Electrically neutral nanofiltration membrane, preparation method and application of electrically neutral nanofiltration membrane in desalination of small molecular dye wastewater

Abstract

The invention provides a nanofiltration membrane with an electrically neutral surface charge property. The nanofiltration membrane is used for printing and dyeing industry small molecule dye 1t; 500Da) wastewater is desalted. The preparation method comprises the following steps: firstly carrying out interfacial polymerization on a water-phase monomer diethylenetriamine and an oil-phase monomer trimesoyl chloride, then carrying out secondary amination modification on an interfacial polymerization layer by using short-chain amine (triethylene tetramine, tetraethylene pentamine and the like) in an alcohol phase for the first time, constructing an electrically neutral selection layer, and realizing efficient separation of crystal violet (408Da) and Na2SO4 in water. While the retention rate of crystal violet in the mixed solution is maintained to be about 99.5%, the retention rate of Na2SO4 is only 16.8%, and the separation efficiency reaches 166.4. Therefore, the prepared nanofiltration membrane is expected to solve the problem of desalination of small-molecule charged dye, and the input cost of enterprises in the aspect of pollution control is reduced.

Description

technical field [0001] The invention relates to a nanofiltration membrane which is oriented to the desalination of small-molecule dye wastewater and has the characteristics of an electrically neutral surface charge and a preparation method thereof, belonging to the technical field of membrane separation materials. Background technique [0002] Separation of small-molecule charged dyes (<500Da) and inorganic salts is a major challenge in today's social development, involving many aspects such as environmental protection, human health and industrial governance. According to the requirements, the typical high-pollution printing and dyeing industry must consider how to efficiently treat the high-salt small molecule charged dye wastewater produced by it, and re-use the salt components in the wastewater to reduce the input cost of enterprises in pollution control. As a newcomer in the field of membrane separation, nanofiltration membrane is expected to solve such desalination p...

AI Technical Summary

Problems solved by technology

First, excess acid chlorides are prone to irreversible hydrolysis during and after IP, severely disturbing the chemistry of the formed selective layer

Second, the ratio between oppositely charged groups in the membrane is difficult to control, resulting in a limited range of charge control [1-2]

Due to the fact that the Donnan effect has an actual impact on all charged ions in the separation system, it interferes with the ion selectivity of the membrane, which directly leads to the desalination problem of small molecule charged dyes with a molecular weight below 500Da

Neutral membranes mainly use size exclusion rather than Donnan equilibrium [9-10], which is very important in ultra-high selectivity separation in highly polluted environments, but there is no good method for nanofiltration membranes in the prior art. A technical means to regulate the surface charge to be neutral

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