Hyunsik Park

Potential utilization of hazardous mining wastes in the production of lightweight aggregates

ABSTRACT Lightweight aggregates from mixtures of gold tailing, red mud and waste limestone were produced using a high-temperature sintering process. Raw materials were quantitatively analyzed, and hazardous materials were identified by chemical analysis. An oxide system corresponding to the major components of the mining waste was carefully designed based on the CaO–FeOx–Al2O3–SiO2 quaternary system similar to lightweight aggregates. Sintering, softening and melting behaviour of the sample was investigated to optimize the sintering conditions. After heating, specimens were analyzed to clarify its sintering mechanism. Phase change during sintering was observed by X-ray diffraction, and the effect of temperature on the structural unit changes of the specimen was confirmed by Fourier transform-infrared spectroscopy. Microscopic analysis by scanning electron microscope-energy dispersive X-ray analysis was carried out to identify the morphological changes of the sample. Physical properties of the specimen were measured, and the compressive strength was improved with less water absorption.

Gold Solubility in Smelting Slags for the Recycling of Industrial and Mining Wastes

Gold is one of the most valuable and precious metals. But, the extraction efficiency of gold from natural resources is very low and labor-intensive due to very low concentration of gold, i.e., 1–5 ppm, which means that gold extraction processes produce extensive amounts of tailings. The gold content in printed circuit board (PCB) of waste mobile phone is about 100–400 ppm, which is enormously greater than that found in natural ores. Consequently, a requirement for recycling waste PCB and gold mine tailings becomes increasing for maintaining sustainable society. Because the pyrometallurgical processes are issued due to economic reasons, it is needed to understand the thermodynamic behavior of gold in smelting slags under oxidizing and reducing atmosphere at high temperatures. Therefore, in this study, the effect of slag chemistry, oxygen potential and temperature on gold solubility in smelting slags are discussed.

Production of Lightweight Aggregate and Ceramic Balls Using Gold Tailings, Red Mud and Limestone

Lightweight aggregate and ceramic balls were produced from a mixture of gold tailings, red mud and limestone by using a high temperature process. Raw materials were quantitatively analyzed and hazardous materials content was checked by chemical analysis. Oxide systems for the lightweight aggregate and ceramic balls were chosen based on the CaO-FeOt-Al2O3-SiO2 quaternary system. Sintering, softening and melting behavior of the samples were investigated to optimize the sintering conditions. Phase change during sintering was observed by X-ray diffraction. Microscopic analysis by SEM / EDS was carried out to check the morphological changes of the samples.

Production of Ceramic Balls by High Temperature Atomization of Mine Wastes

Gold tailing, red mud and waste limestones are industrial wastes that are mostly landfilled near the process plants. These increase the environmental risks as well as the necessity of waste management. Recycling of materials has been limited due to the fine particle sizes, heavy metals and unique oxide compositions. The authors investigated the potential utilization of these industrial wastes by melting and granulation technique. As quartz, hematite, alumina and lime consist more than 90wt% of mine wastes, CaO-FetO-Al2O3-SiO2 quaternary oxide system was applied to the thermodynamic calculations. Compositions of molten oxides were designed considering the lowest melting temperature and the adequate viscosity for atomization. Samples were melted by high frequency induction furnace then the atomization was carried out by air blowing technique. Viscosities of the melts were measured to quantify the optimum melting and atomization condition. Size distribution of the produced ceramic balls was investigated to estimate potential of the product to be used as abrasive materials.