Chemical and Mineral Analysis of Raw and Acid-Treated Clays from Kano Plains, Kisumu County, Kenya
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Date
2016
Authors
Oswago, Moses Owino
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Clays are aluminosilicate minerals which are widely spread in the earth’s crust. They also
naturally contain iron because of its high relative abundance of about 6.5% .They have
many applications such as, use in manufacture of Portland Cement, ceramic products
such as bricks, roofing tiles and high quality ceramic products as crockery. For the
manufacture of high quality ceramic products, the level of iron in the clays should not
exceed 1%. This study was done on clays of Kano plains, Kisumu County, Kenya to find
out the elemental and mineral composition of the clays with special interest on levels of
iron since it affected clays’ use in making high quality ceramics. Further investigation
was done on whether iron levels, if found to be high, would be lowered by mineral acids
of different concentrations at different temperatures to improve clay quality for
manufacture of high quality ceramics. Powdered raw clay samples dried at 105oC for six
hours in a desiccator, digested or pelleted were analysed by AAS, EDTA titrations and
XRF for elemental composition, and by XRD and IR for mineral composition. The
samples were then treated with mineral acids of different concentrations at room and
boiling temperatures for 12 hours to remove as much iron as possible and the residual
clay washed, dried and analysed for Fe, Al and Si contents. The percentage elemental
composition for the raw clays by AAS were expressed as oxides and ranges of identified
elements found to be 45.47±0.18 to 64.70±0.10 SiO2, 12.54±0.37 to17.95±0.19 Al2O3,
3.74±0.08 to 10.28±0.06Fe2O3, 0.44±0.01 to 1.17±0.01MgO, 0.56±0.02 to
2.34±0.01CaO, 2.07±0.013 to 11±0.08 K2O, 0.98±0.1 to 1.86±0.01 Na2O, 0.92±0.02 to
2.49±0.01 TiO2, 0.02±0.01 to 0.25±0.01 MnO and LOI of 9.77±0.15 to 15.40±0.10. The
minerals in the raw clays, identified by XRD included Montmorillonite
(Ca,Na))0.3Al2(Si,Al)4O10(OH)2.xH2O, Kaolinite Al2Si2O5(OH)4, muscovite,
KAl2(Si3Al)O10(OH,F)2, Albite, Na(AlSi3O8), Orthoclase KAlSi3O8 and Dickite
Al2(Si2O6(OH)4. Acid-treated clays gave different mineral composition and saw
Montmorillonite, Kaolinite, Muscovite and Quarts detected in raw samples disappearing
completely, and Ilmenite (Ni.25Mn.25Zn.25Mg.25)TiO3 and (Ni.5Mn.5)TiO3), the titanium
ore, Microcline KAlSi3O8 and Calcite, CaCO3, emerging after acid-treatment. The
findings showed levels of iron reduced by minerals acids from average 8.25% to less than
1% achieved by boiling clays with 6-8 M sulphuric acid. The levels of aluminium were
lowered sparingly from 15.9% to 13.7% while levels of silicon remained unchanged.
Second finding was that acid treatment alters mineral composition and cause
interconversion of the clay minerals. Further, mineral composition given by chemical
formulae showed that iron in the clays was not in the mineral structure and existed as an
accessory component. The findings led to the conclusion that iron levels in raw clays
were high but were lowered to less than 1% by mineral acids which improved their
quality for making high quality ceramics. Data analysis was done by SPSS software
Description
A thesis submitted in partial fulfillment of the requirements for the award of the degree of Master of Science (chemistry) in the school of pure and applied sciences of Kenyatta University, May, 2016