INFLUENCE OF BASICITY AND CHROMATE-BROMIDE ANIONIC COMPOSITION IN THE SYNTHESIS OF THE CANCRINITE–SODALITE SYSTEM

Abstract

The influence of the basicity and anionic composition (CrO4 2- and Br-) was studied in the synthesis of chromate-cancrinite and bromosodalite-type zeolites. The synthesis was carried out starting from zeolite X as a source of Si and Al, different concentrations of NaOH (8, 12 and 16 M) and variable weight proportions [NaBr / (NaBr + K2CrO4)] = 0.00, 0, 25, 0.50, 0.75 and 1.00, so that the total  grams was 1,5 g. The synthesis was performed at 80° C and autogenous pressure for 40 h. Obtained crystals were characterized by Fourier transformed infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD) and qualitatively by the color of the products obtained. Results showed that the bromosodalite was obtained at 100 and 75% Br-  for all used base concentrations; at 50% Br-, a mixture of chromate-cancrinite and bromosodalite was determined. When 25 and 0% Br- was used, chromate-cancrinite was only determined. These results infer that obtained products for this particular anion pair (chromate-cancrinite or bromosodalite) depends on the compositions by weight of each anion in the reaction gel and not the employed base concentration.