| Experimental work was carried on ammonia-ammonium sulfate solutions, sparged with SO2/O2 gas mixture (2% SO2 and 98% O2) to leach copper from pure chalcopyrite and chalcopyrite concentrate. Under these conditions, the SO2/O2 system produced higher and faster extractions than O2 by itself. The effect of temperature, particle size and free ammonia concentration was investigated. The fastest and highest recoveries were obtained at 80°C from a chalcopyrite concentrate with a d80 equal to 13 μm, with about 83 gpl free ammonia, an average pH equal to 8.75 and a stirring speed of 500 rpm. The extraction process was controlled by diffusion through a product layer, according to the shrinking core model, with an activation energy of 41 kJ/mole.; In an effort to develop a process capable of treating both organic and inorganic contaminants present in soil and sediments, experimental work was carried out to test the strong oxidation characteristics of the SO2/O 2 system as a remediation technology. Successful treatment of contaminated sediments was achieved by sparging either 0.5 M NaOH solutions or distilled water with the SO2/O2 gas mixture. Metals such as Cu, Pb, Cr and Cd were successfully removed in a relatively short time. The effect of temperature and pH was investigated. Higher temperatures produced faster and higher recoveries, with Pb and Cr more affected by temperature increase than Cu and Cd. The removal of copper, up to 50% percent, was achieved in alkaline solutions through the formation of copper sulfite complexes. The complete removal of metals such as Cu, Pb, Cr and Cd required that part of the treatment be carried out in acidic solutions. A preliminary cost analysis was carried out. |
