Preparation Of High Boron Removal Reverse Osmosis Membrane By Swelling And Embedding Method

Boron(B)is an essential trace element in living organisms,but the intake of a slight excess of boron can endanger the growth of plants and animals.In seawater desalination,the reverse osmosis membrane can effectively remove up to 99.7% of inorganic salt ions,but the boron removal rate is only 30 to 88%.It is necessary to adjust the p H and the two-way reverse osmosis membrane to achieve the boron standard.The complexity of the production process and the production cost increase by 10% to 20%.Therefore,it is of practical significance to prepare high boron removal reverse osmosis membranes.Our group proposed a new modification method “swelling-embedding-shrinking”(SES).This method makes full use of the swelling effect of alcohol.The interaction between alcohol molecules and polyamide is stronger than the force between polyamides.The distance between the polymer chains provides a place for the embedding of the modified molecules.Then,under the action of pressure and concentration polarization,the modified molecules are selectively inserted into the pores of the polyamide membrane.When the alcohol molecules leave,they are shrinked.The amide film shrinks the immobilized molecules in the polymer network.The "swelling-embedding-shrinking" method was used to embed 4-nitrobenzenesulfonyl chloride into the sea water reverse osmosis membrane(SWRO),and the boron removal rate was increased from 82.12% to 93.10%,and the boron concentration in the permeate was reached China's boron standard(0.5mg/L).Furthermore,the salt rejection of reverse osmosis membrane is increased to 99.57%.The "swelling-embedding-shrinking" method is used to embed fatty acid molecules in the brackish water reverse osmosis membrane(BWRO),which increases the rejection of boron by ?30% and the rejection of Na Cl by ?6%.The boron concentration in the permeate reaches the WTO's boron standard(2011,2.4 mg/L).In order to further analyze the transfer mode of boron molecules in the polyamide membrane,Our group systematically analyzed the effects of polarity and steric hindrance on boron transfer through the separation performance of different boron-containing compounds(having different polarities and different molecular volume,including boric acid,methylboric acid,ethylboric acid and phenylboronic acid).