Abstract
Kaolin (china clay) is a rock material that is very rich in kaolinite. A kaolin ore from Debre Tabor, Ethiopia containing 59.2 wt% SiO2, 24.9 wt% Al2O3, 2.4 wt% Fe2O3, and 8.22 wt% loss on ignition (LOI) was physically beneficiated, chemically leached, and thermally treated for possible industrial use, especially for ceramic membrane fabrication. The leaching experiments were carried out using oxalic acid solutions as leaching reagents for the iron extraction process. The effect of acid concentration, reaction temperature, and contact time on iron leaching was investigated. It was determined that the rate of iron extraction increased with the oxalic acid concentration, leaching temperature, and contact time. A substantial reduction of iron oxide (2.4 to 0.36 wt%) from the raw kaolin was observed at operating conditions of 2.0 M oxalic acid, the temperature of 120 °C, and contact time of 120 min. A maximum kaolin whiteness index of 81.4% was achieved through this leaching process. Finally, the physically beneficiated, chemically leached, and thermally treated kaolin raw material was used to fabricate a low-cost kaolin-based ceramic membrane. After firing at 1100 °C the ceramic membrane was found to have a mass loss of 11.04 ± 0.05%, water absorption of 8.9 ± 0.4%, linear shrinkage of 14.5 ± 0.05%. It was demonstrated to be chemically stable, having less than 3% mass loss in acid solution, and less than 1% mass loss in alkali solution. The newly developed membranes have thus properties comparable to commercial ceramic membranes.
Highlights
One such abundant and inexpensive geomaterial for ceramic membrane fabrication is kaolin [1]
The pH values of the raw, beneficiated & acid leached, beneficiated, acid leached and calcined, and commercial kaolin were 5.85, 5.05, 5.15, and 5.41, respectively. This showed that the surface of the raw, beneficiated & acid leached, beneficiated, acid leached and calcined, and commercial kaolin body is slightly acidic
Similar results are reported in the literature [45] for raw and beneficiated kaolin
Summary
One such abundant and inexpensive geomaterial for ceramic membrane fabrication is kaolin [1]. Kaolin (china clay) is a rock material that is rich in kaolinite. Kaolinite is a common hydrous aluminosilicate mineral found in sediments, soils, and sedimentary rocks, with chemical compositions of Al2Si2O5(HO). Kaolinite normally appears as stacked pseudo hexagonal platelets, with a common booklet-like shape. Each kaolinite layer is considered as a strong dipole, where the siloxane surface is hydrophobic and dominated by negative charges, while the aluminum surface exhibits positive charges and is hydrophilic. The individual layers of kaolinite are strongly bonded with hydrogen and dipolar interactions. The key properties of kaolin are opacity, electrical and mechanical property, whiteness and brightness, and particle shape and size distribution [2]
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