| Reverse osmosis has become one of the most economical techniques in the desalination of seawater and brackish water. However, Reverse osmosis membrane presently possesses inferior chlorine resistance and oxidation resistance. The oxidation of membrane material will ultimately result in the decline of membrane performance, which will badly shorten or affect the service life of membrane. Although great achievement in the synthesis of novel anti-oxidation membrane material and the modification of membrane material has been obtained, the good commercial product has not been got. To develop the application of membrane in the desalination of seawater and brackish water, it is necessary to study and develop the more suitable membrane material and the preparation technology. Polyester-amide reverse osmosis composite membrane was prepared in order to improve the performance of aromatic polyamide membrane in this work. Furthermore, the membrane structure and its performance under relevant experimental conditions were studied in detail.A polyester-amide reverse osmosis composite membrane was prepared by interfacial polymerization of m-phenylenediamine, glucosamine and trimesoyl chloride on the polysulphone support membrane. In order to gain the optimal conditions of membrane-forming, a series of experiments were conducted to investigate the influences of interfacial polymerization conditions on membrane performance, including concentration of reactants, pH, reacting time, curing temperature and time. The optimal preparation conditions of polyester-amide reverse osmosis membrane were given as follows: 1.7% (w/w) m-phenylenediamine and 0.3% (w/w) glucosamine solution in water, pH range from 9 to 10, 0.15% (w/w) trimesoyl chloride in hexane, reacting time range from 45 to 60 seconds at room temperature, curing temperature range from 30 to 40℃and curing time range from 12 to 15 min. The surface composition and structure of membrane were characterized by attenuated total reflectance fourier transform infrared, scanning electronic microscopy and atomic force microscopy. Infrared spectrum suggested ester and acylamide existed in the surface of polyester-amide membrane. Scanning electronic microscopy showed an active layer formed on the polysulfone support membrane. Atomic force microscopy displayed that the surfaces of reverse osmosis membranes appeared the apparent structure of peaks and valleys,and polyester-amide membrane was smoother than polyamide membrane.Additionally, the membrane performances such as salt rejection, flux, anti-fouling and chlorine resistance were also studied. The effects of operating conditions on the performance of polyester-amide reverse osmosis composite membrane were investigated, including operating pressure, operating temperature, electrolyte concentration and electrolyte kinds. By means of the practical running of polyester-amide and polyamide reverse osmosis membranes in the simulated solution of humic acid, anti-fouling ability was studied. Chlorine resistance was studied by static and dynamic experiments. Polyester-amide reverse osmosis composite membrane exhibited high rejection (more than 97.5%) and high flux (more than 27.4 L?m2?h-1) at 1.6MPa for an aqueous solution containing 2000 mg·L-1 of NaCl, MgCl2, Na2SO4 and Mg2SO4, respectively. Polyester-amide reverse osmosis membrane possessed higher resistance ability to humic acid pollution than polyamide reverse osmosis membrane. After exposure to active chlorine (up to 2700 mg·L-1·h), the salt rejection of polyester-amide reverse osmosis membrane kept relatively high, whereas its flux was improved. That is to say, compared with usual polyamide reverse osmosis composite membrane, the polyester-amide reverse osmosis composite membrane possessed relatively high chlorine resistance. |
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