Modification And Treatment Of High-salt Wastewater Of Straw-based Cellulose Acetate Membrane

High salt wastewater exists in chemical production,wastewater treatment,sea water desalination and other water treatment processes.It has a wide range of sources and large amount of water.Due to the variety and structure difference of organic compounds in wastewater,the treatment methods are various,but most of the salt substances in wastewater are Cl^-,Na⁺,SO₄^2-and Ca²⁺.As a new high salt wastewater treatment technology with simple operation and no secondary pollution,membrane separation has been widely used.The membrane separation technique is to obtain the desired target substance by using the different particle size and transmittance of different components in the mixture.Positive osmosis is an environmentally friendly membrane separation technique,which does not require external driving force and is carried out spontaneously from low concentration to high concentration.However,common positive permeable membranes have low water flux and low salt interception efficiency due to internal concentration polarization.Therefore,it is very important to prepare a positive permeable membrane with high mechanical strength,acid and alkali resistance,porous support layer,high water flux and salt interception efficiency.Cellulose acetate is a kind of cheap and renewable raw material with high film-forming property.The cellulose acetate membrane prepared by cellulose acetate has high water flux and retention rate.In this paper,cellulose acetate was extracted from straw,and a single acetate fiber membrane and a doped MIL-101?Fe?acetate fiber composite membrane were prepared by phase conversion method.The structure characterization and properties of the membrane were tested.The results show that both positive permeable membranes have porous supporting layers,and the water flux and salt interception rate are better,which indicates that cellulose acetate is an ideal membrane material.Compared with the two membranes,it was found that the salt interception efficiency of the acetate composite membrane doped with MIL-101?Fe?is better when the water flux difference is not much.This is due to the fact that MIL-101?Fe?is a relatively typical metal-organic framework with stable structure and large specific surface area in water,and the MOFs is connected with the polymer in a noncovalent manner,this interaction will strengthen the interfacial compatibility and thus improve the salt interception performance of the membrane while the water flux changes little.