Preparation method of anti-pollution composite nanofiltration membrane

Abstract

The invention provides a preparation method of an anti-pollution composite nanofiltration membrane. The preparation method includes subjecting a polysulfone ultrafiltration membrane to primary interfacial polymerization by a first aqueous phase solution and an oil phase solution, pouring a second aqueous phase solution containing nonionic hydrophilic polymers onto the surface of the ultrafiltration membrane to conduct secondary interfacial polymerization, removing the second aqueous phase solution, conducting heat treatment, and taking out the membrane for washing to obtain the composite nanofiltration membrane. The preparation method has the advantages that the nonionic hydrophilic polymers containing ether bonds in main chains are embedded in a polyamide layer through the secondary interfacial polymerization, the surface of the modified membrane is smooth, and the surface roughness is lowered; through introduction of nonionic hydrophilic groups, the number of residual carboxyl groupson the surface can be remarkably decreased, pollutant adsorption and salt bridge effect can be effectively reduced, and the anti-pollution performance of the nanofiltration membrane is improved; theoperation process is simple and convenient, and the preparation method is convenient for industrial production and has a broad application prospect in anti-pollution modification of the composite nanofiltration membrane.

Description

technical field [0001] The invention belongs to the technical field of nanofiltration, and in particular relates to a preparation method of an anti-pollution composite nanofiltration membrane. Background technique [0002] Nanofiltration is a pressure-driven membrane separation process between reverse osmosis and ultrafiltration. The core of nanofiltration technology is nanofiltration membrane. It is generally believed that the pore size of the nanofiltration membrane is about 1nm, and the rejection rate of multivalent ions and organic substances with a molecular weight above 200 is relatively high, while the rejection rate of monovalent ions is relatively low, because monovalent ions can pass through the nanofiltration membrane more freely. , the osmotic pressure caused by different ion concentrations on both sides of the membrane is much lower than that of the reverse osmosis membrane, and the required operating pressure is much lower. In recent years, nanofiltration tech...

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Problems solved by technology

For example, CN 1213985 and CN 1923348 provide a method for coating polyvinyl alcohol (PVA) on the surface of the functional layer. The introduction of hydroxyl groups can effectively reduce the charge on the surface of the functional layer and inhibit the adsorption of the film to charged pollutants in water. However, due to PVA molecules have not been cross-linked, and the binding force with the polyamide layer is weak, and it is easy to hydrolyze and fall off during long-term operation, and eventually loses its effect

CN 102363113 and CN 102553458B graft polyols to the surface of the membrane by chemical crosslinking, which can effectively improve the binding force of the anti-pollution layer, but there are many types of chemicals used, and the reaction controllability is poor

If the polymer containing hydrophilic groups is directly added to the aqueous phase solution for interfacial polymerization, it will affect the degree of crosslinking of the polyamide layer of the prepared composite membrane and reduce the separation performance of the membrane.

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