Phase transformation of goethite into magnetite by reducing with carbohydrates

Phase transformations of synthetic goethite and goethite ore from Kryvyi Rih region by reducing with different carbohydrates (starch, glucose, fructose, sucrose and ascorbic acid) were investigated by thermomagnetic analysis. Thermomagnetic analysis was carried-out using laboratory device that allows automatic registration of sample magnetization with the temperature (the rate of sample heating/cooling was 65-80°/min). The reduction reaction of synthetic goethite for all carbohydrates starts at the temperature of ~250°C while reduction of goethite ore for all carbohydrates starts at the temperature of ~450°C. We could relate this increasing of reduction start temperature with shielding effect of admixtures in the ore. Reduction of synthetic goethite at this temperature range leads to formation of magnetic phase with saturation magnetisation ~70 A*m2/kg. At the same time, reduction of goethite ore leads to formation of magnetic phase with saturation magnetisation ~25 A*m2/kg. One could attribute this decreased value of saturation magnetisation to the presence of other minerals (quartz, etc.) in the ore. It was shown by X-Ray Diffraction method that goethite completely transforms into magnetite under heating with different carbohydrates up to 650°C. All carbohydrates reduce goethite to magnetite