Kaolin mining and beneficiation: the role of iron

Mossbauer spectra of raw kaolins generally comprise components from iron bound in the structures of kaolinite minerals and iron in ancillary minerals. Of the latter, iron oxides are among the most detrimental to industrial uses. Although a distinction of structural and oxidic iron is generally possible if the oxides are magnetically ordered, Mossbauer spectra of kaolins are generally complicated as a result of slow paramagnetic relaxation of iron bound in the kaolinite structure. A distinction of iron bound in oxides and the kaolinite structure may therefore require the application of selective dissolution procedures in addition to Mossbauer spectroscopy. Thus Mossbauer spectroscopy, where necessary in conjunction with chemical analyses, enables a quantitative assessment of the iron mineralogy of kaolins to be made at all stages of industrial beneficiation. This allows the efficiency of individual stages of processing and the quality of the final product to be monitored, problems during processing to be identified, and individual processing stages to be fine-tuned.