Synthesis and CO2 Adsorption Features of a Hydrotalcite-Like Compound of the Mg2+-Al3+-Fe(CN)64- System with High Layer-Charge Density

Gang Mao, Masamichi Tsuji and Yutaka Tamaura
Department of Chemistry, Research Center for Carbon Recycling & Utilization Tokyo Institute of Technology, 2-12-1, O-okayama, Meguro-ku, Tokyo 152, Japan

Abstract: Hydrotalcite-like compounds (HT) with 24%–48% Al3+-substitution have been synthesized in the Mg2+-Al3+-Fe(CN)64- system. Conditioning of the synthesized and air-dried compound with K4Fe(CN)64- solution at 80°C was essential to obtain the 80%–90% pure ionic Fe(CN)64- form on an equivalent basis. A linear decrease in ao with an increase in the mole ratio of R = Al3+/(Mg2+ + Al3+) was extended to R = 0.48. The formation of highly Al3+-substituted HTs has been corroborated by the decrease in the hexagonal lattice constant ao down to 3.016 Å. The ao value was independent of the interlayer anions. The CO2 adsorption profiles were dependent upon both the Al3+-substitution and the interlayer distance. The isosteric heat of CO2 adsorption was 43.3 kJ mol-1 in the range of adsorption of 20 to 40 cm3 g-1 at 298 K and 0.1 MPa.

Key Words: Al3+-substitution • CO2 adsorption • Hydrotalcite-like compound • Ion exchange

Clays and Clay Minerals; December 1993 v. 41; no. 6; p. 731-737; DOI: 10.1346/CCMN.1993.0410612
© 1993, The Clay Minerals Society
Clay Minerals Society (www.clays.org)