Exploring the impact of NaOH pre-treatment for H2 and CO2 adsorption on clinoptilolite.

The present investigation involved the treatment of natural clinoptilolite with varying concentrations of NaOH solutions followed by calcination. The samples' composition and structure were characterized and their performance was investigated in the context of hydrogen (H 2) and carbon dioxide (CO 2) adsorption. While a decreasing SiO 2 /Al 2 O 3 ratio was observed in the NaOH-treated samples, the morphological structure obtained from SEM images and the increase in surface area according to BET results exhibited more pronounced alterations, particularly within the 0.5–1 M NaOH concentration range. The alkali treatment resulted in notable peak sharpening, with the most prominent changes observed in the (020), (100), and (101) lattice planes at the same concentration. However, there were no significant alterations in peak intensities. Although H 2 adsorption (4.0192–26.4726 cm3/g) could reach higher values, higher amounts of CO 2 adsorption (5.2308–20.2700 cm3/g) occurred as the concentration of NaOH increased. This phenomenon was attributed to structural modifications in clinoptilolites. • Alkali treated clinoptilolites are high surface area, low Si/Al content, and non-agglomerated. • NaOH concentration change effected the structural and gas adsorptions characteristics. • NaOH concentration is 0.5 M for optimum adsorption and structural properties. • The highest achievable gas adsorption was obtained for H 2 compared to CO 2. [ABSTRACT FROM AUTHOR]