Occurrence of rare earth elements in the crust mainly three: independent minerals: e.g. bastnaesite, monazite, mixed rare earth ore; associated rare earth ore; rare earth element isomorphous replacement form, dispersed in a rock- minerals and rare metal minerals; weathering Crust rare Earth ore: rare earth element is adsorbed to the ionic state was inter-particle surface or certain minerals, such minerals are various clay minerals, mica minerals. Weathered shell leaching type rare earth ore is a unique rare earth mineral resource in China, which is widely distributed in southern provinces and other provinces. For rare earth ions adsorbed on clay minerals, conventional physical beneficiation methods such as re-election, magnetic separation, flotation, etc. cannot enrich the adsorbed rare earth ions into corresponding rare earth mineral concentrates. The chemical beneficiation method is the only technique for extracting such rare earth minerals. The chemical beneficiation method is mainly divided into two steps of leaching and extraction. First, the rare earth is leached from the ore, and then the rare earth is extracted from the exposed liquid. After years of development, the leaching technology has been continuously improved and improved, and a systematic weathering and leaching type rare earth ore leaching process system has been gradually formed. The research progress of its chemical beneficiation technology will be described in detail below. For independent minerals and mixed rare earth minerals (the rare earth elements are still present as independent minerals in mixed rare earth minerals, and the ratios of independent minerals in different mixed rare earth minerals are different), mineral ore concentrates are usually obtained by physical beneficiation. chemically obtained using chemical concentrate for smelting; for rare earth ore beneficiation associated to for phosphate ore mainly in the form of rare earth minerals commonly associated physical beneficiation method of removing impurities in the phosphate rock beneficiation, rich in rare earth elements to obtain the impurities In addition, the chemical concentrates are used to obtain rare earth chemical concentrates. With the development of comprehensive utilization of resources, the research on extracting rare earths from tailings of some low-grade rare earth ores and other mineral physical beneficiation will also increase. The progress of its research will be briefly described below. 1 Research progress on chemical beneficiation of weathered shell leaching rare earth ore A low grade weathering shell leaching rare earth ore leaching The key to the leaching of low-grade weathered leaching type rare earth ore is that the rare earth of the ionic phase is desorbed from the clay mineral and forms a counter ion with the anion to enter the leachate. Studies on the mechanism of ion desorption of rare earth elements show that the desorption capacity of different rare earth element ions is related to the size of ion hydration energy: the leaching rate of low hydration energy leaching agent is lower; the leaching effect of sulfate leaching is stronger than that of hydrochloride . Some researchers have considered that the ammonium leaching agent is suitable as a leaching agent by comparing the leaching effects of several leaching agents. If ammonium leaching is used, the optimum flow rate of the leaching agent during the leaching process can maximize the leaching rate, that is, the condition that the mass transfer effect is better. It has been reported that the effect of using the composite ammonium salt as the leaching penalty is better than that of the single ammonium salt, which may be due to the fact that the different anions of the complex ammonium salt form a multi-ligand with the rare earth element cation. The physicochemical properties of the leaching agent cause changes in the zeta potential of the rare earth ion-loaded phase-clay mineral surface. Studies have shown that the ammonium salt solution concentration and liquid-solid ratio have an effect on the surface zeta potential of clay minerals when leaching with ammonium salts. The larger the liquid-solid ratio, the larger the zeta potential on the surface of clay mineral particles, and the contact of ammonium ions with clay minerals. The increased amount can promote the desorption of rare earth ions. The kinetic study of the low-grade Fenghua shell-lead rare earth ore leaching process focuses on the research of the control steps of the leaching process, which is mainly aimed at improving the mass transfer effect. Studies have shown that in different leaching conditions (such as eluent mass fraction, eluent solid ratio, rinsing speed, ore particle size, etc.), leaching agents (such as complex ammonium salts, leaching agent LPF, ammonia nitrogen wastewater and suppression Under the agent QXY-01, etc., the control steps of the leaching process are different from the physical models describing the process. For example, when leaching with a composite leachant, the leaching hydrodynamics is subject to Darcy's law and the leaching process is a porous solid layer diffusion control, which can be described by the van dermatt equation. The leaching flow rate has a great influence on the leaching and mass transfer effect, and the loading height also has a great influence on the mass transfer effect of the leaching process. Based on the above studies of desorption mechanism and mass transfer effect, new technologies for low-grade weathering shell leaching rare earth ore leaching were proposed, including assisted leaching (Tianjing gel assisted leaching, assisted leaching) and enhanced leaching (ultrasonic strengthening). Technical means such as leaching, magnetic field enhanced leaching). In addition, the use of carboxymethyl phthalocyanine gel is better than the single phthalocyanine leaching effect, and the leaching agent consumes less. The results of the assisted immersion study showed that acetylacetone, triammonium citrate, tartaric acid, LPD and LPF could promote the leaching of rare earth. Adding some reagents during the leaching process can reduce the mass transfer resistance coefficient of the leaching process, thereby reducing the mass transfer resistance of the leaching agent during the leaching exchange process and improving the mass transfer effect of the rare earth leaching process, which is the theoretical basis for enhanced leaching. The use of ultrasonic cavitation can effectively enhance the leaching of rare earths in rare earth ore, thereby increasing the rare earth leaching rate and shortening the analysis time of the total amount of rare earth minerals. Studies have shown that the ultrasonic method has higher leaching efficiency for rare earth than the conventional stirring method, but the leaching rates of the two methods are similar. The study on the leaching and precipitation behavior of rare earth ore under magnetic field conditions shows that the leaching rate and sedimentation rate are improved after magnetization treatment, and the consumption of chemicals is reduced. B Low-grade weathering bright leaching type rare earth ore leaching solution Theoretical studies and technological developments to remove impurity ions during leaching focus on the separation of aluminum and the inhibition of aluminum during the leaching process. Studies have shown that aluminum ions are leached together with rare earth ions during the leaching process, and are the most abundant ions in the leaching ions. The kinetics of rare earth leaching of rare earth ore from weathering crust leaching rare earth ore indicates that the leaching of rare earth and the leaching of aluminum are typical liquid-solid heterogeneous reactions, and the leaching process is in good agreement with the shrinkage unreacted core model. The rare earth leaching is controlled by solid film diffusion, the aluminum leaching process is controlled by chemical reaction, and the apparent activation energy of aluminum leaching is much higher than the apparent activation energy of rare earth leaching. The aluminum leaching rate is much lower than the rare earth leaching rate. . Therefore, it can be considered that the rare earth and aluminum have a separation effect during the leaching process. This is the theoretical basis for the separation of aluminum. The research on the leaching behavior of rare earth and aluminum shows that the leaching behavior of the rare earth element is greatly affected by the ore property, and the leaching behavior of aluminum is greatly affected by the pH value of the leaching agent. The newly developed anti-hybrid leaching technology uses some inhibitors to react with aluminum and iron ions in rare earth ore. The formation of a new stable compound, using the inhibitors QXY-01 and QWJ-05 as inhibitors, achieved aluminum inhibition rate of more than 90%, rare earth leaching rate of more than 96%. The assisted immersion can also inhibit the leaching of aluminum ions. Studies have shown that the use of acetylacetone, triammonium citrate, tartaric acid, LPD, LPE, LPF can promote the leaching of rare earth. In the process of extracting leachate by extraction, pre-extraction impurity removal is also an important means to prevent metal impurity ions from affecting the subsequent extraction process. In addition, new extractants and extraction processes have also been reported. At present, there are three-phase emulsions in the extraction and separation process of most rare earth leachate. Some studies believe that this emulsification phenomenon is due to improper control of flow ratio, mainly due to inorganic (typically A13+) and organic impurities in the leachate. caused. Some researchers used HCI as the stripping acid in the extraction process, and preferentially eluted impurities such as A13+ from the extracting phase, and achieved good results. Other studies have shown that it is feasible to remove aluminum from the concentrate dissolved material directly. The newly reported pre-separation extraction method is to first separate the raw materials to be separated by a small number of stages, and then to carry out a fine separation process in which the number of stages is large and the separation between adjacent elements is performed. The reagents for extracting rare earth from rare earth leachate are di-2-ethylhexylphosphoric acid, Cyanex301, TOPS99, PC88A, CYANEX® 272, CYA-NEX® 302, CYANEX923.CYANEX921, ALAMINE336, ALIQUAT336, etc. There is no significant better extraction than a single extractant. The study of the removal of impurities during the treatment of leachate using the precipitation method is reflected in the use of preferential precipitation flotation. The solution chemistry study on the leachate flotation flotation shows that the weathering shell leaching type rare earth ore leaching impurities (such as AI3+, Fe3+, etc.) can be effectively floated by preferential precipitation, and all effective in the form of hydroxide or pyrophosphate or polyphosphate precipitation. Remove. Qiu Jianning has developed a process to solve the impurity removal and concentration of ionic rare earth ore leaching mother liquor. The technology effectively solves the problem of impurity removal and concentration of the ionic mineral leaching mother liquor. The main route of the process is as follows: the ionic rare earth leaching solution is passed through an adsorption column equipped with a GX rare earth special material, and the iron, aluminum and the like in the rare earth leaching solution are preferentially adsorbed, and the adsorbed liquid does not contain iron or aluminum, and the rare earth, calcium, Magnesium , silicon, etc. remain in the adsorbed liquid; then, after a rare earth special material adsorption, the rare earth, calcium, magnesium, silicon and other impurities adsorbed therein are not adsorbed, thereby realizing the separation and enrichment of rare earth, and obtaining pure rare earth concentration. liquid. The method of removing impurities from the rare earth ore leaching solution by the non-precipitation method is also an ion exchange method or a liquid membrane method. Such related reports are rare in recent years and will not be introduced here. 2 Progress in chemical beneficiation of fluorocarbonate minerals At present, the main methods for treating fluorocarbonate minerals are oxidative roasting-acid leaching-precipitation (or extraction) techniques such as oxidative roasting-sulfuric acid leaching-re-salt precipitation, oxidative roasting-sulfuric acid leaching-extraction separation, oxidative roasting-hydrochloric acid leaching- Alkali decomposition - hydrochloric acid dipping and the like. Among these techniques, the calcination-leaching process is indispensable, and the calcination not only consumes energy and has high running cost, but also the fluorine element escapes in the gas phase during the calcination process, and the fluorine dissolves into the waste liquid during the leaching process. The result is that both fluorine resources are wasted and air pollution and water pollution are caused. Therefore, in recent years, the basic research and technology development of fluorine in the roasting and leaching process of bastnasite ore and the fluorine-fixing and fluorine-inhibiting are gradually increasing. It is found that the use of Ca0 to inhibit the escape of fluorine has achieved good results; the kinetics of the leaching process The research focuses on the leaching control step. The new technologies for fluorine inhibition and fluorine fixation in the leaching process include aluminum salt coordination separation fluorine method, low temperature roasting-low temperature hydrochloric acid catalytic leaching method and two-step acid leaching process. Research progress in chemical beneficiation of mixed rare earth concentrates The mixed rare earth ore represented by Baotou rare earth ore mainly adopts flotation method to remove a large amount of associated minerals and gangue minerals, and then uses chemical beneficiation method to decompose the bastnasite ore and monazite ore to obtain mixed rare earth chloride. Mix rare earth nitrate, mixed rare earth sulfate or mixed rare earth oxide, and then carry out precipitation or extraction separation. At present, the processes for treating mixed rare earth mineral concentrates mainly include acid method (mainly sulphation roasting method), alkali method (mainly caustic soda method, soda ash method) and newly developed chlorination method (mainly carbon thermal chlorination method). Three kinds. In the above process, the acid method, the alkali method, the chlorination method have fluorine escape during the roasting process and the chlorination process, resulting in waste of fluorine and pollution, and thus the roasting process for the decomposition of the mixed rare earth ore in recent years (mainly It is the research on the inhibition of fluorine and nitrogen fixation in the high-temperature chlorination process, mainly in the CaO-NaCl-CaCI2 system roasting, the direct decomposition of mixed rare earth ore by sodium hydroxide concentrated alkali, and the low-temperature roasting of concentrated sulfuric acid. , AlCl3 denitrification-carbon thermal chlorination method, SiCl4 defluorination-carbon thermal chlorination method, and the like. In addition, the research on the leaching process of mixed rare earth ore has also been developed, and a new process of combined leaching is proposed. The research on the role of rare earth elements and extractants in the extraction process has also been reported. 4 Progress in chemical beneficiation of associated rare earth ore phosphate rock The trace rare element associated with phosphate rock is a potential rare earth resource with high development and utilization value. Taking Guizhou Zhijin Xinhua Rare Earth Phosphorus Deposit as an example, the rare earth elements are mainly present in the apatite lattice in the form of isomorphism, and the content of rare earth elements is closely related to the phosphate rock. This structure makes it extremely difficult for rare earths to be separately selected from phosphate rock. At present, the rare earth elements associated with phosphate rock are mainly separated and enriched by flotation and acid leaching-extraction. Acid leaching mainly uses acidic media such as nitric acid, sulfuric acid and mixed acid, while organic solvent extraction and resin adsorption processes are mostly used for extracting rare earth elements from acid leaching solution. In recent years, research on the extraction of associated rare earths in phosphate rock has focused on the reaction mechanism, acid hydrolysis kinetics, and the trend and distribution of rare earths in the acid hydrolysis process. There has been an increasing number of studies in the industrial production of return acid leaching of rare earths using the wet process phosphoric acid process. The study of liquid membrane extraction of rare earths has remained in the laboratory stage and has not been used in industrial applications. The research of extractant is often combined with the extraction process, and there are many developments at home and abroad. 5 Research progress in comprehensive utilization of rare earth minerals in chemical beneficiation With the decline of single rare earth ore grade and difficult treatment, the use of chemical beneficiation technology to extract rare earth from some low grade rare earth ore and other mineral mineral ore tailings has also been reported. Studies on the leaching of rare earth elements from low-grade rare earth ore dominated by pyrite show that the addition of ferric sulfate to the leaching agent can leach the rare earth elements in the ore. And in the process the titanium-containing low-grade rare-earth iron found using K + and A13 + ilmenite lattice may be destroyed to increase the tension, the release of a rare earth element. There are also some advances in tailings and other refractory resources, such as ionic rare earth tailings, red mud hydrochloric acid leaching solution, mixed rare earth ore re-election tailings, and rare earth and celestite associated with rare earths. In addition, the use of natural gas for roasting of rare earth concentrates in the north, the use of concentrated sulfuric acid and activator ripening-baking-leaching methods to comprehensively recycle rare earth, antimony , bismuth and other resources in rare earth concentrates have also been reported.
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