A method for enriching and separating aluminum, silicon, and titanium from iron-removing red mud oxalic acid leachate

Abstract

This invention proposes a method for enriching and separating aluminum, silicon, and titanium from iron-removed red mud oxalic acid leachate, belonging to the field of valuable element recovery technology in red mud. The method includes the following steps: leaching red mud with oxalic acid to obtain a red mud oxalic acid leachate; irradiating the red mud oxalic acid leachate with sunlight until ferrous oxalate precipitate is completely formed; performing solid-liquid separation to obtain iron-removed red mud oxalic acid leachate; adding a regulator to precipitate the iron-removed red mud oxalic acid leachate; performing solid-liquid separation to obtain a calcium oxalate precipitate containing silicon and titanium, and an aluminum oxalate complex solution; calcining and converting the calcium oxalate precipitate containing silicon and titanium, followed by dilute hydrochloric acid decalcification treatment to obtain a titanium-containing silicon dioxide primary product; and using sodium hydroxide solution to remove impurities and precipitate the aluminum oxalate complex solution to obtain a primary aluminum hydroxide product. This method achieves the separation and recovery of aluminum, silicon, and titanium resources from iron-removed red mud oxalic acid leachate, with a silicon and titanium precipitation rate of over 94%, and can obtain titanium-containing silicon dioxide and aluminum hydroxide primary products.

Description

Technical Field

[0001] This invention belongs to the field of valuable metal recovery technology in red mud, and particularly relates to a method for enriching and separating aluminum, silicon and titanium from iron-removed red mud oxalic acid leachate. Background Technology

[0002] Red mud is a solid waste generated during the alumina industrial production process. It contains valuable elements such as iron, aluminum, titanium, and rare earth elements, and has the potential for comprehensive utilization. Currently available technologies for the extraction, separation, and utilization of valuable elements in red mud rarely achieve comprehensive utilization of multiple elements, are costly to meet, and lead to resource waste. Oxalic acid leaching has been reported as an effective method for dissolving and separating iron minerals. Oxalate ions and iron ions in solution form trioxalatoferrate ([Fe(C2O4)3)). 3- The iron is reduced to ferrous oxalate precipitate through photocatalytic reaction or by adding reducing agents, thus separating the iron from the oxalic acid leachate.

[0003] Several methods for leaching and separating iron from red mud using oxalic acid have been disclosed. For example, Chinese patent (application publication number CN102674643A) proposes a method of treating red mud with oxalic acid solution to obtain an iron-containing oxalic acid solution, which undergoes a photochemical reaction under ultraviolet light or sunlight to form a well-crystallized ferrous oxalate precipitate. Another Chinese patent (authorization publication number CN103922416B) proposes leaching iron from red mud with oxalic acid solution, then reducing the ferrous oxalate complex in the resulting leachate to ferrous oxalate precipitate via membrane electrolysis or the addition of a reducing agent, or directly neutralizing and precipitating a mixture of ferric hydroxide and oxalate to separate the iron from the solution. In the above inventions, the oxalic acid leachate after iron extraction is returned to the red mud leaching process for recycling. To achieve comprehensive extraction and recovery of multiple elements from red mud, Chinese patent (publication number CN114480860B) leaches red mud with oxalic acid solution and separates iron-containing leachate and rare earth-containing leachate residue. Further impurity removal is performed on the rare earth-containing leachate residue to selectively dissolve rare earth elements. Chinese patent (publication number CN112941327B) employs oxalic acid-sodium sulfite complexation selective leaching technology, altering the form of vanadium and iron present in red mud, thereby separating iron-rich leachate residue and vanadium-containing leachate. In general, existing inventions have achieved good selective separation of iron by leaching red mud with oxalic acid, and some have also achieved leaching separation of valuable elements such as rare earths and vanadium. However, in addition to iron, rare earths, and vanadium, red mud also contains valuable elements such as aluminum, silicon, and titanium. How to enrich and separate valuable elements such as aluminum, silicon, and titanium from red mud oxalic acid leachate is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for enriching and separating aluminum, silicon, and titanium from iron-removed red mud oxalic acid leachate. A regulating agent is used to precipitate and recover aluminum, silicon, and titanium elements from the iron-removed red mud oxalic acid leachate within different pH ranges, achieving the technical objective of selectively precipitating silicon and titanium from the iron-removed red mud oxalic acid leachate and preparing primary products of aluminum hydroxide and titanium-containing silicon dioxide.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for enriching and separating aluminum, silicon, and titanium from iron-removed red mud oxalic acid leachate.

[0007] A regulator was added to adjust the pH of the iron-removed red mud oxalic acid leachate to induce precipitation, resulting in a calcium oxalate precipitate containing silicon and titanium, as well as an aluminum oxalate complex solution.

[0008] The silicon and titanium-containing calcium oxalate precipitate was converted by calcination and treated with dilute hydrochloric acid to remove calcium, thus obtaining a primary product of titanium-containing silicon dioxide.

[0009] The aluminum oxalate complex solution was purified and precipitated with sodium hydroxide solution to obtain primary aluminum hydroxide product.

[0010] The regulator is calcium carbonate or calcium oxide.

[0011] Preferably, the method for preparing iron-removing red mud oxalic acid leachate includes the following steps:

[0012] Red mud is leached with oxalic acid to obtain red mud oxalic acid leachate. The red mud oxalic acid leachate is irradiated with sunlight until ferrous oxalate precipitate is completely precipitated. Solid-liquid separation is then performed to obtain red mud oxalic acid leachate with iron removed.

[0013] During the oxalic acid leaching of iron, valuable elements such as aluminum, silicon, and titanium are also dissolved in large quantities in the oxalic acid leachate. To recover these valuable elements, this invention adds a regulator to adjust the solution pH, thereby separating and recovering aluminum, silicon, and titanium from the iron-removed red mud oxalic acid leachate and preparing corresponding primary products. In terms of technical benefits, this invention achieves the separation of multiple elements and alleviates the high cost of oxalic acid leaching to some extent. It enables the separation and recovery of aluminum, silicon, and titanium resources from iron-removed red mud oxalic acid leachates, with silicon and titanium precipitation rates reaching over 94% (precipitation rate 94-99%).

[0014] Preferably, the pH of the iron-removing red mud oxalic acid leachate is adjusted to 4.0-5.0.

[0015] Preferably, the pH values ​​for impurity removal and precipitation of the aluminum oxalate complex solution using sodium hydroxide solution are 6.0 and 10.0, respectively.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] The four elements with the highest concentrations in the iron-removing red mud oxalic acid leachate prepared by this invention are, in descending order: aluminum, silicon, sodium, and titanium. The concentrations of aluminum, silicon, and titanium are 4.2 g / L, 3.2 g / L, and 0.88 g / L, respectively, and can be recovered as valuable components. The pH of the solution is then adjusted with calcium carbonate or calcium oxide to ensure that silicon and titanium are basically completely precipitated, thereby achieving effective separation of silicon, titanium, and aluminum elements in the iron-removing red mud oxalic acid leachate and reducing the oxalate content in the solution. This is beneficial for the subsequent preparation and purification of primary aluminum hydroxide products.

[0018] Aluminum, silicon, and titanium precipitate in solution as pH increases. These elements form precipitates within a certain pH range, and the oxalic acid leachate from iron-removing red mud contains a large amount of oxalate ions, which strongly complex with metal ions in the solution, affecting the pH range for precipitation. Directly increasing the solution pH yields amorphous colloidal precipitates of aluminum hydroxide and silica gel, which mix together during filtration and drying, making effective separation impossible. Currently, there are no reports on the recovery of valuable elements in this system. To address these technical problems, this invention utilizes calcium oxide or calcium carbonate to complex oxalate ions in the iron-removing red mud oxalic acid leachate, forming calcium oxalate which is then separated from the solution, reducing the influence of oxalate ions on metal ion precipitation. Through these steps, aluminum, silicon, and titanium are selectively separated from the solution.

[0019] Based on the efficient separation of iron from red mud by oxalic acid leaching, this invention achieves the effective separation of aluminum, silicon, and titanium in the oxalic acid leaching solution of red mud after iron removal, obtaining a primary product of titanium-containing silica with a purity of over 70% and a primary product of aluminum hydroxide with a purity of over 90%. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a flowchart of the method for enriching and separating aluminum, silicon, and titanium from iron-removed red mud oxalic acid leachate according to the present invention. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] In the embodiments of this invention, the red mud used was sourced from an alumina plant in Guizhou Province, and its main elemental contents were as follows: Al2O3 24.97%, SiO2 18.33%, Fe2O3 16.67%, TiO2 3.90%, CaO 14.45%, Na2O 4.58%, K2O 1.77%, and MgO 1.38%. The red mud was leached with oxalic acid and irradiated with sunlight until ferrous oxalate precipitated completely. The pH of the oxalic acid leachate from the iron-free red mud was 0.82, and the concentrations of aluminum, silicon, and titanium were 4.2 g / L, 3.2 g / L, and 0.88 g / L, respectively.

[0028] Figure 1 This is a flowchart of the method for enriching and separating aluminum, silicon, and titanium from iron-removed red mud oxalic acid leachate according to the present invention.

[0029] The technical solution of the present invention will be further illustrated by the following embodiments.

[0030] Example 1

[0031] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The iron-free red mud oxalic acid leachate was then placed on a magnetic stirrer and stirred at a constant speed. The pH was adjusted to 4.0 with calcium carbonate. The precipitation rate of silicon was 94.9%, and the precipitation rate of titanium was 98.9%. After filtration, a calcium oxalate precipitate containing silicon and titanium, as well as an aluminum oxalate complex solution, were obtained. The obtained aluminum oxalate complex solution was adjusted to pH 6.0 with sodium hydroxide solution to remove impurities. After filtration, the pH was further adjusted to 10.0 to obtain a primary aluminum hydroxide product with a purity greater than 90%. The obtained silicon and titanium-containing calcium oxalate precipitate was calcined and converted, and then treated with dilute hydrochloric acid to remove calcium, to obtain a primary titanium-containing silicon dioxide product (with a SiO2 content of 71% and a titanium dioxide content of 9.4%).

[0032] Example 2

[0033] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The iron-free red mud oxalic acid leachate was then stirred uniformly on a magnetic stirrer. The pH was adjusted to 4.5 with calcium carbonate. The precipitation rate of silicon was 97.9%, and the precipitation rate of titanium was 99.9%. After filtration, a calcium oxalate precipitate containing silicon and titanium, as well as an aluminum oxalate complex solution, were obtained. The obtained aluminum oxalate complex solution was adjusted to pH 6.0 with sodium hydroxide solution to remove impurities. After filtration, the pH was further adjusted to 10.0 to obtain the primary aluminum hydroxide product. The obtained silicon and titanium-containing calcium oxalate precipitate was calcined and converted, and then treated with dilute hydrochloric acid to remove calcium, to obtain the primary titanium-containing silicon dioxide product.

[0034] Example 3

[0035] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The iron-free red mud oxalic acid leachate was then placed on a magnetic stirrer and stirred at a constant speed. The pH was adjusted to 5.0 with calcium carbonate. The precipitation rate of silicon was 99.1%, and the precipitation rate of titanium was 99.7%. After filtration, a calcium oxalate precipitate containing silicon and titanium, as well as an aluminum oxalate complex solution, were obtained. The obtained aluminum oxalate complex solution was adjusted to pH 6.0 with sodium hydroxide solution to remove impurities. After filtration, the pH was further adjusted to 10.0 to obtain the primary aluminum hydroxide product. The obtained silicon and titanium-containing calcium oxalate precipitate was calcined and converted, and then treated with dilute hydrochloric acid to remove calcium, to obtain the primary titanium-containing silicon dioxide product.

[0036] Example 4

[0037] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The iron-free red mud oxalic acid leachate was then placed on a magnetic stirrer and stirred at a constant speed. The pH was adjusted to 4.0 with calcium oxide. The precipitation rate of silicon was 96.7%, and the precipitation rate of titanium was 99.3%. After filtration, a calcium oxalate precipitate containing silicon and titanium, as well as an aluminum oxalate complex solution, were obtained. The obtained aluminum oxalate complex solution was adjusted to pH 6.0 with sodium hydroxide solution to remove impurities. After filtration, the pH was further adjusted to 10.0 to obtain the primary aluminum hydroxide product. The obtained silicon and titanium-containing calcium oxalate precipitate was calcined and converted, and then treated with dilute hydrochloric acid to remove calcium, to obtain the primary titanium-containing silicon dioxide product.

[0038] Example 5

[0039] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The iron-free red mud oxalic acid leachate was then placed on a magnetic stirrer and stirred at a constant speed. The pH was adjusted to 4.5 with calcium oxide. The precipitation rate of silicon was 98.3%, and the precipitation rate of titanium was 99.9%. After filtration, a calcium oxalate precipitate containing silicon and titanium, as well as an aluminum oxalate complex solution, were obtained. The obtained aluminum oxalate complex solution was adjusted to pH 6.0 with sodium hydroxide solution to remove impurities. After filtration, the pH was further adjusted to 10.0 to obtain the primary aluminum hydroxide product. The obtained silicon and titanium-containing calcium oxalate precipitate was calcined and converted, and then treated with dilute hydrochloric acid to remove calcium, to obtain the primary titanium-containing silicon dioxide product.

[0040] Example 6

[0041] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The iron-free red mud oxalic acid leachate was then placed on a magnetic stirrer and stirred at a constant speed. The pH was adjusted to 5.0 with calcium oxide. The precipitation rate of silicon was 99.4%, and the precipitation rate of titanium was 99.9%. After filtration, a calcium oxalate precipitate containing silicon and titanium, as well as an aluminum oxalate complex solution, were obtained. The obtained aluminum oxalate complex solution was adjusted to pH 6.0 with sodium hydroxide solution to remove impurities. After filtration, the pH was further adjusted to 10.0 to obtain the primary aluminum hydroxide product. The obtained silicon and titanium-containing calcium oxalate precipitate was calcined and converted, and then treated with dilute hydrochloric acid to remove calcium, to obtain the primary titanium-containing silicon dioxide product.

[0042] If the calcium carbonate / calcium oxide proposed in this invention is not used as a pH adjuster, but instead sodium hydroxide solution is used to directly raise the pH of the red mud oxalic acid leachate to precipitate aluminum, silicon, and titanium, the comparative effects are as follows:

[0043] Comparative Example 1

[0044] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The obtained iron-free red mud oxalic acid leachate was placed on a magnetic stirrer and stirred at a constant speed. The pH was adjusted to 5.0 with sodium hydroxide solution (the pH adjustment endpoint for this comparative example corresponds to Example 3). The precipitation rate of silicon was 0.2%, and the precipitation rate of titanium was 12.3%. At this point, silicon and titanium elements in the solution had not yet precipitated.

[0045] Comparative Example 2 (Based on Comparative Example 1, the pH of the solution was further increased for comparison)

[0046] After drying and grinding the red mud, it was passed through a 200-mesh sieve. 30g of red mud was weighed and added to 450mL of 1mol / L oxalic acid solution. The mixture was placed in a constant-temperature water bath shaker and reacted (at 80℃ for 2 hours) to obtain a red mud oxalic acid leachate. After filtration, the leachate was exposed to sunlight for 3 days until ferrous oxalate precipitate was completely formed. Solid-liquid separation was then performed to obtain an iron-free red mud oxalic acid leachate with a pH of 0.82 and concentrations of aluminum, silicon, and titanium of 4.2g / L, 3.2g / L, and 0.88g / L, respectively. The obtained iron-free red mud oxalic acid leachate was placed on a magnetic stirrer and stirred at a constant speed. The pH was adjusted to 8.0 with sodium hydroxide solution. The precipitation rate of silicon was 99.8%, and the precipitation rate of titanium was 96.1% (the silicon and titanium precipitation rates in this comparative example are close to those in Example 3). At this point, the silicon and titanium elements in the solution precipitated, requiring the pH to be raised to 8.0, necessitating a large amount of sodium hydroxide solution.

[0047] As can be seen from the above comparative examples, although sodium hydroxide can also precipitate silicon and titanium elements in the red mud oxalic acid leachate for iron removal, aluminum, silicon, and titanium elements do not precipitate when the pH of the leachate is low. A larger amount of sodium hydroxide is needed to raise the pH of the leachate, resulting in a higher pH value for precipitation. Moreover, it does not have the beneficial effect proposed in this invention, namely, the precipitation rate of silicon and titanium obtained by adjusting the pH endpoint with calcium carbonate / calcium oxide between 4.0 and 5.0 is above 94%.

[0048] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for enriching and separating aluminum, silicon, and titanium from iron-removed red mud oxalic acid leachate, characterized in that, Add a regulator to adjust the pH of the iron-removed red mud oxalic acid leachate to 4.0-5.0 to induce precipitation, and obtain calcium oxalate precipitate containing silicon and titanium and aluminum oxalate complex solution; The silicon and titanium-containing calcium oxalate precipitate was converted by calcination and treated with dilute hydrochloric acid to remove calcium, thus obtaining a primary product of titanium-containing silicon dioxide. The aluminum oxalate complex solution was purified and precipitated with sodium hydroxide solution to obtain primary aluminum hydroxide product. The regulator is calcium carbonate or calcium oxide; The pH values ​​for impurity removal and precipitation of the aluminum oxalate complex solution using sodium hydroxide solution were 6.0 and 10.0, respectively.

2. The method for enriching and separating aluminum, silicon, and titanium from iron-removed red mud oxalic acid leachate according to claim 1, characterized in that, The method for preparing iron-removing red mud oxalic acid leachate includes the following steps: Red mud is leached with oxalic acid to obtain red mud oxalic acid leachate. The red mud oxalic acid leachate is irradiated with sunlight until ferrous oxalate precipitate is completely precipitated. Solid-liquid separation is then performed to obtain red mud oxalic acid leachate with iron removed.

Images