Removal of humic acids from water by hybrid titanium-based electrocoagulation with ultrafiltration membrane processes

Abstract

Coagulation imposes major impact on the removal of humic acids (HAs) and the reduction of ultrafiltration (UF) membrane fouling. In this study, titanium was used instead of iron and aluminum as a novel alternative sacrificial anode, and the removal of HAs from water by titanium-based electrocoagulation with submerged flat sheet ultrafiltration membrane was investigated. Results clearly indicate that the current intensity did have an apparent effect on the size and fractal structure of flocs. A combination of electrocoagulation with ultrafiltration can increase HAs rejection, reduce membrane fouling and decrease transmembrane pressure. Membrane permeability and the specific resistance of cake layer were controlled directly by coagulated floc structure, which was affected strongly by the applied current intensity. Hydrous titanium dioxide (TiO2) flocs were formed by anodizing of titanium and one-step hydrolysis process with titanium salt solution. TiO2 nanoparticles with large specific surface area produced by the processes showed high photocatalytic activity. Thus, the processes are not only efficient in the removal of HAs from water but also economical in sludge recycling and reduction. It may offer a novel solution to many economic and environmental problems associated with handling iron and aluminum salt coagulation.