THE EFFECT OF TREATMENT: MICROWAVE RADIATION AND CO-PRECIPITATION ON CO-AL AND NI-AL HYDROTALCITES CRYSTAL PROPERTIES

Abstract

The effect of the variables in the synthesis of hydrotalcite-like compounds (HDLs) of composition Co, Al-CO3 and Ni, Al-CO3, by microwave radiation and co-precipitation methods, using a 24-1 fractional factorial experimental design were analyzed. The properties of HDLs obtained were compared by using the Fisher factor. This is an innovative aspect in the inorganic solids synthesis. Fisher value allowed determining the influence of the variables such as: metal or molar ratio, pH, precipitation temperature, crystallization time or radiation. The obtained compounds were characterized by X-ray diffraction (XRD). Lattice parameters a and c, percent relative crystallinity (%CR) and crystal size (ε) by application of the Scherrer equation was estimated corrected by Warren. For all cases, hydrotalcite-type compounds were obtained with carbonate anion placed parallel to brucite sheets for the used methods. The microwave radiation leads to the formation of crystalline solids but a less satisfactory crystal size is obtained, when it is compared with those obtained by the coprecipitation method. From the statistical point of view, the synthesis of HDLs Co-Al and Ni-Al by co-precipitation method, the above mentioned parameters affect significantly studied variables for each series. The microwave radiation method was more versatility in the synthesis conditions, and the studied parameters did not significantly affect any of the evaluated characteristics. It was not found by analysis of variance significant differences between the methods used for producing hydrotalcites of Co-Al and Ni-Al, considering each of the structural characteristics studied.