The Effect of Humic Acid on Ultrafiltration Membrane Fouling

To investigate the fouling phenomena of ultrafiltration membrane caused by humic acid solution, four important parameters such as time,pressure,pH value and calcium ion concentration were considered in the experiment. The changes of various membrane fouling resistances and humic acid retention rates were also analyzed. Moreover, the surface and cross section of the clean and fouled ultrafiltration membranes was observed by emission scanning electron microscope. The results show that a rapid fouling takes place due to internal pore adsorption, pore blocking and a fouling gel developed on the membranes. Concentration polarization plays a main role in initial period. The pH value as the important parameter decided what kind of fouling playing the main role. As pH value ranges between 6 and 9, the membrane fouling is relatively light. Both acid and alkali can aggravate humic acid fouling: acid promotes the formation of the gel layer, while alkali accelerates the blockage of membrane hole. The existence of calcium ion will aggravate the fouling of ultrafiltration membrane and reduce the rejection rate of humic acid.