Optimization of the Asymmetric Cellulose Acetate Membrane Synthesis Variables for Porosity and Pure Water Permeation Flux Using Response Surface Methodology: Microfiltration Application

Abstract

Membranes play a vital role in membrane-based water treatment processes. Thus, improvement in the membrane fabrication stage can greatly affect the overall performance of these technologies. Accordingly, this study focuses on optimizing the fabrication process of a microfiltration cellulose acetate membrane prepared using a pore-templating method. The effects of synthesis variables and their interactions were investigated using face-centered composite design through response surface methodology (RSM). Calcium carbonate (CaCO3) and glycerin concentrations in the casting solution in addition to evaporation time and hydrochloric acid (HCl) bath time were selected as the independent variables, while the membrane porosity and pure water flux were considered as the response variables. Significant increase in both responses was observed by increasing CaCO3 and glycerin concentrations (P value < 0.05). However, the effect of evaporation time was found to be statistically insignificant on both responses. The effect of the HCl bath time was found to significantly affect the membrane porosity but not the pure water flux. RSM models for both responses were statistically evaluated in terms of the coefficient of determination (R2), and the estimated values (96.74% for the porosity model and 83.85% for the flux model) indicated good fit of the model to the experimental values. Multiple response optimization was employed, and the membrane produced at optimum conditions proved to have good agreement with the predicted values (16.2% error in flux and 3.66% error in porosity). The membrane was successfully applied for paint pigment rejection and oil emulsion rejection, and rejection efficiencies of 95.6% and 80% were achieved for color and oil, respectively, confirming the applicability of the membrane produced at the obtained optimum condition for wastewater treatment.