Pillaring of bentonite clay with Al and Co

This work describes the synthesis and characterization of mixed Al/Co pillared clays. The materials were prepared using different Co concentrations: 10%, 25%, 50%, 75% and 100%. The samples were analyzed by XRD, N-2 physisorption, chemical analysis (AA), Al-27 NMR, FTIR and EPMA. The use of small amounts of Co (10% and 25%) resulted in the formation of pillared clays, and the material containing 25% cobalt exhibited superior characteristics compared to an Al pillared clay (basal spacing of 18 angstrom and BET surface area higher than 300 m(2)/g). The Al-22 NMR results confirmed the formation of mixed Al/Co pillars; the ratio of the Al-VI/Al-IV signal intensities decreased, indicating that the Al-VI content decreased while the Co content increased. Thus, the Co ions isomorphically substituted for Al in the Keggin ion structure (pillaring agent). When the Co content was 50%, 75% and 100%, pillared clays did not form. Therefore, it is possible to obtain clays with mixed Al/Co pillars for Co contents of up to 25%. (C) 2014 Elsevier Inc. All rights reserved.