Process for beneficiating sulfide ores

#This invention relates to a means for treating sulfide ores to separate the mineral value(s) from gangue material by selectively enhancing the magnetic susceptibility of the mineral value(s) so that they may be separated from the gangue.

#As is well-known, mining operations in the past for recovering various metals, e.g., lead, copper, have utilized high grade ore deposits where possible. Many of these deposits have been exhausted and mining of lower grade ores is increasing. The processing of these leaner ores consumes large amounts of time, labor, reagents, power and water with conventional processing.

#In addition to the increased expense associated with the extraction of these metals from low grade ores, proposed processes for separation of certain of the sulfide ores are technically very difficult and involve elaborate and expensive equipment. In many cases the expense incurred by such separation would be greater than the commercial value of the metal, such that the mineral recovery, while theoretically possible, is economically unfeasible.

#Samples of different minerals were ground to a minus 65 mesh and mixed with minus 65 mesh silica sand to produce 3 percent synthetic ores with the exception of molybdenite which was a 5 percent ore. A sample of each ore was pretreated with steam by rapidly heating a reactor containing the sample to 200.degree. C. under a nitrogen purge; thereafter the sample was treated for 15 minutes with 200 kilograms of steam per metric ton of sample. The reactor was then cooled under a nitrogen purge. Following this pretreatment, each sample was treated with 8 kilograms of iron pentacarbonyl per metric ton of sample for 30 minutes at the temperature indicated in Table 1. For comparative purposes, a sample of each of these ores was only pretreated with the steam in the manner indicated above. All of the samples were then subjected to a wet magnetic separation process, and the analyses of the products thus obtained are presented below in Table 1.

#TABLE 1 __________________________________________________________________________ Temp. of Fe(CO).sub.5 Treatment Weight Grade Metal Mineral Pretreatment (.degree.C.) Product (%) (%) Metal Distr. __________________________________________________________________________ Galena Steam 135 Magnetic 3.9 52.7 Pb 86.6 Nonmagnetic 96.1 0.33 Pb 13.4 Calculated Feed 100.0 2.37 Pb 100.0 Galena Steam blank -- Magnetic 0.48 17.2 Pb 3.3 Nonmagnetic 99.52 2.42 Pb 96.7 Calculated Feed 100.0 2.49 Pb 100.0 Molybdenite Steam 135 Magnetic 36.4 0.45 Mo 89.0 Nonmagnetic 63.6 0.032 Mo 11.0 Calculated Feed 100.0 0.18 Mo 100.0 Molybdenite Steam blank -- Magnetic 0.48 2.73 Mo 7.8 Nonmagnetic 99.52 0.156 Mo 92.2 Calculated Feed 100.0 0.168 Mo 100.0 Stibnite Steam 85 Magnetic 1.2 24.1 Sb 44.4 Nonmagnetic 98.8 0.367 Sb 55.6 Calculated Feed 100.0 0.652 Sb 100.0 Stibnite Steam Blank -- Magnetic 0.64 4.50 Sb 3.3 Nonmagnetic 99.36 0.847 Sb 96.7 Calculated Feed 100.0 0.87 Sb 100.0 Smaltite Steam 115 Magnetic 0.72 4.96 Co 11.6 Nonmagnetic 99.28 0.275 Co 88.4 Calculated Feed 100.0 0.309 Co 100.0 Smaltite Steam blank -- Magnetic 0.84 2.40 Co 6.6 Nonmagnetic 99.16 0.29 Co 93.4 Calculated Feed 100.0 0.31 Co 100.0 Chalcopyrite Steam 140 Magnetic 4.4 17.1 Cu 81.4 Nonmagnetic 95.6 0.18 Cu 18.6 Calculated Feed 100.0 0.924 Cu 100.0 Chalcopyrite Steam blank -- Magnetic 2.3 26.3 Cu 69.6 Nonmagnetic 97.7 0.271 Cu 30.4 Calculated Feed 100.0 0.87 Cu 100.0 Orpiment Steam 110 Magnetic 12.6 9.06 As 85.8 Nonmagnetic 87.4 [0.22]* As 14.2 Calculated Feed 100.0 1.33 As 100.0 Orpiment Steam blank -- Magnetic 0.61 10.8 As 5.0 Nonmagnetic 99.39 1.27 As 95.0 Calculated Feed 100.0 1.33 As 100.0 Cinnabar Steam 190 Magnetic 3.0 23.9 Hg 54.8 Nonmagnetic 97.0 0.61 Hg 45.2 Calculated Feed 100.0 1.31 Hg 100.0 Cinnabar Steam blank -- Magnetic 0.72 14.9 Hg 7.0 Nonmagnetic 99.28 1.43 Hg 93.0 Calculated Feed 100.0 1.53 Hg 100.0 Bornite Steam 140 Magnetic 15.1 8.95 Cu 89.9 Nonmagnetic 84.9 0.178 Cu 10.1 Calculated Feed 100.0 1.50 Cu 100.0 Bornite Steam blank -- Magnetic 2.4 49.5 Cu 80.0 Nonmagnetic 97.6 0.304 Cu 20.0 Calculated Feed 100.0 1.49 Cu 100.0 Realgar Steam 95 Magnetic 33.3 3.88 As 89.0 Nonmagnetic 67.7 0.24 As 11.0 Calculated Feed 100.0 1.45 As 100.0 Realgar Steam blank -- Magnetic 0.53 2.25 As 0.8 Nonmagnetic 99.47 1.56 As 99.2 Calculated Feed 100.0 1.56 As 100.0 Pentlandite Steam 105 Magnetic 2.6 7.65 Ni 91.1 Nonmagnetic 97.4 0.02 Ni 8.9 Calculated Feed 100.0 0.22 Ni 100.0 Pentlandite Steam blank -- Magnetic 3.0 7.93 Ni 49.5 Nonmagnetic 97.0 0.25 Ni 50.5 Calculated Feed 100.0 0.48 Ni 100.0 Tetrahedrite Steam 117 Magnetic 2.5 4.65 Cu 70.5 Nonmagnetic 97.5 0.05 Cu 29.5 Calculated Feed 100.0 0.165 Cu 100.0 Tetrahedrite Steam blank -- Magnetic 2.9 5.18 Cu 83.8 Nonmagnetic 97.1 0.03 Cu 16.2 Calculated Feed 100.0 0.179 Cu 100.0 __________________________________________________________________________ *Values in brackets are calculated from other analyses.

#Samples of different synthetic ores were prepared as indicated in Example 1. A sample of each of the ores was pretreated with heat and nitrogen by rapidly heating a reactor containing the sample to 400.degree. C. during a nitrogen purge which flowed at a rate of one reactor volume of gas being introduced into the system every 4.3 minutes and maintaining these conditions for 15 minutes. Then the reactor was cooled under the same type of nitrogen purge. Following this pretreatment each sample was treated with 8 kilograms of iron pentacarbonyl per metric ton of sample for 30 minutes at the temperature indicated for the particular ore in Table 1. For comparative purposes, a sample of each of the ores was merely subjected to the heat and nitrogen pretreatment in the manner indicated above. All of the samples were then subjected to a magnetic separation process. The results are presented in Table 2