A method for recovering titanium dioxide from titanium dioxide waste acid

Abstract

The present invention relates to a method for recovering titanium dioxide from waste titanium dioxide acid, comprising the following steps: 1) adding 98% concentrated sulfuric acid to the waste acid produced in the sulfuric acid process for titanium dioxide preparation, wherein the temperature is controlled to not exceed 50°C during the acid preparation process; and 2) aging the mixed solution after the acid preparation process, filtering and separating the mixed solution, and returning the filtrate to the acid hydrolysis step in the sulfuric acid process for titanium dioxide preparation. The method of the present invention can simultaneously reuse the waste acid from the titanium dioxide process and recover titanium by controlling the temperature of the acid preparation process. The method is simple and easy to implement. Furthermore, the method can reduce the titanium content in the ferrous iron (II) obtained from the recovered filter cake, thereby improving the purity and quality of the ferrous iron (II) iron (II).

Description

Technical Field

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

[0002] The main industrial production methods for titanium dioxide are the sulfuric acid method and the chlorination method. Currently, my country primarily uses the sulfuric acid method to produce titanium dioxide, and for every ton of titanium dioxide produced, approximately 20% of the waste acid, or approximately 6 tons, is generated. The waste acid produced by the sulfuric acid method is called titanium dioxide waste acid. Its main components are 18-25% sulfuric acid, approximately 5% iron, and approximately 1% titanium. The Longbai Group alone produces 4 million tons of waste acid annually. Because titanium dioxide waste acid contains a large amount of soluble titanium, the titanium dioxide yield in the titanium dioxide production process has always been low. Therefore, recovering titanium dioxide from titanium dioxide waste acid is an effective way to conserve titanium ore resources and protect the ecological environment.

[0003] Currently, the typical disposal methods for waste titanium dioxide acid from sulfuric acid-based titanium dioxide production are: 1. Concentrate the waste titanium dioxide acid to a 55% acid concentration, which is then returned to the titanium dioxide production system for use as a premix for the acid hydrolysis of titanium concentrate. However, this process raises the temperature to over 110°C during the acid mixing process, causing all soluble TiO2 in the concentrated acid to precipitate into the ferrous metal and become unrecoverable; 2. Use it to produce products such as ammonium sulfate; 3. Use it to produce products such as iron-based water purifiers. These treatment methods reduce titanium dioxide yield by approximately 4%, and because titanium dioxide enters other products, it can affect their quality. Summary of the Invention

[0004] In view of the above-mentioned defects in the prior art, the present invention provides a method for recovering titanium dioxide from titanium dioxide waste acid, the specific scheme is:

[0005] A method for recovering titanium dioxide from titanium dioxide waste acid, characterized by comprising the following steps:

[0006] 1) adding 98% concentrated sulfuric acid to the waste acid produced in the sulfuric acid method for preparing titanium dioxide to prepare the acid, and controlling the temperature not to exceed 50° C. during the acid preparation;

[0007] 2) After the acid preparation is completed, the mixture is aged and then filtered and separated, and the filtrate is returned to the acid hydrolysis step in the sulfuric acid method for preparing titanium dioxide.

[0008] The key to the present invention is controlling the temperature during the acid preparation process. During the acid preparation process, the dilution of 98% concentrated sulfuric acid releases heat, causing the system temperature to rise. Titanyl sulfate in the waste acid hydrolyzes at high temperatures to form metatitanic acid precipitates, or precipitates as a complex salt with ferrous sulfate at high temperatures, resulting in titanium loss. Experimental results show that when the temperature is controlled at no more than 50°C during the acid preparation process, the degree of hydrolysis of titanyl sulfate is low, and most of the titanium remains in solution, allowing titanium to be recovered after reuse.

[0009] Since sulfuric acid concentrations of 55-65% can be used for acidolysis, the sulfuric acid concentration after acid preparation in this method can be controlled within the range of 55-65% according to existing technology.

[0010] Preferably, in step 1), acid preparation is carried out in a shell and tube reactor. In conventional processes, acid preparation with spent acid and concentrated sulfuric acid is carried out in a reactor, and temperature is difficult to control. Even if a cooling interlayer is provided outside the reactor, due to the large viscosity of sulfuric acid, the convective heat transfer efficiency is low, and the temperature distribution in the system is uneven, the provision of a cooling interlayer cannot cool the inside of the reactor in time, and therefore there is still the situation of high-temperature hydrolysis of titanyl sulfate. Therefore, the present invention is preferably carried out in a shell and tube reactor, which has good heat dissipation conditions and can efficiently cool the tubes by a cryogenic medium, making it easy to control temperature, thereby achieving the technical purpose of the present invention.

[0011] Preferably, in step 1), the temperature during acid preparation is controlled not to exceed 20° C. When the temperature is controlled below 20° C. during the acid preparation process, the recovery rate of titanium in the waste acid reaches more than 80%.

[0012] Preferably, the end point of acid preparation is a sulfuric acid concentration of 55%. Since a sulfuric acid concentration of 55% can be used for acid hydrolysis, considering economic efficiency, the end point of acid preparation is controlled at 55% in actual process operation.

[0013] The method of the present invention can recycle waste acid from the titanium dioxide process while controlling the temperature of the acid preparation process to achieve titanium recovery. The method is simple and easy to implement. In addition, the method can also reduce the titanium content in the ferrous yellow obtained by recycling the filter cake, thereby improving the purity and quality of the ferrous yellow. DETAILED DESCRIPTION

[0014] The present invention is described below in detail with reference to specific embodiments of the present invention. The description herein is intended only to explain the present invention and is not intended to limit the present invention. Based on the embodiments of the present invention, any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without creative work in all other embodiments obtained by them should be included within the scope of protection of the present invention.

[0015] Example

[0016] 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.

[0017] Example 1:

[0018] 248 g of 98% concentrated sulfuric acid was slowly added to 658 g of waste acid. The temperature was controlled not to exceed 50 ° C during the entire acid addition process. After the concentrated sulfuric acid was added, it was aged for 3 hours and filtered to obtain 126 g of filter cake and 780 g of filtrate. The filtrate was recovered for the acid hydrolysis process, and the titanium recovery rate was about 70%.

[0019] Example 2:

[0020] 248 g of 98% concentrated sulfuric acid was slowly added to 658 g of waste acid. The temperature was controlled not to exceed 20 ° C during the entire acid addition process. After the concentrated sulfuric acid was added, it was aged for 3 hours and filtered to obtain 122 g of filter cake and 784 g of filtrate. The filtrate was recovered for the acid hydrolysis process, and the titanium recovery rate was about 81%.

[0021] Example 3:

[0022] 248 g of 98% concentrated sulfuric acid was slowly added to 658 g of waste acid. The temperature was controlled not to exceed 30 ° C during the entire acid addition process. After the concentrated sulfuric acid was added, it was aged for 3 hours and filtered to obtain 125 g of filter cake and 781 g of filtrate. The filtrate was recovered for the acid hydrolysis process, and the titanium recovery rate was about 75%.

[0023] Comparative Example 1

[0024] 248g of 98% concentrated sulfuric acid was slowly added to 658g of waste acid. The temperature was controlled not to exceed 70°C during the entire acid addition process. After the concentrated sulfuric acid was added, it was aged for 3h and filtered to obtain 128g of filter cake and 778g of filtrate. The filtrate was recovered for the acid hydrolysis process, and the titanium recovery rate was about 13%.

[0025] Comparative Example 2

[0026] 248 g of 98% concentrated sulfuric acid was slowly added to 658 g of waste acid. The temperature was controlled not to exceed 90 ° C during the entire acid addition process. After the concentrated sulfuric acid was added, it was aged for 3 hours and filtered to obtain 129 g of filter cake and 777 g of filtrate. The filtrate was recovered for the acid hydrolysis process, and the titanium recovery rate was about 6%.

[0027] Comparative Example 3

[0028] 248 g of 98% concentrated sulfuric acid was slowly added to 658 g of waste acid. The temperature was controlled not to exceed 110 ° C during the entire acid addition process. After the concentrated sulfuric acid was added, it was aged for 3 hours and filtered to obtain 131 g of filter cake and 775 g of filtrate. The filtrate was recovered for the acid hydrolysis process, and the titanium recovery rate was about 3%.

[0029] Wherein, Examples 1-3 were carried out in a shell-and-tube reactor, and Comparative Examples 1-3 were carried out in a reactor.

[0030] The titanium content of the filter cake and the filtrate in Examples 1-3 and Comparative Examples 1-3 was measured, and the titanium content was calculated as TiO2 equivalent. The results are as follows:

[0031]

[0032] From the comparison, it can be seen that the temperature control during acid preparation has a great influence on the titanium recovery rate. When the temperature does not exceed 50℃, the titanium recovery rate is significantly improved. When the temperature is above 50℃, most of the titanium enters the precipitate and cannot be recovered, resulting in titanium loss.

Claims

1. A method for recovering titanium dioxide from titanium dioxide waste acid, characterized in that: The following steps are involved: 1) Add 98% concentrated sulfuric acid to the waste acid produced in the sulfuric acid method for preparing titanium dioxide, and control the temperature not to exceed 50°C during the acid preparation process; 2) After the acid preparation is completed, the mixed solution is matured and then filtered and separated. The filtrate is returned to the acid hydrolysis step in the sulfuric acid method for preparing titanium dioxide; The acid preparation in step 1) is carried out in a shell-and-tube reactor.

2. The method for recovering titanium dioxide from titanium dioxide waste acid according to claim 1, wherein: In step 1), the temperature is controlled not to exceed 20°C when preparing the acid.

3. The method for recovering titanium dioxide from titanium white waste acid according to claim 1, wherein: The end point of acid preparation is a sulfuric acid concentration of 55%.

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