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a b s t r a c tClay minerals are widespread in various types of mineral deposits. When present, they contribute to the high content of certain parameters such as silica, aluminium, and magnesium. This study aimed to find selectivity windows to separate hematite from a clay mineral (kaolinite) to allow reduction of the levels of silica and alumina in iron ore. The collectors used were: etheramine Flotigam EDA (EDA) and the ammonium quaternary salts: dodecyltrimethylammonium bromide (DTAB) and Tomamine Q-14-2 PG (AQ142). The depressant used was corn starch. The separation selectivity was achieved using DTAB in the pH range between 4 and 10. Using the collectors EDA and AQ142, the selectivity was obtained only in the presence of starch, at pH 10. Laboratory scale tests showed that as far as the particles size is concerned, better selectivity was achieved with finer particles. Circuit configurations including cleaner and scavenger stages, and pilot scale tests, will be required prior to a possible industrial implementation of the separation.

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-This paper presents the experimental results for the leaching of printed circuit boards (PCB) from obsolete computers for extracting and recovering tin and copper by means of leaching followed by precipitation. Printed circuit boards were dismantled, cut into small pieces, and fed into a cylinder mill. The powder obtained was leached by using the aqueous solutions 2.18N H 2 SO 4 , 2.18N H 2 SO 4 + 3.0N HCl, 3.0N HCl, and 3.0N HCl + 1.0N HNO 3 . The lowest values for the percentage of metal extraction were obtained with 2.18N H 2 SO 4 (2.7% for Sn and lower than 0.01% for Cu), while the 3.0N HCl + 1.0N HNO 3 leach system exhibited an extraction of 98% for Sn and 93% for Cu. Precipitates were obtained at different pH values by neutralizing the leach liquors using NaOH. The 3.0N HCl + 1.0N HNO 3 leach system presented the highest recovery values from the powder feed (84.1% for Sn and 31.9% for Cu), as well as from the leach liquor (85.8% for Sn and 34.3% for Cu).

This experimental work presents the optimization results of obtaining a high indium concentration solution and minimum iron poisoning by solvent extraction with D2EHPA solubilized in isoparaffin and exxsol. The variables studied in the extraction step were D2EHPA concentration, acidity of the aqueous phase and time of contact between phases. Different hydrochloric and sulfuric acid concentrations were studied for the stripping step. The optimum experimental conditions resulted in a solution with 99% indium extraction and less than 4% iron. The construction of a McCabe-Thiele diagram indicated two theoretical countercurrent stages for indium extraction and at least six stages for indium stripping. Finally, the influence of associated metals found in typical sulfate leach liquors from zinc plants was studied. Under the experimental conditions for maximum indium extraction, 96% indium extraction was obtained, iron extraction was about 4% and no Ga, Cu and Zn were co-extracted

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The high grade of copper in the Igarapé Bahia (Brazil) gold-copper ore prevents the direct application of the classic cyanidation process. Copper oxides and sulfides react with cyanides in solution, causing a high consumption of leach reagent and thereby raising processing costs and decreasing recovery of gold. Studies have showm that a feasible route for this ore would be a pretreatment for copper minerals removal prior to the cyanidation stage. The goal of this experimental work was to study the experimental conditions required for copper removal from Igarapé Bahia gold-copper ore by sulfuric acid leaching by applying a statistical approach to the experimental design. By using the Plackett Burman method, it was possible to select the variables that had the largest influence on the percentage of copper extracted at the sulfuric acid leaching stage. These were temperature of leach solution, stirring speed, concentration of sulfuric acid in the leach solution and particle size of the ore. The influence of the individual effects of these variables and their interactions on the experimental response were analyzed by applying the replicated full factorial design method. Finally, the selected variables were optimized by the ascending path statistical method, which determined the best experimental conditions for leaching to achieve the highest percentage of copper extracted. Using the optimized conditions, the best leaching results showed a copper extraction of 75.5%