Old membrane repairing method

Abstract

The invention belongs to the field of membranes, and particularly relates to an old membrane repairing method which comprises the following steps of (1) pretreating a membrane element, (2) reducing the surface of the membrane element, (3) removing membrane pollutants, (4) repairing the surface of the film, and (5) cleaning the membrane. The surface of an old membrane is already uniformly covered with pollutants to play a role in protection, and then an amido bond ismodified by using a solution containing active chlorine in a mixed phase of an organic solvent and water under an alkaline condition; under the acidic condition, part of amido bonds are damaged to a certain extent, residual chlorine and residual metal are washed away through a reducing agent, and original organic pollutants of the old membrane are washed away through sodium dodecyl benzene sulfonate and a sodium hydroxide solution; in citric acid and a sodium citrate buffer solution, water and ethanol form a homogeneous system, phenolic hydroxyl groups in salicylic acid can realize small increase of charges of a membrane filter layer, improvement of hydrophilicity of the membrane is facilitated, then butanol aldehyde is used for modification, reaction proceeding degree is controlled, part of amido bonds are recovered, and regulation and control of membrane desalination rate can be realized. The modified membranes with different desalination gradients are obtained.

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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