Beneficiation of iron-bearing kaolinitic clays from Mukurwe-Ini by mineral acids leaching
Wachira, David Maina
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Clay has many applications; however, its utility depends on its level of purity. Given that iron is the fourth most abundant element on the earth’s crust, it is not possible to find pure clay from anywhere free from iron. The presence of iron in clays has a profound effect on their physico-chemical properties. This study aimed at determining the level of iron present in Mukurwe-ini clay followed by reduction if on the higher side so as to obtain high-grade clay using suitable acid treatment. Studies were carried out on representative samples, which were taken from iron bearing clays from Mukurwe-ini, Nyeri County. Characterization of the clay was done in its natural form, and after acid treatment, to determine its mineralogical and chemical composition. Natural clay was refluxed with sulphuric, and hydrochloric, acids of different concentrations at 100º and 200ºC for 2 hours followed by thorough washing in distilled water to remove the acid matrix. Atomic absorption spectroscopy, X-ray fluorescence spectroscopy, and X-ray diffraction analysis techniques were used to determine the physico-chemical characteristics of natural and acid leached clays. The results indicate that SiO2, Al2O3, and Fe2O3 are the major components of Mukurwe-ini clay, MgO, CaO, K2O, TiO2, MnO, and Na2O are present in trace amounts. XRD characterization shows that Mukurwe-ini clays consist primarily of quartz, kaolinite, albite, and microcline minerals. Iron content was drastically reduced from 2.8% to less than 1% in the acid washed samples.XRD mineralogical analysis of acid-activated clays showed reduced levels of the minerals albite, microcline and kaolinite in comparison to raw clays a clear indication of solubility in the acids. Kaolinite was found to be more soluble in sulphuric acid than hydrochloric acid.