Optimization Aging Parameters of Mg Silica Aerogel Using Box-Behnken Approach

Abstract

The main objective of the present study was to investigate the application of Box–Behnken design which is a type of optimization design of response surface methodology (RSM) to predict and optimize some aging condition of magnesium silica aerogel (MSA) for improving surface properties such as surface area, pore volume and pore size. Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) techniques, tap density method and helium pycnometer were used to characterize aerogels. The operating conditions were optimized as a function of the molar ratio of Mg:Si (0.35, 0.50 and 0.65), aging time (24 h, 60 h and 96 h) and aging temperature (50 oC, 70 oC and 90 oC). Lack of fit test indicates that the quadratic regression model was significant with the high coefficients of determination values for all three properties. Optimized aging factors for synthesis MSA with high BET surface area, high BJH pore volume and average BJH pore size were found to be 0.5 Mg:Si molar ratio, 79.62 oC and 61.51 h, respectively. Under these conditions, magnesium silica aerogels have great properties: 734 m2.g-1 BET surface area, 0.41 cm3.g-1 BJH pore volume and 4.91 nm BJH pore size, 0.12 g.cm−3 density and 95 % porosity. Box-Behnken is useful optimization tool for production of nanoporous magnesium silica aerogel.