DETERMINATION OF CALCIUM OXIDE AND MAGNESIUM OXIDE IN BAUXITE WITH MICROWAVE DIGESTION BY FLAME ATOMIC ABSORPTION SPECTROMETRY

摘要

A method for determining calcium oxide and magnesium oxide in bauxite with microwave digestion by flame atomic absorption spectrometry(FAAS)is described in this paper. It is well known that it is very difficult to dissolve bauxite by common acid dissolving method. So alkalimelting method almost becomes the only conventional and effective dissolving method for bauxite. However a large amount of dissolved salts brought into by alkali melting results is inconvenient for FAAS measurement,and testing results have shown that the blonk from sodium hydroxide dissolving method is higher than that from microwave acid digestion method. We found that the sample could be digested with a mixture of nitrix acid,hydrochloric acid,perchloric acid and hydrofluoric acid by means of microwave digestion,and the results of digestion were satisfactory by adopting our digestion program. The interference of matrix was studied in detail. Adding La~(3+) as releasing agent and 8-hydroxyquinoline as protecting agent could eliminate the effect of aluminum matrix and other co-existed elements. The results of calcium oxide and magnesium oxide determination in bauxite were in agreement with the certificate values. The precision and accuracy were good.