A resource treatment method of iron-containing sludge solid waste, product and application

Abstract

The application relates to the field of industrial waste resource recycling and new materials, and discloses a resource recycling method, product and application of iron-containing sludge solid waste. The titanium dioxide industrial waste sludge is taken as the main body, the titanium dioxide industrial waste sludge is subjected to acidification, solid-liquid separation and drying, and CaSO4 solid powder obtained after the above treatment can be used for industrial gypsum, and high-value-added CaSO4 solid whiskers can also be obtained through a hydrothermal system. The liquid obtained through the solid-liquid separation is subjected to pH adjustment, colloid synthesis, hydrothermal treatment and other technologies, and is used as an iron source to prepare a heterogeneous Fenton catalyst of nano Fe3O4 and iron-doped graphite-phase carbon nitride.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste treatment and material recycling, and particularly relates to a resource treatment method of iron-containing sludge solid waste, a product and application. BACKGROUND

[0002] At present, the process for producing titanium dioxide (main component: titanium dioxide) in China mainly adopts the sulfuric acid method, and the production capacity accounts for 98% of the total production capacity. A significant disadvantage of the sulfuric acid method is that the treatment amount of waste acid and acidic wastewater is large, because the sulfuric acid method needs to acidize and dissolve ilmenite ore, and it is inevitable to form a waste acid solution containing Fe ions. The relatively mature treatment method at present is the neutralization precipitation method, the precipitate is separated from the liquid phase by pressure filtration to achieve the discharge target. However, the filter cake is a typical solid waste, and the composition of the filter cake system formed in the common process is about 60%-70% of calcium sulfate dihydrate, 30%-40% of iron hydroxide, and a small amount of organic matter. At present, the solid waste of the titanium dioxide industry is generally used for low-end building materials such as red gypsum and ordinary cement, and the industrial added value is not high, and the amount used is relatively low.

[0003] In recent years, the call for comprehensive utilization of solid waste in the titanium dioxide industry is getting higher and higher, and currently there are technologies such as ferrous sulfate recovery, red gypsum refining, and nanometerized water treatment agent, but they are still in the development stage, and there is still a lack of a method that can separate the solid waste and then resourcefully utilize different components. SUMMARY

[0004] The purpose of the present application is to provide a resource treatment method of iron-containing sludge solid waste, which uses the iron-containing sludge solid waste generated in the production of titanium dioxide by the sulfuric acid method as raw material, can obtain calcium sulfate whiskers, heterogeneous Fenton catalysts and nanometer ferrite, meets the needs of resource utilization of solid waste and environmental protection, not only efficiently treats the solid waste, but also simultaneously obtains nanometer calcium sulfate whiskers, nanometer ferrite and heterogeneous Fenton catalysts, and is a one-stroke multi-benefit.

[0005] In one aspect, the resource treatment method of iron-containing sludge solid waste of the present application is derived from the iron-containing sludge solid waste generated in the production of titanium dioxide by the sulfuric acid method, and the method comprises the following steps:

[0006] S1: using concentrated sulfuric acid to fully react with Ca(OH)2 in the iron-containing sludge solid waste, and after solid-liquid separation, obtaining a precipitate and a liquid A,

[0007] S2: drying and recrystallizing the precipitate to obtain CaSO4·2H2O whiskers;

[0008] S3: obtaining Fe(OH)3 by colloidal precipitation of the liquid A.

[0009] Optionally, the method further comprises:

[0010] S4: obtaining nano-Fe3O4 by a method of dissolving and reducing controlled precipitation of the Fe(OH)3;

[0011] or, complexing the Fe(OH)3 with terephthalic acid and / or 2-amino terephthalic acid to form MOF material MIL-101(Fe) and / or NH2-MIL-101(Fe), and pyrolyzing the MOF material together with a cyanamide compound to generate nano-iron-containing nitrogen-containing carbon material Fe-CN.

[0012] Optionally, in step S1, the mass ratio of the iron-containing sludge solid waste to the concentrated sulfuric acid is 1:2-1:3.

[0013] Optionally, in step S2, the drying and recrystallization of the precipitate to obtain CaSO4·2H2O whiskers comprises:

[0014] The dried precipitate, i.e., CaSO4 solid, is added to a 40-60℃ water bath to stir a 1-5% mass concentration sodium chloride solution, an acid solution is used to adjust the pH to 3, after the CaSO4 is fully dissolved, anhydrous ethanol is added for recrystallization, after centrifugation, the precipitate is dried to obtain CaSO4·2H2O whiskers.

[0015] Optionally, in step S3, the Fe(OH)3 colloidal precipitate is obtained by colloidal precipitation of the liquid A, comprising:

[0016] The pH of the liquid A is adjusted to 4-8 with ammonia water to obtain a Fe(OH)3 colloidal precipitate, and Fe(OH)3 is obtained after centrifugal washing.

[0017] Optionally, the nano-Fe3O4 is obtained by a method of dissolving and reducing controlled precipitation of the Fe(OH)3, comprising:

[0018] Fe(OH)3 is mixed with hydrochloric acid to obtain a ferric chloride solution; the ferric chloride solution is mixed with ethanol to obtain a uniform mixture, sodium borohydride solution is then added until the solution is stable and black, and the mixture is washed with ethanol several times, and vacuum freeze-drying is performed to obtain magnetic nano-Fe3O4.

[0019] Optionally, the Fe(OH)3 colloidal precipitate is complexed with terephthalic acid and / or 2-amino terephthalic acid to form MOF material MIL-101(Fe) and / or NH2-MIL-101(Fe), and the MOF material is pyrolyzed together with a cyanamide compound to generate nano-iron-containing nitrogen-containing carbon material Fe-CN, comprising:

[0020] The Fe(OH)3 is dissolved in a melamine aqueous solution, hydrochloric acid is added, and then the mixture is uniformly mixed, and then p-diphenic acid and / or 2-amino terephthalic acid is added, and then the mixture is uniformly mixed, and then the hydrothermal reaction is carried out at a temperature of 80-150 DEG C for 12-24 h, and then the obtained solid product is calcined at 550 DEG C for 4 h to obtain the iron-containing and nitrogen-containing carbon material Fe-CN, wherein the mass ratio of the Fe(OH)3 to the melamine is 1:1-1:5; when the p-diphenic acid or the 2-amino terephthalic acid is used alone, the molar ratio of the Fe(OH)3 to the p-diphenic acid or the 2-amino terephthalic acid is 1:1-1:2; when the p-diphenic acid and the 2-amino terephthalic acid are used in combination, the molar ratio of the Fe(OH)3 to the total amount of the p-diphenic acid and the 2-amino terephthalic acid is 1:1-1:2, and the molar ratio of the p-diphenic acid to the 2-amino terephthalic acid is 1:1-1:10.

[0021] Optionally, the volume ratio of the ethanol to the ferric chloride solution is 30:1-10:1; and the concentration of the sodium borohydride solution is 0.1-0.2 mol / L.

[0022] In another aspect, the application also provides a product obtained by any of the above methods, which comprises CaSO4·2H2O whiskers and at least one of nano-Fe3O4 and the nano iron-containing and nitrogen-containing carbon material Fe-CN.

[0023] In still another aspect, the application provides an application of the product, and the nano iron-containing and nitrogen-containing carbon material Fe-CN is used for Fenton-like degradation of organic pollutants.

[0024] The application classifies and separates the main substances in the iron-containing sludge solid waste in the titanium dioxide industry, comprehensively utilizes the solid waste, and realizes value increment by respectively utilizing different components after separation, and obtains an environmental protection product.

[0025] The CaSO4·2H2O whiskers obtained by resource utilization can be used for high-grade polymer fillers, the nano-Fe3O4 can be used for biological targeting medical treatment, medical imaging and new anti-counterfeiting technology, etc. The Fe element in the Fe-CN material forms a stable Fe-N2-O ring ligand, the non-uniform charge distribution of which can improve the activity of the Fe element in the Fenton-like reaction, and at the same time, the stable iron ligand can enhance the Fe 3+ / Fe 2+ Oxidation-reduction cycle. The introduction of the MOF precursor structure can promote the formation of the stable Fe-N2-O ring ligand, and the melamine helps to form a certain graphite phase carbon nitride structure (g-C3N4) to endow the material with a certain visible light catalytic activity, and at the same time, protect the stability of the Fe-N2-O macrocyclic ligand.

[0026] The resource processing method of the iron-containing sludge solid waste provided by the application has a simple reaction process, and the whole process has mild and easy-to-control conditions. BRIEF DESCRIPTION OF DRAWINGS

[0027] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, and are used together with the specific embodiments described below to explain the application, but do not constitute a limitation on the application. In the drawings:

[0028] Figure 1 XRD pattern of CaSO4·2H2O whiskers obtained from Example 1 of the application.

[0029] Figure 2 SEM pattern of CaSO4·2H2O whiskers obtained from Example 1 of the application.

[0030] Figure 3 SEM pattern of nano-Fe3O4 obtained from Example 2 of the application.

[0031] Figure 4 TEM pattern of nano-Fe3O4 obtained from Example 2 of the application.

[0032] Figure 5 Degradation rate curve of the composite material Fe-CN for phenol obtained from Examples 1-6 and Comparative Example 3 of the application. DETAILED DESCRIPTION

[0033] The application is not limited to the following specific embodiments, and those skilled in the art can implement the application in other various specific embodiments according to the content disclosed in the application, or any simple changes or modifications made by using the design structure and ideas of the application, all fall within the protection scope of the application. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other without conflict.

[0034] The solid waste in the production of titanium dioxide is used as raw material, and the calcium sulfate, Fe 3+ and other recyclable resources such as some organic matters are recycled and comprehensively utilized, producing high-value environmental protection products and high-grade polymer fillers, which not only can solve the environmental risk caused by the storage of solid waste in the titanium dioxide industry, but also can form a good demonstration effect for the greenization, resourceization, high value and recycling utilization of solid waste in the titanium dioxide industry, promote the vertical integration development of the titanium dioxide industry, and help achieve the "double carbon" goal.

[0035] In view of the current needs of industry solid waste resource utilization and environmental protection, the application provides a method and application for preparing calcium sulfate whiskers, heterogeneous Fenton catalysts and nano-magnetic iron oxide from iron-containing sludge solid waste as raw material resources in the titanium dioxide industry. The production process is simple, has strong adaptability, and has a wide range of applications. It also helps to promote the further development of solid waste resource utilization in the titanium dioxide industry. Ca(OH)2 in the solid waste is converted to CaSO4 by pH adjustment, and high-grade CaSO4 nanowhiskers are synthesized from CaSO4 by recrystallization. The iron-containing solution obtained by solid-liquid separation is subjected to colloidal precipitation to obtain Fe(OH)3 colloidal precipitate. Nano-Fe3O4 is obtained by dissolving and reducing Fe(OH)3 to control precipitation. On the other hand, after the Fe(OH)3 colloidal precipitate is dissolved, it is combined with p-benzoic acid or 2-amino p-terephthalic acid to form MOF material MIL-101(Fe) or NH2-MIL-101(Fe). The MOF is pyrolyzed with a cyanamide compound to generate a nano-iron-containing nitrogen-containing carbon material, which can be used for efficient Fenton-like degradation of wastewater. The application meets the needs of industrial development and the requirements of industrial production, and has great potential for industrial application in the field of Fenton-like catalytic degradation materials and nanomaterials. Moreover, there is no report on the resource preparation of multifunctional materials from titanium dioxide industry solid waste.

[0036] The resource processing method of the iron-containing sludge solid waste in the specific embodiment of the application is derived from the iron-containing sludge solid waste generated in the production of titanium dioxide by the sulfuric acid method, and comprises the following steps:

[0037] S1: using concentrated sulfuric acid to fully react with Ca(OH)2 in the iron-containing sludge solid waste, and after solid-liquid separation, obtaining a precipitate and a liquid A,

[0038] S2: drying and recrystallizing the precipitate to obtain CaSO4·2H2O whiskers;

[0039] S3: obtaining Fe(OH)3 from the liquid A by colloidal precipitation.

[0040] The resource processing method of the iron-containing sludge solid waste in the specific embodiment of the application has a simple reaction process, and the entire process has mild conditions and is easy to control. The raw materials in the application have wide sources, strong applicability, low cost, and the product can be made from waste.

[0041] CaSO4·2H2O whiskers, and at least one of nano-Fe3O4 and nano-iron-containing nitrogen-containing carbon material Fe-CN can be obtained by the resource processing method of the specific embodiment of the application.

[0042] The CaSO4·2H2O whiskers obtained by the resource utilization method of the embodiment of the present application are used for high-grade polymer fillers, and the nano Fe3O4 is used for biological targeting medical treatment, medical imaging, and new anti-counterfeiting technology.

[0043] The nano Fe-CN containing iron and nitrogen carbon material obtained by the resource utilization method of the embodiment of the present application is used for Fenton-like degradation of organic pollutants:

[0044] The nano Fe-CN containing iron and nitrogen carbon material and peroxy monosulfuric acid (H2SO5, PMS) are added to a solution containing an organic pollutant to be degraded, the mass ratio of the PMS to the organic pollutant to be degraded is 1:2-1:1, and catalytic degradation is carried out at room temperature; the organic pollutant to be degraded is any one or several of rhodamine B, phenol, bisphenol A, and tetracycline.

[0045] The Fe element in the Fe-CN material forms a stable Fe-N2-O ring ligand, and the non-uniform charge distribution can improve the activity of the Fe element in the Fenton-like reaction, and at the same time, the stable iron ligand can enhance the redox cycle of Fe 3+ / Fe 2+ Oxidation and reduction. The introduction of the MOF precursor structure can promote the formation of a stable Fe-N2-O ring ligand, and the melamine helps to form a certain graphite phase carbon nitride structure (g-C3N4) to endow the material with a certain visible light catalytic activity, and at the same time, the stability of the Fe-N2-O macrocyclic ligand is protected.

[0046] The technical solutions of the present application will be further described below in conjunction with examples, but the present application is not limited to the following examples only.

[0047] Example 1

[0048] (1) 6g of iron-containing sludge was mixed with 15g of concentrated sulfuric acid and reacted thoroughly, and a large amount of white solid precipitate was observed at the bottom of the beaker. After filtration, white CaSO4 precipitate and yellow iron sulfate solution were separated. The remaining iron sulfate and CaSO4 precipitate were dried to obtain CaSO4 solid.

[0049] (2) 0.5g of CaSO4 solid was added to a 50ml sodium chloride solution (mass concentration of 3%) prepared in a 60℃ water bath with stirring, and the pH value was adjusted to 3 using hydrochloric acid solution. After the calcium sulfate was fully dissolved, 50ml of anhydrous ethanol was added, and the calcium sulfate was dispersed in the solution in the form of flocculation. The solution and the precipitate were separated by a centrifuge, and CaSO4·2H2O whiskers were obtained by drying at 80℃.

[0050] (3) The red-brown iron hydroxide colloid obtained after adjusting the pH of the acid filtrate separated in step (1) to 5 with ammonia water is separated by using a centrifuge at 4500 r / min for 3 min with alcohol washing several times.

[0051] (4) A certain amount of Fe(OH)3 in step (3) is mixed with 2 mol / L hydrochloric acid to obtain a ferric chloride solution. The above ferric chloride solution is mixed with ethanol (volume ratio 1:20) and stirred well. A prepared sodium borohydride solution (1 mol / L) is added dropwise to the above solution until the solution is stable and black. After ethanol washing several times and vacuum freeze-drying, magnetic nano Fe3O4 is obtained.

[0052] (5) A certain amount of 10.7 g melamine is placed in a beaker, and 10.7 g (0.1 mol) Fe(OH)3 is weighed. 60 ml of distilled water is added, and after stirring to disperse uniformly, 2 mol / L hydrochloric acid solution is added. After fully dissolving, 40 mL of N,N-dimethylformamide (DMF), 8.4 g (0.05 mol) of phthalic acid and 9.05 g (0.05 mol) of 2-amino terephthalic acid are added. After stirring uniformly, hydrothermal treatment is carried out at 110°C for 20h. After drying the solid product, calcination is carried out at 550°C for 4h under nitrogen environment to obtain fluffy Fe-CN.

[0053] (6) The degradation ability of Fe-CN as a Fenton-like catalyst is verified, and the Fe-CN is tested for catalytic degradation of phenol. The specific detection method is as follows:

[0054] 20 mg of the above composite material Fe-CN and 0.1 mg of PMS are weighed and added to 100 mL of 10 mg / L phenol solution. Under stirring conditions, the degradation curve of phenol is obtained by catalytic degradation.

[0055] Through testing, the degradation rate of phenol by Fe-CN within 15 min is 94.6%.

[0056] Example 2

[0057] (1) 6 g of iron-containing sludge is mixed with 15 g of concentrated sulfuric acid and reacts fully. A large amount of white solid precipitate is observed at the bottom of the beaker. After filtration, white CaSO4 precipitate and yellow ferric sulfate solution are separated. The remaining ferric sulfate and CaSO4 precipitate are dried to obtain CaSO4 solid.

[0058] (2) Take 0.5 g of CaSO4 solid and add it to the prepared 50 ml of sodium chloride solution (5% mass concentration) in a 60°C water bath with stirring. Adjust the pH to 3 using hydrochloric acid solution. After the calcium sulfate is fully dissolved, add 50 ml of absolute ethanol. The calcium sulfate is dispersed in the solution in the form of flocs. Separate the solution and the precipitate by centrifugation, and dry at 80°C to obtain CaSO4·2H2O whiskers.

[0059] (3) After adjusting the pH of the acidic filtrate separated in step (1) to 4 with ammonia water, a reddish-brown iron hydroxide colloid is obtained. Use a centrifuge to separate the precipitated Fe(OH)3 by centrifugation at 4500 r / min for 3 min with alcohol washing several times.

[0060] (4) Take a certain amount of Fe(OH)3 from step (3) and mix it with 2 mol / L hydrochloric acid to obtain a ferric chloride solution. Mix the above ferric chloride solution with ethanol (volume ratio 1:10) and stir well. Add the prepared sodium borohydride solution (2 mol / L) dropwise to the yellow solution until the solution stabilizes to black. Wash with ethanol several times, and vacuum freeze-dry to obtain magnetic nano-Fe3O4.

[0061] (5) Take a certain amount of 20 g melamine and place it in a beaker. Take 10.7 g (0.1 mol) of Fe(OH)3, add 60 ml of distilled water, and stir until it is evenly dispersed. Then add 2 mol / L hydrochloric acid solution, fully dissolve, and then add a certain amount of 40 mL N,N-dimethylformamide (DMF) and 16.8 g (0.1 mol) of terephthalic acid. Stir well and hydrothermal at 100°C for 22 h. Dry the solid product and calcine at 550°C for 4 h under nitrogen atmosphere to obtain fluffy Fe-CN.

[0062] (6) Verify the degradation ability of Fe-CN as a Fenton-like catalyst. Test the catalytic degradation of Rhodamine B by Fe-CN. The specific detection method is as follows:

[0063] Take 20 mg of the above composite material Fe-CN and 0.1 mg of PMS, and add them to 100 mL of 10 mg / L Rhodamine B solution. Under stirring conditions, catalytically degrade the phenol to obtain the degradation curve.

[0064] Through testing, the degradation rate of Fe-CN on phenol within 15 min is 98.1%.

[0065] Example 3

[0066] (1) Take 6 g of iron-containing sludge and mix it with 18 g of concentrated sulfuric acid and react thoroughly. Observe the appearance of a large amount of white solid precipitate at the bottom of the beaker. Filter and separate the white CaSO4 precipitate and yellow ferric sulfate solution. Dry the remaining ferric sulfate and CaSO4 precipitate to obtain CaSO4 solid.

[0067] (2) Take 0.5 g of CaSO4 solid and add it to the prepared 50 ml sodium chloride solution (5%) in a 50°C water bath with stirring, adjust the pH to 3 using hydrochloric acid solution, after the calcium sulfate is fully dissolved, add 50 ml of absolute ethanol, the calcium sulfate is flocculated and dispersed in the solution. Separate the solution and the precipitate by centrifuge, dry at 80°C to obtain CaSO4·2H2O whiskers.

[0068] (3) After adjusting the pH of the acid filtrate separated in step (1) to 6 with ammonia water, a reddish brown iron hydroxide colloid is obtained, and the precipitated Fe(OH)3 is separated by using a centrifuge at 4500 r / min for 3 min with alcohol washing several times.

[0069] (4) Take a certain amount of Fe(OH)3 in step (3) and mix with 2 mol / L hydrochloric acid to obtain a ferric chloride solution. Take the above ferric chloride solution and mix with ethanol (volume ratio 1:30) to obtain a yellow solution, and then add a prepared sodium borohydride solution (2 mol / L) dropwise to the solution until the solution is stable black. Wash with ethanol several times, and vacuum freeze-dry to obtain magnetic nano Fe3O4.

[0070] (5) Take a certain amount of 20 g melamine in a beaker, take 10.7 g (0.1 mol) Fe(OH)3, add 60 ml distilled water, stir until evenly dispersed, then add 2 mol / L hydrochloric acid solution, fully dissolve, then add a certain amount of 40 mL N,N-dimethylformamide (DMF) and 18.1 g (0.1 mol) 2-amino terephthalic acid, stir evenly, then hydrothermal at 80°C for 24h. Dry the solid product and calcine at 550°C for 4h under nitrogen atmosphere to obtain fluffy Fe-CN.

[0071] (6) Verify the degradation ability of Fe-CN as a Fenton-like catalyst, test the catalytic degradation of tetracycline by Fe-CN, the specific detection method is:

[0072] Take 20 mg of the above composite material Fe-CN and 0.2 mg of PMS, and put them into 100 mL of 10 mg / L tetracycline solution, under stirring conditions, catalytic degradation of phenol to obtain the degradation curve.

[0073] Through testing, the degradation rate of Fe-CN on phenol within 15 min is 91.3%.

[0074] Example 4

[0075] (1) Take 6g of iron-containing sludge and mix with 15g of concentrated sulfuric acid. After the reaction is complete, filter the white CaSO4 precipitate and yellow iron sulfate solution. Dry the remaining iron sulfate and CaSO4 precipitate to obtain CaSO4 solid.

[0076] (2) Take 0.5g of CaSO4 solid and add to a 50ml sodium chloride solution (5% mass concentration) prepared in a 40℃ water bath. Adjust the pH to 3 using hydrochloric acid solution. After the calcium sulfate is fully dissolved, add 50ml of anhydrous ethanol. The calcium sulfate is dispersed in the solution in a flocculent state. Separate the solution and precipitate by centrifugation and dry at 80℃ to obtain CaSO4·2H2O whiskers.

[0077] (3) Adjust the pH of the acid filtrate obtained in step (1) to 8 using ammonia water to obtain a reddish-brown iron hydroxide colloid. Use a centrifuge to separate the precipitated Fe(OH)3 by centrifugation at 4500r / min for 3min.

[0078] (4) Take a certain amount of Fe(OH)3 from step (3) and mix with 2mol / L hydrochloric acid to obtain a ferric chloride solution. Mix the above ferric chloride solution with ethanol (volume ratio 1:30) and stir well. Add a prepared sodium borohydride solution (1.5mol / L) dropwise to the yellow solution until the solution is stable and black. Wash with ethanol several times and vacuum freeze-dry to obtain magnetic nano-Fe3O4.

[0079] (5) Take a certain amount of 50g melamine and place it in a beaker. Take 10.7g (0.1mol) Fe(OH)3, add 60ml distilled water, stir until evenly dispersed, then add 2mol / L hydrochloric acid solution, fully dissolve, then add a certain amount of 40mL N,N-dimethylformamide (DMF) and 8.4g (0.05mol) phthalic acid and 9.05g (0.05mol) 2-amino terephthalic acid, stir until uniform, then hydrothermal at 150℃ for 12h. Dry the solid product and calcine at 550℃ under nitrogen for 4h to obtain fluffy Fe-CN.

[0080] (6) Test the degradation ability of Fe-CN as a Fenton-like catalyst. Test the catalytic degradation of bisphenol A by Fe-CN. The specific detection method is as follows:

[0081] Take 20mg of the above composite material Fe-CN and 0.2mg PMS and add to 100mL of 10mg / L bisphenol A solution. Under stirring conditions, catalytically degrade the bisphenol A to obtain the degradation curve.

[0082] Through testing, the degradation rate of Fe-CN on phenol within 15min is 88.9%.

[0083] Example 5

[0084] (1) Take 12 g of iron-containing sludge, mix with 36 g of concentrated sulfuric acid and react thoroughly, observe the appearance of a large amount of white solid precipitate at the bottom of the beaker, then filter the white CaSO4 precipitate and yellow iron sulfate solution. The remaining iron sulfate, CaSO4 precipitate is dried to obtain CaSO4 solid.

[0085] (2) Take 0.8 g of CaSO4 solid and add to the prepared 50 ml sodium chloride solution (mass concentration of 3%) in a 55°C water bath with stirring, adjust the pH to 3 using hydrochloric acid solution, and after the calcium sulfate is fully dissolved, add 80 ml of anhydrous ethanol, and the calcium sulfate is dispersed in the solution in a flocculent form. Separate the solution and precipitate by centrifuge, and dry at 80°C to obtain CaSO4·2H2O whiskers.

[0086] (3) After adjusting the pH of the acid filtrate separated in step (1) to 4 with ammonia water, a reddish-brown iron hydroxide colloid is obtained, and the precipitated Fe(OH)3 is separated by using a centrifuge at 4500 r / min for 3 min with alcohol washing several times.

[0087] (4) Take a certain amount of Fe(OH)3 in step (3) and mix with 2 mol / L hydrochloric acid to obtain a ferric chloride solution. Take the above ferric chloride solution and mix with ethanol (volume ratio 1:10) to stir the yellow solution thoroughly, and drop the prepared sodium borohydride solution (1.5 mol / L) into the above solution until the solution is stable black. Wash with ethanol several times, and vacuum freeze-dry to obtain magnetic nano Fe3O4.

[0088] (5) Take a certain amount of 10.7 g melamine in a beaker, take 10.7 g (0.1 mol) Fe(OH)3, add 60 ml distilled water, stir until evenly dispersed, then add 2 mol / L hydrochloric acid solution, fully dissolve, then add a certain amount of 40 mL N,N-dimethylformamide (DMF) and 8.4 g (0.05 mol) terephthalic acid and 9.05 g (0.05 mol) 2-amino terephthalic acid, stir evenly, then hydrothermal at 110°C for 20h. Dry the solid product and calcine at 550°C for 4h under nitrogen environment to obtain fluffy Fe-CN.

[0089] (6) Verify the degradation ability of Fe-CN as a Fenton-like catalyst, test the catalytic degradation of rhodamine B and phenol mixed solution by Fe-CN, the specific detection method is:

[0090] Take 20 mg of the above composite material Fe-CN and 0.15 mg of PMS, and put them into 100 mL of a solution containing 5 mg / L of phenol and 5 mg / L of rhodamine B, under stirring conditions, the degradation curve of the catalytic degradation of phenol is obtained.

[0091] By testing, the degradation rate of Fe-CN on phenol and rhodamine B within 15 minutes is 96.2%.

[0092] Example 6

[0093] (1) Take 12 g of iron-containing sludge, mix with 30 g of concentrated sulfuric acid and react thoroughly, and after a large amount of white solid precipitate is observed at the bottom of the beaker, filter the white CaSO4 precipitate and yellow iron sulfate solution. Dry the remaining iron sulfate, CaSO4 precipitate to obtain CaSO4 solid.

[0094] (2) Take 0.5 g of CaSO4 solid and add it to a 50 ml sodium chloride solution (mass concentration of 4%) prepared in a 60°C water bath with stirring, adjust the pH to 3 using hydrochloric acid solution, and after the calcium sulfate is fully dissolved, add 50 ml of anhydrous ethanol, and the calcium sulfate is dispersed in the solution in a flocculent state. Separate the solution and the precipitate by centrifugation, and dry at 80°C to obtain CaSO4·2H2O whiskers.

[0095] (3) After adjusting the pH of the acid filtrate separated in step (1) to 8 with ammonia water, a reddish-brown iron hydroxide colloid is obtained, and the precipitated Fe(OH)3 is separated by using a centrifuge at 4500 r / min for 3 min with alcohol washing several times.

[0096] (4) Take a certain amount of Fe(OH)3 from step (3) and mix it with 2 mol / L hydrochloric acid to obtain a ferric chloride solution. Take the above ferric chloride solution and mix it with ethanol (volume ratio 1:10) to obtain a yellow solution, and add a prepared sodium borohydride solution (1.5 mol / L) dropwise to the above solution until the solution is stable and black. Wash with ethanol several times, and vacuum freeze-dry to obtain magnetic nano Fe3O4.

[0097] (5) Take a certain amount of 10.7 g melamine in a beaker, take 10.7 g Fe(OH)3, add 60 ml distilled water, stir until evenly dispersed, then add 2 mol / L hydrochloric acid solution, dissolve thoroughly, then add a certain amount of 40 mL N,N-dimethylformamide (DMF) and terephthalic acid (8.4 g) and 2-amino terephthalic acid (9.05 g), stir evenly, then hydrothermal at 110°C for 20 h. Dry the solid product and calcine at 550°C for 4 h under nitrogen environment to obtain fluffy Fe-CN.

[0098] (6) Verify the degradation ability of Fe-CN as a Fenton-like catalyst, test the catalytic degradation of Fe-CN on a mixed solution of tetracycline and phenol, and the specific detection method is as follows:

[0099] Take 20 mg of the above composite Fe-CN, 0.2 mg of PMS, and put them into 100 mL of a solution containing 5 mg / L of phenol and 5 mg / L of tetracycline. Under stirring conditions, the catalytic degradation of phenol is carried out to obtain a degradation curve.

[0100] Through testing, the degradation rate of the Fe-CN for phenol and tetracycline within 15 min is 94.3%.

[0101] Comparative Example 1

[0102] Comparative Example 1 differs from Example 1 in that the mass of sulfuric acid and the mass of the iron-containing sludge are the same (1:1) in step (1), and the other operations are the same as those in step (1) of Example 1. As a result, it is difficult to obtain a pure white precipitate of CaSO4, and the precipitate is red-brown, which is difficult to meet the requirements of whisker synthesis.

[0103] From the results of Comparative Example 1 and Example 1, it can be seen that the insufficient amount of sulfuric acid directly affects the next step of separation and resource treatment.

[0104] Comparative Example 2

[0105] Comparative Example 2 differs from Example 1 in that no sodium borohydride is added in step (4), and the other operations are the same as those in steps (1), (2), (3), and (4) of Example 1. As a result, it is impossible to obtain nano-Fe3O4. From the results of Comparative Example 2 and Example 1, it can be seen that sodium borohydride is very important in the synthesis of nano-Fe3O4.

[0106] From the results of Comparative Example 2 and Example 1, it can be seen that sodium borohydride directly affects the synthesis of nano-Fe3O4.

[0107] Comparative Example 3

[0108] Comparative Example 3 differs from Example 1 in that neither terephthalic acid nor 2-amino terephthalic acid is added in step (5), and the other operations are the same as those in steps (1), (2), (3), (4), and (5) of Example 1.

[0109] The degradation capacity of the composite Fe-CN in Comparative Example 3 as a Fenton-like catalyst is verified, and the Fe-CN is tested for catalytic degradation of a phenol mixed solution. The specific detection method is as follows:

[0110] Take 20 mg of the above composite Fe-CN, 0.2 mg of PMS, and put them into 100 mL of a solution containing 5 mg / L of phenol and 5 mg / L of tetracycline. Under stirring conditions, the catalytic degradation of phenol is carried out to obtain a degradation curve.

[0111] Through testing, the degradation rate of the Fe-CN for phenol within 1 h is only 10.2%.

[0112] From the test results of the above-mentioned Comparative Example 3 and Example 1, it can be seen that the formation of MOF precursors from benzenedicarboxylic acid or 2-aminoterephthalic acid and iron element is very important for obtaining catalytic degradation activity.

[0113] The above merely provides the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, within the technical scope disclosed by the present application, can make equivalent replacements or changes to the technical solutions and concepts of the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for resourceful treatment of iron-containing sludge solid waste, characterized in that, The iron-containing sludge solid waste is derived from the iron-containing sludge solid waste generated in the production of titanium dioxide by the sulfuric acid method, and the method comprises the following steps: S1: fully react concentrated sulfuric acid with Ca(OH)2 in the iron-containing sludge solid waste, and after solid-liquid separation, obtain white solid precipitate and liquid A, the mass ratio of the iron-containing sludge solid waste to the concentrated sulfuric acid is 1:2-1:3; S2: add the dried white solid precipitate, i.e. CaSO4 solid, to a 40-60℃ water bath to stir a 1-5% sodium chloride solution, use acid to adjust the pH to 3, after CaSO4 is fully dissolved, add anhydrous ethanol for recrystallization, after centrifugation, dry the precipitate to obtain CaSO4·2H2O whiskers; S3: adjust the pH of the liquid A to 4-8 with ammonia water to obtain Fe(OH)3 colloidal precipitate, and obtain Fe(OH)3 after centrifugal washing.

2. The method for resourceful treatment of iron-containing sludge solid waste according to claim 1, characterized in that, Further comprising: S4: obtain nano Fe3O4 by a method of controlling precipitation by dissolution and reduction of the Fe(OH)3; Or, complex the Fe(OH)3 with terephthalic acid and / or 2-amino terephthalic acid to form MOF material MIL-101(Fe) and / or NH2-MIL-101(Fe), and pyrolyze the MOF material together with a cyanamide compound to generate nano iron-containing nitrogen-containing carbon material Fe-CN.

3. The method for resourceful treatment of iron-containing sludge solid waste according to claim 2, characterized in that, The method of obtaining nano Fe3O4 by controlling precipitation by dissolution and reduction of the Fe(OH)3 comprises: Mix Fe(OH)3 with hydrochloric acid to obtain a ferric chloride solution; then mix the ferric chloride solution with ethanol uniformly, add sodium borohydride solution to the solution until the solution is black, wash with ethanol several times, and vacuum freeze-dry to obtain nano Fe3O4.

4. The method for resourceful treatment of iron-containing sludge solid waste according to claim 3, characterized in that, The method of complexing the Fe(OH)3 with terephthalic acid and / or 2-amino terephthalic acid to form MOF material MIL-101(Fe) and / or NH2-MIL-101(Fe), and pyrolyzing the MOF material together with a cyanamide compound to generate nano iron-containing nitrogen-containing carbon material Fe-CN comprises: Dissolve the Fe(OH)3 in a melamine aqueous solution, then add hydrochloric acid, mix uniformly, then add terephthalic acid and / or 2-amino terephthalic acid, mix uniformly, and then hydrothermally react at a temperature of 80-150℃ for 12-24h, and calcine the obtained solid product at 550℃ for 4h to obtain iron-containing nitrogen-containing carbon material Fe-CN, wherein the mass ratio of the Fe(OH)3 to melamine is 1:1-1:10; when terephthalic acid or 2-amino terephthalic acid is used alone, the molar ratio of the Fe(OH)3 to the terephthalic acid or 2-amino terephthalic acid is 1:1-1:2; when terephthalic acid and 2-amino terephthalic acid are used together, the molar ratio of the Fe(OH)3 to the total amount of terephthalic acid and 2-amino terephthalic acid is 1:1-1:2, and the molar ratio of the terephthalic acid to the 2-amino terephthalic acid is 1:1-1:

10.

5. The method for resourceful treatment of iron-containing sludge solid waste according to claim 3, characterized in that, The volume ratio of the ethanol to the ferric chloride solution is 30:1-10:1; the concentration of the sodium borohydride solution is 1-2 mol / L.

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