Abstract
Organo-kenyaites were prepared from a cetyltrimethylammonium hydroxide (C16TMAOH) solution and solid sodium kenyaite (Na2Si22O45 center dot 10H(2)O) mixture. The effect of the initial cetyltrimethylammonium solution on the structure of the intercalated materials was investigated by CHN analyses, X-ray diffraction (XRD), thermogravimetric analysis, SEM, and Si-29 and C-13 solid NMR techniques. For C16TMAOH concentration 0.25 mM, the Na+ cations were fully exchanged. initial C16TMAOH concentrations higher than 0.25 mM had little effect on the intercalated amount of C16TMA(+) cations. The organic cations content reached a plateau of 0.66 mmol/g. The arrangement model of C16TMA(+) cations corresponded to a tilt of the organic cations to the silicate layers with an angle of 42 degrees as deduced by XRD studies. The C16TMA(+)cations exhibited mainly trans-configuration of the methyl chains, as was shown by solid C-13 NMR. The thermal stability of the organo-silicates was studied using in situ FTIR and in situ XRD in the range 25-450 degrees C. The C16TMA-kenyaites were stable at temperatures below 200 degrees C. They collapsed at higher temperatures due to the decomposition of the intercalated surfactants. These organo-kenyaites were used to remove the acidic dye molecule, eosin. The removal tests were performed at varying conditions of initial dye concentrations, organic content in the organo-kenyaites and heating temperatures. In general, the organic modification improved the removal capacity of the Na-kenyaite from 2 mg of eosin/g to 60 mg of eosin/g, and this capacity was related to the organic contents and the calcination temperatures of the organo-kenyaites.