Systematic evaluation of TiO2-GO-modified ceramic membranes for water treatment: Retention properties and fouling mechanisms

In this study, modified ceramic membranes functionalized with titanium dioxide (TiO2) graphene oxide (GO) via the vacuum method were prepared, and the effects of the modification on the surface chemistry, retention property and fouling mechanism were systematically investigated. The characterization of the modified membranes demonstrated an extremely high hydrophilicity and negative charge of membrane surface. A higher removal of humic acid (HA), tannic acid (TA), ions and pharmaceuticals and better haloacetic acids formation potential (HAAs-FP) control was observed for the TiO2-GO-modified ceramic membrane compared to the pristine ceramic membrane while maintaining a relatively high permeate flux. The TiO2-GO-modified ceramic membrane also exhibited improved antifouling properties against HA and TA fouling. A modified Hermia's model was fit accurately to the experimental data obtained from long-term TA and HA fouling protocols for both pristine and modified membranes. The TA fouling mechanism transformed from a standard blocking to an intermediate blocking mechanism for the TiO2-GO-modified membrane, indicating a dramatic decrease in the membrane pore size after modification. The gel layer formation model fit well for the modified ceramic membrane during HA filtration, which explained the decrease in the selected pharmaceutical retention by the HA-fouled membranes, while pore blocking governed the HA fouling for the pristine membranes, causing an increase in the pharmaceutical retention by the fouled membranes. The TiO2-GO-modified membrane had a strong effect against bacterial adhesion, but only exhibited a minor inhibition of biofouling after a 24 h protocol in cross-flow filtration.