| Summary: | The article presents comparative characteristics of the pore structure and sorption properties of raw halloysite (R-HAL) and after calcination (C-HAL) at the temperature of 873 K. Structural parameters were determined by optical scanning and transmission electron microscopy methods as well as by mercury porosimetry (MIP, Hg) and low-pressure nitrogen adsorption (LPNA, N<sub>2</sub>, 77 K). The surface area parameter (LPNA) of halloysite mesopores before calcination was 54−61 m<sup>2</sup>/g. Calcining caused the pore surface to develop to 70−73 m<sup>2</sup>/g. The porosity (MIP) of halloysite after calcination increased from 29% to 46%, while the surface area within macropores increased from 43 m<sup>2</sup>/g to 54 m<sup>2</sup>/g. The total pore volume within mesopores and macropores increased almost twice after calcination. The course of CH<sub>4</sub> and CO<sub>2</sub> sorption on the halloysite was examined and sorption isotherms (0−1.5 MPa, 313 K) were determined by gravimetric method. The values of equilibrium sorption capacities increased at higher pressures. The sorption capacity of CH<sub>4</sub> in R-HAL was 0.18 mmol/g, while in C-HAL 0.21 mmol/g. CO<sub>2</sub> sorption capacities were 0.54 mmol/g and 0.63 mmol/g, respectively. Halloysite had a very high rate of sorption equilibrium. The values of the effective diffusion coefficient for methane on the tested halloysite were higher than <i>De</i> > 4.2 × 10<sup>−7</sup> cm<sup>2</sup>/s while for carbon dioxide <i>De</i> > 3.1 × 10<sup>−7</sup> cm<sup>2</sup>/s.
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