Optimal conditions of porous ceramic membrane synthesis based on alkali activated blast furnace slag using Taguchi method

Abstract The main purpose of this research is to synthesize porous ceramic membrane based on alkali-activated blast furnace slag and achieve optimal synthesis conditions for removing over 90% petroleum compounds and flux in the range of microfiltration (MF) and ultrafiltration (UF). The method applied for membrane synthesis is simple, environmentally friendly, and economical. The blast furnace slag as the main starting material was used to fabricate these free sintering and self-supported ceramic membranes. The L 9 orthogonal array of the Taguchi method was employed to determine the optimum conditions of three controlling factors, i.e. hydraulic pressing pressure, alkali-activated blast furnace slag drying time, and pressing time in three levels. Morphology and filtration performance of the synthesized membranes were characterized via SEM images using Image-j software, total porosity determination, and pore size study using bubble point method. Cross-flow filtration of 75 ppm gas oil in water emulsion was performed and COD analysis of permeate was then monitored. Distribution of synthesis parameters and their influences on the membrane fabrication process were investigated using analysis of variance (ANOVA). According to the results, drying time and hydraulic pressing pressure were known as the most effective parameters on COD and permeation flux. Two optimal membranes for COD removal and permeation flux were identified in hydraulic pressing pressure, drying time and pressing time of (400 bar, 6 h, 5 min) and (225 bar, 8 h, 30 min), respectively. COD optimal UF membrane with an average pore size of 0.07 µm and 100% removal of gas oil and permeation flux optimal MF membrane with an average pore size of 0.66 µm and pure water permeation flux of 1960 kg/m 2 h were introduced.