| Based on the strong oxidation of pyrolusite, the reduction of molybdenite and the stability of manganese sulfate, pyrolusite was used to strengthen the oxidation decomposition process of molybdenite concentrates by the coupling of the oxidation-reduction reaction. Meanwhile the reduction decomposition of pyrolusite and the co-production between ammonium molybdate and manganese sulfate were achieved. A novel process of the co-production technology of molybdenite and pyrolusite was developed.The thermodynamic analysis on the co-leaching reaction between molybdenite and pyrolusite was studied, and an E-pH diagram of MoS2-MnO2-H2O systems was obtained, which showed that electric potential was varied in the range of 0.4v-1.0v, and pH value was less than 3, while Mo and Mn could be leached simultaneously and existed in H2MoO4 (MoO3-H2O),Mn2+ form respectively:MoS2+9MnO2+16H+→H2MoO4+ 9Mn2++ 2HSO4-+6H2OEffects on molybdenite and pyrolusite co-leaching process were investigated, such as the ratio of materials, liquid to solid ratio of slurry (L/S), the amount of sulfuric acid and the reaction time and temperature. It's found that the reaction temperature and the amount of acid had great influences. Under the conditions of nMnO2: nMoS2=10.8, L/S of 4, sulfuric acid concentration of 500g/L, temperature at 95℃and the reaction time of 3h, the leaching rate of molybdenite could reach 85.8%. With the increasing of pyrolusite dosage to nMnO2: nMoS2=18.0, the leaching rate of molybdenite only increased by 1.2%, which indicated that only depended on increasing the amount of acid and pyrolusite a better leaching results could not obtain, and the acid consumption and leaching slag increased significantly, then the recovery of manganese dropped sharply, which results in the removal difficulty of the impurity and an increasing consumption of reagent in the subsequent procedure.The oxidation susceptibility of NaMnO4 and Mn3+/Mn2+ redox couple for decomposition of molybdenite concentrates were studied, results showed that the oxidation of NaMnO4 was higher than that of pyrolusite at the same condition, and the leaching rate of Mo could achieve more than 98%. Although Mn3+/Mn2+ had ability to oxidation-decompose of molybdenite and most of manganese ion could be recycled in strong acid medium, the leaching rate of Mo could only reach about 88%.In order to enhance the molybdenite and pyrolusite co-leaching process, NaMnO4 was chosen to co-dissolve the molybdenite with pyrolusite. Some effects had been investigated through Orthogonal test, results showed that the addition of NaMnO4 enhanced the leaching process of Mo efficiently. Under the control of materials ratio nNaMnO4: nMnO2: nMoS2=0.36:10.8:1.0, reaction temperature of 95℃, reaction time of 240 min, stirring speed of 400 rpm, L/S of 4, sulfuric acid concentration of 400g/L, the leaching rate of Mn and Mo increased to 83.2% and 98.8%, respectively. The Mo and Mn were separated by N235 extraction in the leaching solution, and the qualified products of ammonium molybdate and manganese sulfate were generated by existing metallurgical technology. The ultimate recovery of Mo and Mn was 92.8% and 72.5%, respectively (not including the dosage of NaMnO4 added)For the sake of ensuring the leaching effect of Mo, a large amount of pyrolusite was used in the novel technology of molybdenite and pyrolusite co-leaching process (co-leaching molybdenite by using pyrolusite and sodium permanganate), which reached to 90% by weight, and resulted in the content of Mo and the recovery of Mn dropping in the leaching solution (including potassium permanganate, the recovery of Mn was less than 70%). In addition, in order to enhance the oxidation effect of pyrolusite, a large amount of NaMnO4 were added, the dosage has reached 1/4 times of molybdenite concentrations, which resulted in a soaring cost of raw materials.The novel technology of molybdenite and pyrolusite co-leaching process has approved the strong oxidation of pyrolusite as well as the feasibility of the two mineral co-production technologies in practice. In order to overcome its disadvantages, a roasting process has been used to achieve the coupling of the decomposition reaction of molybdenite and pyrolusite. Thermodynamic analysis on the molybdenite and pyrolusite co-roasting system was studied firstly, results indicated that pyrolusite had the ability to enhance the oxidation decomposition of molybdenite through promoting the further oxidation of MoO2 and absorbing SO2 which generated already. Meanwhile the oxidation of MoS2 could realize directly in a solid-solid reaction: MoS2+9MnO2=2MnSO4+MoO3+7MnO (△rGθ(T)=-0.189T-611.5 kJ·mol-1) MnO2+MoO2=MnO+MoO3 (△rGθ(T)=-0.104T-1.906 kJ-mol-1) MnO2+SO2=MnSO4 (△rGθ(T)=0.1847-246.5 KJ·mol-1)Effects such as roasting temperature, roasting time, material ratio and air flow etc. were investigated to characterize the decomposition rate (ηMo) and the the sulfur-retained ratio (ηs) of molybdenite. Under conditions of subsection calefactive mode (450℃x4h+550℃x4h), material ratio nMnO2: nMoS2= 4:1,ηMo andηs could reach 97.5% and 90.6%, respectively. The results indicated that the addition of pyrolusite in molybdenite roasting process, not only enhanced oxidation of molybdenite decomposition, but also could obtain a better sulfur-retained effect. Meanwhile the reduction decomposition of pyrolusite was achieved, and the resources and energy were used reasonablely in this process. The mechanism of molybdenite and pyrolusite co-roasting process was studied by the TGA analysis and the XRD analysis: MoS2+7/2O2→MoO3+2SO2 MoS2+3O2→MoO2+2SO2 9MnO2+MoS2→MnMoO4+6MnO+2MnSO4 MnO2+SO2→MnSO4 MnO2+MoO2→MnMoO4Effects on recovery of Re in molybdenite and pyrolusite co-roasting process were investigated. It was found that the addition of pyrolusite strengthened the enrichment of Re in the calcine, and the recovery of Re in the molybdenite and pyrolusite co-roasting process was 64.3%, which was 33.4% higher than that of the traditional roasting process with the same conditions.The calcine which contained Mo and Mn was leached with sulfuric acid, then Mo was extracted by N235 from the leaching solution. And 70g/L of sulfuric acid solution was used to washing the as-product on organic phase load before ammonia stripping, the extraction rate of Mo and the stripping rate can reach 99.2% and 99.1%, respectively. The ammonium octamolybdate products could be extracted after evaporation, crystallization and other processes from the stripping solution, the overall recovery rate of Mo could achieve to 93.9% in the whole co-roasting process. A research on the properties of raffinate which contained Mn had been studied, a qualified product manganese sulfate (MnSO4·4H2O) was prepared after removaling iron by methods of carphosiderite and natrojarosi, removing heavy metals by sulfide precipitation and purifying the evaporation and crystallization processes, the overall recovery rate of Mn could reach 83.1% in the whole process. In order to increase the value of the Mn as-products and reduce the removal difficulty of the impurity, a chemical manganese dioxide (CMD) was prepared by alkaline oxidation of Mn raffinate, and the ratio of CMD conversion was more than 80%, the main crystalline form in the product wereα-MnO2 andγ-MnO2.Coupling the processes of the roasting oxidation reduction reaction of molybdenite and the decomposition reaction of pyrolusite, the acid leaching technology and N235 solvent extraction technology were adopt to obtain the efficient leaching and a direct separation of Mo and Mn, which existed in the two mineral co-roasting process. The qualified products of ammonium molybdate and manganese sulfate were gained in this method, and a novel process of the co-roasting technology of molybdenite and pyrolusite was developed. The technical and economic analysis of the new molybdenite and pyrolusite co-leaching process were carried out. Compared to the traditional process of roasting-ammonia leaching, the roasting temperature of the new process was lower 50℃and the roasting time was only about half of the traditional process's, while the overall recovery of Mo increased by 3.9%. In the new process, when one ton of ammonium sulfate was produced, another 3.90 tons of manganese sulfate (MnSO4H2O) yielded at the same time, and the output value was 14,820 Yuan more than the traditional process, which indicated that there has greater profit space. In addition, the sulfur-retained ratio of the new co-roasting process was higher than 90%. Compared to the existing molybdenum and manganese metallurgical process, ammonium molybdate and manganese sulfate were prepared simultaneously on this condition. The procedure of the new process was much shorter than others. The process also reduced the emission of the waste gas SO2, CO2 and CO significantly, which finally made a reasonable use of resources and energy and achieved the purpose of the reduction of emission and consumption.
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