Magnetization coupled reverse osmosis (RO): Enhanced inhibition scaling mechanisms and operation optimization

In this study, magnetization pretreatment was applied to the reverse osmosis process. The scale inhibition effect and the mechanism of magnetization treatment were analyzed. The results show that after magnetization, the decay of water flux tended to slow down during RO and the flux recovery increased after cleaning. The Ryznar stability index of the solutions was calculated, which showed that magnetization could increase the solubility of carbonate solution and reduce the trend of carbonate scaling to a certain extent. The infrared spectra of the solutions showed that the hydrogen bonds of water molecules in the solution decreased after magnetization, indicating that the magnetization made the hydrogen bonds of water molecules break to form smaller clusters of water molecules, which might make the water molecules pass through the membrane more easily. After magnetization, the crystal size of the carbonate precipitated decreased and the sedimentation rate slowed down. Different flow rates and magnetization times were selected during the magnetization process. The results showed that when the flow velocity was greater than 0.24 m/s, the RSI, scale size and precipitation rate of the magnetized solution changed significantly compared with that of the unmagnetized solution. At the flow velocity of 0.48 m/s, the optimal magnetization time is 5 min. Moreover, the SEM characterization of the fouled membrane after filtration showed that after magnetization, the calcium carbonate deposited on the membrane surface appeared aragonite crystal, and the fouling was more loose, so it was easier to wash away during the membrane cleaning process.