Preparation And Performance Of Nano-hybrid Polyamide RO Composite Membranes

With the growing of water resource problem worldwidely, reverse osmosis has become one of the most economical and effective techniques the water and wastewater treatment field. However, the cost of reverse osmosis is relatively high because of high energy consumption, poor selectivity, vulnerable to contamination and limited flux, therefore, it is necessary to design and prepare new reverse osmosis composite membrane with high flux, preferential segregation and anti-contamination and low in energy consumption. The traditional polyamide reverse osmosis material can not meet the needs of social development, which makes people seek reverse osmosis materials with better properties. Based on current researches, no big breakthrough has been achieved through improving reaction process, composing polymeric monomers and improving the molecule structure of membrane. Organic/ inorganic nano-hybrid membrane can raise the flux dramatically while guarantees the desalination rate as it has advantages of both organic and inorganic materials. Therefore, nano-hybrid reverse osmosis membrane holds the promising potential for high efficient RO membrane.This thesis studies the preparation and performance of organic/inorganic nano-hybrid membrane. Surface modification is initiated through different means by selecting three inorganic nanoparticles materials including nano-zeolite, nano-titania and nano-silicon dioxide as hybrid material, and modification effects are analyzed by various methods.Nano-silicon dioxide is dispersed into casting solution on the supporting layer, and polysulfone is taken as the casting solution. Dimethylacetamide and dimethylfomamide are two different dissolvent used to prepare hybrid supporting layer for different nano-materials, and polyamide layer is then coated on the supporting layer. The experiment result shows that when the content of silicon dioxide is 4%, the flux of nano-hybrid membrane prepared by using dimethylfomamide as support layer is higher than that of the nano-hybrid membrane prepared by using dimethylacetamide as dissolvent.Take IsoparG as the dissolvent, and disperse three kinds of inorganic nanoparticles without surface modification into oil phase through ultrasonic vibration, then modify the polyamide RO composite membrane by introducing different nano-materials the polyamide layer. After detail investigation and analyzing the impact of the hybridization on the membrane structure obtained. In addition, the impacts of the concentration of the additive nano-materials, ultrasound time and temperature on the properties of the prepared hybrid membrane are investigated. The experiment result shows:when nano-material is put in oil phase for 95 min, at 100℃, three nano-hybrid polyamide RO composite membranes can obtain their best performances. The desalination rate is above 99.5% and membrane flux remains above 450 L/m2h.This thesis assesses stain resistance and chlorine resistance of three nano-hybrid RO membranes. The permeation flux and desalinization rate of the prepared membrane before and after treatment are evaluated by using protein solution and sodium hypochlorite solutions with different concentration. The experiment result shows that polyamide RO composite membrane after nano hybridization has markedly improved its stain resistance, chlorine resistance, tolerable time and stability.