Bimetal sulfide as well as preparation method and application thereof in gas-phase arsenic removal

Abstract

The bimetallic sulfide crystal provided by the invention is small in particle and developed in intergranular gap, the bimetallic sulfide has enough active sites and sulfur vacancies under the optimal palladium-iron ratio (the molar ratio of palladium to iron is 1: 1), the arsenic capture rate of 90% can be kept within 100 minutes, and the bimetallic sulfide has a good arsenic capture rate under the condition of lower than 100 DEG C, and the arsenic capture rate of 90% can be kept within 100 minutes. And a relatively good arsenic removal rate (70-90%) can still be kept, so that a scientific basis is provided for development of a novel arsenic pollution control technology, and powerful support is provided for flue gas arsenic purification in a non-ferrous metal smelting process.

Description

Technical Field

[0001] The present invention relates to the field of gaseous arsenic removal, and in particular to a bimetallic sulfide, a preparation method thereof, and application thereof in gas-phase arsenic removal. Background Art

[0002] Coal-fired power generation dominates China's power structure and is unlikely to change for a considerable period of time. Although the average mass fraction of arsenic in my country's coal is 5 mg / kg, arsenic is highly volatile and enters the atmosphere in different forms during coal combustion. Arsenic in coal flue gas mainly exists in two forms: As2O3 and As2O5. Among them, the toxicity of As2O3 is more than 50 times that of As2O5. As2O3, which is widely distributed and highly toxic in the atmosphere, poses serious hazards to the natural environment and human health.

[0003] Methods for removing arsenic from flue gas are divided into adsorption and oxidation absorption. Currently, research at home and abroad mainly focuses on the adsorption method. However, the adsorption method has many disadvantages, such as the high operating cost and limited adsorption capacity of the activated carbon adsorption method; the fly ash adsorption method is greatly affected by intrinsic factors such as fly ash composition and particle size; the adsorption capacity of the metal oxide adsorption method is greatly affected by the environment; the oxidation absorption method mainly uses various strong oxidants to oxidize the slightly water-soluble As2O3 into the more water-soluble As(V), thereby improving the arsenic removal rate.

[0004] In the existing technology, gas phase arsenic removal has the following difficult-to-solve technical problems:

[0005] (1) When arsenic-containing flue gas flows through the SCR system, it will condense and deposit on the catalyst surface, inhibiting further adsorption of arsenic on the catalyst, thereby causing the catalyst to deactivate rapidly;

[0006] (2) Since the adsorption kinetics are quite slow below 100°C, the adsorption temperature of most arsenic removal agents is generally controlled at 150-350°C when performing gas phase arsenic removal.

[0007] Therefore, the present invention provides a bimetallic sulfide arsenic removal agent, which can efficiently remove arsenic in the gas phase at a relatively low temperature. Summary of the Invention

[0008] In order to solve the technical problems existing in the background technology, the present invention proposes a bimetallic sulfide, wherein the bimetallic sulfide is a Pd-Fe composite sulfide, and the pore volume of the bimetallic sulfide is 0.25-0.5 cm 3 / ɡ.

[0009] The molar ratio of palladium to iron in the bimetallic sulfide is 0.25-2:1;

[0010] Preferably, the molar ratio of palladium to iron in the bimetallic sulfide is 1:1.

[0011] In the present invention, Fe ions can promote electron transfer and sulfur vacancy formation, enhance arsenic adsorption, and the optimal palladium-iron molar ratio can provide more active sites and sulfur vacancies, thereby improving the arsenic capture efficiency. Among them, when the palladium-iron ratio of the bimetallic sulfide is 1:1, the capture efficiency of arsenic is maintained at about 90% within 100 minutes.

[0012] The present invention also provides a method for preparing the above-mentioned bimetallic sulfide, wherein the preparation method of the bimetallic sulfide is one of a coprecipitation method, a hydrothermal synthesis method or a sol-gel method;

[0013] Preferably, the preparation method of the bimetallic sulfide is a co-precipitation method.

[0014] In the present invention, the bimetallic sulfide crystals prepared by the precipitation method have small particles and well-developed pores between the particles, which are conducive to the diffusion of arsenic and enhance the adsorption effect.

[0015] The co-precipitation method comprises the following steps: uniformly mixing a divalent iron salt, a divalent palladium salt and deionized water to obtain a Pd-Fe mixed solution; uniformly mixing an alkali metal sulfide salt and deionized water to obtain an alkali metal sulfide solution; dropwise adding the Pd-Fe mixed solution and the alkali metal sulfide solution into the deionized water; obtaining a composite precipitate of iron sulfide and palladium sulfide after solid-liquid separation; and drying and calcining the composite precipitate to obtain a bimetallic sulfide.

[0016] The molar ratio of the divalent palladium salt, the divalent iron salt and the alkali metal sulfide salt is X:Y:Z, wherein X=0.25-2, Y=1, and Z≥X+Y.

[0017] The drying temperature of the composite precipitate is 120-150° C., and the drying time is 8-12 hours; the calcination temperature of the composite precipitate is 350-450° C., and the calcination time is 2-4 hours.

[0018] In the present invention, calcination allows the composite precipitate to form a more stable crystal phase, thereby improving the catalytic activity of the bimetallic sulfide and the selectivity for gas-phase arsenic adsorption.

[0019] The present invention also proposes an application of the bimetallic sulfide or the bimetallic sulfide obtained by the above preparation method in gas-phase arsenic removal.

[0020] The bimetallic sulfide is used as an adsorption material to adsorb arsenic in arsenic-containing gas;

[0021] Preferably, the flow rate of the arsenic-containing gas is 250 mL min -1 .

[0022] The arsenic-containing gas includes a gaseous arsenic compound and a carrier gas;

[0023] Preferably, the gaseous arsenic compound is As2O3;

[0024] Preferably, the carrier gas is nitrogen.

[0025] The arsenic adsorption temperature is 50-150°C;

[0026] Preferably, the arsenic adsorption temperature is 60-100°C.

[0027] In the present invention, the bimetallic sulfide can efficiently adsorb gaseous arsenic compounds at a relatively low temperature, with an adsorption capacity of ≥90%.

[0028] Beneficial effects of the present invention:

[0029] (1) Compared with the existing technology, bimetallic sulfide has a very strong selectivity for the adsorption of gaseous arsenic, and the adsorption rate of gaseous arsenic reaches more than 90% within 100 minutes;

[0030] (2) Compared with the prior art, the bimetallic sulfide of the present invention can not only maintain a higher adsorption rate in gas-phase arsenic removal, but also has an adsorption temperature of 50-150°C, which is much lower than the conventional gas-phase arsenic removal temperature of 150-350°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a SEM image of the Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 1:1 in Example 1;

[0032] Figure 2 This is the XRD pattern of the Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 1:1 in Example 1. DETAILED DESCRIPTION

[0033] To facilitate understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0035] The technical solution of the present invention is described more clearly and completely below with reference to specific embodiments and comparative examples.

[0036] Example 1

[0037] This embodiment provides a bimetallic sulfide, and the preparation method thereof is as follows:

[0038] 2.78g FeSO4·7H2O was added to 2.0242g PdSO4 aqueous solution to obtain 30mL Pd-Fe mixed solution, and then 1.95g Na2S solid was weighed to prepare 30mL sodium sulfide aqueous solution; the above two solutions were simultaneously stirred at 5mL·min -1 The mixture was slowly added dropwise into a beaker containing 100 ml of deionized water at a rate of 1:1, and the reaction solution in the beaker continuously generated a composite precipitate of palladium sulfide and iron sulfide. The pH value of the reaction solution was maintained at 7 during the addition until the composite precipitate was completely generated. The composite precipitate was vacuum filtered, and the filter cake was washed three times with deionized water. The washed filter cake was vacuum dried at 130° C. for 11 hours, and the vacuum-dried filter cake was calcined at 400° C. for 2.5 hours. The calcined filter cake was ground through a 200-mesh sieve to obtain a Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 1:1.

[0039] Example 2

[0040] This embodiment provides a bimetallic sulfide, and the preparation method thereof is as follows:

[0041] 2.78g FeSO4·7H2O was added to 4.0484g PdSO4 aqueous solution to obtain 30mL Pd-Fe mixed solution, and then 2.73g Na2S solid was weighed to prepare 30mL sodium sulfide aqueous solution; the above two solutions were simultaneously stirred at 3mL·min -1 The reaction mixture was slowly added dropwise into a beaker containing 100 ml of deionized water at a rate of 1:1, and the reaction solution in the beaker continuously generated a composite precipitate of palladium sulfide and iron sulfide. The pH value of the reaction solution was maintained at 7 during the addition process until the composite precipitate was completely generated. The composite precipitate was vacuum filtered, and the filter cake was washed three times with deionized water. The washed filter cake was vacuum dried at 150° C. for 8 h, and the vacuum-dried filter cake was calcined at 350° C. for 3 h. The calcined filter cake was ground through a 200-mesh sieve to obtain a Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 2:1.

[0042] Example 3

[0043] This embodiment provides a bimetallic sulfide, and the preparation method thereof is as follows:

[0044] 2.78g FeSO4·7H2O was added to 1.0121g PdSO4 aqueous solution to obtain 30mL Pd-Fe mixed solution, and 1.56g Na2S solid was weighed to prepare 30mL sodium sulfide aqueous solution; the above two solutions were simultaneously stirred at 5mL·min -1The reaction mixture was slowly added dropwise into a beaker containing 100 ml of deionized water at a rate of 1:1, and the reaction solution in the beaker continuously generated a composite precipitate of palladium sulfide and iron sulfide. The pH value of the reaction solution was maintained at 7 during the addition until the composite precipitate was completely generated. The composite precipitate was vacuum filtered, and the filter cake was washed three times with deionized water. The washed filter cake was vacuum dried at 120° C. for 12 h, and the vacuum-dried filter cake was calcined at 450° C. for 2 h. The calcined filter cake was ground and passed through a 200-mesh sieve to obtain a Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 0.5:1.

[0045] Example 4

[0046] This embodiment provides a bimetallic sulfide, and the preparation method thereof is as follows:

[0047] 2.78g FeSO4·7H2O was added to an aqueous solution containing 0.50605g PdSO4 to obtain a 30mL Pd-Fe mixed solution. 1.17g Na2S solid was then weighed to prepare a 30mL sodium sulfide aqueous solution. The above two solutions were simultaneously stirred at 4mL·min -1 The mixture was slowly added dropwise into a beaker containing 100 ml of deionized water at a rate of 1:1, and the reaction solution in the beaker continuously generated a composite precipitate of palladium sulfide and iron sulfide. The pH value of the reaction solution was maintained at 7 during the addition until the composite precipitate was completely generated. The composite precipitate was vacuum filtered, and the filter cake was washed three times with deionized water. The washed filter cake was vacuum dried at 150° C. for 9 h, and the vacuum-dried filter cake was calcined at 400° C. for 2.5 h. The calcined filter cake was ground and passed through a 200-mesh sieve to obtain a Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 0.25:1.

[0048] Example 5

[0049] This embodiment provides a bimetallic sulfide, and the preparation method thereof is as follows:

[0050] 2.78g FeSO4·7H2O was added to 2.0242g PdSO4 aqueous solution to obtain 30mL Pd-Fe mixed solution, and then 1.95g Na2S solid was weighed to prepare 30mL sodium sulfide aqueous solution; the above two solutions were simultaneously stirred at 5mL·min -1The mixture was slowly added dropwise to a beaker containing 100 ml of deionized water at a rate of , and the reaction solution in the beaker continuously generated a composite precipitate of palladium sulfide and iron sulfide. The pH value of the reaction solution was maintained at 7 during the dropwise addition until the composite precipitate was completely generated. The composite precipitate was vacuum filtered, and the filter cake was washed three times with deionized water. The washed filter cake was vacuum dried at 140° C. for 10 h, and the vacuum-dried filter cake was calcined at 400° C. for 3 h. The calcined filter cake was ground and passed through a 200-mesh sieve to obtain a Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 1:1.

[0051] Comparative Example 1

[0052] This comparative example proposes a metal sulfide, the preparation method of which is the same as that of Example 1, except that "2.78 g of FeSO4·7H2O is added to an aqueous solution containing 2.0242 g of PdSO4 to obtain a 30 mL Pd-Fe mixed solution" is changed to "2.78 g of FeSO4·7H2O is added to deionized water to obtain 30 mL of FeSO4 aqueous solution."

[0053] Comparative Example 2

[0054] This comparative example provides a metal sulfide, the preparation method of which is the same as that of Example 1, except that "2.78 g of FeSO4·7H2O is added to an aqueous solution containing 2.0242 g of PdSO4 to obtain a 30 mL Pd-Fe mixed solution" is changed to "30 mL of an aqueous solution containing 2.0242 g of PdSO4 is prepared."

[0055] Comparative Example 3

[0056] This comparative example proposes a bimetallic sulfide, the preparation method of which is the same as that of Example 1, except that "2.78 g of FeSO4·7H2O is added to an aqueous solution containing 2.0242 g of PdSO4 to obtain a 30 mL Pd-Fe mixed solution" is changed to "2.78 g of FeSO4·7H2O is added to an aqueous solution containing 1.55 g of CoSO4 to obtain a 30 mL Co-Fe mixed solution."

[0057] Comparative Example 4

[0058] This comparative example provides a bimetallic sulfide, the preparation method of which is the same as that of Example 1, except that "2.78 g of FeSO4·7H2O is added to an aqueous solution containing 2.0242 g of PdSO4 to obtain a 30 mL Pd-Fe mixed solution" is changed to "1.51 g of MnSO4 is added to an aqueous solution containing 3.9218 g of Cr2(SO4)3 to obtain a 30 mL Cr-Mn mixed solution."

[0059] Comparative Example 5

[0060] This comparative example proposes a bimetallic sulfide, the preparation method of which is the same as that of Example 1, except that the co-precipitation of Pd-Fe composite sulfide is replaced by the precipitation of palladium sulfide and iron sulfide separately, and then the palladium sulfide and iron sulfide precipitates are simply physically mixed to obtain a Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 1:1. The specific steps are as follows:

[0061] (1) Add 2.78 g of FeSO4·7H2O to deionized water to obtain 30 mL of FeSO4 aqueous solution. Then, add 2.0242 g of PdSO4 to deionized water to obtain 30 mL of PdSO4 aqueous solution. Weigh 3.9 g of Na2S solid to make 60 mL of sodium sulfide aqueous solution. Divide the 60 mL of sodium sulfide aqueous solution equally between two beakers.

[0062] (2) The FeSO4 aqueous solution and 30 mL of sodium sulfide aqueous solution were slowly added dropwise to a beaker containing 100 mL of deionized water. During the addition, the pH value of the solution in the beaker was maintained at 7 until complete precipitation. The solution was then vacuum filtered and the filter cake was washed three times with deionized water. The washed filter cake was vacuum dried at 130°C for 11 h. The vacuum-dried filter cake was calcined at 400°C for 2.5 h. The calcined filter cake was ground through a 200-mesh sieve to obtain an iron sulfide precipitate.

[0063] (3) The above-mentioned PdSO4 aqueous solution and sodium sulfide aqueous solution were slowly added dropwise to a beaker containing 100 ml of deionized water. During the addition process, the pH value of the solution was maintained at 7 until complete precipitation. The mixture was then vacuum filtered and the filter cake was washed three times with deionized water. The washed filter cake was vacuum dried at 130°C for 11 hours. The vacuum-dried filter cake was calcined at 400°C for 2.5 hours. The calcined filter cake was ground through a 200-mesh sieve to obtain palladium sulfide precipitate.

[0064] (4) The palladium sulfide and iron sulfide precipitates were mixed and ball-milled for 2 h to obtain a Pd-Fe composite sulfide adsorbent with a Pd / Fe molar ratio of 1:1.

[0065] Pore volume test: The test refers to GB / T19587-2017, and 3 g of each embodiment and comparative example are weighed and placed in a long tube with a bulb. After pre-treatment at 200°C for 2 hours, the sample is placed in a test equipment TriStar3030 (Mike Company, USA) for testing. The adsorption gas used is N2 (purity: 99.999%), and the test conditions are carried out at 77K. The pore volume of each embodiment and comparative example is obtained by the BET calculation method.

[0066] Adsorption experiment: As2O3 powder is used as the source, and it is sublimated by heating in an oil bath. The generated vapor is carried by N2 into the adsorption section and fully mixed with the adsorbent; the temperature of the oil bath is controlled to maintain the adsorption temperature at 50-150°C, and the amount of adsorbent used in each experiment is 120mg; during the experiment, the total flow rate of simulated flue gas is controlled at 250mL / min, and the adsorption time is 100min. After the adsorption is completed, the sample is cooled to room temperature and collected for subsequent analysis. The unadsorbed As2O3 (g) gas is absorbed by HNO3 / H2O2 absorption liquid and then emptied. The arsenic mass concentration is determined by atomic fluorescence spectrometry. The arsenic concentration before and after the adsorption device is measured;

[0067] Formula for calculating arsenic removal rate:. Where: η is the pollutant removal efficiency, unit: %; C in is the arsenic concentration at the inlet of the bubble reactor, in μg / L; C out is the arsenic mass concentration at the outlet of the adsorption device, in μg / L. ); the results of the pore volume test, adsorption experiment and arsenic removal rate calculation are shown in Table 1 below.

[0068] Table 1 Pore volume of each embodiment and comparative example and As2O3 removal rate under different adsorption conditions

[0069] Pd / Fe (molar ratio) Adsorption temperature T(℃) <![CDATA[Pore volume (cm 3 ·g)]]> <![CDATA[Removal rate of As2O3]]> Example 1 100 0.32 92％ Example 2 150 0.27 80％ Example 3 80 0.35 88％ Example 4 50 0.40 72％ Example 5 60 0.34 90％ Comparative Example 1 100 0.15 41％ Comparative Example 2 100 0.13 47％ Comparative Example 3 100 0.23 53％ Comparative Example 4 100 0.21 51％ Comparative Example 5 100 0.23 58％

[0070] As can be seen from Table 1, the removal rate of gas-phase arsenic by iron sulfide or palladium sulfide (Comparative Example and Comparative Example 2) alone is relatively low at low temperatures (≤100° C.).

[0071] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A bimetallic sulfide, characterized in that: The bimetallic sulfide is a Pd-Fe composite sulfide, and the pore volume of the bimetallic sulfide is 0.25-0.5 cm 3 / ɡ.

2. The bimetallic sulfide according to claim 1, characterized in that: The molar ratio of palladium to iron in the bimetallic sulfide is 0.25-2:1; Preferably, the molar ratio of palladium to iron in the bimetallic sulfide is 1:

1.

3. A method for preparing the bimetallic sulfide according to claim 1 or 2, characterized in that: The preparation method of the bimetallic sulfide is one of a coprecipitation method, a hydrothermal synthesis method or a sol-gel method; Preferably, the preparation method of the bimetallic sulfide is a co-precipitation method.

4. The method for preparing bimetallic sulfide according to claim 3, characterized in that: The co-precipitation method comprises the following steps: uniformly mixing a divalent iron salt, a divalent palladium salt and deionized water to obtain a Pd-Fe mixed solution; uniformly mixing an alkali metal sulfide salt and deionized water to obtain an alkali metal sulfide solution; dropwise adding the Pd-Fe mixed solution and the alkali metal sulfide solution into the deionized water; obtaining a composite precipitate of iron sulfide and palladium sulfide after solid-liquid separation; and drying and calcining the composite precipitate to obtain a bimetallic sulfide.

5. The method for preparing bimetallic sulfide according to claim 4, characterized in that: The molar ratio of the divalent palladium salt, the divalent iron salt and the alkali metal sulfide salt is X:Y:Z, wherein X=0.25-2, Y=1, and Z≥X+Y.

6. The method for preparing bimetallic sulfide according to claim 4 or 5, characterized in that: The drying temperature of the composite precipitate is 120-150° C., and the drying time is 8-12 hours; the calcination temperature of the composite precipitate is 350-450° C., and the calcination time is 2-4 hours.

7. Use of the bimetallic sulfide according to claim 1 or 2 or the bimetallic sulfide obtained by the preparation method according to any one of claims 3 to 6 in gas-phase arsenic removal.

8. The use of bimetallic sulfide in gas phase arsenic removal according to claim 7, characterized in that: The bimetallic sulfide is used as an adsorption material to adsorb arsenic in arsenic-containing gas; Preferably, the flow rate of the arsenic-containing gas is 250 mL min -1 .

9. The use of the bimetallic sulfide in gas phase arsenic removal according to claim 8, characterized in that: The arsenic-containing gas includes a gaseous arsenic compound and a carrier gas; Preferably, the gaseous arsenic compound is As2O3; Preferably, the carrier gas is nitrogen.

10. The use of bimetallic sulfide in gas phase arsenic removal according to claim 9, characterized in that: The arsenic adsorption temperature is 50-150°C; Preferably, the arsenic adsorption temperature is 60-100°C.

Images