Abstract
A characteristic of granulated LTA and SOD zeolites is given. It was determined that LTA zeolite particles have a cube shape with a size of ~2 μm; SOD particles have an irregular shape with a size of 0.5–1 μm. The dimension of the coherent scattering region was calculated to be 760 nm for LTA and 453 nm for SOD. The specific surface area of LTA is 115 m2·g–1 and SOD is 141 m2·g–1. Static tests of granulated zeolite showed that the maximum quantity of absorbed water vapor for LTA was ~30 wt.%, and for SOD ~20 wt.%. It was found LTA zeolite to provide adsorption of water from the gas to a dew point of –50 °C, and SOD zeolite of –9 °C. The apparent activation energies for the desorption of water on zeolites were calculated using isoconversional analysis of Friedman, Ozawa–Flynn–Wall, and Kissinger–Akahira–Sunose.
Highlights
The basic structural unit in the framework of such low-modulus zeolites as LTA and SOD is a β-cell [1]
X-ray powder diffraction data show that the samples are LTA and SOD zeolites (Figure 1), and the unit cell parameters correspond to the data given in the IZA database for LTA and SOD zeolites (Table 2)
Scanning electron microscopy (SEM) images of zeolites show that LTA zeolite particles have a shape close to a cube and a size of about 2 μm (Figure 1, a)
Summary
The basic structural unit in the framework of such low-modulus zeolites as LTA and SOD is a β-cell [1]. Α- and β-cages are available for water molecules; low-modulus zeolites are widely used for drying natural and other process gases [2]. In LTA, βcages are linked via double 4-membered rings to form simple 8-membered rings that form an α-cage with an input size for the 0.4 nm sodium form of the zeolite. Another area of application of porous adsorbents based on zeolites is the purification of rinsing wastewater and spent technological solutions from heavy metal compounds (Cu, Cd, Ni, Fe, Zn, Cr, Co) and radioactive isotopes that cause irreparable damage to the environment. The nonlinearity of water adsorption was shown in the paper [5] based on equilibrium and kinetics
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