Durability of Zeolite Against Repeated Activation Treatments with Microwave Heating

摘要

The durability of zeolite X against repeated treatments with microwave heating was studied, and properties of the zeolite as desiccant were compared and assessed with those of the most popular commercial desiccants (calcium chloride) for home use. Mixed cationic forms of zeolite with a ratio of Na-X/Ca-X = 5 g/45 g in a full hydration was used to achieve desirable properties. The mixture was activated by microwave (2.45 GHz) radiation for 15 min with 500 W, and after full hydration it was reactivated under the same conditions. The treatment was repeated up to twenty-five times. The adsorption capacity of the zeolite for water decreased with increasing number of treatments. Analyzing the curve of decreasing water capacity, the degradation degree at every treatment was determined to be 0.013. From this value, the number of treatments at which the adsorption capacity becomes one half of its original capacity was calculated to be 54 (defined as lifetime) and it was estimated that the zeolite could adsorb 10.7 times of its own dry weight of water by its lifetime. The rates of uptake of commercial desiccants for water were followed for two months and the uptake curves were analyzed. The desiccants reached their lifetimes in ca. 120 days and absorbed 0.8-0.9 times of their own weights of water by their lifetime. The total amount of adsorption by the zeolite is 10 times greater when compared to the commercial desiccants. Since the zeolite desiccant by using the microwave activation method exhibits higher water adsorption abilities, it is promising as a repeatedly usable desiccant for home use and other areas.