Energy-saving nanofiltration membrane for water purification system and preparation method thereof

Abstract

The invention discloses an energy-saving nanofiltration membrane for a water purification system and a preparation method of the energy-saving nanofiltration membrane. The energy-saving nanofiltration membrane is composed of non-woven cloth, a polysulfone supporting layer, a loose polyamide separating layer and a dense positive charge thin layer. By properly hydrolyzing the dense nanofiltration membrane, the molecular weight cut-off of the nanofiltration membrane can be increased, and part of monovalent ions are selectively allowed to permeate while it is guaranteed that small organic molecules are effectively intercepted, so that the nanofiltration membrane still has a high permeation flux under high-salinity water inlet or a high recovery rate, and it is unnecessary to additionally increase operating pressure. By depositing the dense positive charge thin layer on the surface of the loose polyamide separating layer through electrostatic adsorption-chemical crosslinking, interception of the nanofiltration membrane on multivalent cations (such as calcium ions, magnesium ions, heavy metal and other substances harmful to the human body) in water can be easily improved, and drinking water safety can be guaranteed to a great degree; meanwhile, the thickness of the deposition coating can be effectively controlled within a certain range with the electrostatic adsorption technology, and thus substantial increase of permeation resistance can be avoided as far as possible.

Description

technical field [0001] The invention belongs to the technical field of water treatment, and in particular relates to an energy-saving nanofiltration membrane used in a water purification system and a preparation method thereof. Background technique [0002] With the rapid development of the world economy, the problem of environmental pollution has become increasingly prominent, and the concentration and types of pollutants in water bodies have continued to increase, posing a serious threat to the safety of drinking water. At present, most of the drinking water treatment processes in my country adopt conventional treatment processes: coagulation, sedimentation, filtration and disinfection. The main target pollutants of this process are suspended solids and bacteria, but pathogenic microorganisms such as ) cannot be reliably removed. Although ultra-microfiltration membranes can effectively remove pathogenic microorganisms and have become an ideal alternative to traditional proc...

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Problems solved by technology

The nanofiltration membrane separation layer prepared by m-phenylenediamine is relatively dense, with a molecular weight cut-off of about 150 Da, and the removal rate of monovalent ions is generally above 95%, which can effectively remove inorganic salts in drinking water sources, but produces When the water volume is relatively low, especially at high salinity or high recovery rate, a high driving force is required to meet the water production requirements; while the separation layer of the nanofiltration membrane prepared by piperazine is relatively loose, and the molecular weight cut-off is about 300 Da. The removal rate of monovalent ions is generally 40~60%, and the water yield is relatively large, but it cannot effectively remove small organic molecules such as pesticides and endocrine disruptors with a molecular weight of about 200 Da, and cannot guarantee the safety of drinking water

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