| A charged mosaic membrane consists of a set of anion and cation exchange elements arranged in parallel, each element providing a continuous pathway from one bathing solution to the other. When the electrolytes pass the membrane, anions and cations can flow in parallel through their respective exchange elements. This will result in that fact that the charged mosaic membrane has a low Donnan exclusion to ions. These properties, being permeable to salts but meanwhile not to low-molecular-weight non-electrolytes, are desired for desalination of water or purification of biochemical materials or food additives.A charged mosaic membrane with ideal selectivity has apparently advantage over the conventional nanofiltration(NF) membrane, which can be used to concentrate the monovalent salts and bivalent salts. It is well known that NF membrane can only desalinate monovalent salts. However, the separation of bivalent salts from water-soluble organics is very important in modern chemical industry. The charged mosaic membrane can in principle make this possible. It should be noted that the mosaic membranes have not yet become commercially important in separation processes because of the difficulty in upscaling a reproducible process for making mosaics. Most of the preparation processes are quite complicated and time consuming. Therefore, the new methods for preparing charged mosaic membranes are still worth studying and developing.The objective of this study is to develop a novel technique for preparing asymmetric mosaic membrane by introducing both the negative charged and the positive charged groups into the selective layer of interfacial polymerization (IP). Considering the potential application in the dye and food industry in the future, we made the thorough experimental studies on the charged mosaic membrane to purify the dyes, to separate the amino acids, and to desalinate the sugars, etc.In order to make a charged mosaic membrane by IP process, both the anionic and the cationic groups have to be introduced into the selective layer of the membrane by carefully choosing the reactants. For this purpose, 2,5-diaminobenzene sulphonic acid (DABSA )[C6H3(NH2)2SO3H] can be selected as one monomer of IP reaction. The other monomer can be trimesoyl chloride (TMC) [C6H3(COC1)3]. In order to introduce the cationic group into membrane, 4-(chloromethyl) benzoyl chloride ( CMBC ) [CH2C1C6H4(COC1)] could be added into organic phase (TMC) and used for chemical modification after IP process based on the reaction between 4-(chloromethyl) benzoyl chloride and trimethylamine (TMA). Considered its terminating effect on interfacial polymerization reaction, the quantity of 4-(chloromethyl) benzoyl chloride should be limited to some extent. For the IP process investigated, n-dodecane and water can be used as solvents for DABSA and TMC solutions, respectively. Some surfactants and additives might be needed to control the process. After interfacial polymerization, the module was filled with a 10% (wt.%) aqueous trimethylamine solution and kept for 24 hours to convert the chloromethylated groups into cationic quaternary ammonium groups.Through the flux/retention experiments it was shown that when the applied pressure rises, both volume flux and rejection increase, too; and that the higher the feed salt concentration, the lower rejection and volume flux. The charged mosaic membranes could permeate mono-valent and bi-valent inorganic salts, but reject the low-molecular-weight organics.Furthermore, SEM was used to observe the surface and the cross section of the composite membrane. AFM was used to provide information on both size and the surface roughness of the skin. And Mercury Injection Apparatus was also used to test the pore size distribution of the membrane.Besides the experimental study above, the Donnan equilibrium model of charge-mosaic membrane was established on the basis of electrochemical theory and transport mechanism. The distribution coefficient of B-ions in single salt solution or salts mixture are expressed...
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