High-temperature-resistant unsaturated zinc sulfide / selenide as well as preparation method and application thereof

Abstract

The invention discloses high-temperature-resistant unsaturated zinc sulfide / selenide and a preparation method and application thereof.The preparation method comprises the steps that a reducing agent and a sulfur / selenium precursor are mixed, and a solution rich in unsaturated S < 1-> / Se < 1-> ions is obtained; and mixing the solution rich in unsaturated S < 1-> / Se < 1-> ions with zinc salt to prepare the high-temperature-resistant unsaturated zinc sulfide / selenide, and using the high-temperature-resistant unsaturated zinc sulfide / selenide as a mercury adsorbent for adsorbing mercury in mercury-containing flue gas. The mercury adsorption capacity of the prepared unsaturated zinc sulfide / selenide at high temperature (150-250 DEG C) can be unexpectedly improved to be not lower than 0.05 g mercury / g adsorbent and even exceeding the level of 0.1 g mercury / g adsorbent by regulating the ratio of the reducing agent to the sulfur / selenium precursor and carrying out simple precipitation under the conditions of normal temperature and normal pressure, and the mercury adsorption capacity of the prepared unsaturated zinc sulfide / selenide at high temperature (150-250 DEG C) can be improved to be not lower than 0.05 g mercury / g adsorbent and even more than 0.1 g mercury / g adsorbent. The mercury removal efficiency and the mercury adsorption capacity are greatly improved, the mercury removal performance of the low-temperature mercury adsorbent is the same as that of other low-temperature mercury adsorbents and is 20 times higher than that of commercial activated carbon, and the low-temperature mercury adsorbent has a relatively wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental pollution prevention and purification, and specifically relates to a high-temperature resistant unsaturated sulfur / selenide zinc and a preparation method thereof and an application thereof in treating high-temperature mercury-containing flue gas, and can obtain a material with excellent mercury adsorption performance under high-temperature flue gas (150-250°C) conditions. Background Art

[0002] Mercury is a highly toxic heavy metal with global migration effects due to its environmental persistence and bioaccumulation. It is one of the most dangerous environmental pollutants. The sources of mercury emissions can be divided into natural sources and anthropogenic sources. Among them, the main anthropogenic mercury pollution emission sources include coal-fired power plants, metal smelters, steel production plants, cement manufacturing plants, waste incineration plants, etc. Elemental mercury (Hg 0 ), oxidized mercury (Hg 2+ ) and particulate mercury (Hg P ) are the three most common forms of mercury in anthropogenic mercury pollution sources. 2+ and Hg P It can be removed by the flue gas wet purification device and the particulate matter control device respectively, but elemental mercury Hg 0 It is highly volatile and insoluble in water, and is difficult to be removed by existing flue gas purification devices. How to effectively control Hg in anthropogenic mercury pollution emission sources? 0 This is the main challenge facing mercury pollution reduction at this stage.

[0003] Hg is the most mature in industrial application at present. 0 Pollution removal technology is activated carbon adsorption technology. However, the limitations of activated carbon itself significantly restrict the application prospects of this technology, including but not limited to: low mercury adsorption capacity, poor product stability, and high operating costs. In recent years, metal sulfide compounds have been considered as an ideal activated carbon alternative material, which can achieve more economical and environmentally friendly removal of anthropogenic mercury pollution. The main mechanism is: S / Se ions in metal sulfide compounds can react with Hg 0 Efficiently bind Hg 0 Transformed into HgS / HgSe which exists stably in nature. This fully simulates Hg 0 As a natural sedimentation process, HgS / HgSe, as an extremely stable mercury ore, has been used in the smelting and production of mercury for many years.

[0004] However, previous studies have found that most metal chalcogenides, although Hg 0Although the adsorption performance is excellent (the mercury adsorption capacity can reach about 0.05g mercury / g adsorbent, which is more than 20 times that of activated carbon), it only has high mercury removal activity under low temperature conditions. When the reaction temperature exceeds 150°C, its mercury removal performance will decay rapidly, and the mercury adsorption capacity will drop below 0.005g mercury / g adsorbent. Considering that the preparation cost of metal sulfide compounds can be 2-3 times that of activated carbon, there are almost no metal sulfide compounds with industrial application prospects under high temperature conditions, but most industrial flue gas Hg 0 The operating temperature windows of the adsorption scenarios are all above 150 °C, which greatly hinders the application of metal chalcogenides as a mercury adsorbent. Summary of the invention

[0005] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a high-temperature resistant unsaturated sulfur / selenide zinc and a preparation method and application thereof. By adjusting the ratio of the reducing agent and the sulfur / selenium precursor, after simple precipitation at room temperature and pressure, the mercury adsorption capacity of the prepared unsaturated sulfur / selenide zinc at high temperature (150-250°C) can be unexpectedly increased to not less than 0.05g mercury / g adsorbent, and even exceeds 0.1g mercury / g adsorbent. The mercury removal efficiency and mercury adsorption capacity are greatly improved, which is on par with the mercury removal performance of other low-temperature mercury adsorbents and more than 20 times higher than commercial activated carbon, and has a relatively broad application prospect.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] A method for preparing a high temperature resistant unsaturated sulfur / selenide zinc, comprising mixing a reducing agent and a sulfur / selenium precursor to obtain an unsaturated S-rich 1- / Se 1- ions; then the unsaturated S 1- / Se 1- The ion solution is mixed with zinc salt to obtain high temperature resistant unsaturated zinc sulfur / selenide.

[0008] In the preparation process of the unsaturated metal sulfide compound, the ratio of the reducing agent and the S / Se precursor is controlled to regulate the reduction reaction process, thereby obtaining an unsaturated S-rich 1- / Se 1- Anion precursor, directly using unsaturated S 1- / Se 1- Ions react with zinc salts to prepare unsaturated zinc sulfide / selenide.

[0009] Preferably, the reducing agent is selected from one or more of hydrazine hydrate, sodium borohydride, potassium borohydride, ascorbic acid, and tetrahydrofuran.

[0010] Preferably, the sulfur / selenium precursor is selected from one or more of sulfur powder, selenium powder, sulfite, sulfate, selenite and selenate.

[0011] Preferably, the molar ratio of the reducing agent to the sulfur / selenium precursor is not higher than 4:1; more preferably, it is 0.5 to 2:1.

[0012] Preferably, the unsaturated S-rich 1- / Se 1- In the solution of ions, S 1- / Se 1- The proportion of ions is not less than 30% of the total sulfur / total selenium ions. In the present invention, the total sulfur / total selenium ions include S 1- / Se 1- Ion, S 2- / Se 2- Ions and SeO3 2- / SO3 2- / SO4 2- ion.

[0013] Preferably, the zinc salt is selected from one or more of zinc chloride, zinc sulfate, zinc acetate and zinc nitrate, and the molar ratio of the zinc salt to the sulfur / selenium precursor is 0.2 to 2:1.

[0014] The present invention also provides high temperature resistant unsaturated zinc sulfur / selenide prepared by the preparation method.

[0015] The present invention also provides the use of the high temperature resistant unsaturated sulfur / zinc selenide as a mercury adsorbent for adsorbing mercury in mercury-containing flue gas, wherein the temperature of the mercury-containing flue gas is 150-250°C.

[0016] The high temperature resistant unsaturated sulfur / selenide zinc of the present invention can be directly sprayed into flues and flue gas purification devices, or can be formed or loaded on other commonly used carriers for use. Its mercury adsorption capacity at 150-250° C. is not less than 0.05 g mercury / g adsorbent, and even exceeds the level of 0.1 g mercury / g adsorbent. The mercury removal efficiency is increased by more than 10 times compared with saturated sulfur / selenide zinc salts directly prepared from precursors such as Na2S and NaHSe.

[0017] The present invention controls the ratio of the reducing agent and the S / Se precursor to regulate the reduction reaction process, so that the solution is enriched with unsaturated S 1- / Se 1- ions, thereby enriching the unsaturated S in the prepared sulfur / zinc selenide 1- / Se 1- Active site, the specific reaction equation is as follows (taking elemental sulfur and sodium borohydride as an example):

[0018] S 0+4NaBH4+7H2O→2NaHS+Na2B4O7+14H2(appropriate amount of S 0 )

[0019] 2S 0 +2NaHS+Na2B4O7+5H2O→2Na2S2+4H3BO3(excess S 0 )

[0020] During the generation of HgS / HgSe, Hg 0 Must first be oxidized to Hg 2+ In the form of ZnS / ZnSe prepared by conventional methods, since it only contains saturated S 2- / Se 2- ions, and Hg 0 The reaction does not conform to the law of conservation of electrons (i.e., the reaction Hg 0 +S 2- →Hg-S reaction electrons are not conserved), so the demercuration performance of ZnS / ZnSe prepared by conventional methods is very poor, while the unsaturated sulfur / selenide zinc prepared by the method of the present invention is rich in S 1- / Se 1- Ions, which can oxidize and adsorb Hg 0 The role (ie: reaction Hg 0 +2S 1- →S-Hg-S electron conservation), the mercury removal performance under high temperature conditions can be significantly improved.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) The mercury adsorption capacity of the unsaturated sulfur / zinc selenide synthesized by the present invention can reach 0.05 g mercury / g adsorbent, which is more than 10 times higher than that of the sulfur / zinc selenide prepared by conventional methods;

[0023] (2) The demercuration operating temperature window of the unsaturated sulfur / zinc selenide synthesized by the present invention is 150-250°C, which can fill the gap in the current high-temperature mercury adsorbent;

[0024] (3) The unsaturated sulfur / zinc selenide synthesis process designed by the present invention is simple and has great potential for large-scale production;

[0025] (4) The demercuration products obtained by combining the synthesized zinc sulfur / selenide with mercury are mainly HgS / HgSe, which can be used for the smelting and regeneration of mercury resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1(a) and 1(b) are comparison diagrams of the valence states of sulfide ions in zinc sulfide of Example 1(a) and Comparative Example 1(b).

[0027] Figure 2 2(a) and 2(b) are comparison diagrams of the valence states of selenium ions in zinc selenide of Example 2(a) and Comparative Example 2(b).

[0028] like Figure 1 and Figure 2 As shown, the unsaturated sulfur sites in the zinc sulfide prepared by the method of the present invention account for about 35%, while the zinc sulfide prepared by the conventional method does not contain unsaturated sulfur sites; the unsaturated selenium ions in the zinc selenide prepared by the method of the present invention account for about 45%, while the content of unsaturated selenium ions in the commercial zinc selenide powder (Comparative Example 2) is only about 15%. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below through specific embodiments, which are not intended to limit the scope of protection.

[0030] Example 1

[0031] (1) Take 0.01 mol of sulfur powder and dissolve it in a solution containing 0.01 mol of hydrazine hydrate, then mix the above solution with 0.01 mol of zinc sulfate heptahydrate solution and stir for 1 hour. Wash the synthesized sample with deionized water 5 times, place the sample in a drying oven at 60°C for 12 hours after solid-liquid separation, and pass it through a 100-mesh sieve to obtain a zinc sulfide adsorbent rich in unsaturated sulfur sites.

[0032] (2) Weigh 20 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 100 ± 1 μg / m 3 The reaction temperature was 200°C, and the VM3000 mercury meter was used to monitor the elemental mercury concentration at the reactor inlet and outlet. Simulated flue gas N2, N2+5%O2, N2+5%O2+400ppm SO2, N2+5%O2+400ppm SO2+8%H2O were added respectively. After 5h, Hg 0 The removal rates were 99%, 96%, 98% and 93% respectively.

[0033] Example 2

[0034] (1) Take 0.02 mol of sodium selenite and dissolve it in 0.03 mol of sodium borohydride aqueous solution, then mix the above solution with 100 ml of 0.2 mol / L zinc nitrate solution and stir for 1 hour. Wash the synthesized sample with deionized water 5 times, place the sample in a drying oven at 60°C for 12 hours after solid-liquid separation, and pass it through a 100 mesh sieve to obtain a zinc selenide adsorbent rich in unsaturated selenium sites.

[0035] (2) Weigh 5 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 100 ± 1 μg / m 3 The reaction temperature was 150°C, and the VM3000 mercury analyzer was used to monitor the elemental mercury concentration at the reactor inlet and outlet. 0 The adsorption capacity is 0.08 g mercury / g adsorbent.

[0036] Example 3

[0037] (1) Take 7.9g of selenium powder and dissolve it in solutions containing 0.1mol, 0.2mol and 0.3mol of sodium borohydride to produce a dark red mixed solution, then mix the dark red solution with an aqueous solution containing 0.1mol of zinc acetate and stir for 1h. Wash the synthesized sample 5 times with deionized water, place the sample in a drying oven at 60°C for 12h after solid-liquid separation, and pass it through a 100-mesh sieve to obtain unsaturated zinc selenide adsorbents made with different proportions of reducing agents.

[0038] (2) Weigh 20 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 1000 ± 20 μg / m 3 The reaction temperature was 180°C, and the VM3000 mercury meter was used to monitor the elemental mercury concentration at the reactor inlet and outlet. In pure N2 atmosphere, the Hg concentration of zinc selenide adsorbent prepared by using 0.1 mol, 0.2 mol and 0.3 mol sodium borohydride reducing agent was 1.3 mol / L and 1.5 mol / L, respectively. 0 The removal efficiencies were 91%, 94% and 89% respectively.

[0039] Example 4

[0040] (1) Take 0.02 mol of sodium selenite and dissolve it in 0.03 mol of sodium borohydride aqueous solution, then mix the above solution with 100 ml of 0.2 mol / L zinc nitrate solution and stir for 1 hour. Wash the synthesized sample with deionized water 5 times, place the sample in a drying oven at 60°C for 12 hours after solid-liquid separation, and pass it through a 100 mesh sieve to obtain a zinc selenide adsorbent rich in unsaturated selenium sites.

[0041] (2) Weigh 20 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 1000 ± 20 μg / m 3 The concentration of elemental mercury at the reactor inlet and outlet was monitored using a VM3000 mercury meter. The Hg 0The adsorption capacity can reach 0.10, 0.12 and 0.07 g mercury / g adsorbent.

[0042] Comparative Example 1

[0043] (1) Take 0.01 mol of zinc sulfate heptahydrate and 0.01 mol of sodium sulfide nonahydrate and dissolve them in 50 ml of deionized water respectively, pour the sodium sulfide solution into the zinc sulfate solution and stir for 3 hours. Wash the synthesized sample with deionized water 5 times, place the sample in a drying oven at 60°C for 12 hours after solid-liquid separation, and pass it through a 100-mesh sieve to obtain a zinc sulfide adsorbent.

[0044] (2) Weigh 20 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 100 ± 1 μg / m 3 The reaction temperature was 200°C, and the VM3000 mercury analyzer was used to monitor the elemental mercury concentration at the reactor inlet and outlet. 0 The removal rate is 8%.

[0045] Comparative Example 2

[0046] Take 20 mg of commercial zinc selenide powder (Aladdin, 99.9%) and dry it in a drying oven at 60 °C for 12 h to remove moisture from the sample surface. Then place it in a cylindrical quartz glass fixed bed reactor, generate elemental mercury through a mercury permeation tube, and use 1 L / min nitrogen as the carrier gas. The initial mercury concentration is 100 ± 1 μg / m 3 The reaction temperature was 150°C, and the VM3000 mercury analyzer was used to monitor the concentration of elemental mercury at the reactor inlet and outlet. 0 The adsorption capacity is 0.005 g mercury / g adsorbent.

[0047] Comparative Example 3

[0048] (1) Take 0.01 mol of sulfur powder and dissolve it in a solution containing 0.01 mol of hydrazine hydrate, then mix the above solution with 0.01 mol of copper sulfate pentahydrate solution and stir for 1 hour. Wash the synthesized sample with deionized water 5 times, place the sample in a drying oven at 60°C for 12 hours after solid-liquid separation, and pass it through a 100-mesh sieve to obtain a copper sulfide adsorbent prepared by the same method.

[0049] (2) Weigh 20 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 100 ± 1 μg / m 3 The reaction temperature was 200°C, and the VM3000 mercury analyzer was used to monitor the elemental mercury concentration at the reactor inlet and outlet. 0The removal rate is 25%.

[0050] Comparative Example 4

[0051] (1) Take 0.01 mol of sulfur powder and dissolve it in a solution containing 0.01 mol of hydrazine hydrate, then mix the above solution with 0.01 mol of cobalt nitrate hexahydrate solution and stir for 1 hour. Wash the synthesized sample with deionized water 5 times, place the sample in a drying oven at 60°C for 12 hours after solid-liquid separation, and pass it through a 100-mesh sieve to obtain a cobalt sulfide adsorbent prepared by the same method.

[0052] (2) Weigh 20 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 100 ± 1 μg / m 3 The reaction temperature was 200°C, and the VM3000 mercury analyzer was used to monitor the elemental mercury concentration at the reactor inlet and outlet. 0 The removal rate is 13%.

[0053] Comparative Example 5

[0054] (1) Take 7.9g of selenium powder and dissolve it in a solution containing 0.5mol of sodium borohydride to produce a colorless transparent mixed solution, then mix the colorless transparent solution with an aqueous solution containing 0.1mol of zinc acetate and stir for 1h. Wash the synthesized sample with deionized water 5 times, place the sample in a drying oven at 60°C for 12h after solid-liquid separation, and pass it through a 100-mesh sieve to obtain a zinc selenide adsorbent prepared by using an excess reducing agent.

[0055] (2) Weigh 20 mg of adsorbent and place it in a cylindrical quartz glass fixed bed reactor. Generate elemental mercury through a mercury permeation tube and use 1 L / min nitrogen as carrier gas. The initial mercury concentration is 1000 ± 20 μg / m 3 The reaction temperature was 180°C, and the VM3000 mercury analyzer was used to monitor the concentration of elemental mercury at the reactor inlet and outlet. Under pure N2 atmosphere, within 2 hours, Hg 0 The removal efficiency was 18%.

Claims

1. A method for preparing high temperature resistant unsaturated sulfur / zinc selenide, characterized in that: The reducing agent and the sulfur / selenium precursor are mixed to obtain an unsaturated S-rich 1- / Se 1- ions; then the unsaturated S 1- / Se 1- The ion solution is mixed with zinc salt to obtain high temperature resistant unsaturated zinc sulfur / selenide.

2. The preparation method according to claim 1, characterized in that: The reducing agent is selected from one or more of hydrazine hydrate, sodium borohydride, potassium borohydride, ascorbic acid and tetrahydrofuran.

3. The preparation method according to claim 1, characterized in that: The sulfur / selenium precursor is selected from one or more of sulfur powder, selenium powder, sulfite, sulfate, selenite and selenate.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the reducing agent to the sulfur / selenium precursor is not higher than 4:

1.

5. The preparation method according to claim 4, characterized in that: The molar ratio of the reducing agent to the sulfur / selenium precursor is 0.5 to 2:

1.

6. The preparation method according to claim 1, characterized in that: The unsaturated S-rich 1- / Se 1- In the solution of ions, S 1- / Se 1- The proportion of ions is not less than 30% of the total sulfur / total selenium ions.

7. The preparation method according to claim 1, characterized in that: The zinc salt is selected from one or more of zinc chloride, zinc sulfate, zinc acetate and zinc nitrate, and the molar ratio of the zinc salt to the sulfur / selenium precursor is 0.2 to 2:

1.

8. The high temperature resistant unsaturated zinc sulfur / selenide obtained by the preparation method according to any one of claims 1 to 7.

9. The use of the high temperature resistant unsaturated sulfur / selenide zinc according to claim 8, characterized in that: It is used as a mercury adsorbent to adsorb mercury in mercury-containing flue gas, wherein the temperature of the mercury-containing flue gas is 150-250°C.

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