Rice husk ash (RHA) is an abundant agricultural waste in Mekong Delta, Vietnam. The utilization of RHA for zeolites production has been widely studied by pretreating RHA before reaction. In this study, zeolite NaX was synthesized directly using RHA without any pretreatment. Key parameters including molar ratios of SiO2 to Al2O3 and Na2O to Al2O3, reaction time, and aging time were investigated. The results showed that the optimal conditions for the synthesis of zeolite NaX are: molar ratio of SiO2/Al2O3 = 4, molar ratio of Na2O/ Al2O3 = 10, reaction time = 4 h, and without aging. Zeolite NaX with a specific surface area of 388 m2/g and a pore diameter of 12.37 A
was obtained, which were comparable to the published data. The method developed in this work is an energy and time saving, integrated, and environmental friendly process. It has the potential to be applied for synthesizing other types of zeolite