An innovative approach based on microwave radiation for synthesis of zeolite 4A and porosity enhancement

Advantages of microwave radiation in terms of reducing reaction time and enhancing product quality were exploited for template-free zeolite 4A synthesis, in which a domestic microwave oven was purposely utilized instead of a scientific microwave reactor. Experimental data proved that the microwave-assisted hydrothermal synthesized product crystallized at the same phase as the zeolite obtained from the conventional hydrothermal method. Moreover, compared to the hydrothermal synthesis, microwave radiation considerably improves zeolite's properties, including forming more uniform and finer zeolite crystals. However, both synthesis methods produced zeolites with relatively limited surface areas. To solve this problem, an attempt to utilize microwave radiation as a post-washing technique gained a significant improvement of the zeolite's exposed surfaces that revealed effectiveness of microwave on removing the obstacles to release the blocked pores in the zeolite's structure. On that basis, the adsorption characteristics of the 4A zeolites prepared from the two synthesis methods were studied in consideration of the influence of post-washing steps. A comparison on adsorption of these materials was carried out in treating a synthetic dye-containing wastewater of which methylene blue (MB) was used as a model compound. Experiments showed an increment of about quadruple MB uptake achieved from the microwave-assisted method in comparison to the conventional route.