STUDIES ON STRUCTURE OF MAGNESIUM ALUMINU M HYDROXIDE POSITIVE SOL

Using the coprecipitation method, magnesium aluminium hydroxide sol ch arged positive was prepared. The structure and composition were studie d with powder XRD, TEM, TGA-DTA, FT-IR and chemical analysis. Results showed that the structure of magnesium aluminium hydroxide was hydrota lcite-like, and belonged to hexagonal system! lattice constants a and c both increased with the increase of the molar ratio of Mg/Al. The sh ape of magnesium aluminium hydroxide particles is hexagonal plate and the mean particle size is 11.7 nm. Three peaks of obtained magnesium a luminium hydroxide caused by weight losses were detected: the first pe ak(around 160 degrees C) might be attributed to physical adsorption wa ter and interlayer water; the second one (around 258 degrees C) was du e to elimination of crystalline water and the third one(around 400 deg rees C) was due to the dehydroxylation of the mixed metal hydroxide la yers. The first and the second weight loss peaks were superimposed and widen when the molar ratio of Mg/Al was above 2.84.