Interaction of Vermiculite with Aliphatic Amides (Formamide, Acetamide and Propionamide): Formation and Study of Interstratified Phases in the Transformation of Mg- to Nh4-Vermiculite

Antonio Ruiz-Conde
1997 Clays and clay minerals  
The Mg-vermiculite from Santa Olalla has been treated with aliphatic amides--formamide (FM), acetamide (AM) and propionamide (PM)--in aqueous solution. These treatments produce the transformation towards NH4-vermiculite and interstratified NH:vermiculite-Mg-vermiculite phases. The NH 4vermiculite, Mg-vermiculite and interstratified (mixed-layer)~phases have been identifed from basal X-ray diffraction (XRD) interval peaks between 10,3 _~ and 14,4 A, and confirmed by direct Fourier transform
more » ... rier transform method, as well as by atomic absorption spectrometry (AAS), infrared (IR) spectroscopy and thermal analysis. According to their NH:vermiculite/Mg-vermiculite probability coefficients ratio (Pa/PB), and PAA, these interstratified phases can be divided into 3 categories: 1) If the Pa/Pn ratio is --> 7/3 and PAA ~" 0,7, there are interstratified phases with a strong tendency toward segregation (case of FM, AM and PM). 2) If the PA/PB ratio is between 5/5 and 6/4, with PAA in the range 0.45-0.6, there are nearly regular alternating and random interstratified phases (case of AM and PM). 3) If the Pa/PB ratio is --< 5/5 and Pan <-0.45, there are interstratified phases with a strong tendency toward alternation (case of PM). Experimental evidence reported in the present work indicates that the mechanism of interaction of Mg-vermiculite with FM, AM and PM in an aqueous medium takes place by ion exchange of NH 4 between the layers. The hydrolysis of these aliphatic amides leads to the liberation of NHa + into the medium. It has been found that the NH4 § sorption depends on the physico-chemical characteristics of the particular aliphatic amide, and the transformation of Mg-vermiculite to interstratified and/or NH4-vermiculite phases depends on the amide concentration. These treatments allow one to control the formation of interstratified and NH4-vermiculite phases.
doi:10.1346/ccmn.1997.0450302 fatcat:ilhnsxg2trgixmor5a672d56hq