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In an investigation of the removal of antimony impurities in the molybdenum-separation process by selective precipitation, distribution diagrams of antimony-containing ions are constructed from the results of thermodynamic calculations. The sulphurisation of antimony under conditions such as different pH and [S]/[Sb] values is described. An analysis of the effectiveness of selective precipitation and operating factors on antimony removal based on the competitive coordination of sulphide (S2-) ions and a method for the deep removal of antimony impurities are discussed. The results indicate that, at pH values of 7-10 and [S]/[Sb] values of at least 2, over 99% of antimony is present as the thioantimonate(III) monoanion (SbS2)-. The experimental data are in agreement with the theoretical predictions. The removal rates of antimony are 97 and over 90% when a 3:1 ratio of [Cu]/[Sb] and [S]/[Sb], respectively, is used., In an investigation of the removal of antimony impurities in the molybdenum-separation process by selective precipitation, distribution diagrams of antimony-containing ions are constructed from the results of thermodynamic calculations. The sulphurisation of antimony under conditions such as different pH and [S]/[Sb] values is described. An analysis of the effectiveness of selective precipitation and operating factors on antimony removal based on the competitive coordination of sulphide (S2-) ions and a method for the deep removal of antimony impurities are discussed. The results indicate that, at pH values of 7-10 and [S]/[Sb] values of at least 2, over 99% of antimony is present as the thioantimonate(III) monoanion (SbS2)-. The experimental data are in agreement with the theoretical predictions. The removal rates of antimony are 97 and over 90% when a 3:1 ratio of [Cu]/[Sb] and [S]/[Sb], respectively, is used.

A study of the leaching kinetics of a wolframite concentrate (67.66% WO3) with sulphuric/phosphoric acid using the single-factor method is presented. The influence of stirring speed (400-600 rpm), particle size (32-38.5; 38.5-43; 43-50; 50-61; and 61-74 micrometres), temperature (343-373 degrees K), concentration of sulphuric acid (0.5-3.0 mol/l) and concentration of phosphoric acid (1.0-3.5 mol/l) on the leaching rate of tungsten, in order to simulate the kinetics of wolframite dissolution, is described. The results indicate that the leaching process follows an Avrami model, the chemical reaction being the controlling step. The values obtained for the model parameter and the apparent activation energy were 0.83 and 67.54 kJ/mol, respectively. A kinetic equation for wolframite leaching with sulphuric/phosphoric acid is proposed. The X-ray diffraction pattern of the wolframite concentrate and scanning electron microscope images of the concentrate and leaching residues are discussed., A study of the leaching kinetics of a wolframite concentrate (67.66% WO3) with sulphuric/phosphoric acid using the single-factor method is presented. The influence of stirring speed (400-600 rpm), particle size (32-38.5; 38.5-43; 43-50; 50-61; and 61-74 micrometres), temperature (343-373 degrees K), concentration of sulphuric acid (0.5-3.0 mol/l) and concentration of phosphoric acid (1.0-3.5 mol/l) on the leaching rate of tungsten, in order to simulate the kinetics of wolframite dissolution, is described. The results indicate that the leaching process follows an Avrami model, the chemical reaction being the controlling step. The values obtained for the model parameter and the apparent activation energy were 0.83 and 67.54 kJ/mol, respectively. A kinetic equation for wolframite leaching with sulphuric/phosphoric acid is proposed. The X-ray diffraction pattern of the wolframite concentrate and scanning electron microscope images of the concentrate and leaching residues are discussed.

Experiments were carried out using activated carbon, coke, anthracite or lignite as reductant, and the effects of reductant dosage on the Fe and P contents and Fe recovery of the direct reduced iron at a fixed dephosphorisation dosage were investigated. The results showed that the fixed carbon and volatile contents of the reductants had a significant effect on the Fe grade and recovery and that the ash content of the reductant significantly affected the P grade. The Fe and wustite contents of the roasted products increased and decreased, respectively, with increasing reductant dosage. The generation of sodium aluminosilicate from the reaction between the dephosphorisation agent and gangue minerals could be reduced by increasing the reductant dosage. For the same reductant dosage, the highest Fe content in the roasted product was obtained using activated carbon, followed by coke, anthracite and lignite. Lignite provided the best results in relation to direct reduction and synchronous dephosphorisation, followed equally by anthracite and coke, with activated carbon producing the worst results., Experiments were carried out using activated carbon, coke, anthracite or lignite as reductant, and the effects of reductant dosage on the Fe and P contents and Fe recovery of the direct reduced iron at a fixed dephosphorisation dosage were investigated. The results showed that the fixed carbon and volatile contents of the reductants had a significant effect on the Fe grade and recovery and that the ash content of the reductant significantly affected the P grade. The Fe and wustite contents of the roasted products increased and decreased, respectively, with increasing reductant dosage. The generation of sodium aluminosilicate from the reaction between the dephosphorisation agent and gangue minerals could be reduced by increasing the reductant dosage. For the same reductant dosage, the highest Fe content in the roasted product was obtained using activated carbon, followed by coke, anthracite and lignite. Lignite provided the best results in relation to direct reduction and synchronous dephosphorisation, followed equally by anthracite and coke, with activated carbon producing the worst results.

High-pyrite tailings with an iron grade of 17.75% and a sulphur content of 5.87% were generated in the flotation process to recover a pyrite ore from Inner Mongolia, part of a complex sulphide ore in which pyrite is associated with low-grade copper and zinc. To treat these tailings, a series of exploratory tests on increasing Fe content while reducing S were carried out adopting processes of magnetic separation, shaking table, magnetic separation-reverse flotation and direct reduction roasting-magnetic separation. The results show that while it is difficult to obtain an ideal separation index with conventional benefication methods, an iron concentrate with a grade of 93.57% Fe, a sulphur content of 0.39% and 82.01% concentrate recovery from low-intensity magnetic separation can be obtained using the method of direct reduction roasting-magnetic separation. This raises the possibility of a new approach for effective improvement of comprehensive utilisation of the resources., High-pyrite tailings with an iron grade of 17.75% and a sulphur content of 5.87% were generated in the flotation process to recover a pyrite ore from Inner Mongolia, part of a complex sulphide ore in which pyrite is associated with low-grade copper and zinc. To treat these tailings, a series of exploratory tests on increasing Fe content while reducing S were carried out adopting processes of magnetic separation, shaking table, magnetic separation-reverse flotation and direct reduction roasting-magnetic separation. The results show that while it is difficult to obtain an ideal separation index with conventional benefication methods, an iron concentrate with a grade of 93.57% Fe, a sulphur content of 0.39% and 82.01% concentrate recovery from low-intensity magnetic separation can be obtained using the method of direct reduction roasting-magnetic separation. This raises the possibility of a new approach for effective improvement of comprehensive utilisation of the resources.

Experiments were conducted on the direct reduction roasting and synchronous dephosphorisation of Ningxiang-type high-phosphorus oolitic haematite ores containing 43.58% Fe and 0.83% P from Hubei in China. Optimum results were obtained by roasting followed by two-stage grinding and magnetic separation. Roasting conditions were a roasting time of 60 minutes, reductant dosage of 17.5%, TS dosage of 50% and NCP dosage of 2.5%. The first magnetic separation stage involved grinding to 100% -0.025 mm and the use of a magnetic field intensity of 87.58 kA/m, and the second stage grinding to 100% -0.025 mm and a magnetic field intensity of 87.58 kA/m. A concentrate with an Fe grade of 91.58%, an Fe recovery of 84.96% and a P grade of 0.049% was obtained., Experiments were conducted on the direct reduction roasting and synchronous dephosphorisation of Ningxiang-type high-phosphorus oolitic haematite ores containing 43.58% Fe and 0.83% P from Hubei in China. Optimum results were obtained by roasting followed by two-stage grinding and magnetic separation. Roasting conditions were a roasting time of 60 minutes, reductant dosage of 17.5%, TS dosage of 50% and NCP dosage of 2.5%. The first magnetic separation stage involved grinding to 100% -0.025 mm and the use of a magnetic field intensity of 87.58 kA/m, and the second stage grinding to 100% -0.025 mm and a magnetic field intensity of 87.58 kA/m. A concentrate with an Fe grade of 91.58%, an Fe recovery of 84.96% and a P grade of 0.049% was obtained.