Preparation of mullite ceramic microfilter membranes using Response surface methodology based on central composite design

Abstract In this paper effect of free silica removal from mullite microfilter membranes using different sodium hydroxide (NaOH) concentrations at different temperatures and for different removal times was studied. The prepared membranes were subjected to XRD, SEM, porosity analysis, and mechanical strength measurement. Response surface methodology (RSM) based on central composite design (CCD) was used to design the experiments and analyze three operating parameters including; NaOH solution concentration, NaOH solution temperature and removal time. The optimum porosity of 49.4 was obtained with NaOH solution concentration of 35 wt% at temperature 75 °C and removal time equal to 8 h. Water flux and mechanical strength as important characteristics were measured for all the membranes. For the membrane with the optimum porosity, water flux, mechanical strength, and free silica removal percentage were 61.7 kg/m2 h, 21.6 MPa, and 28.2%, respectively. The maximum rejection percentage was 97.2% and emulsion flux for this state was 15.6 kg/m2 h at temperature 25 °C and cross flow velocity of 1.5 m/s.