Analysis and treatment of clays from Mwea to assess their value as a source of aluminium and ceramic products
Karoki, Bernard Kareru
MetadataShow full item record
Clays are alumino-silicate minerals which contain varying amounts of iron, magnesium, calcium and potassium as major contaminants and, trace amounts of many other inorganic elements This study was undertaken with two main objectives The first was to carry out elemental analysis of clays from Mwea, Kirinyaga District, in Kenya. The second objective was to find out whether it is possible to reduce the amount of iron in these clays after some chemical treatment with mineral acids without affecting the quality of the clay. Samples for analysis were collected from various sites at different depths. The results of the study have shown that the main materials, expressed as oxides, make up nearly100% of the total mass .These are:- silica, Si02(43-51%), alumina, A1203(17-22%,) Iron(III) oxide, Fe203(12l6%,) , Rutile, TiO2(3.5-5.2%,), lime CaO(1.6-2.8%,), magnesium (II) oxide, MgO(1.01.3%0,), Manganese (ii) oxide, MnO(0.20-0.40%,), Potash K20(0.15-0.4%,). Mwea clays are, therefore typical clays that could be used as a source of aluminium and aluminium compounds. Titanium was present as the mineral rutile, Ti02. If further studies could be carried out to confirm the extensiveness and depth of deposits, then this clay could be a reliable source of titanium since is recovered economically from deposits 5 % of titanium oxide. The second important finding of this study was that, the iron in the clay could not be extracted completely with mineral acids even when pre-heated to a temperature of 400°C. The iron was, however, readily extracted with concentrations of 8 M and above of the mineral acids if the clay was pre-heated to a temperature of 500°C. Unfortunately, this pretreatment also makes the aluminium in the clay readily removable and hence, the heat pretreatment actually destroys the clay. Elemental analysis was carried out using Atomic Absorption Spectroscopy, X-ray Fluorescence Spectrophotometry, and EDTA titrations. These techniques were used for comparison purposes and, within experimental error; the results were in very good agreement.