Preparation of sodium molybdate from molybdenum concentrate by microwave roasting and alkali leaching

The preparation process of sodium molybdate has the disadvantages of high energy consumption,low thermal efficiency,and high raw material requirement of molybdenum trioxide,in order to realize the green and efficient development of molybdenum concentrate resources,this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching.Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate.The effects of roasting temperature,holding time,and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na_(2)MoO_(4)·2H_(2)O) were investigated.Under the optimal process conditions:roasting temperature of 700℃,holding time of 110 min,and power-to-mass ratio of 110 W/g,the molybdenum state of existence was converted from MoS_(2) to Mo O3.The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated,the optimal leaching conditions include a solution concentration of 2.5 mol/L,a liquid-to-solid ratio of 2 mL/g,a leaching temperature of 60℃,and leaching solution termination at pH 8.The optimum conditions result in a leaching rate of sodium molybdate of 96.24%.Meanwhile,the content of sodium molybdate reaches 94.08wt%after leaching and removing impurities.Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution.This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate,which provides a new idea for the highvalue utilization of molybdenum concentrate.

Recovery of Ferric Oxide from Bayer Red Mud by Reduction Roasting-Magnetic Separation Process

A great amount of red mud generated from alumina production by Bayer process was considered as a low-grade iron ore with a grade of 5wt% to 30wt% iron.We adopted the reduction roastingmagnetic separation process to recover ferric oxide from red mud.The red mud samples were processed by reduction roasting,grinding and magnetic separating respectively.The effects of different parameters on the recovery rate of iron were studied in detail.The optimum techqicalparameters were proposed with 700 ℃roasting for 20 min,as 50wt% carbon and 4wt% additive were added.The experimentalresults indicated that the iron recovery and the grade of totaliron were 91% and 60%,respectively.A novelprocess is applicable to recover ferric oxide from the red mud waste fines.

Valency Study of Vanadium in Stone Coal Ash of Jiangxi Province

Vanadium-bearing stone coal is a new vanadium resource; recovery of V2O5 from the coal has been investigated. It has been found that a satisfactory extraction of V2O5 depends on both the oxidation of V and its reaction with sodium salt. V in the coal ash of Yushan mainly exists in two oxidation states; 98% V (Ⅲ) and 2% V(Ⅳ). The distribution of valency of V shows that organic matter determines V valency at low temperatures, at about 470℃ , V(Ⅲ) is completely oxidized to V (Ⅳ); above 500 ℃, the temperature is the most important factor for the oxidation of V At higher temperatures no more V is oxidized to V(Ⅴ); an equilibrium is established after 92% of V is oxidized to V(Ⅴ). The roles of NaCl in the recovery of V2O5 from the coal ash were discussed. The best conditions for roasting are temperature 750-800℃ for 1 h. under the oxidation-chlorination atmosphere. When the ore : NaCl = 100 :10 by weight, ηroast reaches 85.5%. According to the results, a flowsheet for V2O5 extraction from coal ash has been proposed.

Behavior of phase transformation of Baotou mixed rare earth concentrate during oxidation roasting

Based on the new process named "Combination Method" for metallurgy and separation of Baotou mixed rare earth concentrate(BMREC),the aim of this paper is to clearly elucidate the phase change behavior of BMREC without additives during oxidative roasting at 450-800℃.The results indicate that the bastnaesite in BMREC is decomposed at 450-550℃,the weight loss is about 10.3 wt%,and the activation energy(E) is 144 kJ/mol.The bastnaesite in BMREC is decomposed into rare earth fluoride,rare earth oxides(La_(2)O_(3),Ce_(7)O_(12),Pr_(6)O_(11) and Nd_(2)O_(3)),and CO_(2),particularly,with the increase of roasting temperature,bastnaesite in BMREC is more completely decomposed into LaF_(3),which causes a decrease in leaching rate of La during the HCI leaching process.Additionally,the maximum cerium oxidation efficiency reaches about 60 wt% when the roasting temperature is equal to or above 500℃,and the oxidation reaction rate of cerium increases with the increasing roasting temperature.

Separation chemistry and clean technique of cerium(IV): A review

The separation method of changeable valence RE element of cerium （Ce） was reviewed in this paper. Solvent extraction is the most effective and efficient method to separate Ce（IV） from RE（III）, usually accompanied with fluorine （F） and phosphor （P） from bastnaesite and monazite etc. By roast or wet-air oxidation, Ce（III） of bastnaesite and monazite was oxidized into Ce（IV）, and Cyanex923 and [A336][P507] have been investigated to co-extract and recover Ce（IV）, F and P from H2SO4 leaching liquor, leading to favorable conditions for the subsequent separation of Th（IV） and RE（III）. The interaction of Ce（IV） and F and/or P enhances the roasting, leaching and extraction of Ce（IV） due to increasing of the stability of Ce（IV）, and the formation of CeF3 and CePO4 after reductive stripping will benefit the utilization of F and P. For dealing with RE ores of high-content Ce, the clean process of oxidation roasting and Ce（IV）-F separation for Sichuan bastnaesite highlights the advantages of Ce（IV） based clean technique, which firstly demonstrates the comprehensive utilization of Ce（IV）, Th（IV）, F and RE（III） and prevention of environmental pollution from fountainhead. A preliminary flowsheet of two-step oxidation and extraction of Ce（IV） for Bayan Obo mixed ores was further proposed to process the oxidation and extraction of Ce（IV） in presence of both F and P, indicating the possibility of similar effects with clean process of Sichuan bastnaesite. Ce（IV） separation chemistry and clean technique will open up new realms for light RE resources utilization, meeting“Emission Standards of Pollutants from Rare Earths Industry”promulgated by China’s Ministry of Environment Protection （MOP） in 2011.