A method for preparing high-purity titanium gypsum based on sulfuric acid method acidic wastewater

Abstract

The application discloses a method for preparing high-purity titanium gypsum based on sulfuric acid method acidic wastewater, and specifically comprises the following steps: standing and precipitating the acidic wastewater, filtering and separating the same to obtain filtrate C; adding alkaline substances into deionized water to prepare a suspension A; adding the suspension A into the filtrate C to perform a first-stage neutralization reaction, obtaining a suspension B; when the pH value of the suspension B is 2-5, the adding of the suspension A into the filtrate C is stopped, and solid-liquid separation is performed on the obtained suspension B to obtain a filter cake A and filtrate A; the filter cake A is sequentially subjected to drying and grinding treatment to obtain high-purity titanium gypsum; the suspension A is added into the filtrate A to perform a second-stage neutralization reaction, obtaining a suspension C; when the pH value of the suspension C is 7-10, the adding of the suspension A into the filtrate A is stopped, and solid-liquid separation is performed on the obtained suspension C to obtain a filter cake B and waste water; and the filter cake B is sequentially subjected to reduction roasting and magnetic separation and impurity removal treatment to obtain high-purity titanium gypsum.

Description

Technical Field

[0001] This invention relates to a method for preparing high-purity titanium gypsum based on acidic wastewater from the sulfuric acid process. Background Technology

[0002] Titanium dioxide, with TiO2 as its main component, is known as the "king of white pigments" and is considered to be the most cost-effective white pigment in the world. Due to its chemical stability, strong hiding power, and high whiteness, titanium dioxide is widely used in industries such as coatings, plastics, papermaking, printing inks, textiles, and chemical fibers.

[0003] Currently, there are two main production processes for titanium dioxide: the sulfuric acid process and the chloride process. The main advantage of the sulfuric acid process is its lower requirement for raw material grade (currently, the TiO2 grade in ilmenite is relatively low). However, the industrial-scale sulfuric acid process suffers from drawbacks such as a long process flow, complex procedures, and large amounts of byproducts. Depending on the process flow, the average production of 1 ton of titanium dioxide using the sulfuric acid process generates 5-8 tons of acidic wastewater.

[0004] Currently, a single-stage neutralization method is chosen to treat acidic wastewater generated from the sulfuric acid process. This method typically involves neutralizing slaked quicklime with waste acid, followed by precipitation and separation to obtain dischargeable wastewater and titanium gypsum. However, the slaked quicklime adds a step to the wastewater neutralization process, increasing operating costs. Furthermore, the titanium gypsum produced directly by this method contains a large amount of metal oxide impurities, resulting in low resource utilization. When used in the preparation of cement retarders or composite cementitious materials, the high iron content in this titanium gypsum negatively impacts the performance of building materials compared to natural gypsum, leading to low utilization rates. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for preparing high-purity titanium gypsum based on acidic wastewater from the sulfuric acid process. This method can effectively reduce the environmental pollution caused by acidic wastewater from the sulfuric acid process, significantly improve the quality of the product, and the obtained titanium gypsum has high purity.

[0006] Technical solution: The method for preparing high-purity titanium gypsum based on acidic wastewater from the sulfuric acid process according to the present invention includes the following steps:

[0007] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0008] (2) Add alkaline substances to deionized water to prepare suspension A;

[0009] (3) Add suspension A to filtrate C to carry out a neutralization reaction to obtain suspension B. When the pH value of suspension B is 2 to 5, stop adding suspension A to filtrate C. Perform solid-liquid separation on the obtained suspension B to obtain filter cake A and filtrate A.

[0010] (4) The filter cake A is dried and ground in sequence to obtain high-purity titanium gypsum. After the high-purity titanium gypsum is calcined and aged, building gypsum is obtained.

[0011] (5) Add suspension A to filtrate A to carry out a two-stage neutralization reaction to obtain suspension C. When the pH value of suspension C is 7-10, stop adding suspension A to filtrate A. Perform solid-liquid separation on the obtained suspension C to obtain filter cake B and wastewater that can be discharged.

[0012] (6) The filter cake B was subjected to reduction roasting and magnetic separation to remove impurities in sequence to obtain high-purity titanium gypsum.

[0013] During the first stage of neutralization, pH control effectively prevents the precipitation of most valuable metal ions in the acidic wastewater. After solid-liquid separation, high-whiteness and high-purity titanium gypsum can be directly obtained. The titanium gypsum produced in the first stage of neutralization does not require impurity removal treatment and can be directly processed by grinding, calcination, and aging to prepare building gypsum that meets the 2.0 grade compressive strength standard in GB / T9776-2008 "Building Gypsum". During the second stage of neutralization, pH control allows most valuable metal ions in the acidic wastewater to precipitate. After solid-liquid separation, various metal impurities (especially iron impurities) in the acidic wastewater are enriched in the titanium gypsum. After reduction roasting and magnetic separation, high-purity titanium gypsum with an iron oxide content as low as 6% can be obtained.

[0014] In step (1), the acidic wastewater is the acidic wastewater generated by producing titanium dioxide using the sulfuric acid method, and the pH value of the filtrate C is 0.7 to 1.5.

[0015] In step (1), the mass concentrations of each component in filtrate C are as follows:

[0016] SO4 2- The concentrations ranged from 6514.195 to 15253.6 mg / L, and the Fe content was... 2+ Fe 3+ The concentrations ranged from 2661.228 to 10731.1 mg / L, and the Mg content was... 2+ The concentrations ranged from 103.1 to 345.300 mg / L, and Al... 3+ The concentrations ranged from 124.2 to 331.5 mg / L, and Si... 4+ The concentrations ranged from 4.342 to 238.3 mg / L, and the Ti concentration was... 4+ The concentration ranged from 84.877 to 249.6 mg / L.

[0017] In step (2), the alkaline substance is one or more of carbide slag, lime and heavy calcium carbonate powder, and the particle size of the alkaline substance is less than 0.075 mm.

[0018] In step (2), the mass concentration of alkaline substances in the suspension A is 2-20%.

[0019] In step (3), the reaction conditions for a neutralization reaction are: the reaction temperature is 15℃~50℃, the reaction solution is stirred at a speed of 500r / min~700r / min, and the dropping rate of suspension A is 10mL / min~27mL / min.

[0020] In step (4), the drying temperature is 25-50℃ and the drying time is not less than 1 hour; the grinding time is 1-30 minutes; the calcination temperature is 180-250℃ and the calcination time is 1-3 hours; and the aging process is carried out at room temperature and in the air for 1-30 days. The aging process can prevent over-burning. Water is added at room temperature (to convert anhydrous gypsum into hemihydrate gypsum).

[0021] In step (5), the reaction conditions for the two-stage neutralization reaction are: the reaction temperature is 15℃~50℃, the reaction solution is stirred at a speed of 500r / min~700r / min, and the dropping rate of suspension A is 10mL / min~27mL / min.

[0022] In step (6), the reduction roasting specifically involves: drying filter cake B to obtain iron-enriched titanium gypsum, mixing the iron-enriched titanium gypsum with activated carbon, and roasting the mixed material at 600-850℃ for 15-90 minutes (by roasting and reducing, the iron hydroxide and iron oxide in the titanium gypsum are reduced to magnetic iron(III) oxide and elemental iron. Effective reduction can only be carried out at the corresponding temperature. If the temperature is too low, the reaction will be insufficient, and if the temperature is too high, magnetic iron compounds may not be produced). After roasting, the roasted product is taken out and water-quenched and cooled to room temperature to form a magnetic separation slurry.

[0023] The drying temperature of the filter cake B is 25-50℃.

[0024] The mass ratio of the iron-enriched titanium gypsum to activated carbon is 100:0.5-9.

[0025] In step (6), the magnetic separation for impurity removal specifically involves using a strong magnet with a magnetic field strength of 600 to 1200 mT to perform magnetic separation on the magnetic slurry. The magnetic slurry after the separation of iron oxide becomes a high-purity titanium gypsum slurry, which is then filtered and dried at 25 to 50°C to obtain high-purity titanium gypsum.

[0026] The main components of suspension B are calcium sulfate dihydrate powder and acidic wastewater with a pH of 2-5; the main component of filter cake A is calcium sulfate dihydrate; filtrate A is acidic wastewater with a pH of 2-5, and its main substance is still H2SO4, while also containing a large amount of Fe. 2+ Fe 3+ Al 3+ Mg 2+ The suspension C mainly consists of metal compounds such as calcium sulfate dihydrate, ferrous sulfate, and magnesium sulfate, along with acidic wastewater with a pH of 7-10; the filter cake B mainly consists of metal compounds such as calcium sulfate, titanium dioxide, iron oxide, magnesium oxide, and aluminum oxide.

[0027] When filtrate C is neutralized by suspension A, the following chemical reaction formula applies: Ca 2+ +SO4 2- +2H₂O=CaSO₄·2H₂O(s), 2H + +OH - =H2O, by controlling the pH value of the mixture, Fe can be effectively avoided. 2+ Fe 3+ Al 3+ Mg 2+ The large amount of metal ions precipitated; after appropriate calcination treatment, CaSO4·2H2O in the resulting filter cake A is transformed into active CaSO4·0.5H2O or CaSO4·0.67H2O, which can be hydrated and hardened upon contact with water to form building gypsum with certain mechanical properties.

[0028] Filter cake B is first subjected to high-temperature reducing calcination to dehydrate and decompose the ferric hydroxide in titanium gypsum into ferric oxide. Then, the ferric oxide is reduced to form magnetite or elemental iron (magnetic separation can remove the key impurity iron from titanium gypsum). The reaction equation is shown below:

[0029] 2Fe(OH)3→Fe2O3+3H2O↑

[0030] 3Fe₂O₃ + C → 2Fe₃O₄ + CO↑

[0031] Fe3O4 + 4CO → 3Fe + 4CO2↑

[0032] Fe₂O₃ + 3CO → 2Fe + 3CO₂↑

[0033] Subsequently, magnetic separation equipment is used to separate ferric oxide or elemental iron from titanium gypsum, thereby achieving magnetic separation and impurity removal of titanium gypsum.

[0034] Beneficial Effects: Compared with the prior art, the present invention has the following significant advantages: The method of the present invention achieves the combination of sulfate ions and alkaline calcium ions in acidic wastewater to form calcium sulfate dihydrate through a two-stage neutralization reaction. In the first-stage neutralization reaction, the precipitation of major metal ions in acidic wastewater can be effectively avoided, thereby producing high-purity, white titanium gypsum. This titanium gypsum can be used directly as building gypsum. After the second-stage neutralization reaction, the high-purity titanium gypsum obtained by reduction roasting and magnetic separation can have an iron oxide content as low as 6%, which can be used as a cement retarder. The alkaline raw materials used in the present invention are all industrial wastes. On the one hand, it can produce high-performance titanium gypsum products, and on the other hand, it can achieve a 100% treatment rate of acidic wastewater, thereby improving the resource utilization rate of waste. Detailed Implementation

[0035] The calcium carbide slag used in the examples was obtained from Jiangsu Zhentai Chemical Co., Ltd. It appears as a white powder, and its main chemical component is CaO, containing impurities such as SiO2 and Al2O3. The calcium carbide slag has a flat, blocky morphology, and its main mineral composition is calcium hydroxide (Ca(OH)2), with a median particle size of 38.64 μm. The lime was also obtained from Jiangsu Zhentai Chemical Co., Ltd., and appears as a light yellow powder. The lime's main chemical component is CaO, containing impurities such as SO3, MgO, and SiO2, and its microscopic morphology is spherical, with its main mineral composition being calcite (CaCO3), and a median particle size of 16.55 μm. The heavy calcium carbonate powder is sourced from Jiangsu Zhentai Chemical Co., Ltd. It appears as a brown powder. The main chemical component of the heavy calcium carbonate powder is CaO, and it contains impurities such as SiO2, Al2O3, and MgO. The microscopic morphology of the heavy calcium carbonate powder is similar to that of lime, and it is irregularly spherical. The main mineral composition is calcite (CaCO3), and the median particle size of the heavy calcium carbonate powder is 21.16 μm.

[0036] In the example, the pH value of the filtrate C obtained after the acidic wastewater to be treated by static sedimentation and filtration is 0.7-1.5; the main component is sulfuric acid, and the content of metal impurities is high.

[0037] Table 1 shows the analytical results of the main components of filtrate C (unit: mg / L).

[0038]

[0039] Example 1

[0040] This invention relates to a method for preparing building gypsum from acidic wastewater treated with sulfuric acid, comprising the following steps:

[0041] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0042] (2) Add carbide slag and lime to deionized water at a mass ratio of 6:4 to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0043] (3) At 25℃ and 500r / min, suspension A was added to filtrate C to carry out a neutralization reaction. The dropping rate of suspension A was 10mL / min to obtain suspension B. When the pH value of suspension B was 4.2 (the pH value of the reaction solution was detected every 30s), the addition of suspension A to filtrate C was stopped. The obtained suspension B was subjected to solid-liquid separation to obtain filter cake A and filtrate A.

[0044] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain building gypsum.

[0045] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of building gypsum are shown in the table below.

[0046] Types of alkaline materials A section to neutralize pH Calcium sulfate dihydrate content in filter cake A / % 2-hour compressive strength of building gypsum / MPa Calcium carbide slag and lime 4.2 90.95 3.61

[0047] Example 2

[0048] This invention relates to a method for preparing building gypsum from acidic wastewater treated with sulfuric acid, comprising the following steps:

[0049] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0050] (2) Add carbide slag and lime to deionized water at a mass ratio of 6:4 to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0051] (3) At 25℃ and 500r / min, suspension A was added to filtrate C to carry out a neutralization reaction. The dropping rate of suspension A was 10mL / min to obtain suspension B. When the pH value of suspension B was 3.2 (the pH value of the reaction solution was detected every 30s), the addition of suspension A to filtrate C was stopped. The obtained suspension B was subjected to solid-liquid separation to obtain filter cake A and filtrate A.

[0052] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain building gypsum.

[0053] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of building gypsum are shown in the table below.

[0054] Types of alkaline materials A section to neutralize pH Calcium sulfate dihydrate content in filter cake A / % 2-hour compressive strength of building gypsum / MPa Calcium carbide slag and lime 3.2 88.36 3.02

[0055] Example 3

[0056] This invention relates to a method for preparing building gypsum from acidic wastewater treated with sulfuric acid, comprising the following steps:

[0057] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0058] (2) Add carbide slag and lime to deionized water at a mass ratio of 6:4 to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0059] (3) At 25℃ and 500r / min, suspension A was added to filtrate C to carry out a neutralization reaction. The dropping rate of suspension A was 10mL / min to obtain suspension B. When the pH value of suspension B was 2.2 (the pH value of the reaction solution was detected every 30s), the addition of suspension A to filtrate C was stopped. The obtained suspension B was subjected to solid-liquid separation to obtain filter cake A and filtrate A.

[0060] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain building gypsum.

[0061] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of building gypsum are shown in the table below.

[0062] Types of alkaline materials A section to neutralize pH Calcium sulfate dihydrate content in filter cake A / % 2-hour compressive strength of building gypsum / MPa Calcium carbide slag and lime 2.2 89.55 4.55

[0063] As can be seen from Examples 1-3, the calcium sulfate dihydrate content in filter cake A obtained by the method of the present invention is above 85%, and the compressive strength of the building gypsum reaches above 3 MPa.

[0064] Example 4

[0065] This invention relates to a method for preparing building gypsum from acidic wastewater treated with sulfuric acid, comprising the following steps:

[0066] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0067] (2) Add carbide slag and lime to deionized water at a mass ratio of 4:6 to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0068] (3) At 25℃ and 500r / min, suspension A was added to filtrate C to carry out a neutralization reaction. The dropping rate of suspension A was 10mL / min to obtain suspension B. When the pH value of suspension B was 4.2 (the pH value of the reaction solution was detected every 30s), the addition of suspension A to filtrate C was stopped. The obtained suspension B was subjected to solid-liquid separation to obtain filter cake A and filtrate A.

[0069] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain building gypsum.

[0070] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of building gypsum are shown in the table below:

[0071] Types of alkaline materials A section to neutralize pH Calcium sulfate dihydrate content in filter cake A / % 2-hour compressive strength of building gypsum / MPa Calcium carbide slag and lime 4.2 82.15 2.63

[0072] Example 5

[0073] This invention relates to a method for preparing high-purity titanium gypsum from acidic wastewater from the sulfuric acid process, comprising the following steps:

[0074] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0075] (2) Add carbide slag and lime to deionized water at a mass ratio of 6:4 (this ratio can make the titanium gypsum produced more pure) to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0076] (3) At 25℃ and 500r / min, suspension A was added to filtrate C to carry out a neutralization reaction. The dropping rate of suspension A was 10mL / min to obtain suspension B. When the pH value of suspension B was 4.2 (the pH value of the reaction solution was detected every 30s), the addition of suspension A to filtrate C was stopped. The obtained suspension B was subjected to solid-liquid separation to obtain filter cake A and filtrate A.

[0077] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain building gypsum.

[0078] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of building gypsum are shown in the table below:

[0079] Types of alkaline materials A section to neutralize pH Calcium sulfate dihydrate content in filter cake A / % 2-hour compressive strength of building gypsum / MPa Calcium carbide slag and lime 4.2 90.95 3.61 ;

[0080] (5) Add suspension A to filtrate A at 25℃ and 500r / min for a two-stage neutralization reaction. The dropping rate of suspension A is 10mL / min to obtain suspension C. When the pH of suspension C is 10 (check the pH of the reaction solution every 30s), stop adding suspension A to filtrate A. Perform solid-liquid separation on the obtained suspension C to obtain filter cake B and wastewater that can be discharged (the wastewater is very clear to the naked eye).

[0081] (6) The main components of filter cake B are (obtained by XRF analysis):

[0082] Main components (mass fraction) of filter cake B

[0083]

[0084]

[0085] Filter cake B was dried at 50°C to obtain iron-enriched titanium gypsum. The iron-enriched titanium gypsum was mixed with activated carbon (the mass ratio of iron-enriched titanium gypsum to activated carbon was 100:9). The mixed material was placed in a muffle furnace preheated to a set temperature of 750°C and roasted for 45 minutes with the furnace door closed. After roasting, the roasted product was quickly placed into a beaker containing a sufficient volume of deionized water and cooled by water quenching. After cooling to room temperature, a magnetic separation slurry was formed. The magnetic separation slurry was thoroughly stirred and then magnetically separated using a strong magnet with a magnetic field strength of 1000mT. The magnetic separation slurry after the iron oxide was separated became a high-purity titanium gypsum slurry. After filtration and drying at 30°C, high-purity titanium gypsum was obtained.

[0086] In Example 5, after reduction roasting and magnetic separation to remove impurities, filter cake B had an iron removal rate of 81.77%, and the resulting high-purity titanium gypsum contained 6.70% iron oxide.

[0087] Examples 6 to 12 are exactly the same as steps (1) to (5) of Example 5. The only difference is that the activated carbon content, calcination temperature, calcination time and magnetic separation intensity in step (6) are changed. The iron oxide content in the high-purity titanium gypsum obtained based on filter cake B in Examples 5 to 12 is shown in Table 1.

[0088] Table 1

[0089]

[0090] Comparative Example 1

[0091] A method for preparing titanium gypsum based on acidic wastewater from the sulfuric acid process includes the following steps:

[0092] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0093] (2) Add carbide slag to deionized water to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0094] (3) Add suspension A to filtrate C at 25℃ and 500r / min for neutralization reaction. The dropping rate of suspension A is 10mL / min to obtain suspension B. When the pH value of suspension B is 7 (the pH value of the reaction solution is detected every 30s), stop adding suspension A to filtrate C, and perform solid-liquid separation on the obtained suspension B to obtain filter cake A and filtrate A.

[0095] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain titanium gypsum.

[0096] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of titanium gypsum are shown in the table below.

[0097]

[0098] Comparative Example 2

[0099] A method for preparing titanium gypsum based on acidic wastewater from the sulfuric acid process includes the following steps:

[0100] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0101] (2) Add lime to deionized water to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0102] (3) Add suspension A to filtrate C at 25℃ and 500r / min for neutralization reaction. The dropping rate of suspension A is 10mL / min to obtain suspension B. When the pH value of suspension B is 7 (the pH value of the reaction solution is detected every 30s), stop adding suspension A to filtrate C, and perform solid-liquid separation on the obtained suspension B to obtain filter cake A and filtrate A.

[0103] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain titanium gypsum.

[0104] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of titanium gypsum are shown in the table below.

[0105]

[0106] Comparative Example 3

[0107] A method for preparing titanium gypsum based on acidic wastewater from the sulfuric acid process includes the following steps:

[0108] (1) The acidic wastewater was allowed to settle and then filtered to separate it, resulting in flocculent filter residue and filtrate C.

[0109] (2) Add the heavy calcium carbonate powder to deionized water to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%.

[0110] (3) Add suspension A to filtrate C at 25℃ and 500r / min for neutralization reaction. The dropping rate of suspension A is 10mL / min to obtain suspension B. When the pH value of suspension B is 7 (the pH value of the reaction solution is detected every 30s), stop adding suspension A to filtrate C, and perform solid-liquid separation on the obtained suspension B to obtain filter cake A and filtrate A.

[0111] (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcination, age it in air at room temperature for 5 days to obtain titanium gypsum.

[0112] The content of calcium sulfate dihydrate in filter cake A and the 2-hour compressive strength of titanium gypsum are shown in the table below.

[0113]

Claims

1. A method for preparing high purity titanium gypsum based on sulfuric acid method acidic wastewater, characterized in that, Includes the following steps: (1) The acidic wastewater is allowed to stand and settle, then filtered and separated to obtain flocculent filter residue and filtrate C; the acidic wastewater is the acidic wastewater generated by the sulfuric acid process for the production of titanium dioxide, and the pH value of filtrate C is 0.7~1.5; (2) Add alkaline substances to deionized water to prepare suspension A. The mass concentration of alkaline substances in suspension A is 10%. The alkaline substances are carbide slag and lime, and the mass ratio of carbide slag to lime is 6:

4. (3) Add suspension A to filtrate C at 25℃ and 500r / min for a neutralization reaction. The dropping rate of suspension A is 10mL / min to obtain suspension B. When the pH of suspension B is 4.2, stop adding suspension A to filtrate C and perform solid-liquid separation on the obtained suspension B to obtain filter cake A and filtrate A. (4) First, dry the filter cake A at 50℃ for 1 hour; after drying, grind it for 30 minutes; after grinding, calcine it at 200℃ for 2 hours; after calcine, age it in air at room temperature for 5 days to obtain building gypsum. (5) At 25℃ and 500r / min, suspension A was added to filtrate A to carry out a two-stage neutralization reaction. The dropping rate of suspension A was 10mL / min to obtain suspension C. When the pH value of suspension C was 10, the addition of suspension A to filtrate A was stopped. The obtained suspension C was subjected to solid-liquid separation to obtain filter cake B and wastewater. (6) Dry the filter cake B at 50°C to obtain iron-enriched titanium gypsum. Mix the iron-enriched titanium gypsum with activated carbon at a mass ratio of 100:

9. Place the mixed material in a muffle furnace preheated to a set temperature of 750°C and keep the furnace door closed for 45 minutes. After calcination, take out the calcined product and quickly put it into a beaker containing deionized water. Cool it with water and cool it to room temperature to form a magnetic separation slurry. After the magnetic separation slurry is thoroughly stirred, use a strong magnet with a magnetic field strength of 1000mT to perform magnetic separation on the magnetic separation slurry. The magnetic separation slurry after the iron oxide is separated becomes a high-purity titanium gypsum slurry. After filtration and drying at 30°C, high-purity titanium gypsum is obtained.

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