(381g) Ultrafiltration of Colloidal Silica

Treatment of colloidal wastewater is inevitable in many industries (paper mill, food, beverage, etc.) as it is used to recover valuable products through concentration, and/or to treat effluent to an acceptable discharge level in compliance with applicable regulations. In this work we studied the ultrafiltration of colloidal silica suspension and investigated the effects of membrane structure and operating parameters on permeation performance. The parameters studied were transmembrane pressure, pH, salinity, suspension concentration and turbulence. Flux and rejection were the parameters used to assess membrane performance. As expected, permeate flux decreased significantly with increase in feed concentration indicating that the reduced flux was likely due to concentration polarization. However, non-uniform variation of colloid rejection with feed concentration was observed and possible reasons for such outcome will be discussed. The results also showed that for relatively dilute colloidal suspensions (0.5 – 2.0 weight %), increasing the turbulence beyond 600 rpm has negligible effects on membrane performance. The structure of the membrane also provided valuable insights on the transport through the membrane.