AbstractAbstractThe comparative rates of precipitation of ammonium jarosite and sodium jarosite were determined in Fe(SO4)1.5-H2SO4 media. The apparent activation energy for the precipitation of ammonium jarosite and sodium jarosite is approximately the same; in the presence of 25 g/L of potassium jarosite seed having a surface area of 0.42 m2/g, the value is 87 kJ/mol. Over the temperature range from 70 to 100°C, the rate of ammonium jarosite precipitation is 9 greater (no seed) and 18 greater (25 g/L seed) than the rate of sodium jarosite precipitation. For (NH4)2SO4 or Na2SO4 concentrations ranging from 0.0125 to 0.7 M, the average rate of ammonium jarosite precipitation in the presence of 25 g/L of jarosite seed is 14 higher than that of sodium jarosite precipitation; in the absence of jarosite seed, the average rate of ammonium jarosite precipitation is 11 greater. For ZnSO4 concentrations ranging from 0.0 to 2.0 M, the average rate of ammonium jarosite precipitation in the presence of 25 g/L of potassium jarosite seed is 16 greater than that of sodium jarosite. For solutions containing 1.5 M ZnSO4 and 25 g/L of potassium jarosite seed, the average rate of ammonium jarosite precipitation is 19 greater than that of sodium jarosite precipitation. The rate of precipitation of both ammonium jarosite and sodium jarosite increases as the concentration of potassium jarosite seed increases from 0 to 50 g/L. At 100°C for solutions containing 1.50 M ZnSO4, the average rate of ammonium jarosite precipitation is 20 greater than that of sodium jarosite precipitation. The totality of the present data indicates that the rate of ammonium jarosite precipitation is about 15 greater than that of sodium jarosite precipitation.The comparative rates of precipitation of ammonium jarosite and sodium jarosite were determined in Fe(SO4)1.5-H2SO4 media. The apparent activation energy for the precipitation of ammonium jarosite and sodium jarosite is approximately the same; in the presence of 25 g/L of potassium jarosite seed having a surface area of 0.42 m2/g, the value is 87 kJ/mol. Over the temperature range from 70 to 100°C, the rate of ammonium jarosite precipitation is 9 greater (no seed) and 18 greater (25 g/L seed) than the rate of sodium jarosite precipitation. For (NH4)2SO4 or Na2SO4 concentrations ranging from 0.0125 to 0.7 M, the average rate of ammonium jarosite precipitation in the presence of 25 g/L of jarosite seed is 14 higher than that of sodium jarosite precipitation; in the absence of jarosite seed, the average rate of ammonium jarosite precipitation is 11 greater. For ZnSO4 concentrations ranging from 0.0 to 2.0 M, the average rate of ammonium jarosite precipitation in the presence of 25 g/L of potassium jarosite seed is 16 greater than that of sodium jarosite. For solutions containing 1.5 M ZnSO4 and 25 g/L of potassium jarosite seed, the average rate of ammonium jarosite precipitation is 19 greater than that of sodium jarosite precipitation. The rate of precipitation of both ammonium jarosite and sodium jarosite increases as the concentration of potassium jarosite seed increases from 0 to 50 g/L. At 100°C for solutions containing 1.50 M ZnSO4, the average rate of ammonium jarosite precipitation is 20 greater than that of sodium jarosite precipitation. The totality of the present data indicates that the rate of ammonium jarosite precipitation is about 15 greater than that of sodium jarosite precipitation.On a déterminé les vitesses comparées de la précipitation de jarosite d'ammonium et de jarosite de sodium dans des milieux de Fe(SO4)1.5-H2SO4. L'énergie d'activation apparente pour la précipitation de la jarosite d'ammonium et de la jarosite de sodium est approximativement la même; en présence de 25 g/L de semence de jarosite de potassium ayant une superficie de 0.42 m2/g, la valeur est de 87 kJ/mol. Dans la gamme de température de 70 à 100°C, la vitesse de précipitation de la jarosite d'ammonium est 9 plus élevée (sans semence) et 18 plus élevée (25 g/L de semence) que la vitesse de précipitation de la jarosite de sodium. Pour des concentrations de (NH4)2SO4 ou de Na2SO4 allant de 0.0125 à 0.7 M, la vitesse moyenne de précipitation de la jarosite d'ammonium en présence de 25 g/L de semence de jarosite est 14 plus élevée que celle de la précipitation de la jarosite de sodium; en absence de semence de jarosite, la vitesse moyenne de précipitation de la jarosite d'ammonium est 11 plus élevée. Pour des concentrations de ZnSO4 allant de 0.0 à 2.0 M, la vitesse moyenne de précipitation de la jarosite d'ammonium en présence de 25 g/L de semence de jarosite de potassium est 16 plus élevée que celle de la jarosite de sodium. Pour des solutions contenant 1.5 M de ZnSO4 et 25 g/L de semence de jarosite de potassium, la vitesse moyenne de précipitation de la jarosite d'ammonium est 19 plus élevée que celle de la précipitation de jarosite de sodium. La vitesse de précipitation tant de la jarosite d'ammonium que de la jarosite de sodium augmente à mesure que la concentration de la semence de jarosite de potassium augmente, de 0 à 50 g/L. 100°C pour des solutions contenant 1.50 M ZnSO4, la vitesse moyenne de précipitation de la jarosite d'ammonium est 20 plus élevée que celle de la précipitation de la jarosite de sodium. L'ensemble des données présentes indique que la vitesse de précipitation de la jarosite d'ammonium est d'environ 15 plus élevée que celle de la précipitation de la jarosite de sodium.
The behaviour of the alkaline earth elements (beryllium, magnesium, calcium, strontium, barium and radium) during the precipitation of jarosite-type compounds was investigated over the range of conditions likely to be encountered in hydrometallurgical processes. Negligible amounts (< 0.05 wt%) of beryllium were incorporated in the structure of either potassium jarosite or sodium jarosite; this was a consequence of the small size of the divalent beryllium ion. In contrast, limited magnesium incorporation seemed to occur in the jarosite structure. Up to 0.20 wt% Mg was incorporated in sodium jarosite and up to 0.38 wt% Mg was detected in potassium jarosite; in both species, the amount increased as the magnesium concentration of the synthesis solution increased. Increasing temperatures, ferric ion concentrations and solution pH had only a minor effect on the extent of magnesium incorporation in the jarosite precipitates. In contrast, increasing concentrations of CuSO4 or ZnSO4 significantly reduced the level of Mg incorporation. Regardless of the calcium concentration of the solution, the calcium contents of the well-washed hydronium jarosite, sodium jarosite, potassium jarosite and lead jarosite precipitates were consistently less than 0.05 wt%Ca. The addition of soluble salts of strontiumand bariumto sulphate processing solutions resulted in the extensive precipitation of SrSO4 and BaSO4. However, electron microprobe analyses detected trace amounts of these elements in the potassium jarosite precipitates, suggesting a modest degree of Sr and Ba solid solubility. Picogram quantities of radium are soluble in sulphate media and 60-90% of the dissolved Ra precipitated with the jarosite-type compounds. However, it is not clear whether the radium was incorporated in the structure of the jarosite or whether it was adsorbed on the jarosite particles.
AbstractAbstractKidd Creek raw anode slimes from the bottoms of the refining cells, that consist principally of PbSO4, Ag2Se, AgCuSe, CuSe, Cu3Se2, Cu2O, CuSO4.5H2O, Sn–Cu arsenate and Sb–Bi–As–Pb oxide, were leached in various lixiviants. Reaction with aerated H2SO4 solubilizes Cu2O and CUSO4 5H2O, and also extracts a significant amount of Cu from the copper selenides. Some oxidation of selenium to selenite occurs with the result that CuSeO3 2H2O is detected. Leaching in 4 M NaCl solution dissolves some Cu which reprecipitates as an "oxidate" phase containing traces of Cl and SO4 Lead sulphate also dissolves, but reprecipitates as euhedral crystals which have the approximate composition of Pb2Se2O3 PbCl2. Reaction with 30% acetic acid solubilizes part of the Cu, but does not dissolve PbS04. Leaching in 30% ammonium acetate solution dissolves Cu2O, CuSO4 5H2O and part of the Cu in the copper selenides. Most of the PbSO4 is converted to insoluble PbSeO3; the implication is that significant selenide oxidation also occurs. Reaction with 2 M Na2CO3 solution converts PbSO4 to NaPb2 (CO3)2 (OH), but leaves most of the other slime constituents unaffected. Leaching of the Na2CO3-converted slimes in acetic acid solubilizes most of the Pb; this two-step process was the only effective deleading technique identified. Résumé Les boues anodiques de Kidd Creek, qui sont constituees principalement de PbSO4, de Ag2Se, de AgCuSe, de CuSe, de Cu3Se2, de Cu2O, de CuSO4. 5H2O, d'arseniate de Sn–Cu et d'oxyde de Sb–Bi–As–Pb, ont été extraites avec divers lixiviants. La réaction avec du H2SO4 solubilise le Cu2O et le CuSO4 5H2O et extrait une quantite notable de Cu des seleniures de cuivre. Il y a oxydation d'une certaine partie de sélénium en sélénite, ce qui explique pourquoi on détecte du CuSeO3.2H2O. L'extraction avec une solution de NaCl4 M dissout une certaine quantite de Cu qui reprécipite sous forme d'une phase oxydate contenant des traces de Cl et de SO4 Le sulfate de plomb se dissout aussi, mais reprécipite sous forme de cristaux idiomorphs dont la composition approximative est Pb2Se2O3 . PbCl2. La réaction avec de l'acide acétique à 30% solubilise une partie du Cu, mais ne dissout pas le PbSO4. L'extraction avec une solution d'acétate d'ammonium à 30% dissout le Cu2O, le CuSO4 5H2O et une partie de Cu des séléniurs de cuivre. La plus grande partie du PbSO4 est convertie en PbSeO3 insoluble, ce qui laisse supposer qu'il y a aussi oxidation d'une quantité notable de séléniures. La réaction avec une solution de Na2CO3 2 M convertit le PbS04 en NaPb2 (CO3)2(OH), mais laisse intacts la plupart des autres constituants des boues. L'extraction avec de l'acide acetique des boues traitées avec du Na2CO3 solubilise la plus grande partie du Pb; d'ailleurs, ce procédé à deux étapes constitue la seule technique efficace d'élimination du plomb.
To assess quantitatively the effect of peroxide addition to standard static tests of the neutralization potential (NP) of mine wastes, 10 specimens of carbonate minerals, including five of siderite (FeCO3) and two of rhodochrosite (MnCO3), were analyzed by electron microprobe. The compositions of the siderite span a range from 60 to 86 mol % Fe. Tests of NP for the siderite diluted with 80% (w/w) kaolinite gave values of 647 to 737 kg CaCO3 equivalent per Mg for determinations by the standard Sobek method. However, if it is assumed that the ferrous carbonate component of the mineral does not contribute to NP in field situations because oxidation of Fe(II) to Fe(III) and the subsequent hydrolysis of Fe(III) leads to the release of an equivalent amount of acid, then the calculated NP for the samples ranges from 110 to 390 kg CaCO3 equivalent per Mg. Two different methods involving the addition of peroxide to the test solutions were successful in bringing the measured NP values closer to the theoretical ones. By contrast, the tests with rhodochrosite indicated the Mn(II) to be stable. For long-term environmental planning, especially for wastes from metalliferous sulfide-poor deposits in which gradual dissolution of silicate and aluminosilicate minerals may be involved in attenuating the acidity, consideration in the overall NP budget needs to be given to the ferrous iron content of those minerals. The presence of Fe2+-bearing minerals, especially carbonates, in tested mine-waste materials may lead to overestimated Sobek NP values, thus increasing the risk of poor-quality drainage and the need for costly remediation.
