A method for recovering ferrotitanium from ferrous yellow produced as a byproduct of titanium dioxide

Abstract

The present invention relates to a method for recovering ferrotitanium from yellow ferrous iron, a byproduct of titanium dioxide, comprising the following steps: 1) mixing yellow ferrous iron, a byproduct of titanium dioxide produced by sulfuric acid process, with an alkaline substance for pulping, controlling the neutralization pH value to be between 2.8 and 4.1, and performing solid-liquid separation to obtain a precipitate and a filtrate; 2) dissolving the precipitate obtained in step 1) with sulfuric acid to obtain a mixed solution, and returning the mixed solution to a hydrolysis process or an acidolysis process in a titanium dioxide process produced by sulfuric acid process. The present invention can recover ferrotitanium-sulfur resources in yellow ferrous iron, a byproduct of titanium dioxide, reduce environmental hazards, and a titanium-containing solution can be returned to titanium dioxide production for hydrolysis or acidolysis, thereby increasing the titanium yield of the system by about 1%, and the purity of the byproduct ferrous sulfate solution is relatively high, which can increase the application of ferrous sulfate.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium dioxide preparation, and particularly relates to a method for recovering ferrotitanium from ferrous yellow, a byproduct of titanium dioxide. Background Art

[0002] The treatment method of the waste titanium dioxide acid generated in the production process of titanium dioxide by sulfuric acid is to use compounding or concentration for reuse, increase the sulfuric acid concentration in the waste titanium dioxide acid by ≥50%, and return the concentrated acid to the system. 2 , after concentration, the acid-soluble TiO 2 All of it will be precipitated into ferrous yellow, reducing the titanium yield and the quality of ferrous products. At the same time, the sulfuric acid concentration in the titanium dioxide byproduct ferrous yellow is about 14%, and the storage or transportation is corrosive to the site and facilities. The titanium dioxide byproduct ferrous yellow is mainly used for calcination to produce sulfuric acid. The current amount is small and the treatment method is single. The storage of a large amount of ferrous yellow causes a waste of sulfur, iron and titanium resources and environmental hazards. Summary of the invention

[0003] In view of the above-mentioned defects in the prior art, the present invention provides a method for recovering ferrotitanium from ferrous yellow produced as a byproduct of titanium dioxide, and the specific scheme is:

[0004] A method for recovering ferrotitanium from ferrous yellow produced as a byproduct of titanium dioxide comprises the following steps:

[0005] 1) mixing ferrous yellow, a by-product of titanium dioxide produced by the sulfuric acid process, with an alkaline substance and beating the mixture, controlling the neutralization pH value to be between 2.8 and 4.1, and performing solid-liquid separation to obtain a precipitate and a filtrate;

[0006] 2) The precipitate is dissolved with sulfuric acid and returned to the hydrolysis step or acid hydrolysis step in the sulfuric acid process of titanium dioxide.

[0007] In the present invention, the alkaline substance can be selected from hydroxides or carbonates of potassium, calcium, and sodium. When the pH is greater than 2.8, the titanium in the ferrous iron combines with the hydroxide to form a precipitate of titanium hydroxide. When the pH is less than 4.1, the iron in the slurry still exists in the solution in the form of sulfate and no precipitation is generated.

[0008] After the precipitate is dissolved with sulfuric acid, it returns to the acid hydrolysis process to achieve the recovery of titanium resources.

[0009] Preferably, in step 2), the acidity coefficient of the precipitate after sulfuric acid is added is 2.5-3.5. The precipitate can be completely dissolved by sulfuric acid with an acidity coefficient of 3-3.5 to form a solution with titanyl sulfate and sulfuric acid as the main components, and its acidity coefficient F value is 1.5-2.2. At this time, the solution can be returned to the titanium dioxide production for hydrolysis or acid hydrolysis, increasing the titanium yield of the system by about 1%, or it can be directly hydrolyzed to prepare titanium derivatives, increasing the utilization of waste by-products.

[0010] In this range, it is further preferred that the acidity coefficient after adding sulfuric acid is ≥3.2 and the F value is ≥1.9. At this time, the secondary filtrate has good stability, titanic acid is not separated, and titanium does not precipitate again, and is stably present in the acid solution in the form of solute.

[0011] Preferably, the filtrate is used to prepare battery-grade ferrous sulfate heptahydrate or to prepare polyferric sulfate. The filtrate treated by this method has a very low titanium content and can be directly used to prepare polyferric sulfate or to prepare battery-grade ferrous sulfate heptahydrate.

[0012] Preferably, the alkaline substance is calcium hydroxide.

[0013] Preferably, in step 1), fluorine-containing wastewater is added during mixing and beating; in step 2), a precipitant containing phosphate is added to the filtrate to form a calcium fluorophosphate precipitate, and solid-liquid separation is performed after flocculation to obtain a secondary filtrate, which is then used to prepare ferrous sulfate heptahydrate or polyferric sulfate. By forming a calcium fluorophosphate precipitate, the purity of the obtained ferrous sulfate solution can be further improved, and the treatment of fluorine-containing wastewater can be achieved at the same time.

[0014] The present invention can recycle titanium iron and sulfur resources in the titanium dioxide by-product yellow ferrous iron, thereby reducing environmental hazards. The titanium-containing solution can be returned to the titanium dioxide production for hydrolysis or acid hydrolysis, thereby increasing the titanium yield of the system by about 1%. The by-product ferrous sulfate solution has a high purity, thereby increasing the application of ferrous sulfate. DETAILED DESCRIPTION

[0015] The present invention is described in detail below in conjunction with the specific embodiments of the present invention. The description herein is only used to explain the present invention, but is not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work, any modifications, equivalent substitutions, improvements, etc., should be included in the protection scope of the present invention.

[0016] Example

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0018] Embodiment 1:

[0019] 100g of ferrous iron and 31.04g of calcium hydroxide were mixed and slurried, and clean water was used for slurrying, and the pH value of the slurry was 2.8. The slurry was filtered to separate the precipitate and the filtrate, and the precipitate was dissolved with sulfuric acid with an acidity coefficient of 2.5 to obtain a mixed solution.

[0020] Embodiment 2:

[0021] 100g of ferrous iron and 40.21g of calcium hydroxide were mixed and slurried, and clean water was used for slurrying, and the pH value of the slurry was 3.5. The slurry was filtered to separate the precipitate and the filtrate, and the precipitate was dissolved with sulfuric acid with an acidity coefficient of 3.2 to obtain a mixed solution.

[0022] Embodiment 3:

[0023] 100g of ferrous iron and 46.25g of calcium hydroxide were mixed and slurried, and clean water was used for slurrying, and the pH value of the slurry was 4.1. The slurry was filtered to separate the precipitate and the filtrate, and the precipitate was dissolved with sulfuric acid with an acidity coefficient of 3.5 to obtain a mixed solution.

[0024] Embodiment 4:

[0025] 100g of ferrous iron and 30g of calcium hydroxide were mixed and slurried, and the fluorine-containing wastewater generated after washing with a metatitanic acid filter cloth had a slurry pH of 2.4. The slurry was filtered to separate the precipitate and the filtrate, and the precipitate was dissolved with sulfuric acid with an acidity coefficient of 3.2 to obtain a mixed solution. Diammonium hydrogen phosphate was added to the filtrate to form a calcium fluorophosphate precipitate, and a small amount of flocculant was added for filter pressing to obtain a secondary filtrate.

[0026] Comparative Example 1:

[0027] 100g of yellow iron and 30g of calcium hydroxide were mixed and slurried, and clean water was used for slurrying, and the pH value of the slurry was 2.4. The slurry was filtered to separate the precipitate and the filtrate, and the precipitate was dissolved with sulfuric acid with an acidity coefficient of 3.2 to obtain a mixed solution.

[0028] Comparative Example 2:

[0029] 100g of ferrous iron and 50g of calcium hydroxide were mixed and slurried, and clean water was used for slurrying, and the pH value of the slurry was 4.5. The slurry was filtered to separate the precipitate and the filtrate, and the precipitate was dissolved with sulfuric acid with an acidity coefficient of 3.2 to obtain a mixed solution.

[0030] The filtrate or secondary filtrate obtained in Example 1-4 and Comparative Example 1-2 was tested for titanium and calcium content, and the mixed solution was tested for titanium and iron content. The comparison results are as follows:

[0031]

[0032]

[0033] It can be seen that the control of pH value during mixed pulping has a great influence on the recovery effect of titanium. The mixed solution recovered in Comparative Example 2 has a high content of trivalent iron and is not suitable for reuse in acid hydrolysis or hydrolysis. Using fluorine-containing wastewater for pulping and adding phosphorus to form calcium fluorophosphate precipitation can reduce the calcium content in the secondary filtrate and further improve the purity of the ferrous sulfate product.

Claims

1. A method for recovering ferrotitanium from ferrous yellow produced as a byproduct of titanium dioxide. It is characterized in that The following steps are involved: 1) mixing yellow ferrous iron, a by-product of titanium dioxide produced by the sulfuric acid process, with an alkaline substance and beating the mixture, controlling the neutralization pH value to be between 2.8 and 4.1, and performing solid-liquid separation to obtain a precipitate and a filtrate; 2) The precipitate obtained in step 1) is dissolved with sulfuric acid to obtain a mixed solution, and the mixed solution is returned to the hydrolysis step or the acid hydrolysis step in the sulfuric acid process for titanium dioxide; The alkaline substance is calcium hydroxide; in step 1), fluorine-containing wastewater is added during mixing and pulping; in step 1), a precipitant containing phosphate is added to the filtrate to form calcium fluorophosphate precipitation, and solid-liquid separation is performed after flocculation to obtain a secondary filtrate, which is then used to prepare ferrous sulfate heptahydrate or polyferric sulfate.

2. The method for recovering ferrotitanium from ferrous yellow produced as a byproduct of titanium dioxide according to claim 1, Features: In step 2), the acidity coefficient of sulfuric acid is 2.5-3.5.

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