Changes in the structure, crystallinity, morphology and adsorption property of gamma-irradiated Philippine natural zeolites

Gamma-irradiation of raw, Na-exchanged, NaOH-, and HCl-modified Philippine natural zeolites (PNZ) have been performed at different irradiation doses. XRD, FTIR, and SEM were used to observe the changes in the structure, crystallinity, and morphology of the zeolite samples. The exposure to gamma-rays causes varying effects for raw and chemically modified zeolites with non-linear dependence on the irradiation dose. Irradiation results in a general reduction of unit cell volumes of the component zeolites. At low gamma-irradiation dose (<= 400 kGy), raw and NaOH-modified zeolites, experience an improvement in the crystallinity. Higher irradiation dose (700 kGy) leads to structural degradation. In contrast, the crystallinity of HCl-modified zeolites slightly diminishes at a lower dose but improves at a higher dose. On one hand, the exposure to gamma-radiation at a dose level of 400 kGy generally degrades the crystal structure of Na-exchanged raw zeolites. Further, adsorption experiments were conducted to investigate how gamma-radiation affects the Cu2+ sorption property of zeolites for possible applications in heavy metal decontamination in the semiconductor industry.