Statistical optimization using central composite design for the desilication process of natural zeolite to use in water adsorption from diesel fuel

In this paper, natural zeolite (clinoptilolite) was desilicated to remove water from diesel fuel. Optimization of desilication conditions was done using Design-Expert 7.0.0 software and using response surface methodology. The parameters studied, the concentration of sodium hydroxide solution and the temperature and time of the desilication process were considered. After optimization of desilication process conditions, the water sorption percentage was 95.32% under the optimized conditions, the concentration of sodium hydroxide solution 0.47 molar, temperature 84.05 °C and time of 2.42 hours. To carry out the process of water sorption from fuel, amount of 0.5% w/v of the desilicated zeolite (5 g zeolite/1000 mL of the fuel) was mixed with diesel fuel for 2 h and the water content was measured by the volumetric Karl Fischer technique. The natural zeolite and the desilicated zeolite in the optimum conditions were characterized by XRD, XRF, FTIR and SEM analyses which indicate well desilication process. The results of water sorption before and after the sorption process indicate the acceptable performance of desilicated zeolite.