Iron-removal of Clay Mineral with Oxalic Acid.

Leaching characteristics of iron bearing impurities contained in clay mineral, have been investigated by using oxalic acid (OxA). Two types of samples with different particle size fractions (J-A;-16/+100 mesh and J-B;-100 mesh) were prepared for the experiment. The main components of the clay sample were identified to be sericite, α-quartz, and hydrated iron oxides as main contaminants of iron and iron aluminum silicate hydroxide [K (Fe, Al) 2 (Si, Al) 4O10 (OH) 2] as a second phase of Fe-contamination. With a reaction temperature 100°C, aL/S ratio 5: 1, a spin rate of 500 rpm, a reaction time of 120 min., the optimum leaching percentage was obtained at 0.38 mol/l oxalic acid concentration for J-A and at 0.19 mol/l for J-B. Leaching percentages for J-A and J-B were then 83%and 96%, respectively. The substantial removal of iron reached to 86.2% and 89.6% as Fe2O3, respectively. Instead of high leaching efficiency of iron from the J-B, it is limited to wash out the leached iron species because of a little adsorption of iron species on the surface of clay. The whiteness of the leached clay with oxalic acid decreased with the higher content of iron in the product. The small amount of magnetic materials remained after oxalic acid leaching, could be removed by weakly magnetic separator and identified a mixture of ferrous oxalate by XRD pattern.