A flux enhancing pretreatment for the ultrafiltration of acid whey

The reduction in permeate flux caused by fouling is a drawback in the operation of membrane systems that can be alleviated using mechanical and electrical methods. Alternatively, physicochemical treatments provoking the elimination of fouling agents have been proposed as effective strategies for the enhancement of flux. A procedure (comprising salt addition, pH and temperature modification and centrifugation) that removes calcium and phosphate salts from acid whey without altering the profile of valuable proteins is presented in this research work. It has been demonstrated through the paper that this pretreatment enhances significantly the permeate flux of whey when cross-flow ultrafiltered through a 50 kDa tubular ceramic membrane both in total recycle and continuous diafiltration mode. For modelling purposes, a resistances in series model was applied to explain the effect of transmembrane pressure and a complete-standard blocking model fitted the experimental data of the variation of permeate flux with time.

A pretreatment procedure has been proposed for the clarification of acid whey in order to enhance the permeate flux through ceramic membranes. Its effectiveness was tested employing a 50 kDa tubular membrane in cross-flow operation. This process was able to remove fouling agents but did not affect the composition of individual proteins. As a result, when considering a transmembrane pressure range up to 2 bar, flux was improved by a factor of 3.0–3.5 with respect to the original whey, which could be related to a resistances in series model. With respect to the behaviour of pretreated whey under continuous diafiltration, the final volume of permeate collected after 4 h of operation was triplicated when compared to the unpretreated whey. The time evolution of flux was explained by a mathematical model combining complete and standard blocking. The fitting parameters showed that the pretreatment step provoked a decrease in the fraction of pores susceptible of being completely blocked but accelerated the fouling mechanisms.