Method for preparing titanium phosphate from waste residues generated in synthesis of iron phosphate from titanium dioxide by-product

Abstract

The invention discloses a method for preparing titanium phosphate by using waste residues generated in synthesis of iron phosphate from titanium dioxide by-products, which comprises the following steps: mixing solid waste residues generated in the synthesis of iron phosphate from titanium dioxide by-products with acidic mother liquor in the production process of iron phosphate, adding water and stirring to obtain slurry; adding iron powder into the slurry, and reducing ferric iron; filtering the slurry, washing filter residues by using acidic washing water in the iron phosphate production process, and drying the filter residues; mother liquor obtained by filtering the slurry is concentrated and crystallized to obtain ferrous sulfate heptahydrate, and the ferrous sulfate heptahydrate is put into an iron phosphate production line again; washing water is guided into an iron phosphate production line, and ferrous sulfate heptahydrate is dissolved; and calcining the dried filter residues to obtain titanium phosphate. According to the method, the waste residues generated by synthesizing the titanium dioxide by-product into the iron phosphate are recycled, and the waste water generated in the iron phosphate production link is fully utilized, so that the cost is saved; iron powder is used for reducing ferric iron in the solid waste residues to generate ferrous iron, and after washing, impurities in titanium phosphate are reduced, and the purity is improved.

Description

Technical Field

[0001] The present invention belongs to solid waste recycling, and particularly relates to a method for preparing titanium phosphate from the waste residue generated in the synthesis of iron phosphate using by-products of titanium dioxide. Background Art

[0002] With the development of the electric vehicle and energy storage industries, the demand for lithium iron phosphate has increased sharply. Its precursor, iron phosphate, is mainly prepared by reacting ferrous sulfate heptahydrate, a by-product of titanium dioxide, with a phosphate source. However, during the purification process of ferrous sulfate heptahydrate, solid waste residues containing sulfate, phosphate, and metal impurities such as iron, titanium, magnesium, manganese, calcium, and aluminum are generated. Existing technologies such as Chinese invention patent CN107324302A only target the treatment of titanium white waste acid and cannot solve the problem of recycling such high-impurity solid waste residues. Summary of the Invention

[0003] Object of the Invention: The object of the present invention is to provide a method for preparing titanium phosphate from the waste residue generated during the purification process using ferrous sulfate heptahydrate, a by-product of titanium dioxide, as an iron source, and to solve the problems of complex impurities and difficult recycling in the waste residue of iron phosphate production.

[0004] Technical Solution: The method for preparing titanium phosphate from the waste residue generated in the synthesis of iron phosphate using by-products of titanium dioxide according to the present invention comprises the following steps:

[0005] (1) Mix the solid waste residue generated during the synthesis of iron phosphate using by-products of titanium dioxide with the acidic mother liquor in the iron phosphate production process, add water and stir to obtain a slurry;

[0006] (2) Add iron powder to the slurry to reduce ferric iron to ferrous iron and stir;

[0007] (3) Filter the slurry, wash the filter residue with the acidic washing water in the iron phosphate production process, and dry the filter residue;

[0008] (4) Concentrate and crystallize the mother liquor obtained by filtering the slurry in step (3) to obtain ferrous sulfate heptahydrate, and reintroduce it into the iron phosphate production line; introduce the washing water in step (3) into the iron phosphate production line to dissolve ferrous sulfate heptahydrate;

[0009] (5) Calcinate the dried filter residue in step (3) to obtain titanium phosphate.

[0010] Preferably, the mass ratio of the acidic mother liquor to the solid waste residue in step (1) is 1 - 8.

[0011] More preferably, the mass ratio of the acidic mother liquor to the solid waste residue in step (1) is 4.

[0012] Preferably, the water stirring time in step (1) is 2 - 8 h.

[0013] Further preferably, the stirring time in step (1) is 4 h.

[0014] Preferably, the molar ratio of iron powder to ferric iron in step (2) is 1.0 - 1.5:1.

[0015] Further preferably, the molar ratio of iron powder to ferric iron in step (2) is 1.1:1.

[0016] Preferably, the stirring time in step (2) is 1 - 4 h.

[0017] Further preferably, the stirring time in step (2) is 2 h.

[0018] Preferably, the drying temperature in step (3) is 100 - 400 °C.

[0019] Further preferably, the drying temperature of the filter residue in step (3) is 150 °C.

[0020] Preferably, the pH value of the acidic mother liquor in step (1) is 0.5 - 1.

[0021] Preferably, a small amount of hydrogen gas generated in the reaction in step (2) is treated by ignition.

[0022] Preferably, the pH value of the acidic washing water in step (3) is 1 - 3.

[0023] Preferably, the filtration method in step (3) is a plate and frame filter press, and the washing process is carried out on the filter press.

[0024] Preferably, the calcination temperature in step (5) is 800 - 1200 °C.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: 1. When recovering solid waste residues, the acidic wastewater in the production process of iron phosphate is utilized, saving production costs; 2. Iron powder is used to reduce ferric iron in the solid waste residues to generate ferrous iron. After washing, the impurities in titanium phosphate are reduced and the purity is improved; 3. Ferrous sulfate in the solid waste residues is recycled and used for the production of iron phosphate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the process flow chart of the present invention; 1 represents the waste residue from the synthesis of iron phosphate from titanium dioxide by-products, 2 represents the acidic mother liquor of the iron phosphate production line, 3 represents the dissolution tank, 4 represents iron powder, 5 represents the reduction reaction tank, 6 represents the plate and frame filter press, 7 represents the filter residue of the plate and frame filter press, 8 represents drying, 9 represents calcination, 10 represents the washing water of the plate and frame filter press, 11 represents the mother liquor of the plate and frame filter press, 12 represents evaporation and crystallization, and 13 represents the iron phosphate production line. DETAILED DESCRIPTION OF THE INVENTION

[0027] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0028] Example 1

[0029] A method for preparing titanium phosphate from the waste residue obtained by synthesizing iron phosphate using the by - product of titanium dioxide includes the following steps:

[0030] (1) Mix the solid waste residue generated during the synthesis of iron phosphate from the by - product of titanium dioxide with the acidic mother liquor in the iron phosphate production process, add water and stir to obtain a slurry;

[0031] (2) Add iron powder to the slurry to reduce ferric iron to ferrous iron and stir;

[0032] (3) Filter the slurry, wash the filter residue with the acidic washing water in the iron phosphate production process, and dry the filter residue;

[0033] (4) Concentrate and crystallize the mother liquor obtained by filtering the slurry in step (3) to obtain ferrous sulfate heptahydrate, and re - input it into the iron phosphate production line; introduce the washing water in step (3) into the iron phosphate production line to dissolve ferrous sulfate heptahydrate;

[0034] (5) Calcinate the dried filter residue in step (3) to obtain titanium phosphate.

[0035] The mass fraction of the obtained ferrous sulfate heptahydrate is above 85%, and the impurity content of the obtained titanium phosphate is ≤0.5%.

[0036] Example 2

[0037] A method for preparing titanium phosphate from the waste residue obtained by synthesizing iron phosphate using the by - product of titanium dioxide includes the following steps:

[0038] (1) Mix the solid waste residue generated during the synthesis of iron phosphate from the by - product of titanium dioxide with the acidic mother liquor in the iron phosphate production process, add water and stir to obtain a slurry; the mass ratio of the acidic mother liquor to the solid waste residue is 1; the water - adding and stirring time is 2 h; the pH value of the acidic mother liquor is 1;

[0039] (2) Add iron powder to the slurry to reduce ferric iron to ferrous iron and stir; the molar ratio of iron powder to ferric iron is 1.0:1; the stirring time is 1 h;

[0040] (3) Filter the slurry, wash the filter residue with the acidic washing water in the iron phosphate production process, and dry the filter residue; the drying temperature is 100 °C; the pH value of the acidic washing water is 3;

[0041] (4) Concentrate and crystallize the mother liquor obtained by filtering the slurry in step (3) to obtain ferrous sulfate heptahydrate, and re - input it into the iron phosphate production line; introduce the washing water in step (3) into the iron phosphate production line to dissolve ferrous sulfate heptahydrate;

[0042] (5) Calcinate the dried filter residue in step (3) at a calcination temperature of 800 °C to obtain titanium phosphate.

[0043] The mass fraction of ferrous sulfate heptahydrate obtained in this group is above 85%, the residual Ti content is ≤0.3%, and the impurity content of the obtained titanium phosphate is ≤0.5%.

[0044] Example 3

[0045] A method for preparing titanium phosphate from the waste residue of synthesizing iron phosphate using titanium white by - products, comprising the following steps:

[0046] (1) Mix the solid waste residue generated during the synthesis of iron phosphate from titanium white by - products with the acidic mother liquor in the iron phosphate production process, add water and stir to obtain a slurry; the mass ratio of the acidic mother liquor to the solid waste residue is 8; the water - adding and stirring time is 8 h; the pH value of the acidic mother liquor is 0.5;

[0047] (2) Add iron powder to the slurry to reduce ferric iron to ferrous iron and stir; the molar ratio of iron powder to ferric iron is 1.5:1; the stirring time is 4 h;

[0048] (3) Filter the slurry, wash the filter residue with the acidic washing water in the iron phosphate production process, and dry the filter residue; the drying temperature is 400 °C; the pH value of the acidic washing water is 1;

[0049] (4) Concentrate and crystallize the mother liquor obtained by filtering the slurry in step (3) to obtain ferrous sulfate heptahydrate, and re - input it into the iron phosphate production line; introduce the washing water in step (3) into the iron phosphate production line to dissolve ferrous sulfate heptahydrate;

[0050] (5) Calcinate the dried filter residue in step (3) at a calcination temperature of 1200 °C to obtain titanium phosphate.

[0051] The mass fraction of ferrous sulfate heptahydrate obtained in this group is above 85%, the residual Ti content is ≤0.1%, and the impurity content of the obtained titanium phosphate is ≤0.3%.

[0052] Example 4

[0053] A method for preparing titanium phosphate from the waste residue of synthesizing iron phosphate using titanium white by - products, comprising the following steps:

[0054] (1) The water content of the solid waste residue is about 70%, the mass fraction of sulfate radical in the solid impurities is about 6.5%, phosphate radical is 12%, titanium content is 4.5%, iron content is 5.3%, and the rest are a small amount of impurities such as magnesium, manganese, calcium, and aluminum. Add an acidic mother liquor with pH 0.7 to dissolve the filter residue. The mass ratio of the acidic mother liquor to the solid waste residue is 4:1, add water and stir for 4 h, and the pH of the slurry is 1.3;

[0055] (2) It is measured that the proportion of ferric iron content in the slurry is about 0.5 g / L. Add iron powder with a molar ratio of 1.1 to ferric iron, stir for 2 h to reduce ferric iron to ferrous iron, and ignite and treat the small amount of hydrogen generated.

[0056] (3) Use a filter press to filter the slurry in step (2), wash the filter cake with acidic wash water at pH 2.2 during the production process of iron phosphate, and dry the washed filter cake at a drying temperature of 105 °C.

[0057] (4) Concentrate the mother liquor obtained by filtering the slurry in step (3), cool and crystallize to obtain ferrous sulfate heptahydrate, and reintroduce it into the iron phosphate production line; introduce the washing water in S3 into the iron phosphate production line for dissolving ferrous sulfate heptahydrate.

[0058] (5) Feed the dried filter cake in step (3) into a kiln for calcination at a calcination temperature of 900 °C.

[0059] The mass fraction of the obtained ferrous sulfate heptahydrate is above 85%, and the impurity content of the obtained titanium phosphate is ≤ 0.4%.

[0060] Example 5

[0061] A method for preparing titanium phosphate from the waste residue of synthesizing iron phosphate using titanium white by-products, comprising the following steps:

[0062] (1) Dry the solid waste residue. The mass proportion of sulfate radical in the waste residue is about 30%, phosphate radical 40.5%, titanium content 11%, iron content 18.3%, and the remaining 0.2% is a small amount of impurities such as magnesium, manganese, calcium, and aluminum. Add acidic mother liquor at pH 0.6 to dissolve the filter residue. The mass ratio of the acidic mother liquor to the solid waste residue is 4:1, add water and stir for 4 h, and the pH of the slurry is 1.1.

[0063] (2) It is measured that the proportion of ferric iron content in the slurry is about 1.2 g / L. Add iron powder with a molar ratio of 1.1 to ferric iron, stir for 2 h to reduce ferric iron to ferrous iron, and ignite and treat the small amount of hydrogen generated.

[0064] (3) Use a filter press to filter the slurry in step (2), wash the filter cake with acidic wash water at pH 1.9 during the production process of iron phosphate, and dry the washed filter cake at a drying temperature of 150 °C.

[0065] (4) Concentrate the mother liquor obtained by filtering the slurry in step (3), cool and crystallize to obtain ferrous sulfate heptahydrate, and reintroduce it into the iron phosphate production line; introduce the washing water in step (3) into the iron phosphate production line for dissolving ferrous sulfate heptahydrate.

[0066] (5) Feed the dried filter cake in step (3) into a kiln for calcination at a calcination temperature of 950 °C.

[0067] The mass fraction of ferrous sulfate heptahydrate obtained by this group is above 85%, and the impurity content of titanium phosphate obtained is ≤0.3%.

[0068] Comparative Example 1

[0069] A method for preparing titanium phosphate from the waste residue of synthesizing iron phosphate using titanium white by - products, comprising the following steps:

[0070] (1) Mix the solid waste residue generated during the synthesis of iron phosphate from titanium white by - products with the acidic mother liquor in the iron phosphate production process, add water and stir to obtain a slurry; the mass ratio of the acidic mother liquor to the solid waste residue is 8; the water - adding and stirring time is 8 h; the pH value of the acidic mother liquor is 1;

[0071] (2) Filter the slurry, wash the filter residue with the acidic washing water in the iron phosphate production process, and dry the filter residue; the drying temperature is 400 °C; the pH value of the acidic washing water is 3;

[0072] (3) Concentrate and crystallize the mother liquor obtained by filtering the slurry in step (2) to obtain ferrous sulfate heptahydrate, and re - input it into the iron phosphate production line; introduce the washing water in step (2) into the iron phosphate production line to dissolve ferrous sulfate heptahydrate;

[0073] (4) Calcinate the filter residue dried in step (3) at a calcination temperature of 1200 °C to obtain titanium phosphate.

[0074] The content of iron phosphate in the impurities of titanium phosphate obtained by this group is relatively high, about 0.3%, and the impurity content of titanium phosphate is ≥1%.

[0075] Comparative Example 2

[0076] A method for preparing titanium phosphate from the waste residue of synthesizing iron phosphate using titanium white by - products, comprising the following steps:

[0077] (1) Mix the solid waste residue generated during the synthesis of iron phosphate from titanium white by - products with the acidic mother liquor in the iron phosphate production process, add water and stir to obtain a slurry; the mass ratio of the acidic mother liquor to the solid waste residue is 8; the water - adding and stirring time is 8 h; the pH value of the acidic mother liquor is 1;

[0078] (2) Add iron powder to the slurry to reduce ferric iron to ferrous iron and stir; the molar ratio of iron powder to ferric iron is 1.5:1; the stirring time is 4 h;

[0079] (3) Filter the slurry, wash the filter residue with pure water, and dry the filter residue; the drying temperature is 400 °C;

[0080] (4) Concentrate and crystallize the mother liquor obtained by filtering the slurry in step (3) to obtain ferrous sulfate heptahydrate, and reintroduce it into the iron phosphate production line; introduce the washing water in step (3) into the iron phosphate production line to dissolve ferrous sulfate heptahydrate;

[0081] (5) Calcinate the dried filter residue in step (3) at a calcination temperature of 1200 °C to obtain titanium phosphate.

[0082] The titanium phosphate impurities obtained by crystallizing this group of mother liquors have a relatively high content of ferrous hydroxide, and the content of titanium phosphate impurities obtained is ≥ 2%.

[0083] Comparative Example 3

[0084] A method for preparing titanium phosphate from the waste residue of synthesizing iron phosphate using titanium white by-products, comprising the following steps:

[0085] (1) Dissolve the solid waste residue generated during the synthesis of iron phosphate from titanium white by-products in pure water and stir to obtain a slurry; the mass ratio of pure water to solid waste residue is 8; the stirring time with water addition is 8 h;

[0086] (2) Add iron powder to the slurry to reduce ferric iron to ferrous iron and stir; the molar ratio of iron powder to ferric iron is 1.5:1; the stirring time is 4 h;

[0087] (3) Filter the slurry, wash the filter residue with acidic washing water during the iron phosphate production process, and dry the filter residue; the drying temperature is 400 °C; the pH value of the acidic washing water is 3;

[0088] (4) Concentrate and crystallize the mother liquor obtained by filtering the slurry in step (3) to obtain ferrous sulfate heptahydrate, and reintroduce it into the iron phosphate production line; introduce the washing water in step (3) into the iron phosphate production line to dissolve ferrous sulfate heptahydrate;

[0089] (5) Calcinate the dried filter residue in step (3) at a calcination temperature of 1200 °C to obtain titanium phosphate.

[0090] This group of solid waste residues is difficult to dissolve, and the content of titanium phosphate impurities obtained is ≥ 5%.

Claims

1. A method for preparing titanium phosphate using waste residue from the synthesis of iron phosphate as a byproduct of titanium dioxide, characterized in that: The following steps are involved: (1) mixing the solid waste residue generated in the process of synthesizing ferric phosphate from titanium dioxide byproduct with the acidic mother liquor in the production process of ferric phosphate, adding water and stirring to obtain a slurry; (2) adding iron powder to the slurry to reduce the trivalent iron to divalent iron, and stirring; (3) filtering the slurry, washing the filter residue with acidic washing water from the iron phosphate production process, and drying the filter residue; (4) Concentrating and crystallizing the mother liquor obtained by filtering the slurry in step (3) to obtain ferrous sulfate heptahydrate, and re-introducing it into the iron phosphate production line; introducing the washing water in step (3) into the iron phosphate production line to dissolve the ferrous sulfate heptahydrate; (5) calcining the filter residue dried in step (3) to obtain titanium phosphate.

2. The method for preparing titanium phosphate using waste residue from synthesizing iron phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: In step (1), the mass ratio of the acidic mother liquor to the solid waste residue is 1 to 8.

3. The method for preparing titanium phosphate using waste residue from synthesizing iron phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: The stirring time of adding water in step (1) is 2 to 8 hours.

4. The method for preparing titanium phosphate using waste residue from synthesizing iron phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: In step (2), the molar ratio of iron powder to ferric iron is 1.0 to 1.5:

1.

5. The method for preparing titanium phosphate using waste residue from synthesizing ferric phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: The stirring time in step (2) is 1 to 4 hours.

6. The method for preparing titanium phosphate using waste residue from synthesizing ferric phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: The drying temperature in step (3) is 100-400°C.

7. The method for preparing titanium phosphate using waste residue from synthesizing ferric phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: The pH value of the acidic mother liquor in step (1) is 0.5-1.

8. The method for preparing titanium phosphate using waste residue from synthesizing ferric phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: The small amount of hydrogen generated by the reaction in step (2) is ignited.

9. The method for preparing titanium phosphate using waste residue from synthesizing ferric phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: The pH value of the acidic washing water in step (3) is 1 to 3.

10. The method for preparing titanium phosphate using waste residue from synthesizing ferric phosphate as a byproduct of titanium dioxide according to claim 1, characterized in that: The calcination temperature in step (5) is 800-1200°C.

Images