Influence of synthesis methodology and post treatments on structural and textural variations in MgAlCO3 hydrotalcite

MgAl-CO3 hydrotalcite was synthesized by a new method namely instantaneous precipitation (IP) and compared for structural and textural variations for both fresh and aged samples with the conventionally synthesized coprecipitated (COP) sample. PXRD showed a pattern similar to pure hydrotalcite, irrespective of synthesis methodology used, however, crystallinity and crystallite size was higher for both fresh and aged samples synthesized by IP method than for the corresponding samples synthesized by COP method. Significant variation in the particle morphology was noted, wherein nearly aggregated spherical particles were observed with IP method while elongated hexagonal platelets were observed with COP method. N2 adsorption measurements showed a Type-IV isotherm for aged samples, however, pore size distribution varied with synthesis methodology. Particle size variations showed, a broad distribution for both fresh and aged samples synthesized by IP method while a size distribution for fresh COP sample changed to a bimodal distribution upon aging with a concomitant increase in average particle size. The difference in the properties of these samples with the variation in synthesis methodology and post treatments may be ascribed for variations in local hydrothermal effects, mixing at both microscopic and macroscopic levels and in degree of supersaturation.