Influence of acid activation on hydrogen adsorption properties of analcime-rich tuff from Turkey

Abstract

In this study, structural, thermal, and hydrogen (H 2 ) adsorption properties of natural analcime-rich zeolite tuff (A) from Trakya (Turkey) and that of acid-treated forms investigated. Analcime mineral was treated with 0.1, 0.5, 1, 2, and 3 M HCl solutions at 80 °C for 5 h. Differences in structural and thermal behaviors of the analcime samples before and after acid-treatment were examined by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy with detector x-ray energy dispersive (SEM-EDX), thermal analysis (TG-DTG-DTA) and nitrogen adsorption methods. Micropore volume, micropore area, and specific surface area values of the acid-treated analcimes were very high compared to the natural analcime sample. It was found that the acid-treated analcime zeolites with a high SiO 2 /Al 2 O 3 ratio exhibited higher H 2 adsorption capacity and thermal stability. H 2 adsorption capacities of natural and acid-treated analcimes at 77 K up to 100 kPa were found between 0.255 and 0.632 mmol/g. The hydrogen adsorption capacities of analcime samples increases in the order A < 05HA < 01HA < 1HA < 2HA < 3HA. Additionally, it was determined that the hydrogen adsorption capacity of analcime samples had an almost linear connection to the BET surface areas.