Preparation technology of high purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method

Abstract

The invention discloses a preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method, and belongs to the technical field of ferrous sulfate impurity removal. The invention comprises the following steps: 1) reacting excess iron sheet with sulfuric acid solution, adjusting the pH value of the solution to 4 after the reaction, precipitating impurity elements with a hydrolysis pH value lower than 4, filtering, and separating to obtain a ferrous sulfate solution after preliminary impurity removal; 2) adding iron sheet to the ferrous sulfate solution after preliminary impurity removal, maintaining the pH value of the solution to 4, heating the solution to a temperature of 60°C and keeping it warm, and precipitating ferrous sulfate crystals. The method of the invention does not introduce new impurities, has a simple preparation process, and is low in cost; the method of the invention improves the purity of ferrous sulfate by adjusting the pH value of the solution twice, the pH value of the solution is adjusted to 4 for the first time, and the impurity elements with a hydrolysis pH value lower than 4 are precipitated; the pH value of the solution is adjusted to 4 for the second time and assisted by a heat preservation operation, so that ferrous sulfate is efficiently extracted.

Description

Technical Field

[0001] The invention belongs to the technical field of ferrous sulfate impurity removal and relates to a preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method. Background Art

[0002] At present, high-purity ferrous sulfate is mainly produced by reacting reduced iron powder with sulfuric acid, but this method has high requirements on the quality of reduced iron powder on the one hand, and the price of reduced iron powder is high on the other hand, and the production cost is high. Considering the comprehensive production cost, the by-product ferrous sulfate can be prepared in the production process of titanium dioxide by sulfuric acid method, but due to the high impurity content of titanium dioxide by-product ferrous sulfate, it needs to be purified. If impurity removers are used in the purification process, there will be the problem of introducing new impurity elements. Summary of the invention

[0003] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0005] The preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method comprises the following steps:

[0006] 1) reacting excess iron scale with sulfuric acid solution, adjusting the solution pH to 4 after the reaction, hydrolyzing impurity elements with a pH value lower than 4 to precipitate, filtering, and separating to obtain a preliminarily impurity-free ferrous sulfate solution; the concentration of the sulfuric acid solution is 40-60wt.%;

[0007] 2) adding iron scale to the ferrous sulfate solution obtained in step 1) after preliminary impurity removal, maintaining the pH value of the solution at 4, heating the solution to 60° C. and keeping the temperature, and precipitating ferrous sulfate crystals.

[0008] Furthermore, in step 1), the concentration of the sulfuric acid solution is 50-60 wt.%.

[0009] Furthermore, in step 1), the pH value of the solution is adjusted by adjusting the amount of iron sheet.

[0010] Furthermore, in step 2), the temperature is kept at 2-3 hours.

[0011] Furthermore, in step 2), the impurity removal rate of ferrous sulfate crystals is not less than 99%.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) The method of the present invention does not introduce new impurities, the preparation process is simple, and the cost is low;

[0014] (2) The method of the present invention improves the purity of ferrous sulfate by adjusting the pH value of the solution twice. The pH value of the solution is adjusted to 4 for the first time to precipitate impurity elements with a hydrolysis pH value lower than 4; the pH value of the solution is adjusted to 4 for the second time and a heat preservation operation is performed to extract the ferrous sulfate, and further remove other impurities except the ferrous sulfate, thereby purifying the ferrous sulfate produced as a byproduct of titanium dioxide, and providing a data reference for industrial application. DETAILED DESCRIPTION

[0015] The present invention is further described below in conjunction with specific embodiments. These embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit and substance of the present invention, the modification or replacement of the inventive method, step or condition, all belong to the scope of the present invention. In the following examples, if there is no special explanation, the technical means used in the examples are conventional means well known to those skilled in the art.

[0016] The ferrous sulfate heptahydrate in the following examples is derived from Jiangsu Yuxing Technology Co., Ltd.

[0017] Example 1

[0018] The preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method comprises the following steps:

[0019] 1) reacting excess iron scale with sulfuric acid solution, the concentration of the sulfuric acid solution is 50wt.%, after the reaction, adjusting the pH value of the solution to 4 by adjusting the amount of iron scale, on the one hand, without introducing new impurity elements, the impurity elements with a hydrolysis pH value lower than 4 (such as Ti) are precipitated, on the other hand, Fe is used as a reducing agent, and S is produced in the process of the sulfuric acid reaction. 2- , and Co 2+ 、Ni 2+ 、Zn 2+ The insoluble matter is formed, filtered, and separated to obtain the ferrous sulfate solution after preliminary impurity removal;

[0020] 2) To avoid the Fe in the ferrous sulfate solution after preliminary impurity removal 2+ Oxidized to generate Fe(OH)3 precipitation, add iron scale to the ferrous sulfate solution after preliminary impurity removal, keep the solution pH value at 4, heat the solution to 60℃ and keep it warm for 2h, precipitate ferrous sulfate crystals, and reversely remove impurity elements with a hydrolysis pH value higher than 4 (such as Mn 2+ Mg 2+ ).

[0021] Comparative Example 1

[0022] The preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method comprises the following steps:

[0023] 1) reacting excess iron sheet with a sulfuric acid solution, wherein the concentration of the sulfuric acid solution is 50wt.%, and after the reaction is completed, adjusting the pH value of the solution to 2 by adjusting the amount of iron sheet, precipitating impurity elements with a hydrolysis pH value lower than 2, filtering, and separating to obtain a preliminarily impurity-free ferrous sulfate solution;

[0024] 2) Add iron scale to the ferrous sulfate solution after preliminary impurity removal, maintain the pH value of the solution at 2, heat the solution to 60°C and keep it warm for 2 hours to precipitate ferrous sulfate crystals.

[0025] Comparative Example 2

[0026] The preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method comprises the following steps:

[0027] 1) reacting excess iron sheet with a sulfuric acid solution, wherein the concentration of the sulfuric acid solution is 50wt.%, and after the reaction is completed, adjusting the pH value of the solution to 8 by adjusting the amount of iron sheet, precipitating impurity elements with a hydrolysis pH value lower than 8, filtering, and separating to obtain a preliminarily impurity-free ferrous sulfate solution;

[0028] 2) Add iron scale to the ferrous sulfate solution after preliminary impurity removal, maintain the pH value of the solution at 8, heat the solution to 60°C and keep it warm for 2 hours to precipitate ferrous sulfate crystals.

[0029] Comparative Example 3

[0030] The preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method comprises the following steps:

[0031] 1) reacting excess iron sheet with a sulfuric acid solution, wherein the concentration of the sulfuric acid solution is 30 wt.%, and after the reaction is completed, adjusting the pH value of the solution to 4 by adjusting the amount of iron sheet, precipitating impurity elements with a hydrolysis pH value lower than 4, filtering, and separating to obtain a preliminarily impurity-free ferrous sulfate solution;

[0032] 2) Add iron scale to the ferrous sulfate solution after preliminary impurity removal, maintain the pH value of the solution at 4, heat the solution to 60°C and keep it warm for 2 hours to precipitate ferrous sulfate crystals.

[0033] Comparative Example 4

[0034] The preparation process of high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method comprises the following steps:

[0035] Excess iron sheet is reacted with sulfuric acid solution, the concentration of the sulfuric acid solution is 50wt.%, and after the reaction is completed, the pH value of the solution is adjusted to 4 by adjusting the amount of iron sheet, and the impurity elements with a hydrolysis pH value lower than 4 are precipitated, filtered, and separated to obtain a ferrous sulfate solution after preliminary impurity removal; the solution is heated to a temperature of 60°C and kept warm for 2h to precipitate ferrous sulfate crystals.

[0036] The impurity content of the ferrous sulfate crystals precipitated in each embodiment is shown in Table 1 below:

[0037] Table 1

[0038] w(Mn)% w(Ni)% w(Zn)% w(Mg)% w(Ti)% Example 1 0.025 0.015 0.010 0.230 0.280 Comparative Example 1 0.029 0.019 0.016 0.252 0.315 Comparative Example 2 0.035 0.023 0.020 0.280 0.350 Comparative Example 3 0.031 0.019 0.017 0.254 0.333 Comparative Example 4 0.054 0.018 0.015 0.370 0.285

Claims

1. A process for preparing high-purity ferrous sulfate in the production process of titanium dioxide by sulfuric acid method, characterized in that: The following steps are involved: 1) reacting excess iron scale with sulfuric acid solution, wherein the concentration of the sulfuric acid solution is 50wt.%, after the reaction is completed, adjusting the pH value of the solution to 4 by adjusting the amount of iron scale, precipitating impurity elements with a hydrolysis pH value lower than 4, filtering, and separating to obtain a preliminarily impurity-free ferrous sulfate solution; 2) adding iron scale to the ferrous sulfate solution obtained in step 1) after preliminary impurity removal, maintaining the pH value of the solution at 4, heating the solution to 60° C. and keeping the temperature for 2 hours, precipitating ferrous sulfate crystals, and removing impurity elements with a hydrolysis pH value higher than 4 in reverse, wherein the impurity mass percentage of the precipitated ferrous sulfate crystals is Mn: 0.025%, Mg: 0.230%, Ti: 0.280%, Ni: 0.015%, and Zn: 0.010%; and the impurity removal rate of the ferrous sulfate crystals is not less than 99%.