A method for strengthening the dissolution and iron separation and recovery of a diaspore type bauxite

Abstract

The present application belongs to the field of metallurgy, and particularly relates to a method for strengthening dissolution of monohydrate bauxite and separation and recovery of iron. The method comprises the following steps: (1) configuring monohydrate bauxite, sodium aluminate circulating mother liquor and an additive into a mixed ore slurry; the additive is chitin biomass or a derivative thereof; (2) heating the mixed ore slurry obtained in step (1) to 190-280 DEG C to perform a dissolution reaction, obtaining a dissolution slurry and a dissolution residue, and separating and recovering the iron concentrate from the dissolution residue by magnetic separation. The method can realize efficient dissolution of bauxite, solve the problem of combination of iron minerals and silicon minerals in high-iron bauxite, and more efficiently and at a lower cost solve the problem of difficult utilization of iron resources in high-iron bauxite.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metallurgy, and particularly relates to a method for strengthening dissolution and iron separation and recovery of monohydrate bauxite. BACKGROUND

[0002] Compared with trihydrate bauxite, monohydrate bauxite needs higher temperature and alkalinity for dissolution. In the process of bauxite dissolution, due to the replacement of aluminum-iron isomorphism, there may be aluminum goethite (Fe 1- x Al x OOH) in the ore, which is difficult to release aluminum elements under the high-temperature (230-260℃) Bayer process dissolution conditions, thereby reducing the dissolution rate of alumina. At the same time, the bauxite generally contains 2-4% of titanium minerals in the form of rutile, anatase and brookite. In the process of Bayer process dissolution of monohydrate bauxite, titanium minerals can significantly reduce the dissolution rate of alumina. Due to the blocking effect of titanium minerals on the dissolution of alumina, lime is generally added in industry to eliminate its harm. However, the addition of lime brings problems such as increased loss of alumina, increased amount of red mud and washing water, and increased carbonate reverse causticization in alumina production. In addition, when producing alumina by the traditional bauxite dissolution method, only single aluminum resources are collected, and high proportion of iron minerals are generally discarded as red mud waste components, which not only causes serious environmental problems, but also causes great waste of iron resources.

[0003] Therefore, if the dissolution of alumina in high-iron monohydrate bauxite can be strengthened without adding lime in the production process of bauxite dissolution, and the dissociation and separation of iron minerals and silicon minerals are carried out at the same time, the iron components can be recovered, which not only can greatly reduce the amount of red mud waste discharged in the production process of alumina, but also can obtain high-grade iron minerals for utilization, which takes into account the environmental and economic benefits. Therefore, it is necessary to improve the existing dissolution method to realize the efficient dissolution of aluminum and the separation and recovery of iron in high-iron monohydrate bauxite.

[0004] Patent CN107201441A discloses a comprehensive utilization method of high-iron bauxite and an additive for high-iron bauxite treatment. The method first mixes fine ground high-iron bauxite with the additive, forms a block, and dries it. Then, the block is reduced by using coal as a reducing agent for reduction roasting. After roasting, the block is crushed, ground, and then the iron component is separated by magnetic separation. This method requires an additional high-temperature roasting process, and the subsequent utilization of aluminum resources needs to be realized through a two-step wet process of acid dissolution and alkali neutralization. The steps are more, the production cost is high, and a large amount of low-value by-products are produced. Patent CN102976375B discloses a high-pressure dissolution method of diaspore-type bauxite. At least one of iron powder and ether cellulose is used as an additive to have a physical and chemical reaction with the surface of titanium minerals, thereby reducing the concentration of titanium acid ions in the solution and eliminating the blocking effect of titanium minerals on the dissolution of aluminum oxide. This patent mainly promotes the dissolution of aluminum oxide and does not involve promoting the dissociation and separation of iron minerals and silicon minerals. Patent CN102976377B discloses a dissolution method of diaspore-type bauxite. During the dissolution of bauxite, a mixture of one or more of alcohol, sugar, aldehyde, alkane, activated carbon, graphite, coal, coal tar, and wheat bran is used as an additive instead of traditional lime to solve the hindering of titanium minerals on the dissolution of bauxite, and to magnetically transform iron minerals. This method also does not pay attention to the influence of silicon mineral impurities on the recovery of iron components. The mass percentage of total iron (TFe) in the obtained iron concentrate (56.30% to 62.12%) and the recovery rate of iron in bauxite (37.82% to 50.26%) are not high. Patent CN117208946A discloses a dissolution and iron recovery method of high-iron diaspore-type bauxite. A mixture of one or more of organic bases, carboxylic acids, and amino acids is used as an additive to enrich and remove silicon impurities from iron minerals during the dissolution of bauxite, and to convert them into easily separable magnetic iron minerals. The selected additives have strong volatility characteristics or high cost, and proper storage needs to be considered in industrial applications.

[0005] Therefore, there is an urgent need to develop a method for the dissolution and iron separation and recovery of diaspore-type bauxite, which has simple process, low production cost, low equipment demand, cheap and easily available additives, and good industrialization prospect. SUMMARY

[0006] In view of the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a method for strengthening the dissolution and iron separation and recovery of diaspore-type bauxite. The method can realize efficient dissolution of bauxite and solve the problem of combination of iron minerals and silicon minerals in high-iron bauxite, and more efficiently and cost-effectively solve the problem of iron resource utilization in high-iron bauxite.

[0007] The purpose of the present application is achieved by the following technical solutions:

[0008] A method for enhancing the leaching and iron separation and recovery of monohydrate gibbsite bauxite includes the following steps:

[0009] (1) A mixed slurry is prepared by combining monohydrate gibbsite bauxite, sodium aluminate circulating mother liquor and additives; the additives are chitin-based biomass or its derivatives.

[0010] (2) The mixed slurry obtained in step (1) is heated to 190-280℃ for leaching reaction to obtain leaching slurry and leaching residue. The leaching residue is then separated and recovered by magnetic separation to obtain iron concentrate.

[0011] Further, the boehmite-type bauxite mentioned in step (1) refers to high-iron boehmite-type bauxite whose main component is boehmite and whose iron mineral content is >15% (in the form of Fe2O3 by mass percentage). It includes gibbsite-type bauxite or boehmite-type bauxite.

[0012] Furthermore, the Na2O in the sodium aluminate circulating mother liquor described in step (1) k The concentration is 160–280 g / L, and the Al2O3 concentration is 75–140 g / L.

[0013] Furthermore, the mass ratio of the added monohydrate gibbsite to the mass-volume ratio of the sodium aluminate circulating mother liquor in step (1) is 130–360 g / L.

[0014] Further, the mass ratio of the additive added in step (1) to the mass-volume ratio of the circulating mother liquor is 0.5 to 50 g / L.

[0015] Further, the chitinous biomass mentioned in step (1) includes at least one of shrimp shells and crab shells; the derivatives include at least one of chitin and chitosan.

[0016] The present invention has verified that the additives described in step (1) can promote better dissolution of alumina in bauxite, and at the same time have good interface regulation function and reducing properties. They can significantly promote the reduction reaction of iron minerals in the ore to generate magnetic magnetite or elemental iron, and promote the dispersion and dissociation of iron minerals and silicon mineral impurities in high-iron gibbsite type bauxite, thereby improving the iron recovery rate of bauxite and reducing the silicon impurity content in the iron concentrate obtained by magnetic separation of bauxite leaching slag.

[0017] Furthermore, the dissolution reaction time in step (2) is 30 to 90 minutes, preferably 80 minutes.

[0018] Further, the leaching slurry described in step (2) is diluted and then subjected to fine filtration. Seed crystals are added to the filtrate to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide. Solid-liquid separation is performed, and the obtained aluminum hydroxide solid is calcined to obtain alumina product. The liquid is returned to the leaching process for continued use.

[0019] The principle of the present application is that by adding a reducing additive with the function of adjusting the surface interface properties, the iron minerals in the bauxite ore are reduced to generate magnetite or iron element with magnetism during the bauxite dissolution process, and the surface properties of the iron minerals are adjusted to make the closely connected silicon mineral impurities dispersed and dissociated, so that the iron minerals can be separated and enriched by simple magnetic separation. At the same time, the reducing additive has a physical and chemical effect on the surface of titanium minerals, reducing the concentration of titanium acid root ions in the solution, thereby eliminating the blocking effect of titanium minerals on the dissolution of alumina.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] (1) Compared with the traditional dissolution method by adding lime, the additive amount of the present application is low, the dissolution efficiency of alumina is improved, the amount of discharged red mud is greatly reduced, and the environmental protection advantage is significant, and the full use of aluminum resources is realized; the enrichment and removal of silicon impurities of iron minerals are realized during the bauxite dissolution process, and the iron minerals are converted into magnetic iron minerals which are easy to separate, greatly improving the recovery efficiency of iron resources.

[0022] (2) The present application uses chitin biomass or its derivative additive to reduce iron minerals, which expands the use range of chitin biomass, and compared with other reducing biomass additives, it can better strengthen the dissolution of alumina and the enrichment and removal of silicon impurities of iron minerals, thereby achieving better dissolution and separation recovery efficiency.

[0023] (3) The additive selected by the present method is safe, non-toxic, stable in nature, easy to store, cheap and easy to obtain, does not need to add other large equipment in the existing dissolution production process, has low cost, and is simple and easy to implement. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below in combination with examples, but the embodiments of the present application are not limited thereto.

[0025] Example 1

[0026] A high-iron diaspore type bauxite ore (mineral composition: Al2O3 60.60%, Fe2O3 25.61%, SiO2 10.76%) is prepared into a mixed ore slurry with 200 mL of circulating mother liquor and an additive of shrimp shell. Among them, in the circulating mother liquor: Na2O kThe mixed ore slurry was loaded into a steel bomb and placed in a salt bath furnace for leaching reaction at 260°C for 60 min to obtain a leaching slurry and a leaching residue. Under this condition, the leaching residue obtained was subjected to magnetic separation at a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the obtained iron concentrate was 81.51% (total iron mass percentage = iron mass (calculated as Fe2O3) in the iron concentrate / iron concentrate mass x 100%), the silicon impurity (calculated as SiO2) mass percentage was 8.68%, and the iron recovery rate in the bauxite was 71.66% (iron recovery rate = iron mass (calculated as Fe2O3) in the iron concentrate / iron mass in the bauxite x 100%). The relative leaching rate of alumina was 98.53% (relative leaching rate of alumina = (iron-silicon ratio of the bauxite-iron-silicon ratio of the leaching residue) / (iron-silicon ratio of the bauxite-1) x 100%). The leaching slurry was diluted and subjected to fine filtration treatment, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, after the second solid-liquid separation, aluminum hydroxide solids were obtained, and further calcination obtained alumina products, and the liquid was returned to the leaching process for continuous use. The obtained alumina product meets the GB / T24487-2022 standard.

[0027] Example 2

[0028] A high-iron diaspore type bauxite (mineral composition is the same as that of Example 1), 200 mL of circulating mother liquor and an additive crab shell were prepared into a mixed ore slurry. Among them, in the circulating mother liquor: Na2O k The concentration was 260 g / L, the Al2O3 concentration was 125 g / L, the ratio of the mass of the bauxite added to the volume of the circulating mother liquor was 360 g / L, and the ratio of the mass of the additive added to the volume of the circulating mother liquor was 12.2 g / L; the mixed ore slurry was loaded into a steel bomb and placed in a salt bath furnace for leaching reaction at 270°C for 90 min to obtain a leaching slurry and a leaching residue. Under this condition, the leaching residue obtained was subjected to magnetic separation at a magnetic field strength of 160 kA / m, and the total iron (calculated as Fe2O3) mass percentage of the obtained iron concentrate was 72.28%, the silicon impurity (calculated as SiO2) mass percentage was 8.17%, and the iron recovery rate in the bauxite was 70.18%. The relative leaching rate of alumina was 98.76%. The leaching slurry was diluted and subjected to fine filtration treatment, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide, after the second solid-liquid separation, aluminum hydroxide solids were obtained, and further calcination obtained alumina products, and the liquid was returned to the leaching process for continuous use. The obtained alumina product meets the GB / T24487-2022 standard.

[0029] Example 3

[0030] A high-iron diaspore type bauxite (mineral composition same as Example 1), 200 mL of recycled mother liquor and an additive chitosan were prepared into a mixed ore slurry. In the recycled mother liquor: Na2O k The concentration of the mixed ore slurry was 250 g / L, the concentration of Al2O3 was 125 g / L, the ratio of the mass of bauxite added to the volume of recycled mother liquor was 224 g / L, and the ratio of the mass of additive added to the volume of recycled mother liquor was 22.4 g / L; the mixed ore slurry was loaded into a steel bomb and placed in a salt bath furnace for leaching reaction at 270°C for 80 min to obtain a leaching slurry and a leaching residue. The leaching residue obtained under this condition was subjected to magnetic separation under a magnetic field strength of 160 kA / m, and the mass percentage of total iron (calculated as Fe2O3) in the obtained iron concentrate was 75.37%, the mass percentage of silicon impurities (calculated as SiO2) was 8.68%, and the recovery rate of iron in the bauxite was 69.23%. The relative leaching rate of alumina was 101.32%. The leaching slurry was diluted and subjected to fine filtration treatment, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, after the second solid-liquid separation, aluminum hydroxide solids were obtained, and further calcination obtained an alumina product, and the liquid was returned to the leaching process for continuous use. The obtained alumina product met the GB / T24487-2022 standard.

[0031] Example 4

[0032] A high-iron diaspore type bauxite (mineral composition same as Example 1), 200 mL of recycled mother liquor and an additive chitosan were prepared into a mixed ore slurry. In the recycled mother liquor: Na2O k The concentration of the mixed ore slurry was 250 g / L, the concentration of Al2O3 was 125 g / L, the ratio of the mass of bauxite added to the volume of recycled mother liquor was 224 g / L, and the ratio of the mass of additive added to the volume of recycled mother liquor was 22.4 g / L; the mixed ore slurry was loaded into a steel bomb and placed in a salt bath furnace for leaching reaction at 270°C for 80 min to obtain a leaching slurry and a leaching residue. The leaching residue obtained under this condition was subjected to magnetic separation under a magnetic field strength of 160 kA / m, and the mass percentage of total iron (calculated as Fe2O3) in the obtained iron concentrate was 75.37%, the mass percentage of silicon impurities (calculated as SiO2) was 8.68%, and the recovery rate of iron in the bauxite was 69.23%. The relative leaching rate of alumina was 101.32%. The leaching slurry was diluted and subjected to fine filtration treatment, the obtained filtrate was added with seed crystals to promote the decomposition of sodium aluminate in the solution to form aluminum hydroxide, after the second solid-liquid separation, aluminum hydroxide solids were obtained, and further calcination obtained an alumina product, and the liquid was returned to the leaching process for continuous use. The obtained alumina product met the GB / T24487-2022 standard.

[0033] Comparative Example 1

[0034] This comparative example was the same as Example 1 except that an equal amount of CMC (carboxymethyl cellulose) additive was used instead of shrimp shells.

[0035] The total iron mass percentage of the iron concentrate obtained by dissolution and magnetic separation recovery of the present comparative example is 66.32%, the silicon impurity mass percentage is 11.57%, the iron recovery rate in bauxite is 59.84%, and the relative dissolution rate of alumina is 82.92%.

[0036] Comparative Example 2

[0037] The present comparative example is the same as Example 1 except that an equal amount of wheat bran additive is used to replace the shrimp shells.

[0038] The total iron mass percentage of the iron concentrate obtained by dissolution and magnetic separation recovery of the present comparative example is 68.15%, the silicon impurity mass percentage is 10.39%, the iron recovery rate in bauxite is 61.70%, and the relative dissolution rate of alumina is 87.26%.

[0039] Comparative Example 3

[0040] The present comparative example is the same as Example 1 except that an equal amount of starch additive is used to replace the shrimp shells.

[0041] The total iron mass percentage of the iron concentrate obtained by dissolution and magnetic separation recovery of the present comparative example is 65.48%, the silicon impurity mass percentage is 11.45%, the iron recovery rate in bauxite is 59.55%, and the relative dissolution rate of alumina is 80.46%.

[0042] From the comparison results of the above Comparative Examples 1-3 and the example, it can be seen that the chitin-based biomass or derivative additive used in the present application can better strengthen the dissolution of alumina and the enrichment and removal of silicon impurities from iron minerals compared to conventional reducing biomass additives, thereby achieving better dissolution and separation recovery efficiency.

[0043] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A method for enhancing the leaching and iron separation and recovery of monohydrate gibbsite, characterized in that, Includes the following steps: (1) Prepare a mixed slurry by mixing boehmite, sodium aluminate circulating mother liquor and additives; the additives are at least one of shrimp shells, crab shells, chitin, and chitosan, and the mass-volume ratio of the additives to the sodium aluminate circulating mother liquor is 0.5 to 50 g / L; the mass-volume ratio of the boehmite to the sodium aluminate circulating mother liquor is 130 to 360 g / L. (2) The mixed slurry obtained in step (1) is heated to 190-280℃ for leaching reaction to obtain leaching slurry and leaching residue. The leaching residue is then separated and recovered by magnetic separation to obtain iron concentrate.

2. The method for enhancing the leaching and iron separation and recovery of gibbsite according to claim 1, characterized in that, The boehmite-type bauxite mentioned in step (1) refers to high-iron boehmite-type bauxite whose main component is boehmite and whose iron mineral content is >15%.

3. The method for enhancing the leaching and iron separation and recovery of gibbsite according to claim 1, characterized in that, The Na2O in the sodium aluminate circulating mother liquor mentioned in step (1) k The concentration is 160~280g / L, and the Al2O3 concentration is 75~140g / L.

4. The method for enhancing the leaching and iron separation and recovery of gibbsite according to claim 1, characterized in that, The dissolution reaction time in step (2) is 30~90 min.

5. The method for enhancing the leaching and iron separation and recovery of gibbsite according to claim 1, characterized in that, The leaching slurry described in step (2) is diluted and then finely filtered. Seed crystals are added to the filtrate to promote the decomposition of sodium aluminate in the solution to generate aluminum hydroxide. Solid and liquid are separated, and the resulting aluminum hydroxide solid is calcined to obtain alumina product. The liquid is returned to the leaching process for continued use.