pH, Ionic strength and flow velocity effects on the NOM filtration with TiO2/ZrO2 membranes

The effects of pH, ionic strength and flow velocity on the volumetric permeate flux and the rejection of dissolved organic carbon (DOC) in a 15 kDa ceramic ultrafiltration membrane are evaluated. The decrease of pH produces a drop in the elimination of DOC, despite humic acid accumulation in the surface of membrane. Membrane has a lower humic acid flux resistance when pH decreases due to molecular compression of humic acid. Ionic strength has a relevant influence in humic substances processed with ceramic ultrafiltration membranes. A significant permeate flux reduction is approached when ionic strength increases as well as DOC removal reduction. Regarding the ionic strength rise, it can be observed that the resistance of the cake layer falls as in the case of falling pH. On the other hand, permeate flux rises due to the reduction of the effective size of the molecule. Concerning flow velocity, permeate flux reduction plays a significant role in contrast to DOC removal. Low flow velocity allows cake layer formation that considerably reduces flux permeate. Experiments carried out at neutral pH and low ionic strength, to analyse flow velocity, show no electro kinetic effects that influence the cake layer formation and flux permeate. (c) 2006 Elsevier B.V. All rights reserved.