Improved desorption performance of NaA zeolite by rare earth (Re = La, Nd) ion exchange

With a characteristic of type I water adsorption isotherms, NaA zeolite has been considered as a very promising candidate for the utilization in adsorptive rotary wheel dehumidification system for deep dehumidification. However, high desorption temperature of the zeolite is not conducive to the system energy saving. In this research, the La-modified, Nd-modified and the binary La/Nd-modified NaA zeolites were synthesized by microwave-assisted to reduce the desorption temperature. The structural and the composition of the modified products were characterized using X-ray diffraction (XRD) and X-ray Energy Dispersive Spectrometry (EDS), and their adsorption/desorption performances were evaluated by static adsorption, thermogravimetry (TG) and temperature programmed desorption (TPD). TG results exhibited that, Nd-modified zeolite with the highest ion-exchange degree (alpha) of 63.35% was more effective in reducing the desorption temperature of NaA zeolite. TPD analysis also demonstrated that the binary modified adsorbent had a lower desorption activation energy (E-d), which indicates that the binary modified zeolite as deep dehumidification adsorbent has an excellent desorption performance.