: Zeolites are porous crystalline materials with various attractive properties that are widely used in chemical processindustries because of their adsorption capacity, thermal stability, ion exchange, strong acidity, high surface area, and molecularsieving. Today, synthetic zeolites are used commercially more often than natural zeolites due to the purity ofcrystalline products and the uniformity of particles and pore sizes. Short crystallization time has always beenpursued from the commercial viewpoint since it is associated with high synthesis efficiency, low energyconsumption, and thus low production cost. Pore size of zeolite is a property that differs between different types of zeolites and improvement/tuning ofpore size of zeolites has recently received much attention. Size of zeolite crystalline and uniformity of zeolite grains are properties thatare significant in synthesis and application of these materials. Uniform small-sized zeolites show better catalytic andadsorptive properties than large-sized ones because of increased surface area, increased ion exchange capacity,decreased diffusion limitations, and improvement of mass transfer. Crystal size distribution of zeolites is influencedby different parameters such as initial chemical composition of precursors, the silicon and aluminum source, temperature, time ofcrystallization, pH of solution, processes of ageing, stirring, and use of surfactants during the synthesis of the zeolites.Microemulsions usually consist of small droplets of water-in-oil or oil-in-water formed by the dispersion in continuous oil or water phases inside of a surfactant layer. Microemulsions are generally prepared by using asurfactant, a co-surfactant, an oil phase, and water phase. Under appropriate conditions, a variety of reactants can beintroduced into the nanometer-sized aqueous domains for reaction, leading to materials with controlled size andshape. There are two advantages in using microemulsions as a medium for zeolite growth during the synthesisprocess. On one hand the microemulsion with small aqueous domains can be viewed as micro/nanoreactors forsynthesis of zeolite nanocrystals, and on the other hand, the surfactant will coordinate to the crystallographic facesofthe growing crystals and affect the growth of the zeolite crystals.In this research project, ZSM-5 and mordinite nanocrystals were synthesized using sodium silicate as the silica source and aluminum sulfate as the source of alumina via nanoemulsion-ultrasound method, and the effects of the pertinent parameters such as concentration of the surfactant, concentration of the aluminosilicate gel and intensity of the ultrasound on nanostructural modifications were investigated. Pb 2+ adsorption tests were performed to determine the effect of nanoemulsion-ultrasound technique on adsorption property of ZSM-5 zeolite.XRD, SEM, and FTIR were utilized to study and characterize crystal phases and crystalinity, morphology of crystals, and phase purityof ZSM-5 and mordenite prepared samples. The celebrated Scherer equation was used to determine the crystalline size of samples.Results show that the nanoemulsion-ultrasound technique compared with the conventional hydrothermal synthesis, allows rapid crystallization of both ZSM-5 and mordenite, and leads into much smaller crystals and zeolite grains with smaller and uniform morphologies. Results show that the crystals and grain sizes of ZSM-5 samples prepared by nanoemulsion-ultrasound technique compared with samples produced via the conventional method are reduced to from 113 nm to 17nm and from 39 µm to 1.5µm,respectively. These results for the case of mordenite zeolite were from 112.70 nm to 65.08 nm and from 15.6µm to 3.5µm. It was revealed that nanoemulsion-ultrasound synthesis method produces smaller and purer zeolite nanocrystals. The improved adsorption of Pb 2+ is attributed to larger pore apertures compared with ZSM-5 cryst als prepared by conventional synthesis methods. In addition, adsorption isotherms of Pb 2+ were studied. Results show that the adsorption of Pb 2+ onto both zeolitesfollow a second-order Freundlich model. Key words: ZSM-5 and Mordenite zeolites, surfactant, microemulsion, nanoemulsion, ultrasound, adsorption, Freundlich isotherm