Method for preparing aluminum oxide and extracting lithium from lithium-rich bauxite waste rock

Abstract

The invention provides a method for preparing aluminum oxide and extracting lithium from lithium-rich bauxite waste rocks, and belongs to the technical field of solid waste comprehensive utilization. The method comprises the following steps: crushing and grinding the lithium-rich bauxite waste rocks, mixing with an acid mixed solution, leaching to remove iron to obtain a low-iron filter cake, adding concentrated sulfuric acid, roasting, curing, leaching with water, carrying out hot filtration to obtain a filtrate, adding a crystallizing agent, dissolving, evaporating to obtain a steel belt crystallizer crystal, stirring and washing a saturated solution to obtain a lithium-containing solution and low-iron aluminum ammonium sulfate, purifying the lithium-containing solution to remove impurities, and precipitating lithium with sodium carbonate to prepare lithium carbonate; and calcining the low-iron ammonium aluminum sulfate to prepare aluminum oxide. The method provided by the invention has the advantages of simple process, low energy consumption in roasting and leaching of aluminum and lithium, high recovery rate of valuable components of aluminum and lithium, high iron removal rate, high separation efficiency of aluminum and lithium, low extraction cost of aluminum and lithium, recyclability of the crystallizing agent and the like, is easy for industrial implementation, and greatly improves the comprehensive utilization value of the lithium-rich bauxite waste rocks.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of comprehensive utilization of solid waste, and particularly relates to a method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock. BACKGROUND

[0002] Bauxite is usually mined by open-pit mining, and a large amount of waste rock and surrounding rock needs to be stripped during the mining process, resulting in a huge discharge amount. A small amount of bauxite waste rock is used for pit backfill, and a large amount of waste rock is stored, which occupies a large amount of land. Generally, the alumina content in bauxite waste rock can reach 40-50%, or even higher, and is often associated with a certain amount of lithium oxide, especially in the top and bottom plates of bauxite (aluminous clay rock), lithium is more easily enriched, and the commonly associated Li2O content is greater than 0.05%, which has a high comprehensive utilization value.

[0003] However, compared with hard rock type lithium ore resources such as lepidolite and spodumene, the lithium content in bauxite waste rock is relatively low. The lithium in bauxite waste rock is generally not in an independent phase, but mainly occurs in clay minerals such as illite, kaolinite and pyrophyllite, which is difficult to enrich by conventional beneficiation methods. In addition, these clay minerals are structurally stable at normal temperature and pressure, and are not easily extracted by acid or alkali leaching agents, and need to be assisted by roasting or high temperature and high pressure harsh chemical conditions, resulting in a significantly higher extraction cost of associated lithium in waste rock than lepidolite and spodumene. Moreover, the iron-containing minerals in bauxite waste rock are finely disseminated, which is difficult to remove by magnetic separation, and a large amount of impurities enters the leaching solution during the leaching process, increasing the cost of impurity removal. Therefore, the economic efficiency of separate recovery of lithium in bauxite waste rock is poor.

[0004] The aluminum in bauxite waste rock mainly occurs in minerals such as diaspore, kaolinite, illite and pyrophyllite, with an alumina content of about 40-50% and an aluminum-silicon ratio usually less than 2.5, which is not suitable for Bayer process and sintering process recovery. In the conventional roasting-acid leaching process, the alumina leaching rate is low (usually 30-45%), and the cost of separate recovery of alumina in bauxite waste rock is high, with poor economic benefits.

[0005] Therefore, it is of great significance to realize the synergistic and efficient utilization of lithium and aluminum valuable components in bauxite waste rock, which not only can improve the overall economic efficiency, but also can effectively improve the comprehensive utilization level of bauxite solid waste, save solid waste storage land resources, and enhance the lithium resource guarantee capacity.

[0006] Broadly speaking, the associated lithium resources in bauxite waste rock belong to clay-type lithium resources. At present, there are mainly three methods for the co-extraction of aluminum and lithium from clay-type lithium resources: (1) The clay-type lithium ore is crushed and ground, and then separated and enriched by flotation. The flotation concentrate is a lithium-rich product, and the flotation tailings are a bauxite concentrate product. The lithium-rich product is prepared into lithium carbonate product through sulfuric acid curing-water leaching-pH regulation to remove aluminum and iron-carbonate sodium high-temperature lithium precipitation. This method comprehensively recovers the valuable components of aluminum and lithium in sedimentary lithium ore, but the valuable component aluminum in the leaching solution of the lithium-rich product is not recovered and utilized, but removed as impurities, resulting in high cost of impurity removal and large amount of residue. (2) Pressure leaching is used to separate aluminum and lithium to prepare aluminum hydroxide. This method can comprehensively recover the valuable components of aluminum and lithium by leaching the clay lithium ore with nitric acid under pressure, but the investment of nitric acid pressure leaching process is large, the equipment corrosion is serious, and the consumption of reagents such as sodium hydroxide / sodium carbonate is large, resulting in high cost. (3) Concentrated sulfuric acid is added to the clay-type lithium ore for sulfuric acid curing-water leaching to obtain a leaching solution and a Si enrichment residue, which can be used as a Si extraction raw material. The leaching solution is sequentially purified, concentrated, and high-temperature pyrolyzed to obtain a pyrolysis product and flue gas. The flue gas is collected and acid is prepared to obtain sulfuric acid, which is recycled to the sulfuric acid curing process. The pyrolysis product is washed with water to obtain an Al2O3 product and a Li enrichment solution. The Li enrichment solution is adjusted with alkali and lithium precipitated to obtain a Li2CO3 product. In this process, the leaching solution is purified and concentrated into aluminum sulfate solution, and the pyrolysis consumes a lot of energy. In addition, a large amount of iron enters the leaching solution during the sulfuric acid curing leaching process, resulting in high cost of purification and impurity removal. In addition, the conventional acid method for extracting aluminum and lithium from clay-type lithium resources also faces the problems of difficulty in separating lithium and aluminum in high-concentration aluminum sulfate solution, difficulty in separating iron and lithium, large loss of lithium in the process of separating aluminum and lithium, and difficulty in impurity removal. SUMMARY

[0007] To solve the above technical problems, the present application provides a method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock. The method is simple, has high recovery rates of lithium and aluminum, high iron removal rate, low iron removal cost, reusable crystallization agent, low evaporation amount of leaching solution, low extraction cost of aluminum and lithium, low energy consumption, and is easy to implement industrially.

[0008] To achieve the above purpose, the present application provides the following technical solutions:

[0009] The present application provides a method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, comprising the following steps:

[0010] The lithium-rich bauxite waste rock is crushed and ground, then mixed with an acid mixture and stirred to remove iron by leaching. After solid-liquid separation, a low-iron filter cake is obtained. Concentrated sulfuric acid is added to the low-iron filter cake and roasted to cure, then water leaching is performed and hot filtration is carried out to obtain a filtrate.

[0011] The steel belt crystallizer crystals are obtained after the filtrate is added with a crystallization agent, dissolved, evaporated, stirred and washed with a saturated solution to remove impurities, and the lithium-containing solution and low-iron aluminum ammonium sulfate are obtained after solid-liquid separation;

[0012] The lithium-containing solution is subjected to impurity removal and lithium precipitation with sodium carbonate to prepare lithium carbonate;

[0013] The low-iron aluminum ammonium sulfate is calcined to prepare alumina, and the high-temperature flue gas in the calcination process is reused in the dissolution and evaporation step.

[0014] Further, the proportion of the particle size ≤74 μm in the lithium-rich bauxite waste rock is 60-85 wt.%; preferably, the proportion of the particle size ≤74 μm is 60-80 wt.%.

[0015] Further, the acid mixed solution is a mixed solution of sulfuric acid and oxalic acid or a mixed solution of hydrochloric acid and oxalic acid, and the concentration of the acid mixed solution is 0.5-5 mol / L; preferably, the concentration of sulfuric acid, oxalic acid or hydrochloric acid in the acid mixed solution is 1-1.5 mol / L.

[0016] Further, the leaching temperature for iron removal is 40-100℃, the leaching time is 0.5-5h, and the leaching solid-liquid ratio is 1g:(2-10)mL; preferably, the leaching temperature for iron removal is 70-80℃, the leaching time is 2h, and the leaching solid-liquid ratio is 1g:(3-6)mL.

[0017] Further, the process of roasting and curing with concentrated sulfuric acid is to heat to 160-240℃, keep for 0.5-5h, continue to heat to 300-350℃, and keep for 1-8h, and the mass ratio of the low-iron filter cake to the concentrated sulfuric acid used for roasting and curing is 0.5:1-3:1; preferably, the process of roasting and curing with concentrated sulfuric acid is to heat to 180℃, keep for 2h, continue to heat to 330℃, and keep for 3h, and the mass ratio of the low-iron filter cake to the concentrated sulfuric acid used for roasting and curing is 1.5:1.

[0018] Further, the temperature of the water immersion is 90-100℃, the time is 20-120min, the solid-liquid ratio is 1g:(2-3)mL, and the temperature of the hot filtrate is 80-100℃; preferably, the temperature of the water immersion is 95℃, the time is 0.5h, the solid-liquid ratio is 1g:2mL, and the temperature of the hot filtrate is 80-90℃.

[0019] Further, the washing water generated by hot filtration is returned to the water immersion step, and the flue gas generated in the concentrated sulfuric acid roasting step is recovered to prepare sulfuric acid.

[0020] Further, the crystallization agent is ammonium sulfate or potassium sulfate, the molar ratio of the added amount of the crystallization agent to Al in the filtrate is 0.5:1-1:2, the temperature of the dissolving and evaporating is 90-100℃, and the evaporating is performed until the Al concentration is 60-100g / L; preferably, the molar ratio of the added amount of the crystallization agent to Al in the filtrate is 0.5:1-0.65:1, the temperature of the dissolving and evaporating is 90℃, and the evaporating is performed until the Al concentration is 60-80g / L.

[0021] Further, the saturated solution is a saturated dodeca-hydrated aluminum ammonium sulfate solution or a saturated dodeca-hydrated aluminum potassium sulfate solution, the washing solution and the crystallization agent are unified, and no new impurities are introduced.

[0022] Further, the temperature of the stirring and washing is 4-20℃, the time is 0.5-2h, and the solid-liquid ratio is 1g:(2-10)mL; preferably, the temperature of the stirring and washing is 10℃, the time is 0.5h, and the solid-liquid ratio is 1g:(2-4)mL.

[0023] Further, the low-iron aluminum ammonium sulfate is prepared into alumina through two-stage calcination, and the two-stage calcination comprises: heating to 200-300℃ and keeping for 2h, and then heating to 1180-1280℃ and keeping for 2-5h; preferably, the two-stage calcination comprises: heating to 250℃ and keeping for 2h, and then heating to 1200-1250℃ and keeping for 2h.

[0024] Further, in the two-stage calcination process, the steam generated in the first-stage calcination can be reused in the water immersion process, and the high-temperature flue gas in the second-stage calcination process can be reused in the dissolving and evaporating process; after the low-iron aluminum potassium sulfate is calcined, alumina and potassium sulfate products are obtained, after the water immersion and solid-liquid separation, alumina products and a potassium sulfate solution are obtained, and after the potassium sulfate solution is evaporated and crystallized, potassium sulfate is obtained, and the potassium sulfate can be reused in the dissolving and evaporating process.

[0025] Technical principle of the application:

[0026] The lithium-rich bauxite waste rock is first crushed and ground in the application, so that the specific surface area of the waste rock is increased, and sufficient contact conditions are provided for subsequent reactions; in the acid mixed solution, oxalic acid can form a stable complex with Fe 3+ , and selectively dissolve iron impurities, while Al 3+ , Li +Under this condition, the dissolution is little (aluminum and lithium loss rate <5%), the iron is removed from the source (iron removal rate >80%), and the high cost of subsequent solution iron removal is avoided. The obtained low-iron filter cake has aluminum and lithium existing in stable clay minerals such as illite and kaolinite, which is difficult to leach at room temperature, so concentrated sulfuric acid is added, and the mineral crystal structure is destroyed when the section roasting is carried out at 160-350 DEG C, so that Al and Li are converted into water-soluble sulfate, and the sulfate is fully dissolved by water leaching at 90-100 DEG C, and the aluminum and lithium concentrations in the filtrate are ensured by hot filtration at 80-100 DEG C to prevent the sulfate from cooling and crystallizing out. Ammonium sulfate / potassium sulfate (crystallizing agent) and Al 3+ Form aluminum ammonium sulfate / potassium sulfate complex salt, which contains a large amount of crystal water and complete crystal, and the solubility changes significantly with temperature; 90-100 DEG C evaporation concentration to Al concentration 60-100 g / L, combined with high-efficiency crystallization of steel belt crystallization machine, can greatly reduce the water that needs to be evaporated (reduce evaporation energy consumption), and the crystal is not easy to carry lithium; saturated aluminum ammonium sulfate / potassium sulfate solution with twelve water is used to prevent crystal dissolution by using the same ion effect, and at the same time, the lithium-containing solution attached to the surface of the crystal is washed away, realizing efficient separation of aluminum and lithium; the lithium-containing solution is impurity-removed (calcium, magnesium, etc. are removed) and then reacts with Na2CO3 and Li2SO4 to generate Li2CO3 precipitate; low-iron aluminum ammonium sulfate is calcined in two stages (200-300 DEG C to remove crystal water, 1180-1280 DEG C to decompose) to generate Al2O3, and the calcination flue gas (NH3, SO3) is recycled for dissolution and evaporation, realizing resource recycling.

[0027] Compared with the prior art, the method has the following advantages and technical effects:

[0028] (1) Compared with the prior art, the method has the following advantages: simple process, low energy consumption of aluminum and lithium roasting and leaching, high recovery rate of valuable components of aluminum and lithium, high iron removal rate, high separation efficiency of aluminum and lithium, low extraction cost of aluminum and lithium, and recyclable crystallizing agent. It is easy to implement industrialization, greatly improves the comprehensive utilization value of rich lithium bauxite waste rock, and provides a new method for the development and utilization of rich lithium bauxite waste rock and clay-type lithium ore resources.

[0029] (2) The present application removes iron impurities in bauxite waste rock through the iron leaching process, and the iron removal rate is more than 80%; at the same time, the loss rate of aluminum and lithium is less than 5%. The iron impurities into the leaching solution are reduced from the source, the cost of subsequent solution iron removal is greatly reduced, and the content of iron impurities in aluminum oxide is effectively reduced. The present application makes full use of the characteristics of ammonium sulfate / potassium sulfate and aluminum sulfate to form a large amount of crystal water and complete crystals which are easy to filter, and combines with the efficient crystallization of the steel belt crystallization machine, further greatly reduces the water that needs to be evaporated, and significantly reduces the evaporation energy consumption. In addition, by using the characteristics of complete ammonium aluminum sulfate / potassium aluminum sulfate crystals and not easy to carry lithium during the crystallization process, the efficient separation of aluminum and lithium is realized by stirring and washing the ammonium aluminum sulfate / potassium aluminum sulfate crystals, the aluminum removal rate is more than 99.5%, and the lithium recovery rate is more than 95%. In addition, NH3, SO3 and other gases generated by calcining ammonium aluminum sulfate can be used for the dissolution and evaporation process, and the decomposition products of potassium aluminum sulfate crystals are Al2O3, SO3 and K2SO4, wherein SO3 can be used for preparing sulfuric acid and returned to the sulfuric acid curing roasting process; the roasting product of potassium aluminum sulfate crystals can obtain alumina product and potassium sulfate solution after water immersion treatment, and the prepared potassium sulfate can be returned to the dissolution and evaporation process. Therefore, the recycling of the crystallizing agent is realized, and the raw material cost of the crystallizing agent is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0030] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the illustrative embodiments of the present application and their description are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0031] Figure 1 It is a flowchart for preparing alumina and extracting lithium sulfate from lithium-rich bauxite waste rock in embodiment 1 of the present application;

[0032] Figure 2 It is an XRD pattern of lithium-rich bauxite waste rock in embodiment 1 of the present application;

[0033] Figure 3 It is an XRD pattern of low-iron ammonium aluminum sulfate crystals after calcination in embodiment 1 of the present application. DETAILED DESCRIPTION

[0034] Now, various exemplary embodiments of the present application will be described in detail, which should not be considered as limitations on the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0035] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentration, intensity, and time, an intermediate value of the range can be specifically recited; however the

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference is not an admission that it is prior art with respect to the present application.

[0037] Many modifications and variations of this application of the application can be made without departing from its spirit or scope, which will be apparent to those skilled in the art. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. For example, the specification can be used to design other embodiments of the application. It is intended that the specification and examples be considered as exemplary only, with a true scope of the application being indicated by the following claims.

[0038] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional, unrecited elements or method steps.

[0039] The embodiment of the present application provides a method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, comprising the following steps:

[0040] The lithium-rich bauxite waste rock is crushed and ground, then mixed with an acid mixture and stirred to leach iron, and a low-iron filter cake is obtained after solid-liquid separation. Concentrated sulfuric acid is added to the low-iron filter cake and roasted and cured, then water leaching and hot filtration are performed to obtain a filtrate;

[0041] The steel belt crystallization machine crystals are obtained by adding a crystallization agent to the filtrate and dissolving and evaporating. The steel belt crystallization machine crystals are washed and impurities are removed by stirring with a saturated solution, and a lithium-containing solution and low-iron aluminum ammonium sulfate are obtained after solid-liquid separation;

[0042] The lithium-containing solution is impurity-removed and lithium is precipitated with sodium carbonate to prepare lithium carbonate;

[0043] The low-iron aluminum ammonium sulfate is calcined to prepare alumina, and the high-temperature flue gas in the calcination process is reused in the dissolving and evaporating step.

[0044] In the preferred embodiment of the present application, the proportion of particle size ≤74 μm in the used lithium-rich bauxite waste rock is 60-85 wt.%, the specific surface area of fine particles (≤74 μm) is larger, the acid and iron impurities are more fully contacted during acid leaching and iron removal, the iron removal rate is higher, the fine particles can be uniformly mixed with concentrated sulfuric acid during concentrated sulfuric acid roasting, the mineral structure is more completely destroyed, the conversion rates of Al and Li are higher, the problem of insufficient reaction caused by coarse particles is reduced, and valuable components are avoided to be left in the waste rock.

[0045] The specific chemical composition of the lithium-rich bauxite waste rock used in the embodiment of the present application is shown in Table 1.

[0046] Table 1 Chemical composition of lithium-rich bauxite waste rock

[0047] Ingredients Al2O3 SiO2 Fe2O3 Li2O Na2O K2O TiO2 MgO CaO Loss on ignition Others Content (wt. %) 41.51 37.99 3.34 0.68 0.07 0.23 2.44 0.33 0.56 10.83 2.02

[0048] In the preferred embodiment of the present application, the acid mixture is a mixture of sulfuric acid and oxalic acid or a mixture of hydrochloric acid and oxalic acid, and the concentration of the acid mixture is 0.5-5 mol / L. As a complexing agent, oxalic acid can form a stable complex with Fe 3+ , promoting the dissolution of iron oxides; sulfuric acid / hydrochloric acid provides H + for the environment, enhances the complexing ability of oxalic acid, and at the same time inhibits the dissolution of Al 3+ , Li + dissolution (avoiding aluminum and lithium loss); the concentration is controlled in the range of 0.5-5 mol / L, and when the concentration is too low, the iron dissolution is insufficient and the removal rate is low; when the concentration is too high, Al 3+ , Li + dissolution (loss rate increases) and the cost of acid consumption and equipment corrosion increases, and this concentration range can balance the iron removal rate and the retention rate of aluminum and lithium.

[0049] In the preferred embodiment of the present application, the leaching temperature for iron removal by leaching is 40-100℃, the leaching time is 0.5-5h, and the solid-liquid ratio of leaching is 1g: (2-10) mL.

[0050] In the preferred embodiment of the present application, the process of concentrated sulfuric acid roasting and curing is to heat to 160-240℃, keep warm for 0.5-5h, then continue to heat to 300-350℃, keep warm for 1-8h, and the mass ratio of low-iron filter cake to concentrated sulfuric acid used for concentrated sulfuric acid roasting and curing is 0.5:1-3:1.

[0051] In the preferred embodiment of the present application, the temperature of water immersion is 90-100℃, the time is 20-120min, the solid-liquid ratio is 1g: (2-3) mL, and the temperature of the filtrate filtered while hot is 80-100℃.

[0052] In the preferred embodiment of the present application, the washing water generated by hot filtration is returned to the water immersion step, and the flue gas generated in the concentrated sulfuric acid roasting step is recovered to prepare sulfuric acid.

[0053] In the preferred embodiment of the present application, the crystallization agent is ammonium sulfate or potassium sulfate, the molar ratio of the amount of the crystallization agent added to Al in the filtrate is 0.5:1-1:2, the temperature of the dissolution and evaporation is 90-100℃, and the evaporation is performed until the Al concentration is 60-100g / L.

[0054] In the preferred embodiment of the present application, the saturated solution is saturated dodeca-hydrated aluminum ammonium sulfate or saturated dodeca-hydrated aluminum potassium sulfate solution, and the washing solution is the same as the crystallization agent without introducing new impurities.

[0055] In the preferred embodiment of the present application, the temperature of the stirring washing is 4-20℃, the time is 0.5-2h, and the solid-liquid ratio is 1g:(2-10)mL.

[0056] In the preferred embodiment of the present application, the low-iron aluminum ammonium sulfate is calcined in two stages to obtain alumina, the two-stage calcination includes: heating to 200-300℃ for 2h, then heating to 1180-1280℃ for 2-5h, in the two-stage calcination process, the steam generated in the first-stage calcination can be recycled for the water leaching process, and the high-temperature flue gas in the second-stage calcination process can be recycled for the dissolution and evaporation process; after the low-iron aluminum potassium sulfate is calcined, alumina and potassium sulfate products are obtained, after the solid-liquid separation by water leaching, alumina products and potassium sulfate solution are obtained, and the potassium sulfate solution is evaporated and crystallized to obtain potassium sulfate, which can be recycled for the dissolution and evaporation process.

[0057] For example, in an embodiment of the present application, a method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock includes the following steps:

[0058] (1) The lithium-rich bauxite waste rock is crushed and finely ground to obtain a lithium-rich bauxite waste rock powder, wherein the proportion of the lithium-rich bauxite waste rock with a particle size of ≤74μm is 60-85wt.%;

[0059] (2) The lithium-rich bauxite waste rock powder is leached with a sulfuric acid and oxalic acid solution to remove iron, the concentration of the sulfuric acid is 0.5-5mol / L, the concentration of the oxalic acid is 0.5-5mol / L, the leaching temperature is 40-100℃, the leaching time is 0.5-5h, and the solid-liquid ratio is 1g:(2-10)mL, after filtration, washing, and solid-liquid separation, a low-iron filter cake is obtained;

[0060] (3) The obtained low-iron filter cake is added into 98% concentrated sulfuric acid, the acid-rock mass ratio is 0.5:1-3:1, the mixture is heated to 160-240℃ in a muffle furnace for 0.5-5h, then the temperature is continuously increased to 300-350℃ for 1-8h to obtain a calcined sand, the calcined sand is water leached, the water leaching temperature is 90-100℃, the water leaching time is 20-120min, the solid-liquid ratio of the calcined sand and water is 1g:(2-3)mL, the mixture is filtered while hot, the filtration temperature is controlled to be 80-100℃, a filtrate and a filter cake are obtained, the filter cake is washed with hot water, the hot water temperature is 80-90℃, and the washing solution is returned to the next round of water leaching process;

[0061] (4) adding a crystallization agent (ammonium sulfate or potassium sulfate) in the filtrate to dissolve and evaporate, the dissolving and evaporating temperature is 90-100 DEG C, the crystallization agent is added in a molar ratio of 0.5:1-1:2 with Al ions in the leaching solution, the Al concentration in the filtrate is about 50 g / L, and the filtrate is evaporated to an Al concentration of 60-100 g / L, and the filtrate is extracted to crystallize through a steel belt crystallizer to obtain crystals containing almost no free water;

[0062] (5) taking the saturated solution (saturated aluminum ammonium sulfate dodecahydrate solution or saturated aluminum potassium sulfate dodecahydrate solution) for crystallization, stirring and washing, the stirring and washing temperature is 4-20 DEG C, the stirring time is 0.5-2 h, the solid-liquid ratio is 1 g:(2-10) mL, after filtration, the crystals are washed with the saturated aluminum ammonium sulfate dodecahydrate solution, the obtained filtrate is a lithium-containing solution, and the obtained crystals are low-iron aluminum ammonium sulfate;

[0063] (6) the low-iron aluminum ammonium sulfate crystals are placed in a muffle furnace and heated to 200-300 DEG C and kept for 2 h, the water in the crystals is mainly decomposed in this section, the steam is recycled to the calcined bauxite water leaching process, then the temperature is continuously increased to 1180-1280 DEG C and kept for 2-5 h to obtain alumina, and the smoke is recycled to the evaporation and concentration process.

[0064] The room temperature in the embodiment of the application refers to "25±3 DEG C".

[0065] The technical scheme of the application is further described through the following examples.

[0066] Example 1

[0067] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock (see the flowchart Figure 1 ), specifically comprising the following steps:

[0068] (1) crushing and finely grinding the lithium-rich bauxite waste rock to obtain a lithium-rich bauxite waste rock with a particle size of less than or equal to 74 μm, and the proportion of the lithium-rich bauxite waste rock is 80 wt.%, to obtain a powder;

[0069] (2) leaching and removing iron from the lithium-rich bauxite waste rock powder with a sulfuric acid and oxalic acid solution, the sulfuric acid concentration is 1.5 mol / L, the oxalic acid concentration is 1.5 mol / L, the leaching temperature is 80 DEG C, the leaching time is 2 h, and the solid-liquid ratio is 1 g:3 mL, after filtration, washing and solid-liquid separation, a low-iron filter cake is obtained;

[0070] The removal rate of iron is calculated according to the formula: P=100%-mf×wf / (Wf×Mi).

[0071] In the formula, wf is the iron mass content of the low-iron filter cake, %, mf is the mass of the low-iron filter cake, g, Mi is the weight of the raw ore, g, and Wf is the iron mass content in the raw ore, %.

[0072] The removal rate of iron in this embodiment is 80.12% by calculation.

[0073] (3) The obtained low-iron filter cake is added into 98% concentrated sulfuric acid, the mass ratio of acid to ore is 1.5:1, and then is heated to 180°C in a muffle furnace for 2 hours, and then is continuously heated to 330°C for 3 hours to obtain calcined sand. The calcined sand is water leached at a water leaching temperature of 95°C for 0.5 hours, and the solid-liquid ratio of the calcined sand to water is 1g:2mL. The hot filtration is performed at a filtration temperature of 80-90°C to obtain a filtrate and a filter cake. The filter cake is washed with hot water at a hot water temperature of 80-90°C, and the washing liquid is returned to the next water leaching process;

[0074] The component content in the filtrate and the washing liquid is determined to calculate the leaching rate of lithium and the leaching rate of aluminum.

[0075] The leaching rate calculation formula is: P=(mi×Vi+ni×vi) / (Mi×Wi)×100%;

[0076] In the formula, mi is the metal ion concentration in the filtrate, g / L; Vi is the constant volume of the filtrate, L; ni is the metal ion concentration in the washing liquid, g / L; vi is the constant volume of the filtrate, L; Mi is the weight of the low-iron filter cake used for leaching, g; and Wi is the mass content of the metal in the low-iron filter cake, %.

[0077] The leaching rate of lithium is 98.50% and the leaching rate of aluminum is 70.42% by calculation.

[0078] (4) Ammonium sulfate is added to the filtrate for dissolution and evaporation, the dissolution and evaporation temperature is 90°C, the molar ratio of the added amount of ammonium sulfate to Al ions in the leaching solution is 0.6:1, the Al concentration in the filtrate is about 50g / L, and the evaporation is performed until the Al concentration is about 60g / L. The filtrate is extracted and crystallized through a steel belt crystallizer to obtain crystals containing almost no free water;

[0079] (5) The obtained crystals are stirred and washed with saturated aluminum ammonium sulfate dodecahydrate solution, the stirring and washing temperature is 10°C, the stirring time is 0.5 hours, the solid-liquid ratio is 1g:3mL, and then the crystals are washed with saturated aluminum ammonium sulfate dodecahydrate solution after filtration. The obtained filtrate is a lithium-containing solution, and the obtained crystals are low-iron aluminum ammonium sulfate;

[0080] The lithium recovery rate calculation formula is: P=(m×Vi) / (M×W)×100%;

[0081] In the formula, m is the Li ion concentration in the lithium-containing solution, g / L; Vi is the constant volume of the lithium-containing solution, L; M is the Li concentration of the solution extracted into the steel belt crystallizer, g / L; and W is the volume of the solution extracted into the steel belt crystallizer, L.

[0082] The aluminum removal rate calculation formula is: P=100%-(ma×Va) / (Ma×W)×100%

[0083] In the formula: ma- Al ion concentration in the lithium-containing solution, g / L; Va- the volume of the lithium-containing solution, L; Ma- the Al concentration of the solution drawn into the steel strip crystallizer, g / L; W- the volume of the solution drawn into the steel strip crystallizer, L.

[0084] It is calculated that the recovery rate of lithium in the embodiment is 95.12%, and the removal rate of aluminum is 99.12%.

[0085] (6) The low-iron aluminum ammonium sulfate crystal is placed in a muffle furnace and heated to 250 DEG C and kept for 2h, this section of calcination is mainly for the decomposition of crystal water, and the steam is returned to the calcine water immersion process, and then the temperature is continuously increased to 1200 DEG C and calcined for 2h to obtain alumina, and the smoke is returned to the evaporation concentration process.

[0086] The XRD pattern of the lithium-rich bauxite waste rock in Example 1 of the present application is shown in Figure 2 , and the XRD pattern of the low-iron aluminum ammonium sulfate crystal after calcination is shown in Figure 3 It can be seen that the main mineral composition of the lithium-rich bauxite waste rock is pyrophyllite, diaspore, chlorite, and anatase, and no independent phase of lithium is found; the product after calcination of the low-iron aluminum ammonium sulfate crystal is alpha-Al2O 3。

[0087] Example 2

[0088] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, specifically comprising the following steps:

[0089] (1) The lithium-rich bauxite waste rock is crushed and finely ground to a particle size of 80wt.% of the lithium-rich bauxite waste rock with a particle size of less than 74 microns, to obtain a powder;

[0090] (2) The lithium-rich bauxite waste rock powder is leached with a sulfuric acid and oxalic acid solution to remove iron, the sulfuric acid concentration is 1 mol / L, the oxalic acid concentration is 1 mol / L, the leaching temperature is 80 DEG C, the leaching time is 2h, the solid-liquid ratio of leaching is 1g:3mL, after filtration, washing and solid-liquid separation, a low-iron filter cake is obtained;

[0091] (3) The obtained low-iron filter cake is added into 98% concentrated sulfuric acid, the acid-mineral mass ratio is 1.5:1, and placed into a muffle furnace and heated to 180 DEG C and kept for 2h, and then continuously heated to 330 DEG C and kept for 3h to obtain calcine, the calcine is immersed in water, the water immersion temperature is 95 DEG C, the water immersion time is 0.5h, the solid-liquid ratio of calcine and water is 1g:2mL, and hot filtration is carried out, the filtration temperature is controlled to be 80-90 DEG C, to obtain a filtrate and a filter cake, the filter cake is washed with hot water, the hot water temperature is 80 DEG C-90 DEG C, and the washing liquid is returned to the next round of water immersion process;

[0092] (4) adding ammonium sulfate in the filtrate to dissolve and evaporate, the temperature of dissolving and evaporating is 90℃, the molar ratio of the added ammonium sulfate to Al ions in the leaching solution is 0.6:1, the Al concentration in the filtrate is about 50g / L, and the filtrate is extracted to crystallize through a steel belt crystallizer after evaporating to an Al concentration of about 80g / L, so as to obtain crystals containing almost no free water;

[0093] (5) stirring and washing the saturated aluminum ammonium sulfate dodecahydrate solution for crystallization, the stirring and washing temperature is 10℃, the stirring time is 0.5h, the solid-liquid ratio is 1g:3mL, and after filtration, the crystals are washed with a saturated aluminum ammonium sulfate dodecahydrate solution, so as to obtain a filtrate containing lithium and crystals of low-iron aluminum ammonium sulfate;

[0094] (6) placing the low-iron aluminum ammonium sulfate crystals in a muffle furnace and heating to 250℃, and keeping the temperature for 2h, this section of calcination is mainly for the decomposition of crystal water, and the steam is recycled to the calcined bauxite water leaching process, and then the temperature is continuously increased to 1200℃, and calcination is performed for 2h, so as to obtain alumina, and the smoke is recycled to the evaporation and concentration process.

[0095] Example 3

[0096] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, specifically comprising the following steps:

[0097] (1) crushing and finely grinding the lithium-rich bauxite waste rock to obtain a powder, and the proportion of the lithium-rich bauxite waste rock with a particle size of ≤74μm is 80wt.%;

[0098] (2) leaching and removing iron from the lithium-rich bauxite waste rock powder with hydrochloric acid and oxalic acid solution, the concentration of hydrochloric acid is 1.5mol / L, the concentration of oxalic acid is 1.5mol / L, the leaching temperature is 80℃, the leaching time is 2h, and the solid-liquid ratio is 1g:3mL, and after filtration, washing and solid-liquid separation, a low-iron filter cake is obtained;

[0099] (3) adding the obtained low-iron filter cake into 98% concentrated sulfuric acid, the acid-mineral mass ratio is 1.5:1, placing into a muffle furnace and heating to 180℃ and keeping the temperature for 2h, continuously increasing the temperature to 330℃ and keeping the temperature for 3h, so as to obtain calcined bauxite, water leaching the calcined bauxite, the water leaching temperature is 95℃, the water leaching time is 0.5h, the solid-liquid ratio of the calcined bauxite and water is 1g:2mL, hot filtration is performed, the filtration temperature is controlled to be 80-90℃, so as to obtain a filtrate and a filter cake, hot water washing the filter cake, the hot water temperature is 80-90℃, and the washing liquid is returned to the next round of water leaching process;

[0100] (4) adding ammonium sulfate in the filtrate to dissolve and evaporate, the temperature of dissolving and evaporating is 90℃, the molar ratio of the added ammonium sulfate to Al ions in the leaching solution is 0.6:1, the Al concentration in the filtrate is about 50g / L, and the filtrate is extracted to crystallize through a steel belt crystallizer after evaporating to an Al concentration of about 80g / L, so as to obtain crystals containing almost no free water;

[0101] (5) The low-iron ammonium aluminum sulfate crystals are placed in a muffle furnace and heated to 250°C for 2 hours. This stage of calcination is mainly for the decomposition of crystal water, and the steam is recycled to the calcined bauxite water immersion process. Then the temperature is continuously increased to 1200°C and calcined for 2 hours to obtain alumina. The smoke is recycled to the evaporation and concentration process.

[0102] (6) The low-iron ammonium aluminum sulfate crystals are placed in a muffle furnace and heated to 250°C for 2 hours. This stage of calcination is mainly for the decomposition of crystal water, and the steam is recycled to the calcined bauxite water immersion process. Then the temperature is continuously increased to 1200°C and calcined for 2 hours to obtain alumina. The smoke is recycled to the evaporation and concentration process.

[0103] Example 4

[0104] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, specifically comprising the following steps:

[0105] (1) The lithium-rich bauxite waste rock is crushed and finely ground to a particle size of ≤ 74 μm, and the proportion of lithium-rich bauxite waste rock is 80 wt.%. The powder is obtained.

[0106] (2) The lithium-rich bauxite waste rock powder is leached with hydrochloric acid and oxalic acid solution to remove iron. The concentration of hydrochloric acid is 1 mol / L, the concentration of oxalic acid is 1 mol / L, the leaching temperature is 70°C, the leaching time is 2 hours, and the solid-liquid ratio is 1g:3mL. After filtration and solid-liquid separation, a low-iron filter cake is obtained.

[0107] (3) The obtained low-iron filter cake is added to 98% concentrated sulfuric acid, and the acid-ore mass ratio is 1.5:1. It is placed in a muffle furnace and heated to 180°C for 2 hours. Then the temperature is continuously increased to 330°C and kept for 3 hours to obtain calcined bauxite. The calcined bauxite is immersed in water at a temperature of 95°C for 0.5 hours, and the solid-liquid ratio of the calcined bauxite and water is 1g:2mL. Hot filtration is carried out, and the filtration temperature is controlled at 80-90°C. The filter cake is washed with hot water at a temperature of 80-90°C, and the washing liquid is returned to the next round of water immersion process.

[0108] (4) Ammonium sulfate is added to the filtrate for dissolution and evaporation. The dissolution and evaporation temperature is 90°C, the molar ratio of ammonium sulfate to Al ions in the leaching solution is 0.6:1, and the Al concentration in the filtrate is about 50g / L. Evaporate to an Al concentration of about 60g / L. The filtrate is extracted and crystallized by a steel belt crystallizer to obtain crystals containing almost no free water.

[0109] (5) The low-iron ammonium aluminum sulfate crystals are placed in a muffle furnace and heated to 250°C for 2 hours. This stage of calcination is mainly for the decomposition of crystal water, and the steam is recycled to the calcined bauxite water immersion process. Then the temperature is continuously increased to 1200°C and calcined for 2 hours to obtain alumina. The smoke is recycled to the evaporation and concentration process.

[0110] (6) The low-iron ammonium aluminum sulfate crystal is placed in a muffle furnace and heated to 250°C and kept for 2 hours. This stage of calcination is mainly for the decomposition of crystal water, and the steam is recycled to the calcined ore water leaching process. Then the temperature is continuously increased to 1200°C and kept for 2 hours to obtain alumina. The smoke is recycled to the evaporation and concentration process.

[0111] Example 5

[0112] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, specifically comprising the following steps:

[0113] (1) The lithium-rich bauxite waste rock is crushed and finely ground to obtain a lithium-rich bauxite waste rock with a particle size of ≤74 μm, accounting for 80 wt.%, to obtain a powder;

[0114] (2) The lithium-rich bauxite waste rock powder is leached with a sulfuric acid and oxalic acid solution to remove iron. The sulfuric acid concentration is 1 mol / L, the oxalic acid concentration is 1 mol / L, the leaching temperature is 80°C, the leaching time is 2 hours, and the solid-liquid ratio is 1 g:3 mL. After filtration, washing, and solid-liquid separation, a low-iron filter cake is obtained;

[0115] (3) The obtained low-iron filter cake is added to 98% concentrated sulfuric acid with an acid-ore mass ratio of 1.5:1, and placed in a muffle furnace and heated to 180°C for 2 hours. Then the temperature is continuously increased to 330°C and kept for 3 hours to obtain calcined ore. The calcined ore is leached with water at a temperature of 95°C for 0.5 hours. The solid-liquid ratio of the calcined ore and water is 1 g:2 mL. The filtration temperature is controlled at 80-90°C. The filter cake is washed with hot water at a temperature of 80-90°C. The washing liquid is returned to the next round of water leaching process;

[0116] (4) Potassium sulfate is added to the filtrate to dissolve and evaporate. The dissolution and evaporation temperature is 90°C. The amount of ammonium sulfate added is in a molar ratio of 0.55:1 to the Al ions in the leaching solution. The Al concentration in the filtrate is about 50 g / L. The filtrate is evaporated to an Al concentration of about 60 g / L. The filtrate is extracted and crystallized by a steel belt crystallizer to obtain crystals containing almost no free water;

[0117] (5) The crystals are washed with saturated twelve-water aluminum potassium sulfate solution by stirring at a temperature of 10°C for 0.5 hours with a solid-liquid ratio of 1 g:3 mL. After filtration, the crystals are washed with saturated twelve-water aluminum potassium sulfate solution. The obtained filtrate is a lithium-containing solution, and the obtained crystals are low-iron ammonium aluminum sulfate;

[0118] (6) The low-iron ammonium aluminum sulfate crystal is placed in a muffle furnace and heated to 250°C for 2h, and this section of calcination is mainly for the decomposition of crystal water, and the steam is recycled to the calcine water leaching process. Then it is continuously heated to 1200°C for 2h, and the calcination product is leached with water. The leaching temperature is 80°C, the liquid-solid ratio is 1:2 (g / mL), and the leaching time is 2h. After filtration, the alumina product is obtained, and the filtrate is a potassium sulfate solution. After evaporation and concentration, potassium sulfate is prepared and recycled to the dissolution and evaporation process.

[0119] Example 6

[0120] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, specifically comprising the following steps:

[0121] (1) The lithium-rich bauxite waste rock is crushed and finely ground to a particle size of ≤ 74 μm, and the proportion of lithium-rich bauxite waste rock is 80wt.%. The powder is obtained;

[0122] (2) The lithium-rich bauxite waste rock powder is leached with sulfuric acid and oxalic acid solution to remove iron. The sulfuric acid concentration is 1 mol / L, the oxalic acid concentration is 1 mol / L, the leaching temperature is 80°C, the leaching time is 2h, and the solid-liquid ratio is 1g:3mL. After filtration, washing, and solid-liquid separation, a low-iron filter cake is obtained;

[0123] (3) The obtained low-iron filter cake is added to 98% concentrated sulfuric acid with an acid-rock mass ratio of 1.5:1, and heated to 180°C in a muffle furnace for 2h. Then it is continuously heated to 330°C for 3h to obtain calcine. The calcine is leached with water at a temperature of 95°C for 0.5h. The solid-liquid ratio of calcine to water is 1g:2mL. Hot filtration is performed at a temperature of 80-90°C to obtain a filtrate and a filter cake. The filter cake is washed with hot water at a temperature of 80-90°C. The washing liquid is returned to the next round of water leaching process;

[0124] (4) Ammonium sulfate is added to the filtrate for dissolution and evaporation. The dissolution and evaporation temperature is 90°C. The molar ratio of ammonium sulfate to Al ions in the leaching solution is 0.65:1. The Al concentration in the filtrate is about 35g / L. The filtrate is evaporated to an Al concentration of about 60g / L. The filtrate is extracted and crystallized by a steel belt crystallizer to obtain crystals containing almost no free water;

[0125] (5) The crystals are washed with saturated twelve-water ammonium aluminum sulfate solution by stirring. The stirring and washing temperature is 10°C, the stirring time is 0.5h, and the solid-liquid ratio is 1g:4mL. After filtration, the crystals are washed with saturated twelve-water ammonium aluminum sulfate solution. The obtained filtrate is a lithium-containing solution, and the obtained crystals are low-iron ammonium aluminum sulfate;

[0126] (6) The low-iron aluminum ammonium sulfate crystals are placed in a muffle furnace and heated to 250°C for 2 hours. This calcination mainly decomposes the crystal water, and the steam is recycled to the calcine water leaching process. Then the temperature is continuously increased to 1200°C for 2 hours to obtain alumina. The smoke from this section is recycled to the evaporation and concentration process.

[0127] Example 7

[0128] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, specifically comprising the following steps:

[0129] (1) The lithium-rich bauxite waste rock is crushed and finely ground to obtain a powder with a particle size of ≤ 74 μm, and the proportion of lithium-rich bauxite waste rock is 80 wt.%;

[0130] (2) The lithium-rich bauxite waste rock powder is leached with sulfuric acid and oxalic acid solution to remove iron. The sulfuric acid concentration is 1 mol / L, the oxalic acid concentration is 1 mol / L, the leaching temperature is 75°C, the leaching time is 2 hours, and the solid-liquid ratio is 1g:6mL. After filtration and washing, the low-iron filter cake is obtained;

[0131] (3) The obtained low-iron filter cake is added to 98% concentrated sulfuric acid with an acid-rock mass ratio of 1.5:1, and heated to 180°C in a muffle furnace for 2 hours. Then the temperature is continuously increased to 330°C for 3 hours to obtain calcine. The calcine is leached with water at a temperature of 95°C for 0.5 hours. The solid-liquid ratio of calcine to water is 1g:2mL. The filter is heated to 80-90°C. The filtrate and filter cake are obtained. The filter cake is washed with hot water at a temperature of 80-90°C. The washing liquid is returned to the next water leaching process;

[0132] (4) Ammonium sulfate is added to the filtrate for dissolution and evaporation. The dissolution and evaporation temperature is 90°C. The molar ratio of ammonium sulfate to Al ions in the leaching solution is 0.5:1. The Al concentration in the filtrate is about 60g / L. The filtrate is evaporated to an Al concentration of about 80g / L. The filtrate is extracted and crystallized by a steel belt crystallizer to obtain crystals containing almost no free water;

[0133] (5) The crystals are washed with saturated twelve-water aluminum ammonium sulfate solution by stirring. The stirring temperature is 10°C, the stirring time is 0.5 hours, and the solid-liquid ratio is 1g:4mL. After filtration, the crystals are washed with saturated twelve-water aluminum ammonium sulfate solution. The obtained filtrate is a lithium-containing solution, and the obtained crystals are low-iron aluminum ammonium sulfate;

[0134] (6) The low-iron aluminum ammonium sulfate crystals are placed in a muffle furnace and heated to 250°C for 2 hours. This calcination mainly decomposes the crystal water, and the steam is recycled to the calcine water leaching process. Then the temperature is continuously increased to 1200°C for 2 hours to obtain alumina. The smoke from this section is recycled to the evaporation and concentration process.

[0135] Example 8

[0136] A method for preparing alumina and extracting lithium from lithium-rich bauxite waste rock, specifically comprising the following steps:

[0137] (1) crushing and fine grinding the lithium-rich bauxite waste rock to a particle size of ≤ 74 μm, with the lithium-rich bauxite waste rock accounting for 80 wt.%, to obtain a powder;

[0138] (2) leaching the lithium-rich bauxite waste rock powder with a sulfuric acid and oxalic acid solution to remove iron, with a sulfuric acid concentration of 1 mol / L, an oxalic acid concentration of 1 mol / L, a leaching temperature of 75℃, a leaching time of 2 h, a solid-liquid ratio of 1 g:6 mL, and after filtration, washing, and solid-liquid separation, obtaining a low-iron filter cake;

[0139] (3) adding the obtained low-iron filter cake to 98% concentrated sulfuric acid with an acid-rock mass ratio of 1.5:1, placing it in a muffle furnace and heating to 180℃ for 2 h, and then continuing to heat to 330℃ for 3 h to obtain calcined sand, water leaching the calcined sand at a temperature of 95℃ for 0.5 h, with a solid-liquid ratio of 1 g:2 mL, filtering while hot, controlling the filtering temperature at 80-90℃, to obtain a filtrate and a filter cake, washing the filter cake with hot water at a temperature of 80-90℃, and returning the washing liquid to the next round of water leaching process;

[0140] (4) adding ammonium sulfate to the filtrate to dissolve and evaporate, with a dissolution and evaporation temperature of 90℃, an ammonium sulfate addition amount with an Al ion molar ratio in the leaching solution of 0.5:1, an Al concentration in the filtrate of about 60 g / L, evaporating to an Al concentration of about 80 g / L, and extracting the filtrate through a steel belt crystallization machine to obtain crystals containing almost no free water;

[0141] (5) taking the crystals and washing them with saturated twelve-water aluminum ammonium sulfate solution, with a stirring and washing temperature of 10℃, a stirring time of 0.5 h, and a solid-liquid ratio of 1 g:2 mL, and after filtration, washing the crystals with saturated twelve-water aluminum ammonium sulfate solution, to obtain a filtrate containing lithium and crystals of low-iron aluminum ammonium sulfate;

[0142] (6) placing the low-iron aluminum ammonium sulfate crystals in a muffle furnace and heating to 250℃ for 2 h, with this section of calcination mainly being the decomposition of crystal water, and the steam being recycled to the calcined sand water leaching process, and then continuing to heat to 1250℃ for 2 h to obtain alumina, and the smoke being recycled to the evaporation and concentration process.

[0143] The main component determination results of the low-iron filter cake in each example are shown in Table 2.

[0144] Table 2 Main components of low-iron filter cake (%)

[0145] Example Al2O3 Li2O Fe2O3 1 43.91 0.68 0.70 2 43.21 0.68 0.72 3 43.35 0.69 0.69 4 44.12 0.70 0.73 5 43.21 0.68 0.72 6 43.21 0.68 0.72 7 43.21 0.68 0.72 8 43.21 0.68 0.72

[0146] The main component results of the sulfuric acid maturation water leaching filtrate of the low-iron filter cake in each example are shown in Table 3.

[0147] Table 3 Main components of low-iron filter cake sulfuric acid mature water leaching filtrate / (g / L)

[0148] Example Al Li 1 48.81 0.93 2 49.21 0.94 3 50.12 0.92 4 47.12 0.89 5 50.02 0.94 6 35.14 0.62 7 48.59 0.92 8 49.10 0.91

[0149] The main component results of the lithium-containing solution in each example are shown in Table 4.

[0150] Table 4 Main components of lithium-containing solution / (g / L)

[0151] Example Al Li 1 0.81 1.18 2 0.82 0.94 3 0.90 0.92 4 0.83 0.89 5 0.75 1.12 6 0.91 1.30 7 1.0 1.20 8 1.0 1.52

[0152] According to the method in Example 1, the removal rate of iron, the leaching rate of lithium, the leaching rate of aluminum, the recovery rate of lithium, and the removal rate of aluminum in each example were tested, and the results are shown in Table 5.

[0153] Table 5 Comprehensive recycling results in each example

[0154] Example Removal rate of iron Leaching rate of lithium Leaching rate of aluminum Recovery rate of lithium Removal rate of aluminum 1 80.12% 98.50% 70.42% 95.12% 99.12% 2 78.86% 98.42% 68.58% 95.05% 99.15% 3 82.35% 98.38% 69.14% 94.52% 99.20% 4 78.98% 98.32% 68.35% 95.38% 99.13% 5 79.03% 98.23% 68.88% 95.42% 99.08% 6 79.26% 98.39% 70.08% 95.28% 99.38% 7 80.05% 98.19% 69.15% 95.42% 99.07% 8 79.79% 98.45% 68.56% 94.99% 99.10%

[0155] Comparative Example 1

[0156] The existing process: The mineral composition of the lithium-rich bauxite waste rock is similar to that of clay lithium ore, and the roasting and acid leaching process is usually used. In order to improve the leaching rate of lithium, the roasting temperature of the roasting and acid leaching process is usually 600-900°C. The lithium-rich bauxite waste rock is roasted at 600°C, and leached with 1.5 mol / L sulfuric acid at 90°C for 2h, with a solid-liquid ratio of 1:3 (g / mL). The leaching rate of lithium is 95.48%, the leaching rate of aluminum is 48%, and the leaching rate of iron is 62.15%, which leads to a low aluminum leaching rate, high aluminum recovery cost, and low aluminum recovery rate. The aluminum in the leaching solution is removed together with the iron as impurities, and the cost of impurity removal is high.

[0157] Comparative Example 2

[0158] The same as Example 1, the only difference is that the mixed acid is replaced by sulfuric acid and hydrochloric acid, and the concentration of sulfuric acid and hydrochloric acid is still 1.5 mol / L, and the other conditions are exactly the same. The removal rate of iron is only 38.52%, the leaching rate of lithium is 98.12%, the leaching rate of aluminum is 67.85%, and the removal rate of aluminum is 99.05%. The leaching solution still contains a large amount of iron ions, and the removal effect of iron is poor.

[0159] In summary, compared with the prior art, the process of the present application realizes comprehensive utilization of aluminum and lithium valuable components in bauxite waste rock, the yield of aluminum can reach more than 70%, the yield of lithium can reach 95%, at the same time, efficient separation of aluminum and lithium in sulfuric acid system is realized, the removal rate of aluminum is more than 99%, in addition, through the iron removal process, the removal rate of iron is more than 80%, which greatly reduces the iron impurities into the leaching solution from the source, greatly reduces the impurity removal cost; fully utilize the characteristics of aluminum ammonium sulfate dodecahydrate / aluminum potassium sulfate dodecahydrate rich in crystal water, after crystallization by steel belt crystallization agent, the water evaporation amount can be greatly reduced, energy can be saved; has the advantages of low energy consumption, low extraction cost, simple process, crystallization agent can be recycled, high recovery rate of aluminum and lithium valuable components, easy to industrial application and the like, provides a new way for comprehensive utilization of aluminum and lithium valuable components of lithium-rich bauxite waste rock, low-grade lithium-containing bauxite and clay-type lithium ore.

[0160] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A process for the production of alumina and extraction of lithium from lithium-rich bauxite waste rock characterised in that, The method comprises the following steps: The lithium-rich bauxite waste rock is crushed and ground, mixed with an acid mixture, and stirred to leach iron, and a low-iron filter cake is obtained after solid-liquid separation; concentrated sulfuric acid is added to the low-iron filter cake, roasting and curing are performed, water leaching is performed, and hot filtration is performed to obtain a filtrate; A crystallization agent is added to the filtrate, dissolution and evaporation are performed, a steel belt crystallization machine is used to obtain steel belt crystallization machine crystals, the steel belt crystallization machine crystals are stirred and washed with a saturated solution to remove impurities, and solid-liquid separation is performed to obtain a lithium-containing solution and low-iron aluminum ammonium sulfate; The lithium-containing solution is subjected to impurity removal and lithium precipitation with sodium carbonate to prepare lithium carbonate; The low-iron aluminum ammonium sulfate is calcined to prepare alumina; The acid mixture is an oxalic acid-containing mixture.

2. The process for the preparation of alumina and extraction of lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The proportion of particle size ≤ 74 μm in the lithium-rich bauxite waste rock is 60-85 wt.%.

3. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The acid mixture is a sulfuric acid and oxalic acid mixture or a hydrochloric acid and oxalic acid mixture, and the concentration of the acid mixture is 0.5-5 mol / L.

4. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The leaching temperature for leaching iron is 40-100°C, the leaching time is 0.5-5 h, and the solid-liquid ratio is 1 g:(2-10) mL.

5. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The process of roasting and curing with concentrated sulfuric acid is as follows: the temperature is increased to 160-240°C, the temperature is maintained for 0.5-5 h, the temperature is then increased to 300-350°C, and the temperature is maintained for 1-8 h; the mass ratio of the low-iron filter cake to the concentrated sulfuric acid used for roasting and curing is 0.5:1-3:

1.

6. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The water leaching temperature is 90-100°C, the time is 20-120 min, the solid-liquid ratio is 1 g:(2-3) mL, and the temperature of the hot filtrate is 80-100°C.

7. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The crystallization agent is ammonium sulfate or potassium sulfate, the molar ratio of the amount of the crystallization agent added to Al in the filtrate is 0.5:1-1:2, and the dissolution and evaporation temperature is 90-100°C.

8. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The saturated solution is a saturated aluminum ammonium sulfate dodecahydrate solution or a saturated aluminum potassium sulfate dodecahydrate solution.

9. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The stirring and washing temperature is 4-20°C, the time is 0.5-2 h, and the solid-liquid ratio is 1 g:(2-10) mL.

10. The process for producing alumina and extracting lithium sulfate from lithium-rich bauxite rejects as claimed in claim 1 wherein, The low-iron aluminum ammonium sulfate is calcined in two stages to prepare alumina, and the two-stage calcination comprises the following steps: the temperature is increased to 200-300°C and maintained for 2 h, and then the temperature is increased to 1180-1280°C and maintained for 2-5 h.

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