The experiments were carried out in two steps, in which ultrasound irradiation under atmospheric pressure was followed by a conventional hydrothermal treatment under autogenesis pressure using an autoclave reactor in an end-over-end oven. The clinoptilolite was subjected to US-irradiation and then conventional hydrothermal treatment in such a way that total treatment time was kept constant for 5 h at 90 °C. The sonication time, however, was varied between 0.5 and 5 h. In Fig. 5a, XRD patterns of the US-assisted synthesized NaP zeolites are compared with the parent natural clinoptilolite. It is clear that after 1 h of sonication and 4 h of hydrothermal crystallization, zeolite NaP was formed, in which characteristic peaks at 2θ: 12.5, 21.7, 28.1 and 33.4°, ascertain the formation of a new zeolitic phase. It can be concluded that under the studied condition, the conversion of clinoptilolite to zeolite NaP took place without having any intermediate meta-stable phase. It has been reported that ultrasonic Kartogenin helps to improve yields, rates and properties of products of a chemical reaction. In this reaction, clinoptilolite partially dissolved under ultrasonic irradiation at elevated temperature to form an amorphous gel. Then nucleation of NaP from this aluminosilicates gel begins on the surface of un-dissolved zeolite particulates and the rate of crystal growth increases under hydrothermal treatment at controlled temperature  and . The crystallization of zeolite started earlier by using ultrasound and also a significant increase in nucleation rate and a decrease in indication time were observed. By using US-assisted hydrothermal treatment, the zeolitic phase transformation occurred faster and re-crystallization was completed in 5 h. These results show a significant reduction in crystallization time and induction period by application of the ultrasonic irradiation. US-assisted hydrothermal treatment increases the zeolite NaP crystal growth rate by increasing the concentration of soluble silicate and aluminate precursors needed for formation of NaP. The acoustic cavitation provides enough activation energy to collapse clinoptilolite structure and increases the concentration of soluble Si and Al species that are needed for re-crystallization and growth of NaP zeolitic phase . By increasing the sonication time from 1 to 5 h and decreasing the hydrothermal treatment time from 4 to 0 h, a relatively constant intensity of NaP peaks is emerged in the product. It can be concluded that sonochemical energy is the dominant factor that controls zeolite transformation under the studied condition.