| The use of membrane on particle adsorption, retention and separation by microfiltration technology has been developing rapidly. Among the membrane materials, PTFE microporous membrane due to its acid and alkali resistance, high temperature resistance, strong regulation of pore structure has been widely used in environmental protection, filtration, textile, medical, military and so on. However, because of extremely low surface energy and strong hydrophobicity, PTFE's application in aqueous filtration is still limited. So, studies on the hydrophilic modification of PTFE membrane become necessary.Traditional chemical modification including sodium-naphthalene chemical treatment can damage PTFE material itself. This paper, after analyzing the influence of chemical treatment on PTFE, put forward an idea of physical modification.The method of physical modification was as follows: firstly, Fe3+ were adsorbed and deposited on the surface of PTFE microporous membrane, then according to the theory of coordination bonding, hydrophilic monomer were polymerized on PTFE membrane which had adsorbed Fe3+. This method of physical hydrophilic modification on PTFE microporous membrane did not affect the performance of membrane itself on the whole. The structure and properties of modified membrane were studied by means of FTIR, SEM,ζpotential, ultrasonic oscillation, contact angle, water flux and so on. The results showed that the hydrophilic performance of PTFE membrane was improved significantly.The main contents and conclusions in research are as follows:(1) The ultrasonic oscillation and FTIR results showed that Fe(OH)3 colloid can be adsorbed on the PTFE membrane stably. The Fe(OH)3 and PTFE membrane were interacted through intermolecular forces. The contact angle of water on the membrane was decreased and the surface tension was increased after Fe(OH)3 adsorption. The best conditions of adsorption were as fellows: dipping solution,20mL boiling water /FeCl3 Solution(1mol/L)7.5mL /NaOH Solution(2mol/L)1.5mL; dipping time 20h, and dipping temperature 15℃。(2) Ionic characteristics and adsorption were theoretically analyzed based on electronegativity and ionic radius, which was validated byζpotential test of PTFE membrane in MgCl2 solution, CuCl2, FeCl3 solution and so on. The results showed that PTFE and Fe3+ had a special affinity, which was derived from the larger electronegativity of Fe3+ than other metal ions'and the larger ionic radius of Fe3+ than H+'s. Besides, in comparison with Cu(OH)2, Fe3+ has a strong tendency of hydrolysis and becomes colloid easily, it can absorb onto the PTFE membrane stably.(3) In order to further enhance the membrane hydrophilicity which had adsorbed Fe(OH)3 colloid, the membrane was further put into acrylic acid (AA) aqueous solution and acrylic acid polymerization was carried out. The structure of polyacrylic acid (PAA) and Fe(OH)3 was analyzed by FTIR, the results showed that the connection between PAA and Fe(OH)3 were dependent on bridge coordination. (4) In this paper, the factors influencing the weight gain ratio of polyacrylic acid onto the PTFE membrane had been studied, and the relationship between membrane weight gain ratio and water flux had been established. The best conditions of polymerization were as fellows: 25% AA monomer concentration, 1% (NH4)2S2O8 (initiator) of the total monomer weight, polymerization temperature 60℃, polymerization time 60min. Under the best conditions of polymerization, membrane weight gain ratio was 7.9%, the contact angle of water on the membrane was decreased from 146°to 76°, the surface tension was increased from 1.15×10-2N·m-1 to 5.92×10-2N·m-1, the water flux was increased from 0 to 0.069 m3·m-2·h-1. The effect of hydrophilic modification was obvious, and the performance of water permeation through the membrane was improved significantly. The method put forward in this paper not only broadens the ways of hydrophilic modification on PTFE, but also provides a new processing method by combination of organic and inorganic materials.
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