Research on Influencing Factors and Cleaning Effect of Forward Osmosis Membrane Fouling

In order to study the attenuation regularity of membrane flux in the process of forward osmosis (FO) concentration, the fouling rule of FO membrane affected by different parameters including ionic strength, BSA concentration in the feed and membrane orientation was studied with Bovine serum albumin (BSA) as the primary typical pollutants. In order to improve the membrane flux and rejection rate, the type and concentration of draw solution and the flow rate of feed solution were optimized and the appropriate membrane cleaning scheme was optimized. The results showed that the initial flux of FO membrane decreased with the increasing of ionic strength in feed solution, but the flux of FO membrane with BSA solution containing salt ions was higher than that of pure BSA solution as the running time went on. The lower the concentration of BSA, the lighter the membrane fouling was, and the water flux in FO mode (13.82±3.2 L/m²·h) was higher than that in PRO mode (5.08±2.1 L/m²·h), which indicated that FO mode should be adopted for concentration. Under the optimal operating conditions, the 1.5 mol/L NaCl as the draw solution and the flow rate of both feed and draw solution controlled at 2.89 m/s, FO flux was 11.23±2.13 L/m²·h, BSA retention rate was 97.83%, and reverse solute flux Js was 0.14 mol/m²·h. After the fouled membrane was immersed in 0.05% NaOH for 4 min, the flux recovery rate reached 98.39% and the flux recovery rate was still exceed 98% after reusing and cleaning many times, which indicated that the membrane had good cleaning resistance. This study would provide a certain technical reference for protein recovery from food materials.