Synthesis of potassium-type zeolites by the reverse-micelle method with microwave heating

Potassium-type zeolites (K-zeolites) containing a chabazite phase were synthesized using the reverse-micelle method with microwave heating. The reverse micelle acts as a space-confining reactor, and treatment by microwave irradiation provides fast, homogeneous, and preferential heating of the aqueous phase where the zeolites are synthesized. As control experiments, K-zeolites were also synthesized using the reverse-micelle method with external oil bath heating, the conventional method with microwave heating, and the conventional method with external heating. Based on dynamic light scattering and scanning electron microscopy analyses, we confirmed that small zeolite crystals could be successfully prepared using the reverse-micelle method. We also found that the crystallization rate of zeolites obtained using the reverse-micelle microwave heating method was larger than those obtained using other methods. Furthermore, we evaluated the adsorption performance of the synthesized zeolites via ammonium adsorption experiments. The rates of ammonium adsorption and the maximum adsorption capacities of the zeolites obtained by the reverse-micelle method were larger than those of the zeolites obtained by the conventional method.