A method for resource utilization of pickling waste liquid and wastewater

Abstract

The present application belongs to the technical field of resource recycling, and discloses a method for resource utilization of pickling wastewater. First, the nitric acid and hydrofluoric acid pickling solution of titanium material is filtered to remove insoluble solids as raw water, and an organic complexing agent is added to complex fluoride ions. Then, CaO is added to the solution to adjust the pH, and after filtration, a filtrate and a titanium-rich precipitate are obtained. H2O2 / Fe is added to the filtrate to oxidize and break the complex, and then CaO is added to adjust the pH. After filtration, a filtrate and a fluorine-rich precipitate are obtained. A composite adsorbent is added to the filtrate for deep defluorination, and after filtration, the solution is concentrated by high-salt reverse osmosis to obtain a 15-18 wt.% calcium nitrate solution. Ammonium calcium nitrate is added to supplement nitric acid and ammonia water, and finally the solution is evaporated to obtain a solid ammonium calcium nitrate product. Concentrated liquid can also be obtained, which can be directly used for drip irrigation. The method can effectively utilize the titanium material pickling solution resources, and has great economic and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology and relates to a method for the resource utilization of pickling waste liquid. Technical Background

[0002] Titanium pickling solution is a chemical solution used to remove contaminants from the surface of titanium materials. It includes acidic substances, corrosion inhibitors, surfactants, and depressants. During the production and processing of titanium materials, the pickling solution gradually loses its effectiveness and accumulates impurities, becoming waste liquid or being discharged as wastewater. Traditional treatment methods, such as neutralization and precipitation with lime and alkali solutions, not only create sludge but also waste resources and pollute the environment. Therefore, developing methods for the resource utilization of titanium pickling solution is particularly important.

[0003] Traditional treatment methods for common steel pickling waste liquid typically involve neutralization with lime, carbide slag, or Ca(OH)2, a product of lime nitration. However, this method generates difficult-to-treat sludge and wastes acid and metal resources. In contrast, resource-based treatment methods can turn waste into valuable resources while treating it. Methods for the resource utilization of pickling solutions include complexation precipitation, concentration crystallization, and neutralization. These methods not only reduce environmental pollution but also effectively recover and utilize useful components, possessing significant economic and environmental value.

[0004] For example, in the Chinese invention patent "Method for Recycling Waste Water from Pickling Titanium and its Titanium Alloys" (patent number: CN86104454), Cao Junqing and Wang Guoxing of the Northwest Nonferrous Metals Research Institute adopted a complexation precipitation method by adding sodium fluoride to precipitate titanium ions and other impurity ions from the waste pickling solution. The filtrate was then replenished with 20% nitric acid and 80% hydrofluoric acid to achieve the effect of freshly prepared acid. The precipitate can be used for corrosion prevention, enamel, and plastics industries, and can also be converted into hydrofluoric acid and titanium dioxide. In the Chinese invention patent "A Regeneration Method for Waste Water from Pickling Titanium Metal" (patent number: CN202411214292.9), Zhang Jingtao et al. invented a regeneration method for waste water from pickling titanium metal. A fluorosilicic acid solution was added to the waste water and mixed thoroughly. Then, a potassium salt solution was added, and the mixture was stirred and reacted at room temperature. After the reaction was completed, the mixture was separated by centrifugation or filtration. The solid part was a potassium fluorotitanate / potassium fluorosilicate complex; the liquid part was the regenerated waste water from pickling titanium metal. In the Chinese invention patent "A Method for Preparing Nano-Anatase Titanium Dioxide from Cold-Rolled Titanium Pickling Waste Liquid" (Patent No.: CN202010543554.1), Wei Keyi et al. invented a method for preparing nano-anatase titanium dioxide from cold-rolled titanium pickling waste liquid, including the following steps: ① Adjusting the pH of the cold-rolled titanium pickling waste liquid to 1-3, then aging the solution and separating it, drying the obtained precipitate to obtain a metatitanic acid precursor; ② Calcining the metatitanic acid precursor obtained in step ①, and cooling it to obtain the aforementioned nano-anatase titanium dioxide. This invention can directly obtain nano-anatase titanium dioxide, achieving efficient recycling of titanium resources. Other methods involve adding acid and then heating and distilling to recover hydrofluoric acid or nitric acid. The main problems with these acid recovery methods are the unavoidable increase in corrosiveness, high equipment requirements, and low product quality. Furthermore, the sodium nitrate or ammonium nitrate produced after neutralization of nitrates also poses a risk of explosion.

[0005] To address the issue of nitrate ions being prone to explosion and to solve the problem of wastewater resource utilization, it is necessary to seek non-explosive nitrate substances. Agricultural fertilizer ammonium calcium nitrate, due to the presence of calcium, has a lower nitrogen content than ordinary ammonium nitrate, and its hygroscopicity is lower, thus improving its caking resistance and thermal stability. It is less prone to fire and explosion during storage and transportation, making it a safe nitrate nitrogen fertilizer. As a modified alternative to ammonium nitrate, it meets current and future market demands and has broad development prospects.

[0006] Therefore, this invention has developed a method for the resource utilization of pickling solution for titanium materials. From the perspective of resource reuse, the pickling waste liquid or wastewater of titanium materials is enriched with metallic elements titanium and fluorine, and further ammonium nitrogen and titanium nitrate nitrogen in it are used to prepare calcium ammonium nitrate products, thereby realizing resource utilization and industrial chain extension. Summary of the Invention

[0007] To address the aforementioned problems, this invention aims to provide a novel method for the resource utilization of acidic waste liquid and wastewater from titanium materials. This method effectively treats the acidic waste liquid and wastewater from titanium materials, thus avoiding environmental pollution, while also enriching titanium and fluorine in the acidic waste liquid and wastewater. Furthermore, the final product, calcium ammonium nitrate, can be used as fertilizer, greatly improving both economic and environmental benefits.

[0008] The technical solution of the present invention:

[0009] A method for the resource utilization of pickling waste liquid includes the following steps:

[0010] Titanium materials were cleaned using nitric acid and hydrofluoric acid of different concentrations. First, the waste liquid and wastewater obtained after cleaning were filtered to remove insoluble solids, resulting in waste liquid and wastewater free of insoluble solids, which were used as raw water. Then, an organic complexing agent was added to the raw water to complex fluoride ions, followed by the addition of CaO to adjust the pH. Filtration yielded filtrate 1 and titanium-rich precipitate. A complex-breaking agent was added to filtrate 1 to oxidize and break the complex, followed by the addition of CaO to adjust the pH. Filtration yielded filtrate 2 and fluoride-rich precipitate. A composite adsorbent was added to filtrate 2 for deep defluorination. The filtered solution was then concentrated through a multi-stage concentration membrane to obtain a 15-18 wt% calcium nitrate solution. Nitric acid and ammonia were added according to the ammonium calcium nitrate ratio, and the solution was then evaporated to obtain the ammonium calcium nitrate product.

[0011] The organic complexing agent is a substance containing hydroxyl or amino and anthraquinone functional groups, such as 1,2-dihydroxyanthraquinone, 3-methylamine-alizarin diacetic acid; the mass ratio of the organic complexing agent to fluorine is 1-1.5:1 to ensure that fluoride ions in the solution are completely complexed;

[0012] CaO was used to adjust the pH of filtrate 1 to 3-4;

[0013] The complex-breaking agent is the addition of H2O2 and / or elemental Fe, or Fe 2+ Among them, elemental Fe and Fe 2+ It is not advisable to add too much to avoid introducing more impurities. The amount of Fe added is used to break the complex structure of fluoride ions. The amount added is related to the concentration of fluoride ions in the raw water. The molar ratio of Fe to F ions should be between 0.7 and 2. The amount of H2O2 added should also be controlled so that the molar ratio of H2O2 to F ions is between 0.7 and 2.

[0014] CaO was used to adjust the pH of filtrate 2 to 8.5-9;

[0015] The composite adsorbent is a composite adsorbent of bone char and inorganic magnesium aluminum oxide, and the dosage is controlled to meet the requirement of fluoride ≤1mg / L or lower after defluorination.

[0016] The membranes used in the concentration membrane unit are RO membranes and HSRO membranes, employing a multi-stage concentration method to concentrate calcium nitrate to a concentration of 15-18 wt% (all percentages mentioned in the text are mass fractions); the effluent meets the requirements of TDS≤1000mg / L and pH 6.5-9.5;

[0017] The chemical formula of the obtained calcium ammonium nitrate product is 5Ca(NO3)2·NH4NO3·10H2O.

[0018] Add nitric acid and ammonia to the solution to achieve n(Ca):n(NO) 3- ): n(NH 4+ The ratio of 5:11:1 was used to obtain a solid product containing water of crystallization through evaporation.

[0019] The beneficial effects of this invention are:

[0020] Nitrate solids are mostly controlled as explosive substances. Wastewater resource recovery requires evaporating the solids to obtain solids. Nitrates such as sodium nitrate, ammonium nitrate, and calcium nitrate have high explosion-proof requirements for evaporation and are subject to strict management. They require a safer production environment and equipment, and the preparation cost is high as a waste resource recovery method.

[0021] Calcium ammonium nitrate is a safe fertilizer material with low explosion safety and easy production, making it suitable as a product for the resource utilization of nitrate wastewater. The wastewater resource targeted by this patent is wastewater with nitrate, ammonium, and calcium ions as its main components, and is suitable for conversion using the design method of this patent.

[0022] Currently, there is no technology available for the production of calcium ammonium nitrate from wastewater. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention;

[0024] Figure 2 Infrared spectra of the composite adsorbent before and after adsorption;

[0025] Figure 3 The infrared spectrum of the product in Example 1;

[0026] Figure 4 The infrared spectrum of the product in Example 2 is shown. Detailed Implementation

[0027] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0028] Example 1: Resource recovery of titanium pickling waste liquid

[0029] The pH of 1 L of acidic waste liquid used to remove insoluble solids was determined to be 0.80. The concentrations of various ions in the solution were determined using ICP-OES, the nitrate nitrogen concentration was determined using ultraviolet spectrophotometry, and the fluoride ion concentration was determined using a fluoride ion electrode. The results are shown in Table 1.

[0030] Table 1. Ion concentrations in acidic waste liquid and wastewater from titanium materials.

[0031]

[0032] The acidic waste liquid and wastewater contained approximately 7.8 g / L of nitrate nitrogen (equivalent to NO3). - The concentration of fluoride was approximately 34.54 g / L, and the concentration of fluoride was approximately 7.2 g / L. This was due to the large amount of F in the solution. - The existence of Ca 2+ The concentration was close to 0, and Mg, P, As and other heavy metal elements were not detected.

[0033] The first step involved adding an equimolar amount of the organic complexing agent 3-methylamine-alizarin diacetic acid to the solution based on the fluoride concentration. Then, CaO powder was added to adjust the pH to 3.7, followed by filtration. Analysis of the precipitate and filtrate revealed that the precipitate mainly consisted of Ca and Ti, with contents of 39.2% and 20.4%, respectively. Small amounts of Al and Fe were also present in the precipitate. At this point, the F concentration in the solution was... - Slightly decreased, while NO3 - The concentration remained essentially unchanged, indicating that Al and Fe in the solution had completely precipitated.

[0034] The second step is to add an appropriate amount of H2O2 and a small amount of Fe to the filtrate from the first step. 2+ Oxidation complex breaking was performed, followed by adding CaO powder to the filtrate to adjust the pH to 8.5, and then filtering. Analysis of the precipitate and filtrate revealed that the precipitate was mainly composed of CaF₂, with trace amounts of Fe. At this point, the F content in the solution was... - The concentration is 90 mg / L, NO3 - The concentration remained essentially unchanged, Ca 2+ The concentration is 11.2 g / L, meaning the main component in the solution is Ca(NO3)2.

[0035] Third, add 20g of bone char / LDH composite adsorbent to the filtrate from the second step, shake to adsorb for 1 hour, filter, and measure F. - Concentration, after adsorption, F - Concentration less than 1 mg / L. Infrared spectra of the bone char / LDH adsorbent before and after adsorption are attached. Figure 2 As shown.

[0036] The fourth step involves adding the solution to a flat-sheet membrane device for concentration. The membrane module consists of an RO membrane and a HSRO membrane. After five concentrations, the calcium nitrate concentration in the solution reaches 15%. The effluent TDS is 800 mg / L, and the pH is measured to be 7.5.

[0037] Fifth step: Add 3.7 ml of nitric acid and 3.8 ml of ammonia (based on nitrate concentration) to the concentrated Ca(NO3)2 solution, then place the solution in an evaporating dish for evaporation. After evaporation, a yellowish-white solid is obtained; the infrared spectrum is shown below. Figure 3 As shown in the figure. It can be seen from the figure that, compared to dry calcium ammonium nitrate, the product obtained in Example 1 has a diameter of 3219.6 cm⁻¹. -1 A distinct absorption peak appears nearby, caused by the vibration of the -OH bond in H2O, indicating the presence of water of crystallization in the obtained product. Other absorption peaks in Example 1 correspond to those of calcium ammonium nitrate, and are located in the range of 1450–1300 cm⁻¹. -1 A noticeable amount of NO3 was observed at the location. - Absorption peak.

[0038] Example 2: Wastewater from titanium pickling in a combined pool of a titanium material production enterprise

[0039] The wastewater composition, pH=3, was analyzed. The concentrations of various ions in the solution were determined using ICP-OES, the nitrate nitrogen concentration was determined using ultraviolet spectrophotometry, and the fluoride ion concentration was determined using a fluoride ion electrode. The results are shown in Table 1.

[0040] Table 2. Ion concentrations in acidic waste liquid and wastewater from titanium materials.

[0041]

[0042] The first step involved adding an equimolar amount of the organic complexing agent 1,2-dihydroxyanthraquinone (used to complex fluoride) to the solution according to the fluoride concentration. Then, CaO powder was added to adjust the pH to 4, followed by filtration. Analysis of the precipitate and filtrate revealed that the precipitate mainly consisted of Ca and Ti, with contents of 40.2% and 19.9%, respectively. Small amounts of Al and Fe were also present in the precipitate. At this point, the F concentration in the solution was... - The concentration decreased by about 5%, while NO3 - The concentration remained essentially unchanged, indicating that Al and Fe in the solution had completely precipitated.

[0043] The second step is to add H2O2 and a small amount of Fe to the filtrate from the first step. 2+ Oxidation complex breaking was performed, followed by adding CaO powder to the filtrate to adjust the pH to 9, and then filtering. Analysis of the precipitate and filtrate revealed that the precipitate mainly consisted of CaF₂. At this point, the F₂ in the solution... - The concentration is 10 mg / L, NO3 - The concentration remained essentially unchanged, Ca 2+The concentration is 11.8 g / L, meaning the main component in the solution is Ca(NO3)2.

[0044] Third, add 15g of composite adsorbent to the filtrate from the second step, shake to adsorb for 1 hour, filter, and measure F. - Concentration, after adsorption, F - Concentration less than 1 mg / L.

[0045] The fourth step involves adding the solution to a flat-sheet membrane device for concentration. After five concentration cycles, the calcium nitrate concentration in the solution reaches 15%. The effluent TDS is 950 mg / L, and the pH is measured to be 8.4.

[0046] Fifth, add 10.4 ml of nitric acid and 4.4 ml of ammonia (based on calcium ion concentration) to the concentrated Ca(NO3)2 solution, then place the solution in an evaporating dish for evaporation. After evaporation, a yellowish-white solid is obtained; the infrared spectrum is shown below. Figure 4 As shown in the figure. It can be seen from the figure that only at 3202.2cm... -1 The product obtained in Example 2, except for the difference in water of crystallization and the fluctuation in the hydroxyl peak, corresponds to the absorption peaks of dried calcium ammonium nitrate, and the absorption peaks are all similar to those of calcium ammonium nitrate in the range of 1450–1300 cm⁻¹. -1 A noticeable amount of NO3 was observed at the location. - Absorption peak.

Claims

1. A method for resource utilization of spent pickling liquor wastewater, characterized in that, The steps are as follows: The titanium material is cleaned using different concentrations of nitric acid and hydrofluoric acid, the waste liquid and waste water obtained after cleaning are filtered to remove insoluble solids, and the waste liquid and waste water without insoluble solids are obtained as raw water; then, an organic complexing agent is added to the raw water to complex fluoride ions, CaO is added to adjust the pH, and the filtrate 1 and titanium-rich precipitate slag are obtained by filtration; an oxidation complex breaking agent is added to the filtrate 1 to break the complex, CaO is added to adjust the pH, and the filtrate 2 and fluorine-rich precipitate are obtained by filtration; a composite adsorbent is added to the filtrate 2 for deep defluorination, and the solution is concentrated by a multi-stage concentration membrane group to obtain a 15-18 wt% calcium nitrate solution; ammonium calcium nitrate is added according to the ratio, and nitric acid and ammonia water are added, and then the solution is evaporated to obtain the ammonium calcium nitrate product.

2. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The organic complexing agent is a substance containing hydroxyl or amino groups and an anthraquinone functional group.

3. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The organic complexing agent is 1,2-dihydroxyanthraquinone or 3-methylamine-alizarin diacetic acid.

4. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The CaO adjusts the pH of the filtrate 1 to 3-4.

5. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The breaking agent is H2O2 and Fe element or H2O2 and Fe 2+ The molar ratio of the added Fe element to F ion should be between 0.7 and 2; the amount of added H2O2 should also be controlled so that the molar ratio of H2O2 to F ion is between 0.7 and 2.

6. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The CaO adjusts the pH of the filtrate 2 to 8.5-9.

7. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The composite adsorbent is a bone carbon and inorganic magnesium aluminum oxide composite adsorbent, and the defluorination amount is controlled to meet the requirement of ≤1 mg / L of fluorine.

8. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The filter membrane used in the concentration membrane group is an RO membrane and an HSRO membrane, and the concentration of the concentrated calcium nitrate is 15-18 wt% by using a multi-stage concentration method; the effluent meets the requirement of ≤1000 mg / L of TDS and 6.5-9.5 of pH. The filter membrane used in the concentration membrane group is an RO membrane and an HSRO membrane, and the concentration of the concentrated calcium nitrate is 15-18 wt% by using a multi-stage concentration method; the effluent meets the requirement of ≤1000 mg / L of TDS and 6.5-9.5 of pH.

9. The method for resource utilization of spent pickling liquor wastewater according to claim 1, characterized in that, The nitric acid and ammonia water were added to the solution to make n(Ca):n(NO3 - ):n(NH4 + )=5:11:1, and the solid product containing crystal water was obtained by evaporation.

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