Study On The Mechanism Of The Influence Of External Magnetic Field On Reverse Osmosis Membrane Fouling In Water Treatmen

Reverse osmosis（RO）membrane separation technology is one of the most widely used desalination technologies at present,but membrane scaling is a major limiting factor in RO process.Membrane scaling not only decreases the membrane performance,but also increases the cost of RO operation.The traditional method is adding chemicals to achieve membrane scale inhibition.,but some chemicals cause refouling and higher cost.Therefore,it is the main problem to slow down membrane fouling by developing an anti-scaling method which is both environmentally friendly and cost-effective,and clarifying its effect and mechanism.In the study,we applied magnetization pretreatment to the RO process and analyzes scale inhibition effect and mechanism of action,which provided a guideline for the membrane scaling control in RO process.Firstly,the magnetization device was designed and combined with the RO process to clarify the effect of magnetization in the membrane system.The magnetic field simulation of the magnetization device with different magnet configurations was carried out by Comsol Multiphysics software,and the"S"type magnetization device was designed.The magnetization effect of RO membrane scaling was analyzed using a simulated solution with Ca²⁺as the raw water.It was found an optimal condition（magnetization strength 500 m T,magnetization time 10 min）in magnetization treatment process.The decreasing rate of membrane flux decreased after magnetization treatment,the flux recovery rate increased after hydraulic flushing,and the mutual attraction between scale-membrane-scale decreased.This indicated that the magnetization treatment could slow down the membrane scaling effectively.Secondly,the magnetization mechanism of Ca CO₃ crystals in solution and hydrogen bonding in the solvent were analyzed to reveal the mechanism of magnetization mitigating membrane scaling.It was found that the reason for the of magnetization enhancement on RO membrane scale inhibition mainly lies in to the water molecules hydrogen bonds breaking with magnetization treatment between,which not enhanced the permeability of water in the RO membrane but reduced the Ca CO₃ crystals size.The crystal size led to the interfacial forces between scale-scale and scale-membrane decreasing,which improved the retention time of crystals in the concentrate.The crystal changes made the scale be flushed easier and less likely to accumulate to the membrane surface.Finally,it was investigated the magnetization effect on the treatment of effluent from the secondary sedimentation tank of a sewage treatment plant.The results showed that the magnetization treatment could reduce the membrane flux decreasing and improve the flux recovery rate effectively.Compared with the simulated solution,the magnetization treatment was more effective in real effluent in flux decreasing and rate flux recovery control.