Titanium dioxide waste acid resource recycling method

Abstract

The invention discloses a titanium dioxide waste acid resource recycling method which comprises the following steps: (1) performing reverse osmosis treatment on acid washing water through a first-stage RO (Reverse Osmosis) procedure, a second-stage RO procedure and a third-stage RO procedure in sequence, and recycling produced water generated by the third-stage RO procedure; (2) performing nanofiltration treatment and evaporation treatment on the waste acid through a special acid-resistant NF program, a first acid-resistant NF program and an MVR program in sequence, and recycling sulfuric acid generated in the MVR program; a base membrane material of a nanofiltration membrane in the special acid-resistant NF procedure is modified polyether sulfone; the modified polyethersulfone is prepared by carrying out graft modification on polyethersulfone through fluorine-containing silylene. According to the titanium dioxide waste acid resource recycling method, equipment has excellent acid resistance, and resource recycling of waste acid can be completed efficiently at low cost.

Description

Technical Field

[0001] The invention relates to the technical field of resource recovery, and in particular to a method for recovering waste acid from titanium dioxide. Background Art

[0002] Titanium dioxide is widely used in the coating manufacturing industry, fiber synthesis industry, plastic manufacturing industry, metallurgical manufacturing industry and printing and dyeing industry. Titanium dioxide is mainly produced by sulfuric acid method. This process uses ilmenite as raw material, acid hydrolysis to generate soluble titanyl sulfate, and then sedimentation, vacuum crystallization, ferrous separation, controlled filtration to remove insoluble impurities, and then vacuum concentration, atmospheric pressure hydrolysis to obtain titanic acid, and then the titanic acid is washed and rinsed to remove residual impurities, and then calcined and dehydrated to obtain TiO 2 , and then the intermediate product is crushed and post-processed to produce high-grade rutile titanium dioxide.

[0003] In the existing technology, the production of titanium dioxide is mainly based on the sulfuric acid process. This method uses cheap and easily available ilmenite and sulfuric acid as raw materials. It has mature technology, simple operation, low investment and low production cost. However, the production process produces about 15%-20% waste acid and a large amount of acid wash water. The acid waste water mainly contains 5% sulfuric acid, ferrous ions and other metal ions. If it is directly neutralized, it will not only waste a lot of resources, but also produce a large amount of red gypsum that needs to be stored and landfilled and high-salt wastewater that needs to be discharged, which will cause secondary pollution of the water environment and cannot truly solve the environmental protection problem. Therefore, how to effectively treat this kind of waste acid as a resource has always been a technical problem facing titanium dioxide production workers and environmental protection workers.

[0004] For the treatment of titanium dioxide waste acid, the existing technology mainly adopts a single evaporation and concentration method, which directly evaporates and concentrates the waste acid to 45-70%, and then mixes it with concentrated sulfuric acid and returns it to the ilmenite leaching section to achieve the recovery of the acid component. However, this process will produce ferrous sulfate monohydrate with high impurity content and high viscosity. The disposal of this kind of low-quality ferrous sulfate monohydrate is also a headache for enterprises. The single evaporation and concentration method only recovers sulfuric acid, but ferrous sulfate is lost as waste, and the energy consumption is very high.

[0005] The subsequent solid-liquid separation + membrane concentration method mainly involves solid-liquid separation of the acid first, followed by membrane concentration to increase the acid concentration to 23%, followed by evaporation concentration, and then the use of membrane filter press to separate the iron salt from the acid. Compared with the traditional evaporation concentration method, this method purifies the acid by separating the pollutants in the acid, but the membrane material of the current process has insufficient acid resistance and small membrane flux, and there are serious corrosion problems and insufficient efficiency. In addition, there are many filter membranes and the cost is high.

[0006] Therefore, there is an urgent need for a method for recycling waste acid from titanium dioxide that has excellent corrosion resistance, is efficient and low-cost. Summary of the invention

[0007] Purpose of the invention: In view of the defects of the prior art, the purpose of the present invention is to provide a method for resource recovery of waste acid from titanium dioxide with excellent corrosion resistance and high efficiency and low cost.

[0008] Technical solution: A method for recycling waste acid from titanium dioxide comprises the following steps: (1) The acid wash water is sequentially subjected to the primary RO process, the secondary RO process and the tertiary RO process for reverse osmosis treatment, and the produced water from the tertiary RO process is reused; (2) The waste acid is sequentially subjected to the special acid-resistant NF process, the first acid-resistant NF process and the MVR process for nanofiltration treatment and evaporation treatment, and the sulfuric acid produced in the MVR process is reused; The base membrane material of the nanofiltration membrane in the special acid-resistant NF procedure is modified polyethersulfone; The modified polyethersulfone is prepared by grafting polyethersulfone with fluorine-containing silene; The fluorine-containing silicene has a structure as shown in the following formula A: .

[0009] Furthermore, the concentrated water produced by the primary RO process is introduced into the second acid-resistant NF process, the produced water produced by the second acid-resistant NF process is introduced into the concentrated water RO process, and the concentrated water produced by the concentrated water RO process is introduced into the MVR process to generate sulfuric acid for reuse.

[0010] Furthermore, the produced water produced by the concentrated water RO process is introduced into the tertiary RO process; and the concentrated water produced by the secondary RO process is introduced into the concentrated water RO process.

[0011] Furthermore, the concentrated water produced by the tertiary RO process is reintroduced into the secondary RO process; and the concentrated water produced by the first acid-resistant NF process is reintroduced into the special acid-resistant NF process.

[0012] Furthermore, the fluorine-containing silicene is prepared by the following steps: adding perfluorooctanesulfonyl chloride, di(dimethylamino)methylvinylsilane and a catalyst into a reactor, heating to 70-80° C., stirring and refluxing for 4-6 hours, cooling, washing and drying to obtain the fluorine-containing silicene.

[0013] The present invention uses fluorinated silicene to perform radiation grafting modification on polyethersulfone. On the one hand, the perfluoroalkyl structure and the sulfonyl structure in the fluorinated silicene have excellent chemical stability and stability to acidic substances, and can significantly improve the acid resistance and the filtering ability of polyethersulfone to acidic substances; on the other hand, the quaternary ammonium structure in the fluorinated silicene can improve the uniformity of the grafting reaction during the radiation grafting process, thereby preparing a uniform and stable base membrane material, and can improve the dispersibility between various particles on the nanofiltration membrane, avoid clogging of the filter membrane, and significantly improve the membrane flux of the nanofiltration membrane, thereby improving the filtration efficiency.

[0014] Furthermore, the molar ratio of the perfluorooctanesulfonyl chloride to bis(dimethylamino)methylvinylsilane is 2.3-2.5:1.

[0015] Furthermore, the catalyst is selected from one of triethylamine, triethylenediamine or N,N'-dimethylaniline.

[0016] Furthermore, the modified polyethersulfone is prepared by the following steps: (1) Adding polyethersulfone and an organic solvent into a reactor, stirring to dissolve, then adding fluorinated silene and a polymerization inhibitor, stirring and mixing to obtain a mixed solution; (2) adding the mixed solution into a radiation tube, introducing high-purity nitrogen gas and performing irradiation grafting; after the grafting is completed, using methanol as a precipitant, precipitating, filtering, washing, and drying to obtain the modified polyethersulfone.

[0017] The base membrane material of the nanofiltration membrane in the special acid-resistant NF process of the present invention is modified polyethersulfone, the sulfone group and ether bond in its structure can effectively improve the chemical stability of the base membrane, so that it has excellent acid resistance, and the sulfone group and ether bond can improve the hydrophilicity and flexibility of polyethersulfone, which can further improve the membrane flux and pressure resistance of the nanofiltration membrane, and can allow the nanofiltration membrane to perform more efficient filtration treatment.

[0018] Furthermore, the polymerization inhibitor is selected from one of p-hydroxyanisole, p-benzoquinone or 1,1-diphenyl-2-trinitrophenylhydrazine; and the mass ratio of polyethersulfone to fluorine-containing silene is 6-8:1.

[0019] Furthermore, the conditions for the irradiation grafting are: the radiation source is 60 Co γ-ray, total radiation dose 30-35 kGy, radiation dose rate 30-50 Gy·min -1 .

[0020] Beneficial effects:

[0021] (1) The method for recycling waste acid from titanium dioxide of the present invention uses an acid-resistant RO membrane to directly concentrate the acid wash water and then passes it through a nanofiltration membrane to separate the acid and ferrous iron, thereby reducing the number of nanofiltration membranes and thus saving investment costs. The waste acid is removed by nanofiltration before entering the MVR system, thereby reducing the precipitation of ferrous iron and other metal ions with changes in temperature and pressure, which block pipes and heat exchangers and affect normal production.

[0022] (2) The method for recycling waste acid from titanium dioxide of the present invention uses a full membrane method to treat wastewater. No chemicals need to be added during the process, and the water produced by the three-stage RO process can be directly reused in the production of titanium dioxide.

[0023] (3) The method for recycling waste acid from titanium dioxide of the present invention uses a special acid-resistant NF membrane and a conventional acid-resistant NF membrane in combination, which can effectively improve the average water production membrane flux of the nanofiltration system. The acid-resistant NF concentrated water and the special acid-resistant NF concentrated water contain high concentrations of ferrous sulfate, which can be transported to ferrous sulfate manufacturers for recycling.

[0024] (4) In the method for recycling waste acid from titanium dioxide of the present invention, the base membrane material of the nanofiltration membrane in the special acid-resistant NF process is modified polyethersulfone, the sulfone group and ether bond in its structure can effectively improve the chemical stability of the base membrane, making it have excellent acid resistance, and the sulfone group and ether bond can improve the hydrophilicity and flexibility of polyethersulfone, which can further improve the membrane flux and pressure resistance of the nanofiltration membrane, allowing the nanofiltration membrane to perform more efficient filtration treatment.

[0025] (5) In the method for recycling waste acid from titanium dioxide of the present invention, polyethersulfone is modified by radiation grafting with fluorinated silicene. On the one hand, the perfluoroalkyl structure and sulfonyl structure in the fluorinated silicene have excellent chemical stability and stability to acidic substances, which can significantly improve the acid resistance and filtration ability of polyethersulfone to acidic substances. On the other hand, the quaternary ammonium structure in the fluorinated silicene can improve the uniformity of the grafting reaction during the radiation grafting process, thereby obtaining a uniform and stable base membrane material, and can improve the dispersibility between various particles on the nanofiltration membrane, avoid clogging of the filter membrane, and significantly improve the membrane flux of the nanofiltration membrane, thereby improving the filtration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of the method for recycling waste acid from titanium dioxide in this application. DETAILED DESCRIPTION

[0027] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0028] The acid-resistant NF membrane is ECNF150-8040AC acid-resistant special separation nanofiltration membrane purchased from Intuo Water Technology Co., Ltd.; the remaining reagents and equipment are conventional reagents and equipment in this technical field.

[0029] Preparation of fluorinated silicene The fluorinated silicene was prepared by the following steps: In a reactor, 0.025 mol of perfluorooctanesulfonyl chloride, 0.01 mol of di(dimethylamino)methylvinylsilane and 0.3 g of N,N'-dimethylaniline were added, heated to 70°C, stirred and refluxed for 6 hours, and then cooled, washed and dried to obtain the fluorine-containing silene; Mass spectrometric data of fluorinated silicene: The product was analyzed by LC-MS, and the m / z of the product was 562.00 (100.0%), 562.62 (40.8%), 563.07 (12.9%), and 563.58 (2.8%).

[0030] Preparation of modified polyethersulfone-1 Modified polyethersulfone-1 was prepared by the following steps: (1) In a reactor, add 6 g of polyethersulfone and 100 mL of dimethylacetamide, stir to dissolve, then add 1 g of fluorinated silene and 0.3 g of p-hydroxyanisole, stir and mix to obtain a mixed solution; (2) Add the mixed solution into the radiation tube, introduce high-purity nitrogen and place it under the radiation source. 60 Co γ-ray, total radiation dose 35 kGy, radiation dose rate 40 Gy·min -1 The irradiation grafting is carried out under the following conditions, and after the grafting is completed, methanol is used as a precipitant, and the modified polyethersulfone-1 is obtained after precipitation, filtration, washing and drying.

[0031] Preparation of modified polyethersulfone-2 The preparation method is basically the same as that of modified polyethersulfone-1, except that the fluorinated silene is replaced by an equal amount of perfluorooctylethyl methacrylate.

[0032] Preparation of modified polyethersulfone-3 The preparation method is basically the same as that of modified polyethersulfone-1, except that the fluorinated silene is replaced by an equal amount of 5-hexenyltriethoxysilane.

[0033] Preparation of special acid-resistant NF membrane-1 The special acid-resistant NF membrane-1 was prepared by the following steps: (1) Prepare a solution by taking 15 g of modified polyethersulfone-1, 100 g of N,N'-dimethylformamide and 3 g of nano-silicon dioxide, and vacuum degassing and filtering the solution for later use; (2) scraping the solution obtained by filtering in step (1) onto a non-woven fabric, immersing it in water to precipitate a support layer, and washing away the solvent to obtain a porous base membrane; (3) 10 g of amyl alcohol, 1 g of o-phenylenediamine, 0.1 g of sodium dodecylbenzene sulfonate and 30 mL of deionized water were mixed evenly to obtain an aqueous phase solution, and 10 g of trimesoyl chloride was dissolved in 50 g of n-hexane to obtain an oil phase solution; (4) Pour the aqueous solution onto the porous base membrane, remove the aqueous solution after 3 minutes of contact, dry naturally, then add the oil solution, remove the oil solution after 1 minute of contact, and dry to obtain the special acid-resistant NF membrane-1.

[0034] Preparation of special acid-resistant NF membrane-2 The preparation method is basically the same as that of special acid-resistant NF membrane-1, except that the modified polyethersulfone-1 is replaced by an equal amount of modified polyethersulfone-2.

[0035] Preparation of special acid-resistant NF membrane-3 The preparation method is basically the same as that of special acid-resistant NF membrane-1, except that the modified polyethersulfone-1 is replaced by an equal amount of modified polyethersulfone-3.

[0036] Example like Figure 1 As shown, the waste acid of titanium dioxide is recycled through the following steps: (1) The acid wash water is sequentially subjected to the primary RO process, the secondary RO process and the tertiary RO process for reverse osmosis treatment, and the produced water from the tertiary RO process is reused; (2) The waste acid is sequentially subjected to the special acid-resistant NF process, the first acid-resistant NF process and the MVR process for nanofiltration treatment and evaporation treatment, and the sulfuric acid produced in the MVR process is reused; (3) The concentrated water produced by the primary RO process is introduced into the second acid-resistant NF process, the produced water produced by the second acid-resistant NF process is introduced into the concentrated water RO process, and the concentrated water produced by the concentrated water RO process is introduced into the MVR process to generate sulfuric acid for reuse; (4) The produced water from the concentrated water RO process is introduced into the third-level RO process; the concentrated water from the second-level RO process is introduced into the concentrated water RO process, the concentrated water from the third-level RO process is re-introduced into the second-level RO process, and the concentrated water from the first acid-resistant NF process is re-introduced into the special acid-resistant NF process; The special acid-resistant NF process uses the special acid-resistant NF membrane-1; the acid-resistant NF uses the acid-resistant NF membrane.

[0037] Comparative Example 1 The method is basically the same as Example 1, except that the special acid-resistant NF membrane-1 is replaced by an acid-resistant NF membrane.

[0038] Comparative Example 2 The method is basically the same as Example 1, except that the special acid-resistant NF membrane-1 is replaced by the special acid-resistant NF membrane-2.

[0039] Comparative Example 3 The method is basically the same as Example 1, except that the special acid-resistant NF membrane-1 is replaced by the special acid-resistant NF membrane-3.

[0040] Performance Testing

[0041] 1. Recovery rate detection: detect the recovery rate of sulfuric acid and various valuable metals in concentrated water and sulfuric acid produced by special acid-resistant NF program, acid-resistant NF program and MVR program; The calculation method for the recovery rate of various valuable metals is: recovery rate = amount of concentrated water / content in titanium dioxide waste acid*100%; the calculation method for the recovery rate of sulfuric acid is: recovery rate = amount of sulfuric acid generated by the MVR program / amount of sulfuric acid in titanium dioxide waste acid*100%.

[0042] The test results are shown in Table 1 below: Table 1

[0043] According to the comparison of the test results of the embodiment and the comparative example 1, it can be seen that the method for recycling waste acid from titanium dioxide provided by the present invention can effectively recycle various valuable metals and sulfuric acid, thereby realizing the recycling and reuse of resources.

[0044] According to the comparison of the test results of the embodiment with those of comparative examples 2 and 3, the method for resource recovery of waste acid from titanium dioxide provided by the present invention can effectively recover sulfuric acid, ferrous ions and other metal ions by adding a special acid-resistant NF program, and can significantly improve the recovery rate of various substances, and is more suitable for the resource recovery program of waste acid from titanium dioxide.

[0045] 2. Water flux and acid resistance test: The initial water flux and ferrous sulfate retention rate-1 of the special acid-resistant NF program in Examples and Comparative Examples 1-3 were tested respectively, and the ferrous sulfate retention rate-2 was tested again after running for 168 hours.

[0046] The test results are shown in Table 2 below: Table 2

[0047] According to the comparison of the test results of the embodiment and comparative example 1, it can be seen that the special acid-resistant NF program in the resource recovery method of titanium dioxide waste acid provided by the present invention has higher membrane flux and ferrous sulfate retention rate, which can significantly improve the resource recovery efficiency of titanium dioxide waste acid.

[0048] According to the comparison of the test results of the embodiment with those of comparative examples 2 and 3, it can be seen that the special acid-resistant NF membrane in the method for resource recovery of waste acid from titanium dioxide provided by the present invention can significantly improve the membrane flux of the NF membrane and the retention rate of various substances by irradiating and grafting polyethersulfone with fluorinated silicene, and has excellent acid resistance, and can recycle waste acid from titanium dioxide in a long-term and effective manner.

[0049] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling waste acid from titanium dioxide, characterized in that: The following steps are involved: (1) The acid wash water is sequentially subjected to the primary RO process, the secondary RO process and the tertiary RO process for reverse osmosis treatment, and the produced water from the tertiary RO process is reused; (2) The waste acid is sequentially subjected to the special acid-resistant NF process, the first acid-resistant NF process and the MVR process for nanofiltration treatment and evaporation treatment, and the sulfuric acid produced in the MVR process is reused; The base membrane material of the nanofiltration membrane in the special acid-resistant NF procedure is modified polyethersulfone; The modified polyethersulfone is prepared by grafting polyethersulfone with fluorine-containing silene; The fluorine-containing silicene has a structure as shown in the following formula A: 。 2. The method for recycling waste acid from titanium dioxide according to claim 1, characterized in that: The concentrated water produced by the primary RO program is introduced into the second acid-resistant NF program, the produced water produced by the second acid-resistant NF program is introduced into the concentrated water RO program, and the concentrated water produced by the concentrated water RO program is introduced into the MVR program to generate sulfuric acid for reuse.

3. The method for recycling waste acid from titanium dioxide according to claim 2, characterized in that: The produced water produced by the concentrated water RO process is introduced into the third-stage RO process; the concentrated water produced by the second-stage RO process is introduced into the concentrated water RO process.

4. The method for recycling waste acid from titanium dioxide according to claim 1, characterized in that: The concentrated water produced by the three-stage RO process is reintroduced into the two-stage RO process; the concentrated water produced by the first acid-resistant NF process is reintroduced into the special acid-resistant NF process.

5. The method for recycling waste acid from titanium dioxide according to claim 1, characterized in that: The fluorine-containing silicene is prepared by the following steps: adding perfluorooctanesulfonyl chloride, di(dimethylamino)methylvinylsilane and a catalyst into a reactor, heating to 70-80° C., stirring and refluxing for 4-6 hours, cooling, washing and drying to obtain the fluorine-containing silicene.

6. The method for recycling waste acid from titanium dioxide according to claim 5, characterized in that: The molar ratio of the perfluorooctanesulfonyl chloride to bis(dimethylamino)methylvinylsilane is 2.3-2.5:

1.

7. The method for recycling waste acid from titanium dioxide according to claim 5, characterized in that: The catalyst is selected from one of triethylamine, triethylenediamine or N,N'-dimethylaniline.

8. The method for recycling waste acid from titanium dioxide according to claim 1, characterized in that: The modified polyethersulfone is prepared by the following steps: (1) Adding polyethersulfone and an organic solvent into a reactor, stirring to dissolve, then adding fluorinated silene and a polymerization inhibitor, stirring and mixing to obtain a mixed solution; (2) adding the mixed solution into a radiation tube, introducing high-purity nitrogen gas and performing irradiation grafting; after the grafting is completed, using methanol as a precipitant, precipitating, filtering, washing, and drying to obtain the modified polyethersulfone.

9. The method for recycling waste acid from titanium dioxide according to claim 8, characterized in that: The polymerization inhibitor is selected from one of p-hydroxyanisole, p-benzoquinone or 1,1-diphenyl-2-trinitrophenylhydrazine; the mass ratio of polyethersulfone to fluorine-containing silene is 6-8:

1.

10. The method for recycling waste acid from titanium dioxide according to claim 8, characterized in that: The conditions for the irradiation grafting are: the radiation source is 60 Co γ-ray, total radiation dose 30-35 kGy, radiation dose rate 30-50 Gy·min -1 .

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