Preparation And Properties Of Polyamide Composite Membrane Doped By AgO/TiO₂

With the world’s population growth and industrialization progress,the demand of fresh water resources has dramatically increased.Hence,improving the current water treatment technologies becomes an urgent matter.Membrane separation technology,as a new separation method,is widely used in the drinking water purification procedure.The high cross-linked polyamide composite membrane prepared by interfacial polymerization has the advantages of high flux and high retention,which has become the hotspot in the field of membrane research.However,the attenuation of water flux that caused by membrane fouling restricts its further development.Surface hydrophilicity is used to improve membrane stain resistance,but this method could not solve its side-effect of microbiological water pollution.Therefore,in this paper,by adding in two chemicals AgO and TiO₂ to the composite membrane,both the preparation condition and the antimicrobial properties of the composite membrane will be studied.Also,to solve the problem caused by microbial contamination of the membrane,the effects of the addition quantity and method of AgO and TiO₂ on the water flux and retention rate of the composite membrane will be investigated.（1）The polyacetone as the support layer,MPD and TMC as the reactive monomer,triethylamine as the acid acceptor,SDS as the surfactant,the polyamide composite film is prepared by the method of interfacial polymerization method and the scanning electron microscopy.Infrared spectrometer were used to characterize the surface morphology and structure of polyamide composite films.The effect of interfacial polymerization conditions on the separation performance of PA film was investigated by orthogonal experiment with distilled water and 500mg/L PEG-20000 as the reference.The experimental results showed that the PA film prepared at the concentration of MPD in aqueous phase was 2%,the concentration of oil phase TMC was about 0.15%,and the heat treatment temperature was 55℃,the water flux was 88.5 L/m2·h-1,and the retention rate was about 82.8%.（2）By using AgNO₃ as a raw material,NaOH as precipitant and K₂S₂O₈ as oxidant,and high oxidation silver is prepared with liquid oxidation method.AgO was added to the polyamide composite membrane in two ways,and the AgO polyamide composite film was prepared by interfacial polymerization.The effects of the amount of AgO added in and the method used on the separation performance,surface morphology,Water effects,and the antibacterial properties of the membrane were tested.The experimental results show: when the amount of AgO is 0.3%,the surface morphology of the composite membrane integrity,no collapse,forming a network of pore structure and pore size;water flux up to 161.48 L/m2·h-1,the rejection rate is 88.5%;the smallest contact angle,the strongest hydrophilicity.The antibacterial experiment showed that the polyamide composite membrane had no antibacterial property.When AgO is added to the polyamide composite membrane,the membrane functions with an antibacterial property.Moverover,this property is enhanced with the increasing amount of AgO.（3）The TiO₂ was prepared by sol-gel method with tetrabutyl titanate,ethanol and glacial acetic acid as raw materials.There are two ways to add in TiO₂ into the polyamide composite membrane prepared by interfacial polymerization that help to explore the effect of Ti O2 on two addition separation performance,surface morphology and hydrophilicity of the composite membrane.These two experiments show that when TiO₂ is added to the oil phase,composite membrane water flux maximum is 176.5L/m2·h-1 with a maximum retention rate of 92.4%;the surface morphology,finger like pore structure with no collapse;the contact angle of the minimum value is 25.12°.When TiO₂ was added into the aqueous phase,composite membrane water flux increases to a maximum rate of 165.2 L/m2·h-1 and the rejection rate of 92.5%.The surface of the composite membrane is the part where the least amount of TiO₂ goes to because the rest of them go through the membrane pores and lead to a pore collapse.the minimum contact angle is 45.64°.Therefore,the separation performance,surface morphology and hydrophilicity of the composite membrane prepared by adding in TiO₂ to the oil phase is better than that in the aqueous phase.