With the rapid development of steel industry, China's manganese alloy of iron and manganese metal production of rapid growth, consumption of manganese ore has increased year by year. In recent years, although many provinces in China have discovered manganese deposits in succession, they are unevenly distributed, rich in rich ore, thin in mineral deposits, fine in size of mineral inlays, difficult to collect, difficult to select, and there is a serious shortage of rich ore. The average grade is only 22%, so each year Millions of tons of manganese ore must be imported for use with domestic manganese-poor ore. To this end, in view of the characteristics of China's manganese ore resources and the status quo of the manganese industry, the development of effective technologies and processes for the rational use of manganese-poor ore, and energy saving, has become a hot issue of academic and business circles. So far, many scholars at home and abroad have conducted more research on the utilization of lean manganese ore, and some of the results have been successfully applied to industrial production. For the wet utilization of rhodochrosite, the most important is the leaching and impurity removal technology and process. This paper introduces the method and research progress of the sulphur removal and removal of rhodochrosite, and reviews the rational development and utilization of manganese ore resources in China.

I. Research progress at home and abroad on the leaching process of rhodochrosite

It can be seen from the current mechanism research that the leaching rate of the manganese ore is not only the macroscopic factors such as reaction temperature, reaction time, leaching agent concentration, ore particle size, but also the composition of the rhombohedral mineral phase and even the impurity elements. Micro factors. In order to improve the leaching rate of rhodochrosite, many scholars at home and abroad have carried out research on the leaching process. According to the characteristics of the process, the leaching of rhodochrosite can be mainly divided into: pre-baking leaching method, direct acid leaching method, reduction leaching method, SO 2 leaching method, electrochemical leaching method and bacterial leaching method.

(1) Pre-baking and leaching

Pre-baking minerals and then leaching is one of the common methods for processing low-grade ores. After calcination at high temperature, the material not only enhances the activation, but also removes some volatile impurities and causes phase change of the active ingredient. When the leaching agent is added, thermal stress and defects are generated in the crystal lattice due to the rapid heat quenching of the calcined material itself, and cracks are generated in the particles, making the leaching reaction more feasible. A large number of studies have shown that the leaching reaction performance of ore after roasting decomposition can be significantly improved.

Yan Xiaozhu et al reported that the ammonium salt was calcined at a certain temperature, the manganese in the mineral was converted into a soluble manganese salt, the calcined material was leached in hot water, and the ammonia gas and CO 2 gas generated during the roasting process were passed through the leachate. In the middle, manganese is precipitated to obtain manganese concentrate, and the filtrate is evaporated, concentrated, and crystallized and reused, and the recovery rate of manganese is over 90%. The method is characterized in that the recycling of raw materials in the production process is realized, and no waste water or exhaust gas is discharged; the hot water leaching method greatly reduces the leaching of impurities such as aluminum , iron, calcium and silicon, and the subsequent removal. Miscellaneous processes are also advantageous. Of course, this method needs to deal with the corrosion problem of the gas escaping after the decomposition of NH 4 Cl. Petkov I calcined manganese ore at a high temperature of 500 °C for 45 min, and then reacted with the calcined material with a SO 2 solution. The leaching rate of manganese was above 90% at a liquid-solid ratio of 8:1 and a temperature of 20 °C. The SO 2 used can be obtained by roasting pyrite or by using SO 2 -containing waste gas from a sulfuric acid plant or a smelting plant, which can reduce the cost of leaching and effectively utilize the sulfur-containing waste gas.

In short, through the pre-baking treatment, the quality of manganese ore can be effectively improved, the grade of manganese ore can be improved, and the leaching rate of manganese can be significantly improved. However, the method has large energy consumption, high cost, and a high temperature working environment, and some environmentally harmful gases such as SO 2 are generated during the roasting process. Therefore, if it can effectively solve the problems of energy consumption, pollution, etc., the pre-baking and leaching method will still be one of the main methods of use in the manganese industry.

(2) Direct acid leaching

The direct use of sulfuric acid leaching of rhodochrosite is a traditional hydrometallurgical technology and is also widely used in domestic and foreign manganese enterprises. Aiming at the direct acid leaching method of rhodochrosite from different producing areas, domestic scholars have carried out a lot of research work, and deeply discussed the factors such as reaction temperature, liquid-solid ratio of reaction system, stirring rate, material particle size and concentration of leaching agent. The optimization of process parameters can make the leaching rate of manganese reach over 80%, even up to 98%.

Yuan Mingliang used catalysts to improve the surface activity of mineral particles, increase the adsorption of ore particles on hydrogen ions, increase the rate of leaching reaction, and at the same time allow the reaction to proceed at room temperature, at a leaching temperature of 5 to 30 ° C, and reaction time. At 60 min, the manganese leaching rate is 95%, which saves a lot of energy. In 2001, Dai Enbin proposed an in-situ leaching method integrating geology, mining, mineral processing and metallurgy. That is, the leachate is directly injected into the ore body to obtain a leachate, and the leaching rate can reach 96%. Zhou Luozhong also published a similar patent in 2004. The process of the process is simpler than other methods. The ore does not require pre-treatment such as grinding, which reduces the investment of the equipment. The process of immersion does not require heating and stirring, and the leaching effect is very good. Well, companies close to the mine can significantly reduce production costs. However, the entire production process of this method takes a long time, which is not cost-effective for small-scale enterprises. In addition, some scholars have also studied the mixed mineral acid leaching method with a variety of manganese phases. The results show that under certain conditions, the complex leaching of two different components of manganese ore can accelerate the leaching rate and increase the manganese. Recovery rate; total manganese recovery rate is higher than single manganese ore leaching, and the time is shorter. However, the mechanism research on the improvement of total manganese leaching rate of mixed ore has not been reported. It is estimated that it is caused by the different composition of ore, that is, when two different ores are in contact, it leads to the generation of new leaching reaction sites. It promotes the progress of the leaching reaction, thereby increasing the leaching rate of a single ore.

As the simplest processing technology of rhodochrosite, direct acid leaching has a simple production process and mature technology, so it is still the main means of wet smelting manganese in the future. However, there are still some problems worthy of further discussion in the actual production process. For example, the leaching of impurity elements during the leaching process is difficult to control, which makes the impurity content in the leaching solution high, which causes great pressure on the subsequent impurity removal stage. The amount of sulfuric acid used in leaching is very large, and the corrosion resistance of the equipment is relatively high.

(3) Reduction leaching method

The reduction leaching refers to the use of a reducing agent to reduce the high-priced manganese which is not easily leached in the ore to a low-cost state which is easy to be leached, thereby achieving the purpose of extracting manganese. Some rhodochrosite ore contains more high-valence manganese components such as pyrolusite and manganese silicate, and it is difficult to obtain an ideal leaching effect. In this case, a reduction leaching method is required. Commonly used reducing agents are aniline, glucose, cellulose, sodium hydrogen sulfite, and the like.

Yao Jun et al added some organic and inorganic substances during the leaching process to increase the leaching rate of manganese. Studies have shown that acid dosage, leaching time and additives are the main factors affecting the leaching rate; the effect of organic additives on leaching The impact is even more pronounced. Li Debin announced a patent for the extraction of manganese containing more than 8% manganese ore by rice husk and sulfuric acid: the ore is mixed with the rice husk and placed in the reaction tank. Dilute sulfuric acid is added and the exothermic reaction is carried out at room temperature to obtain manganese sulfate. Solution. The method of reducing the labor intensity, with coal fuel savings, reduce production costs, elimination of noise, dust and other pollution.

The reduction leaching method has obvious effect on the rhodochrosite with high valence of high manganese. In fact, when the content of pyrolusite in the rhombohedral ore is not high, an oxidizing agent is added in the leaching process to oxidize the ferrous ions in the ore, and the pyrolusite is used as the oxidant. Therefore, the analysis of rhodochrosite, pyrolusite composition, analysis of redox mechanism in the leaching process, exploration of rhodochrosite, soft manganese ore mixed leaching process and conditions, is of great significance for the utilization of low-grade rhodochrosite and pyrolusite.

(4) Other methods

Meng Yunsheng conducted a bacterial leaching test on the low-grade rhodochrosite in Jianshui, Yunnan Province. The manganese ore was put into the leaching agent of the bacteriological pyrite leaching agent, and the leaching rate of manganese could reach more than 60%. Compared with the traditional leaching method, as long as there are relatively few energy sources and reagents, the cost is very low, the economic benefits are obvious, and the environmental pollution is small; but the speed is very slow, and there are special requirements for the production conditions. Report on industrial production. When Arsen'ev VA or the like performs acid leaching of rhodochrosite, a high-energy pulse is simultaneously input into the tank, and the ore in the tank is activated by collision, thereby improving the mandability of the manganese ore. Experiments show that when the ore particle size is reduced to -0.16 mm, the leaching rate of manganese is close to 100%. The Arsen'ev VA team also studied the possibility of increasing the leaching rate by reducing the surface tension of the leaching agent. The inorganic sulphate was chosen to reduce the surface tension of the leaching agent, thereby increasing the affinity of the ore and the leaching agent, so that the leaching agent It is more likely to react with ore and increase the leaching rate.

Second, rhodochrosite ore removal process

(1) Purification of aluminum and iron

In the manganese ore, iron is mainly in the form of iron carbonate, and there are also FeSiO 3 , magnetite, pyrite, etc.; and the main form of aluminum is kaolin . During the leaching of manganese, a part of iron and aluminum are dissolved into the solution. At present, the main methods for removing iron in industrial production are neutralization method, goethite method, jarosite method, magnetite method, adsorption iron removal method, etc., and aluminum removal is mainly based on neutralization method. Because the goethite method, the jarosite method, the magnetite method, etc. need to be carried out at a higher temperature, at the same time, the solution still contains a certain amount of iron after de-ironing, which is not suitable for the purification of low-grade manganese ore leachate. In addition to iron, the oxidation neutralization method is the most economically viable method for removing iron from manganese ore leachate.

Since Fe 3+ is more likely to precipitate in the form of hydroxide than Fe 2+ , in the actual process, Fe 2+ is usually oxidized to Fe 3+ for subsequent processes. Pyrolusite or air is generally used as an oxidant to oxidize Fe 2+ to Fe 3+ and prevent the introduction of other impurities. In the actual production process, the manganese content in the manganese sulfate leach solution is about 30-40 g/L, and at pH 5, the divalent manganese in the solution does not hydrolyze. For aluminum, since the hydrolyzate is a neutral compound, Al(OH) 3 is converted to metaaluminate at 25 ° C and pH greater than 5.0. Therefore, the pH should be controlled to 4 to 5 to remove high-priced iron and aluminum in the solution without causing loss of manganese. However, the problem of removing aluminum and iron by the hydrolysis precipitation method is also prominent, mainly because the hydroxide precipitate is gelatinous, it is not easy to settle and the filtration performance is poor, which brings inconvenience to the separation.

In hydrometallurgy, the effective purification of iron and aluminum has always been the focus of research. In addition to the iron removal process mentioned above, in recent years, with the continuous improvement of production processes, some novel purification methods have been continuously proposed. For example, extraction methods, ion exchange methods, microbial methods, etc., some of which have been applied in the smelting of some metals, but have not been reported in the smelting industry for technical reasons.

(2) Purification of heavy metals

During the extraction of manganese, heavy metal ions zinc ore, copper, lead and the like is usually accompanied by the dissolution of the ore into the leaching solution, and their presence will seriously affect the deposition of manganese, resulting in decrease of the current efficiency . At present, the most commonly used purification method is a sulfide precipitation method, and the vulcanizing agent generally has an organic vulcanizing agent (such as SDD, etc.) and an inorganic vulcanizing agent (such as BaS, Na 2 S, (NH 4 ) 2 S, etc.). According to reports in the literature, natural manganese oxides and hydroxides have good surface adsorption activity. In different media, they can adsorb Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd to different extents . heavy metal ions 2+. Zhao Zhong

In 2004, Wei announced a patent for deep purification of manganese sulfate solution, adding oxidant or electrification oxidation in manganese sulfate solution to oxidize a small amount of Mn 2+ ions to form manganese dioxide, and to make impurity ions and manganese dioxide in solution Coprecipitation is removed. The oxidizing agent used is one or a combination of hydrogen peroxide, persulfuric acid, nitric acid, oxygen, etc., and the removal rate of heavy metal impurities is generally more than 90% within the scope of the patent. In this way, in addition to heavy metals, no other impurity elements are introduced during the operation, and the operation is simple, the reagent consumption is small, the cost is low, and the environment is not polluted. For manganese leaching solution, this is an ideal green impurity removal process, but due to the oxidation of Mn 2+ to MnO 2 during the impurity removal process, it has an effect on the manganese content in the leaching solution. Strictly control the reaction conditions to avoid loss. The patents published by Zou Xing et al. in 2006 indicate that most of the heavy metals in the solution can be removed by metal manganese replacement without introducing other impurity elements. However, the conditions of the replacement method are harsh, and the oxygen, hydroxide and hydrogen ions in the solution will have an influence on the replacement process. In the replacement process, the air should be prevented from contacting the solution as much as possible to avoid the waste of manganese metal; and with the purification process As a result, the difference in concentration between the impurity ions and the manganese ions will become larger and larger, which will make the potential difference between the two smaller, which is not conducive to the displacement reaction. Therefore, the use of displacement methods to remove heavy metal impurities requires more research in order to achieve the desired results.

(3) Purification of other impurities

1. Removal of phosphorus

Among the identified deposits, the average P/Mn of China's manganese ore is as high as 0.01, which belongs to high-phosphorus manganese ore, while the manganese ore for metallurgy generally requires P/Mn<0.003. Therefore, such ore must pass through manganese-rich and phosphorus-reducing industries. value. Since a large part of the phosphorus in the ore is distributed in non-magnetic mud and siliceous materials, and manganese carbonate is a weak magnetic mineral, it is a very effective method to reduce phosphorus by strong magnetic separation by utilizing the difference in their magnetic properties. At present, the strong magnetic phosphorus reduction process is generally combined with other methods to reduce costs or achieve better results. When Zhang Yimin and other high-phosphorus manganese ore with P/Mn ratio of 0.046 were treated, the ore was delimed, strongly magnetically selected, and then reversed by flotation, and a manganese concentrate with a P/Mn of 0.002 and a manganese grade of 78.87% was obtained. Cui Enjing et al. reported a strong magnetic separation-calcination-acid leaching method to convert a poor ore with a phosphorus content of 1.09% and a manganese grade of 10.88% into a qualified manganese concentrate containing less than 0.2% phosphorus and more than 30% manganese. The high-phosphorus manganese ore in Andhra Pradesh and southern Orissa has also adopted the method of roasting dephosphorization to effectively improve the grade of ore. Zhang Yongwei studied the high-phosphorus manganese ore in the South Qinling Manganese Mine by microwave radiation-strong magnetic separation method. For the 0.120 mm grain-level manganese ore, the microwave radiation-strong magnetic separation combined beneficiation process and simple strong magnetic separation process were compared. The results show that the former has better manganese-rich effect and has a certain phosphorus-reducing effect. The phosphorus reduction rate of raw ore is 10.71%~48.00%. In the former Soviet Union, the method of preparing black manganese ore from low-phosphorus manganese concentrate using phosphorus-bearing manganese carbonate ore was developed from 1960 to 1964, and the possibility of using this method to treat mixed ore and oxidized ore was studied. The main principle is to treat manganese carbonate at 800~. It is calcined at a high temperature of 1000 ° C to convert it into a manganese ore (Mn 3 O 4 ) which is stable and hardly soluble in dilute acid. During the roasting process, the crystal lattice of the manganese ore is rearranged, and the insoluble phosphorus is converted into easily soluble phosphorus, which can be decomposed by the dilute acid and enters the liquid phase. In the acid leaching study of high-phosphorus manganese ore, we found that by controlling the leaching process conditions, more than 99% of the dephosphorization rate can be obtained, and at the same time, a high manganese leaching rate can be achieved.

In recent years, people have been paying more and more attention to the application of biotechnology in the metallurgical industry. Guan Xiaohui et al. proposed a microbial manganese-rich dephosphorization technology for high-phosphorus-rich manganese ore, which proposed a new way for the development and utilization of high-phosphorus-rich manganese carbonate ore resources in China. Microbial dephosphorization has the advantages of no pollution, low energy consumption and other methods, but it requires high professional technology and special experimental conditions. It is believed that this will be a very effective way with the development of technology.

2. Removal of magnesium and calcium

When manganese ore is leached, the magnesium and calcium in the ore can basically enter the leachate, so that the content in the leachate is very high, even reaching saturation, and it is easy to form crystals to block the pipeline and become a production process. A big problem. Benrath V A. et al. studied the effect of MgSO 4 and MnSO 4 on the solubility of each other in aqueous media. The results show that as the solubility of one substance increases, the solubility of the other substance decreases. Helen E. Farrah et al. also investigated the solubility of CaSO 4 in MnSO 4 solution. It was also found that when the temperature is lower than 80 °C, the solubility of CaSO 4 increases with the increase of sulfuric acid concentration in the solution, but the concentration of manganese increases. Will cause its solubility to decrease. Therefore, in theory, the amount of MgSO 4 and CaSO 4 dissolved in the solution can be inhibited by increasing the concentration of MnSO 4 in the solution to achieve the purpose of removing magnesium and calcium. However, for leachate containing a large amount of magnesium and calcium, the impurity removal process needs to be repeated many times, resulting in a decrease in the recovery rate of manganese and an increase in production cost; and in this complicated system, MnSO 4 and MgSO 4 will The formation of a eutectic or mixed crystal affects the solubility of the two crystals, thereby affecting the magnesium removal effect. Yuan Mingliang et al. analyzed the phase diagram of MnSO 4 - MgSO 4 -H 2 O in Benrath and proposed a medium temperature manganese sulfate crystallization method. By controlling the evaporation of water to control the residual manganese sulfate in the solution, the loss rate of manganese is only about 5 %about. In addition, since magnesium and calcium ions easily form insoluble precipitates with some anions (such as F - , C 2 O 4 2 - etc.), their solubility is smaller than that of magnesium sulfate and calcium sulfate, and therefore, it can be used in the leachate. A salt containing such an anion is added to cause magnesium or calcium ions in the solution to form CaF 2 , MgF 2 , or precipitate CaC 2 O 4 and MgC 2 O 4 to make them more easily separated from the solution. Some people also use special magnesium reagents to separate magnesium from manganese after aging for 24 hours at room temperature. However, magnesium reagents are more expensive and are not conducive to promotion.

III. Conclusions and prospects

After more than a century of development, the wet method of manganese technology has been developed and researched and practiced by numerous researchers and enterprises. However, there are still many problems in the actual production process, such as manganese recovery. The rate is not high, the impurities cannot be completely removed, and the electrolysis efficiency is low, which may have a serious impact on the normal production of the enterprise.

Throughout the domestic and international research on the leaching of rhodochrosite, it can be seen that environmental protection, energy conservation, and process simplification are the main research and development directions of the smelting manganese industry. For example, the traditional process of high-temperature pre-baking and leaching will gradually fade out of actual production due to high energy consumption and serious environmental pollution. Other methods have their own defects, and some have special requirements for the leaching environment (such as bacterial method). It is only for certain special ores (such as reduction methods, etc.), so it can not be well promoted, only staying at the laboratory level. At present, the direct acid leaching process is more promising due to its simple operation steps and less environmental pollution, but the impurity content in the solution is relatively high, and the requirements for the impurity removal process are higher. In order to fully exploit and utilize China's abundant low-grade manganese ore resources to achieve sustainable and healthy development of manganese metallurgy in China, the following problems must be solved:

(1) Accelerate the popularization of new mineral processing technologies. At present, China has not been able to fully realize mechanized beneficiation, which makes the grade of manganese ore uneven, thus affecting the normal production of metallurgical enterprises.

(2) Increase investment in research on wet manganese smelting. Pyrometallurgy is too polluting to the environment. Green and environmentally friendly hydrometallurgical technology is bound to be the mainstream of the future metallurgical industry. However, there are still many problems in hydrometallurgy, which require further research to solve.

(3) Strengthening the research and development of deep processing technology for manganese products. China's manganese ore reserves are among the best in the world and are also the world's major manganese production bases. However, in view of China's manganese industry, low-end products such as manganese ore powder and electrolytic manganese metal are still mainly produced, and the research and development and production of high value-added manganese deep processing products are still extremely lacking.

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