A STUDY OF ORGANO-HECTORITE CLAY CRYSTALLIZATION

A method has been developed to synthesize organo-hectorite clays direc tly from a Mg-silicate gel containing organic or organometallic molecu les that are expected to be incorporated within the interlayer space. Complete crystallization occurs upon aqueous reflux for 48 h. The prog ress of clay layer formation was monitored by X-ray powder diffraction (XRD), differential thermal gravimetry (DTG), and infrared (IR) spect roscopy. Evidence of clay XRD peaks occurs after just 4 h of hydrother mal treatment, and Mg(OH)(2) is no longer observable after 14 h. Obser vable changes in DTG and IR occur at about this time as well. Warren l ine-shape analysis of the 110 reflection indicates that when growth is complete the clay lamellae are on average similar to 50% and 25% of t he size of natural hectorites and montmorillonites, respectively. The N-2 BET surface areas for all materials are also compared. Small angle neutron scattering shows that addition of tetraethyl ammonium (TEA) i ons does not alter the structural integrity over that of the purely in organic form of Li-hectorite, but that use of a cationic polymer does significantly alter the microstructure. The effect of temperature is c ritical, for at room temperature only the layered Mg hydroxide mineral brucite crystallizes unless very long time scales are used. The cryst allizations carried out at room temperature show that clay will form a fter about 3 months, but that the presence of organics (at least TEA) acts to hinder this process greatly. The role of the organic molecules on silicate clay layer formation is compared with the role of organic s in zeolite synthesis.