Abstract
A technique for leaching molybdenum from low-grade roasted molybdenite concentrate was proposed by the aqueous solution containing sodium chlorate and sodium carbonate. The effect of molar ratio of sodium chlorate to molybdenum, leaching time, liquid–solid ratio, leaching temperature, sodium carbonate concentration and agitating speed on leaching rate of molybdenum was studied. The experimental results showed that the temperature and concentration of sodium carbonate are key factors to influence the leaching efficiency of molybdenum, and leaching rate achieves above 98% when the molar ratio of sodium chlorate to molybdenum is up 13.5, the temperature is 343.15 K, the agitating speed is 500 rpm, the liquid–solid ratio is 10:1 and the concentration of sodium carbonate is above 10 g/L. The leaching process was mainly controlled by chemical reaction and mass transfer. The leaching time is shorter and the heavy metal content in leaching aqueous solution is lower in basicity than those in acid situations.
Similar content being viewed by others
Explore related subjects
Discover the latest articles, news and stories from top researchers in related subjects.Avoid common mistakes on your manuscript.
1 Introduction
Molybdenum is a refractory metal with high boiling point and high melting point, mainly used in nonferrous metallurgy, oil and gas industry, and is a strategic metal for industrial, pharmaceutical, human and plant essential elements [1].
Molybdenite is the main raw material for the extraction of molybdenum, and the method of molybdenum ore treatment includes fire and wet two categories [2]. Whether it is a fire or a wet method, the common point is that the sulfide ore is to be oxidized to an oxide or its salt, and then the impure intermediate product is further purified to a pure molybdenum compound.
Molybdenite concentrate roasting process is a complex physical and chemical process, the entire oxidation process can be divided into four categories [1, 3]: the reaction that MoS2 oxidation to MoO3; the occurrence of redox reaction among molybdenum sulfide, molybdenum oxide and oxygen; Other metal sulfide oxidation reaction; MoS2 reacts with other metal oxides, sulfates and carbonates to produce molybdates. The roasting method can probably be divided into three types, such as direct oxidizing roasting, soda roasting and lime roasting, et al. The adopted equipment is mainly reverberatory furnace, fluidized bed, multiple hearth furnace and rotary kiln Li et al. [4].
Oxidation roasting is the dominant method for the treatment of molybdenite concentrate by pyrometallurgy methods. However, the release of sulfur dioxide in the process poses a great threat to the environment. Therefore, it is of great significance to study and develop the desulfurization process or wet treatment process. Since the 1970s, research on Mo wet alkali and acidic leaching has attracted more attention [5, 6], the oxygen pressure process [7], nitric acid decomposition [8], sodium hypochlorite [9], electro-oxidation and bio-leaching [10,11,12,13,14] method have been developed one after another.
Oxygen pressure process and nitric acid oxidation consumed cheap oxidants or air. This process not only need high temperature and high pressure but also require high demands for chemical reactor. It’s difficult to control this leaching process, and there are certain security risks in the production those technologies are barely applied by small and medium sized manufacturers, so some domestic manufacturers have already discarded it. The sodium hypochlorite method has moderate reacting conditions, low equipment investment, and is easy to control when compared with the above two former processes. But it has a main disadvantage that large reagent consumption, and it is mainly used in low-grade molybdenum, tailings leaching, and molybdenum reclamation from the traditional process [15,16,17,18,19].
The leaching molybdenum from low-grade molybdenite concentrate has been widely investigated, mainly in relation to acidic oxidative leaching for the direct extraction of molybdenum [20,21,22]. The advantages lie in no SO2 emission but the impurities such as iron, calcium, magnesium, phosphorus and arsenic et al. are also dissolved in the leaching solutions. In fact, the advantage of leaching molybdenum under basicity and common temperature and pressure conditions from low-grade roasted molybdenite concentrate is in evidence, although the process lets out the harmful gas but it can be deleted through adding Na2CO3, NaNO3 or NaCl in roasting process [23,24,25,26,27], but the main existing methods leaching molybdenum with sodium carbonate or ammonium hydroxide aqueous solution need multi-stage leaching process, following more equipment, longer time and lower leaching efficiency [28, 29].
The purpose of the present work tries to leach molybdenum from low-grade roasted molybdenite concentrate using sodium chlorate as the oxidant in basic condition under common temperature and pressure. Several influential parameters, such as the molar ratio of sodium chlorate to molybdenum, leaching time, liquid–solid ratio, leaching temperature, sodium carbonate concentration, and stirring speed, on leaching rate of molybdenum were investigated.
2 Materials and methods
The roasted concentrate used in this study, belonging to porphyry mineralization, was provided by Liaoning, China. The main chemical composition was shown in Table 1. X-ray diffraction of the roasted ore was as shown in Fig. 1. As can be seen from the figure, MoO3, MoO2, MoS2 and other metal oxide and sulfide were detected. Sodium chlorate was obtained directly from Kai tong Chemical Reagent Co., Ltd. (Tianjin, China). Sodium carbonate was provided by Wind Boat Chemical Reagent Technology Co., Ltd. (Tianjin, China). All reagents were of analytical grade and were directly used. The distilled water was used in all experiments.
Leaching experiments were carried out in a 100 mL beaker. The beaker was heated with a water bath. The mixture was stirred by a rotor and the temperature and agitation speed were set by a constant temperature heated intelligent magnetic stirrer (ZNCL-GS, Yuhua Instrument Company Limited, Gongyi, China).
Typically, a certain amount of sodium chlorate and roasted molybdenite concentrate were mixed with the sodium carbonate in a beaker and then heated. When the water bath was heated to the desired temperature, the slurry was stirred. After leaching the residue was filtered and thoroughly washed. The washing water was mixed with the leach liquor, so called leaching mixture.
The molybdenum concentration in leaching mixture was determined with using thiocyanate photometric method by visible spectrophotometer (1800P, Shanghai, China). The other components were analyzed by inductively couple plasma atomic emission spectrometry (ICP-AES 6300 Radial, Themo Scientific, USA).
3 Results and discussion
3.1 Effect of sodium chlorate concentration
In our present study, we studied the effect of the molar ratio of sodium chlorate to molybdenum (mol/mol) ranging from 0 to 18 on the leaching efficiency of the roasted molybdenum.
The effect of sodium chlorate concentration on leaching rate was shown in Fig. 2. When the molar ratio of sodium chlorate to molybdenum increased from 0 to 13.5, the leaching rate of molybdenum increases from 85.75 to 98.70%, but has no significant effect as a further increase above 13.5 in the molar ratio of sodium chlorate to molybdenum. Therefore the optimum the molar ratio of sodium chlorate to molybdenum appears to be 13.5. The results showed that a small quantity of MoO2 and MoS2 oxidized incompletely in roasted ore was oxidized by sodium chlorate to form MoO4− into aqueous phase. The main ionic chemical reaction can be described by the Eqs. (1) and (2):
The oxidizing ability of sodium chlorate is closely related with acidity and basicity in aqueous solution. The standard reduction potential of sodium chlorate is higher under acidic condition than that in alkaline condition, which indicated that the oxidation of sodium chlorate is stronger under acidic condition than that in alkaline condition, so the leaching is more favor under acidic condition than in alkaline condition, but the more impurity was transferred into aqueous phase under acidic condition and the smaller mineral particles were required for nonporous molybdenite concentrate. The leaching roasted molybdenite concentrate in alkaline condition had the advantages on controlling impurity in leaching liquor and adopting the bigger mineral particles for porous roasted ore, although the oxidant dosage is higher than that under acidic condition [5].
3.2 Effect of leaching time
Under the conditions of liquid-to-solid ratio 10:1, temperature 343.15 K, agitation speed 500 r/min, sodium carbonate concentration 20 g/L, and the molar ratio of sodium chlorate to molybdenum is 13.5, we studied the effect of leaching time on molybdenum extraction. It is shown from the Fig. 3 that the leaching rate of molybdenum increases from 87.4 to 98.1% as increasing leaching time from 1 to 2 h and is no significant increase beyond 2 h, so all further experiments were carried out at 2 h. The behavior of molybdenum leaching in these tests was similar to some previous experiments [11, 30, 31]. However, the specific leaching time in this experiment is far shorter than that in acid leaching condition, because the roasted molybdenite concentrate is porous and provides the greater mass transfer area, leading to the higher leaching efficiency.
3.3 Effect of leaching temperature
Leaching temperature also affects the leach of molybdenum. Under the low temperature conditions, it is difficult to achieve high molybdenum leaching rate in a short time, and if choose a high temperature, there is a need for higher energy shortcomings. Therefore, in this study, the medium temperature range from 323.15 to 363.15 K was selected, and its effect on molybdenum leaching rate was shown in Fig. 4 under the conditions of a liquid-to-solid ratio of 10:1, agitation speed of 500 rpm, sodium carbonate concentration of 20 g/L, mixing time of 2 h, molar ratio of sodium chlorate to Molybdenum of 18. It is clear from the figure that the molybdenum leaching rate increases from 44.65 to 98.16% when the temperature increases from 323.15 to 343.15 K, but has no significant effect with a further increase in temperature to 363.15 K. The behavior of molybdenum leaching with the increase in the leaching temperature was similar to some former experiments [32, 33]. Therefore 343.15 K is the optimum temperature and all further experiments were carried out at this temperature.
3.4 Effect of agitating speed
The effect of agitating speed on leaching process was shown in Fig. 5 under the conditions of 323.15 K and 343.15 K. It is can be seen from the figure that the molybdenum leaching rate increases from 85.19 to 98.9% when the agitation speed increases from 300 to 500 rpm, and has no significant effect when agitation speed increase up to 700 rpm at 343.15 K, and increases from 75 to 92% with increasing the agitation speed from 300 to 600 rpm at 323.15 K. So the influence of the agitation speed on molybdenum leaching rate has relationship with the leaching temperature, indicating that the leaching process was mainly controlled by chemical reaction rate and mass transfer rate. This rule is different from some previous studies, where the leaching process was controlled by diffusion process due to molybdenite concentrate was leached directly without roasting process [5, 34]. The optimization value of agitation speed was maintained at 500 rpm at 343.15 K.
3.5 Effect of liquid-to-solid ratio
When leaching temperature is 343.15 K, agitation speed is 500 rpm, sodium carbonate concentration is 20 g/L, mixing time is 2 h, and the molar ratio of sodium chlorate to molybdenum is 13.5, the effect of liquid-to-solid ratio (volume/mass) from 5:1 to 20:1 on molybdenum leaching rate was shown in Fig. 6, it is clear from the figure that the leaching rate of molybdenum gradually increases with increasing liquid-to-solid ratio, which is beneficial to leaching, because increasing liquid-to-solid ratio can enlarge mass transfer area of solid–liquid two phase, and benefit reactive medium diffusion in the two phase, and then making the reaction more enough [35, 36], but increasing the ratio is not helpful to leaching rate when liquid-to-solid ratio up to 10:1, and the leaching rate of molybdenum can get to 98.85% within 2 h, in addition, a higher liquid-to-solid ratio would decreases molybdenum concentration in leaching liquor and raises the cost for next procedure, so liquid-to-solid ratio of 10:1 was selected.
3.6 Effect of sodium carbonate concentration
When temperature was 343.15 K, agitation speed was 500 rpm, a liquid-to-solid ratio was 10:1, mixing time was 2 h, and the molar ratio of sodium chlorate to molybdenum was 18, the effect of sodium carbonate concentration on leaching rate of molybdenum was shown in Fig. 7, it is obvious from the figure that the leaching rate of molybdenum increases from 6 to 98% as increasing sodium carbonate concentration from 0 to 20 g/L, indicating that the oxidation of sodium chlorate to molybdenum was evidently influenced by basicity in solution, which can be seen from the reaction Formula (1) and (2). This rule is the same as the previous study by Pradhan et al. [11].
Under above optimization experimental conditions, that was a liquid-to-solid ratio 10:1, temperature 343.15 K, agitation speed 500 rpm, sodium carbonate concentration 20 g/L, mixing time was 2 h, and the molar ratio of sodium chlorate to molybdenum was 13.5, the molybdenum leaching rate reached to above 98% for two parallel experiments, which is shown in Table 2.
The main chemical composition of the leaching and washing mixture solution is shown in Table 3. We can see from the table that the leaching solution is essentially free of Fe3+, Mg2+ and Zn2+, the reason is that the solution is alkaline by the addition of sodium carbonate and these elements form salt carbonate precipitates, but the content of aluminum and silicon in the mixture solution is higher and removing silicon from leaching solution is necessary before extracting and separating molybdenum.
4 Conclusion
A new method on leaching molybdenum from low-grade roasted molybdenite concentrate was proposed by sodium chlorate and sodium carbonate aqueous solution under the conditions of common temperature and pressure. The experiments proved that sodium chlorate is an effective oxidant to a little MoO2 and MoS2 in roasted molybdenite concentrate in alkaline condition. The alkaline environment is in favor of oxidation of molybdenum and restrains formation of heavy metal molybdate precipitate by adding sodium carbonate to the slurry, leading to a little heavy metal ions content in the leaching liquor, and increases the leaching rate of molybdenum. The effects of leaching temperature and agitating speed on leaching rate are all outstanding, showing that the leaching process was mainly controlled by chemical reaction rate and mass transfer rate, for the porous roasted minerals provide greater mass transfer area and smaller mass transfer resistance for reaction and diffusion in liquid–solid two phases. The optimum operating parameters were established as follows: leaching time is 2 h; sodium carbonate concentration is 20 g/L; liquid-to-solid ratio is 10:1; leaching temperature is 343.15 K; agitation speed is 500 rpm, the molar ratio of NaClO3 to Mo is 13.5. Under these experimental conditions, the leaching rate of molybdenum is above 98% in single stage. The leaching efficiency of molybdenum is superior to the traditional methods with sodium carbonate and ammonium hydrate aqueous solution.
References
Wang M, Wang X, Liu W (2009) A novel technology of molybdenum extraction from low grade Ni–Mo ore. Hydrometallurgy 97:126–130
Lasheen TA, El-Ahmady ME, Hassib HB, Helal AS (2015) Molybdenum metallurgy review: hydrometallurgical routes to recovery of molybdenum from ores and mineral raw materials. Miner Process Extra Metall Rev 36:145–173
Lindsay DG (2013) Endako roasting practice. Can Metall Q 16:32–36
Li DC, Hong T, Tang LX (2008) Molybdenum concentrates fluidized roasting system and process analysis. China Molybd Ind 32:18–21
Chen Y, Feng Q, Shao Y, Zhang G, Ou L, Lu Y (2006) Investigations on the extraction of molybdenum and vanadium from ammonia leaching residue of spent catalyst. Int J Miner Process 79:42–48
Cao ZF, Zhong H, Qiu ZH, Liu GY, Zhang WX (2009) A novel technology for molybdenum extraction from molybdenite concentrate. Hydrometallurgy 99:2–6
Zhao Z, Zhang G, Huo G, Li H (2009) Kinetics of atmospheric leaching molybdenum from metalliferous black shales by air oxidation in alkali solution. Hydrometallurgy 97:233–236
Khoshnevisan A, Yoozbashizadeh H, Mozammel M, Sadrnezhaad SK (2012) Kinetics of pressure oxidative leaching of molybdenite concentrate by nitric acid. Hydrometallurgy 111–112:52–57
Padilla R, Letelier H, Ruiz MC (2013) Kinetics of copper dissolution in the purification of molybdenite concentrates by sulfidation and leaching. Hydrometallurgy 137:78–83
Olson GJ, Clark TR (2008) Bioleaching of molybdenite. Hydrometallurgy 93:10–15
Pradhan D, Patra AK, Kim DJ, Chung HS, Lee SW (2013) A novel sequential process of bioleaching and chemical leaching for dissolving Ni, V, and Mo from spent petroleum refinery catalyst. Hydrometallurgy 131–132:114–119
Abdollahi H, Manafi Z, Shafaei SZ, Noaparast M, Moorkani MN (2013) Removal of copper from molybdenite concentrate by mesophilic and extreme thermophilic microorganisms. Int Min Sci Technol (China) 23:827–834
Abdollahi H, Shafaei SZ, Noaparast M, Manafi Z, Aslan N (2013) Bio-dissolution of Cu, Mo and Re from molybdenite concentrate using mix mesophilic microorganism in shake flask. Trans Nonferrous Met Soc China 21:213–230
Abdollahi H, Shafaei SZ, Noaparast M, Manafi Niemelä SI, Tuovinen OH (2014) Mesophilic and thermophilic bioleaching of copper from a chalcopyrite containing molybdenite concentrate. Int J Miner Process 128:25–32
Antonijevic MM, Pacovic NV (1992) Investigation of molybdenite oxidation by sodium dichromate. Miner Eng 5:223–233
Barr DS, Scheiner BJ, Hendrix JL (1977) Examination of the chlorate factor in electro-oxidation leaching of molybdenum concentrates using flow-through cells. Int J Miner Process 4:83–88
Juneja JM, Sohan S, Bose DK (1996) Investigations on the extraction of molybdenum and rhenium values from low-grade molybdenite concentrate. Hydrometallurgy 4:201–209
Romano P (2001) Comparative study on the selective chalcopyrite bioleaching of a molybdenite concentrate with mesophilic and thermophilic bacteria. FEMS Microbiol Lett 196:71–75
He DS, Feng QM, Zhang LM, Lu YP (2007) An environmentally-friendly technology of vanadium extraction from stone coal. Miner Eng 20:1184–1186
Hu L, Xiao LS, Zhang GQ, Zeng L (2012) Experimental study on leaching molybdenum at high pressure with soda from low-grade molybdenum calcine with high impurities. Min Metall Eng 32:66–70
Wang MY, Wang XW (2010) Extraction of molybdenum and nickel from carbonaceous shale by oxidation roasting, sulphation roasting and water leaching. Hydrometallurgy 102:50–54
Zeng L, Xiao LS, Xiao CL, Gong BF (2013) Study on leaching of molybdenum and nickel from Ni–Mo ore using sodium chlorate. Can Metall Q 52:335–341
Deng GC, Xing NN, Lv GF, Ju ZN, Ye LL (2009) Effect of roasting fluxes for recovery of molybdenum on low grade molybdenum concentrate. J. Liaoning Univ Nat Sci Ed (China) 36:349–352
Aleksandrov PV, Medvedev AS, Milovanov MF, Imideev VA, Kotova SA, Moskovskikh DO (2017) Molybdenum recovery from molybdenite concentrates by low-temperature roasting with sodium chloride. Int J Miner Process 161:13–20
Aleksandrov PV, Medvedev AS, Imideev VA, Moskovskikh DO (2017) Chemistry and mechanism of interaction between molybdenite concentrate and sodium chloride when heated in the presence of oxygen. Metall Mater Trans B 48:878–888
Rajic S, Zlatanovic D (1988) Chemical reactions between molybdenum disulfide and sodium chloride in a stream of oxygen in the temperature range 470–900 K. Thermochim Acta 124:163–169
Zlatanović D, Purenović M, Zec S, Miljković M (1998) The role of NaCl in chlorine roasting of MoS2. Mater Sci Forum 282–283:349–354
Quan XW, Dang SY, Luan QY (1991) Pressure-hot leaching molybdenum from ammonia leaching residue. Inorg Chem Ind (China) 6:19–20
Zhang YQ (2002) Study on the reacting dynamics of leaching low-grade roasted molybdenite with sodium carbonate solution. Inorg Chem Ind (China) 34:8–10
Wang SF, Wei C, Deng ZG, Li CX, Li CB, Wu J, Wang MS, Zhang F (2013) Extraction of molybdenum and nickel from Ni–Mo ore by pressure acid leaching. Trans Nonferrous Met Soc China 23:3083–3088
Xian PF, Zhou SF, Wang MY, Wang XW, Chen BF (2017) Extraction of molybdenum and nickel from roasted Ni–Mo ore by hydrochloric acid leaching, sulphation roasting and water leaching. Trans Nonferrous Met Soc China 27:220–226
Liu Y, Zhang Y, Chen F, Zhang Y (2012) The alkaline leaching of molybdenite flotation tailings associated with galena. Hydrometallurgy 129–130:30–34
Wang M, Wei C, Fan G, Li M, Deng Z, Wang S (2015) Selective extraction of Mo from a Ni–Mo ore using pressure alkaline leaching. Hydrometallurgy 153:6–11
Abdollahi H, Noaparast M, Shafaei SZ, Manafi Z, Erust C, Akcil A (2015) Acidic leaching with chlorate as oxidizing agent to extract Mo and Re from molybdenite flotation concentrate in a copper plant. Sep Sci Technol 50:2396–2404
Liu J, Qiu Z, Yang J, Cao L, Zhang W (2016) Recovery of Mo and Ni from spent acrylonitrile catalysts using an oxidation leaching-chemical precipitation technique. Hydrometallurgy 164:64–70
Liu ZX, Sun L, Hu J, Wu XW, Xiao Y, Xiang YH (2017) Selective extraction of molybdenum from copper concentrate by air oxidation in alkaline solution. Hydrometallurgy 169:9–15
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Conflict of interest
The authors declare that they have no conflict of interest.
Human and animal rights and informed consent
The authors declare that the research has no involving on Human Participants and/or Animals Informed consent.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Wang, P., Pan, Y., Sun, X. et al. Leaching molybdenum from a low-grade roasted molybdenite concentrate. SN Appl. Sci. 1, 311 (2019). https://doi.org/10.1007/s42452-019-0326-6
Received:
Accepted:
Published:
DOI: https://doi.org/10.1007/s42452-019-0326-6