Old film repair method

Abstract

The invention belongs to the field of membranes, and in particular relates to a method for repairing an old membrane. (1) membrane element pretreatment; (2) membrane element surface reduction; (3) membrane pollutant removal; (4) membrane surface repair; cleaning. The surface of the old membrane has been covered with uniform pollutants, which plays a protective role, and then in a mixed phase of organic solvent and water, the amide bond is modified with a solution containing active chlorine under alkaline conditions; under acidic conditions, to a limited extent. Let some amide bonds be destroyed, and then use a reducing agent to wash off residual chlorine and residual metals, and use sodium dodecylbenzenesulfonate and sodium hydroxide solution to wash away the original organic pollutants of the old membrane; citric acid and sodium citrate buffer solution In salicylic acid, water and ethanol form a homogeneous system, and the phenolic hydroxyl group in salicylic acid can achieve a small increase in the charge of the membrane filter layer, which is conducive to improving the hydrophilicity of the membrane, and then modified by butanol aldehyde to control the degree of reaction and restore part of the amide bond, which can realize the regulation of membrane desalination rate and obtain modified membranes with different desalination gradients.

Description

technical field [0001] The invention belongs to the field of membranes, and in particular relates to a method for repairing old membranes. [0002] technical background [0003] Production-oriented industrial enterprises are equipped with a circulating water system for equipment cooling. The so-called circulating water system means that the temperature of the cooling water rises after cooling the equipment. It is first sent to the cooling tower to cool down, and then returned to the pool to continue recycling. During the operation of the circulating water system, impurities such as dust are gradually mixed in the water, and the water is gradually concentrated as the recycling time increases, resulting in a continuous increase in conductivity and turbidity. Therefore, it is necessary to continuously discharge part of the sewage and replenish part of the new water at the same time. This part of the discharged sewage is called circulating sewage. In addition, most steam-produci...

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Problems solved by technology

[0006] For example: Chinese patent CN100493683C aimed at waste aromatic polyamide roll-type membrane elements, used hexahydroxydiphenolic acid to form a film on the surface of the membrane, and restored the performance of the membrane, but the process of re-film formation is complicated and requires high equipment

Chinese patent CN111437729A aims at physically coating the degraded polyamide membrane elements with tannic acid to increase the charge capacity of the membrane, and then chemically modifying the membrane with butanol aldehyde to repair the desalination performance of the membrane. This scheme is similar to the previous scheme, but also It is equivalent to forming a film on the surface of the membrane element, and the cost is high

Chinese patent CN201520333079 uses a desalination membrane with an operating pressure of 0.7 MPa in the third stage of reverse osmosis to operate using residual water pressure to save energy. However, the operating pressure of the front stage reverse osmosis is still high, and the reuse effect of the membrane elements is not ideal.

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