Sustainable Iron Reduction in Natural Clays for Ceramic Industry Applications

The research examines how three raw clay materials consisting of ABS, PS and NUR22 receive mineralogical and chemical treatment for beneficiation before ceramic suitability evaluation. The naturally occurring fine-grained materials hydrous aluminum silicates which are the main constituents of clays show industrial ceramic potential because they exhibit plasticity alongside thermal stability and sintering behavior. The color and surface quality of fired products suffer when iron oxides exist in ceramic materials because they impede high-quality ceramic applications. The research aimed to decrease the Fe₂O₃ concentration for industrial ceramic applications because it improves both whiteness and functional properties of the clays. The initial research involved granulometric separation followed by X-ray fluorescence (XRF) and X-ray diffraction (XRD) analysis to study the chemical makeup and mineral structure in different particle sizes. Different magnetic field strengths at 240 mT, 520 mT, and 930 mT were applied during magnetic separation tests to determine its effectiveness for iron-bearing mineral extraction from clay samples. The method proved unsuccessful because it generated minimal recoverable material together with small Fe₂O₃ content reductions. Magnetic separation proved ineffective as a processing method for these specific clay materials in this research. Oxalic acid bleaching (0.35 M, 100 °C, 700 rpm) for durations up to 120 minutes achieved substantial iron elimination. The separation of particles smaller than 63 µm decreased the Fe₂O₃ content without resulting in any detectable color alteration which proves that additional chemical processing must occur to reach ceramic-grade standards. The application of oxalic acid treatment reduced Fe₂O₃ amounts by 69.5% in ABS bulk and 32.2% in PS bulk and 62.6% in NUR22 bulk samples thus achieving significant reductions. XRF test results showed that iron extraction did not harm the structural components of SiO₂ and Al₂O₃. XRD analysis supported these trends because it demonstrated the complete disappearance of Fe-associated minerals kaolinite, illite and montmorillonite after bleaching while maintaining the structural integrity of quartz and albite. Oxalic acid exhibits specific dissolving properties which make it appropriate for ceramic applications in clay purification. Bleached ABS and NUR22 clays displayed substantial whiteness improvements during 1200°C firing tests. The PS sample failed to undergo sintering because of its high carbonate content. Visual and instrumental colorimetric evaluation confirmed improved ceramic quality after bleaching. The research demonstrates that magnetic separation is not appropriate for these clays yet oxalic acid bleaching emerges as a successful method to extract iron from clays that will be used in advanced ceramic manufacturing.