Determination of chemicals bound to mineral surfaces in flotation processes

Combustion and extraction methods were developed for quantitative analysis of collectors adsorbed on minerals in phosphate ore processing. The combustion analysis is based on the oxidation of carbon in a high purity oxygen stream followed by an IR detection of the evolved carbon dioxide. A commercial combustion analyser, LECO RC-412, was modified to meet the high demands of sensitivity and selectivity for analysing small amounts of collectors in the presence of carbon-bearing minerals. In the extraction method, the chemicals adsorbed on mineral surfaces were extracted into chloroform, potassium bromide was added and the chloroform evaporated. Finally, the dry potassium bromide containing the organic chemicals was pressed in a standard manner to produce a KBr disc for IR analysis. As little as ca. 20 g collector per one ton of ore could be determined, thus demonstrating the suitability of the developed methods for flotation practise. By combining the results of the collector analysis and mineralogical analysis with the process data, the distribution of flotation chemicals on individual minerals can be calculated by solving a set of linear equations. This is demonstrated in a case where apatite is floated from low-grade calcareous phosphate ore.