Effects of pH and Ionic Strength on Colloidal Fouling of Charged Nanofiltration Membranes

Abstract

The fouling potential of a colloidal silica suspension as the feed phase at varied solution chemistry has been investigated using negatively charged polyamide thin-film-composite nanofiltration (NF) membranes. Specifically, the effects of solution chemistry, feed pH and ionic strength, and colloidal particle size on the fouling potential measurement have been investigated. The effect of pH on the measurement of the fouling potential is different for different membranes. An alkaline feed solution pH is preferred because of its minimal tendency to foul the membranes. Colloidal size does not have a remarkable effect on the fouling potential measurement for the size range studied herein (about 10 nm), but larger particles result in less fouling, as observed normally. Ionic strength also plays an important role in the fouling of silica colloid suspensions, with lower ionic strength resulting less fouling.