Ceramic nanofiltration membranes for efficient fouling mitigation through periodic electrolysis

Abstract

Ceramic membranes are gaining importance in several mainstream membrane applications. Their high chemical and thermal resistance stability make them ideal candidates for oil/water separation, dye rejections, in dairy production, catalyst recovery and in treating a variety of wastewater effluents. Although ceramic microfiltration and ultrafiltration membranes are a predominant research area, there is still limited research on ceramic nanofiltration membranes, especially on controlling its fouling propensity. High flux values in such membranes can cause rapid fouling which lead to a compromise in membrane performance. In this work, we have modified commercial ceramic TiO2 NF membrane by coating it with titanium through an e-beam deposition process. Coating with titanium did not bring about any change in the inherent membrane properties such as its thermal resistance, structure and hydrophilicity. The superhydrophilic membrane showed good electrical conductivity, which enabled us to test the membrane for its self-cleaning ability through periodic electrolysis. Sodium alginate, yeast, humic acid and their mixtures were used as model foulants. A cross-flow filtration setup was used where the membrane acted as a cathode and a potential of 2–4.5 V was applied periodically depending upon the type of foulant. Without membrane cleaning, a sharp decline in flux to even till 10 % of its original value was noticed during some filtration tests. However, a high flux recovery from 88 to 98 % was achieved when the membrane was subjected to intermittent cleaning. The Ti-coated NF ceramic membrane showed efficient surface cleaning. The generation of hydrogen bubbles helped in sweeping away the cake layer formed as a result of concentration polarization. These electro-ceramic NF membranes allow us to address critical problems associated with such pressure driven processes where biofouling is a major problem.