Study On Clean Metallurgy Technology And Mechanism Of Molybdenum

In the traditional ammonia leaching process of processing molybdenum calcine to produce ammonium molybdate products,there are problems such as ammonia nitrogen pollution and poor impurity separation effect during the leaching process,a novel process of replacing NH₃·H₂O with MgO,leaching molybdenum calcine cleanly and then producing ammonium molybdate by solvent extraction is proposed in this paper.The technological process includes the preparation of magnesia leaching molybdenum calcine,N235 extraction of molybdenum and ammonium molybdate products.The process conditions and mechanisms were studied in this paper.The research content and conclusions of the paper are as follows:The technology and mechanism of clean leaching of molybdenum calcine by MgO were investigated.The results of leaching process showed that the leaching rate of molybdenum is 89.34%under the conditions that the dosage of MgO is 1.2 times the theoretical dosage,the temperature is 90?,the liquid-solid ratio of L/S=10 m L/g,the reaction time is 2 h,stirring speed is 350 r/min.Besides,through SEM and XRD analysis for leaching residue,the formation of insoluble molybdate and magnesium molybdate are easily adsorbed on the surface of impurities,which is the main reason for the low molybdenum leaching rate.And then the relationship between the standard reaction Gibbs free energy change and temperature of MgO leaching molybdenum calcine was drawn,and the thermodynamic diagram was used to conduct thermodynamic analysis of the process of MgO leaching molybdenum calcine.The results showed that the order of molybdate formation to easy is Ca Mo O₄,Fe₂(Mo O₄)₃,Cu Mo O₄,Mg Mo O₄ when the temperature is 300?400 K.It is difficult for insoluble molybdate to react with MgO.Moreover,metal impurity elements are not conducive to molybdenum leaching,and the adverse effect from large to small is Ca,Fe,Cu.The verification experiment shows that the actual situation is consistent with the theory.The effects of temperature and particle size on the leaching reaction rate of molybdenum calcine were investigated,and the kinetics of the leaching process was studied.The results showed that at a temperature of 30?90?,the leaching process conforms to the nuclear shrinkage model.Compared with the particle size,the temperature has a greater effect on the leaching rate.The apparent activation energy of the leaching reaction is 41.22 k J/mol,which conforms to the surface chemical reaction as the reaction rate control step.The technology and mechanism of high-purity ammonium molybdate prepared by high magnesium leaching solution extraction method were investigated.The effect of temperature and other basic technological parameters on extraction and stripping was investigated,and the composition of the ammonium molybdate product was analyzed.The test results show that the optimal extraction condition is to select the organic phase composition:15%N235+10%2-octanol+75%kerosene,the p H of the feed liquid is 3.2,and the extraction time is 6 min.O/A=1.5/1,4-stage countercurrent extraction,the extraction rate of molybdenum can reach 99.89%,and the removal rate of impurities is high.The best conditions for stripping are 13.64%NH₃·H₂O,and the stripping time is 10 min.O/A=4/1,2-stage countercurrent stripping,the stripping rate of molybdenum exceeds 99.42%.The concentration of molybdenum in the stripping solution can reach 120.25 g/L,and ammonium molybdate products that meet the national standard of"GB/T 3460-2017"can be obtained.And infrared spectroscopy was used to characterize the organic phase of the extraction process,and the extraction mechanism was studied.The results showed that the extraction of molybdenum is an anion exchange process.This novel process to treat molybdenum calcine effectively solves the problem of the ammonia leaching process that easily produces ammonia nitrogen wastewater and poor impurity separation effect.Pure ammonium molybdate product can be obtained after N235 extraction treatment of high magnesium molybdenum solution and other procedures.The research results lay a theoretical guidance for the development of new clean smelting technology of molybdenum in this paper.