Influence Of Solution Chemistry On The Interaction Forces Between Membranes And Foulant

To clarify the influence of solution chemistry(p H, ionic strength and hydrophilic/hydrophobic organic matters) on ultrafiltration(UF) membrane fouling, the paper prepared the carboxyl group probe and the PVDF membrane material probe with physical sintering method, combined with laboratory- made probe preparation device. Then we prepared different pollutants probe with the solution soak method. To further clarify the effects of pH and ionic strength on the interaction forces between typical membrane materials and the carboxyl group, which is a typical functional group of membrane foulants, the interaction forces between the PVDF or EVOH membrane and carboxyl group were measured by atomic force microscopy in conjunction with a self- made carboxyl colloidal probe. And it was substituted sodium alginate(SA) for hydrophilic organic matter, substituted humic acid(HA) for hydrophobic organic matter. The interaction forces between the PVDF membrane and foulant were measured by AFM in conjunction with a self- made PVDF membrane material probe, and the adhesive forces between foulant and foulant were measured with different pollutants probe. Therefore, comprehensive analysis of fouling experiments and the removal rate of dissolved organic carbon was carried out. Results show:(1) The PVDF-carboxyl and EVOH-carboxyl adhesion forces weakened with increasing p H, whereas they firstly increased and then decreased with an increase in ionic strength. The interaction forces between membranes and carboxyl groups were in accordance with the classic Derjaguin, Landau, Verwey, and Overbeek(DLVO) theory at low ionic strength(0-10 mM), indicating that interactio n increased with an increase in ionic strength. However, the adhesive forces decreased with an increase at high ionic strength(>10 mM), which can be attributed to a hydration force.(2) Moreover, the PVDF-carboxyl adhesion force was much stronger than the EVOH-carboxyl interaction force for given solution conditions, which is mainly due to the stronger hydrogen bonding between the PVDF and carboxyl groups.(3) For a single pollutant, the adhesive force between PVDF and hydrophilic pollutants were stronger than that between PVDF and hydrophobic pollutants, and hydrophilic organic matter caused the speed of flux decline significantly, stronger than the influence of hydrophobic organic compo unds on the membrane flux, show that the hydrophilic organic matter influence on PVDF ultrafiltration membrane pollution is more serious.(4) For the hydrophilic/hydrophobic mixed pollutants, the corresponding interaction forces increased with the increase of hydrophilic organic matter content, at the same time as measured by the corresponding interaction forces increased with increasing membrane fouling, causing membrane pollution.