Sorption of CO 2 and CH 4 on Raw and Calcined Halloysite-Structural and Pore Characterization Study

• Published in: Materials Vol. 13; no. 4
• Main Authors: Pajdak, Anna, Skoczylas, Norbert, Szymanek, Arkadiusz, Lutyński, Marcin, Sakiewicz, Piotr
• Format: Journal Article
• Language: English
• Published: Switzerland 19.02.2020
• Subjects: sorption capacity of CH4 and CO2; halloysite; effective diffusion coefficient; kinetics of diffusion; pore structure
• ISSN: 1996-1944; 1996-1944

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 , 77 K). The surface area parameter (LPNA) of halloysite mesopores before calcination was 54-61 m /g. Calcining caused the pore surface to develop to 70-73 m /g. The porosity (MIP) of halloysite after calcination increased from 29% to 46%, while the surface area within macropores increased from 43 m /g to 54 m /g. The total pore volume within mesopores and macropores increased almost twice after calcination. The course of CH and CO 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 in R-HAL was 0.18 mmol/g, while in C-HAL 0.21 mmol/g. CO 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 > 4.2 × 10 cm /s while for carbon dioxide > 3.1 × 10 cm /s.