A method for regenerating and activating a mercury-removed waste adsorbent based on an unsaturated sulfur system containing selenium, a regenerated adsorbent and applications

Abstract

The application relates to the technical field of resource recycling, and provides a regeneration activation method of mercury-removed waste adsorbent based on a selenium-containing unsaturated sulfur system, regenerated adsorbent and application. The regeneration activation method is as follows: elemental selenium is dissolved in a Na2S solution to form a mixed solution of active selenium-containing unsaturated sulfur ions; waste adsorbent from which mercury has been removed in advance is added into the mixed solution to react; the pH value of the system is adjusted to be reduced, so that part of the elemental selenium is in-situ nucleated and precipitated on the surface and pores of the waste adsorbent to form selenium active sites, and after solid-liquid separation, the regenerated mercury adsorbent is obtained. According to the application, the newly introduced selenium particles not only effectively make up for the structural defects and active site loss caused by mercury removal treatment, but more importantly, the material is endowed with a brand-new and powerful mercury adsorption capacity which surpasses that of a native copper sulfide material.

Description

Technical Field

[0001] This application relates to the field of resource recycling and reuse technology, specifically to a method for regenerating and reactivating mercury removal waste adsorbent based on a selenium-containing unsaturated sulfur system, the regenerated adsorbent, and its application. Background Technology

[0002] In industrial processes such as non-ferrous metal smelting and coal-fired power generation, mercury and its compounds are among the main toxic pollutants. Copper sulfide (CuS) is widely used as a highly efficient adsorbent for both gaseous and ionic mercury due to its high affinity for mercury. However, adsorbents have a limited lifespan. Once saturated, to recover the rare metal mercury and avoid secondary pollution, industrial processes typically employ methods such as thermal desorption or chemical elution to remove mercury from the adsorbent. Although these methods can effectively recover mercury resources, studies have shown that the active sulfur sites on the surface of the spent copper sulfide adsorbent after mercury removal treatment are largely lost or deactivated due to high temperatures or strong chemical reactions. Simultaneously, the microporous structure of the adsorbent may be damaged, collapsed, or blocked due to pre-treatment processes (such as sintering during pyrolysis or structural damage caused by strong elution), leading to a decrease in its specific surface area and pore volume. These changes in structure and chemical properties collectively result in a sharp decline in the ability of the spent adsorbent to recapture mercury after mercury removal; its adsorption capacity may even be less than one-third of the original material, making direct recycling difficult. This not only resulted in a huge waste of adsorbent materials, but also increased the burden of solid waste treatment.

[0003] Existing conventional regeneration methods, such as simple heat treatment or acid-base washing, often only partially restore the pore structure of the adsorbent, failing to fundamentally repair its surface active sites and thus failing to address the problem of active sulfur site loss. Therefore, there is an urgent need to develop an efficient, economical, and environmentally friendly method to completely revitalize mercury-deactivated adsorbents, enabling them not only to restore their original performance but also to surpass the adsorption capacity of the virgin material, thereby achieving high-value recycling of the adsorbent. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned problems in the prior art and provides a method for regenerating and reactivating mercury removal waste adsorbent based on a selenium-containing unsaturated sulfur system, the regenerated adsorbent, and its application.

[0005] To achieve the above objectives, the first aspect of this application provides a method for regenerating and reactivating mercury removal waste adsorbent based on a selenium-containing unsaturated sulfur system, comprising the following steps:

[0006] (1) Dissolve elemental selenium in Na2S solution and react to form an active mixed solution containing selenium-containing unsaturated sulfur ions; (2) Add the pre-removed mercury waste adsorbent to the mixed solution obtained in step (1) to carry out the reaction; (3) Adjusting the pH value of the system after the reaction in step (2) causes some elemental selenium to nucleate and precipitate in situ on the surface and pores of the waste adsorbent, forming selenium active sites. After solid-liquid separation, the regenerated mercury adsorbent is obtained.

[0007] In the above-mentioned regeneration and activation method, preferably, in step (2), the waste adsorbent refers to the waste metal sulfide adsorbent, and the method of pre-removing mercury refers to treating the waste metal sulfide adsorbent by thermal desorption or chemical elution.

[0008] In the above-mentioned regeneration and activation method, preferably, the waste metal sulfide adsorbent is a waste copper sulfide adsorbent.

[0009] In the above-mentioned regeneration and activation method, preferably, in step (1), the mass fraction of the Na2S solution is 10%-30%; the mass ratio of elemental selenium to the solute in the Na2S solution is 1:2-1:4; and the reaction is carried out at room temperature.

[0010] In the above-described regeneration and activation method, preferably, in step (1), the active mixed solution containing selenium-containing unsaturated sulfide ions includes at least […]. , , , One or more combinations thereof.

[0011] In the above-mentioned regeneration and activation method, preferably, in step (2), the mass ratio of the waste adsorbent from which mercury has been removed beforehand to the mass ratio of the mixed solution obtained in step (1) is 1:2-1:5.

[0012] In the above-mentioned regeneration and revitalization method, preferably, in step (2), the reaction process is stirred, the stirring speed is 800-1200 r / min, the reaction temperature is 10-35℃, and the reaction time is 0.75-1.25 h.

[0013] In the above-mentioned regeneration and activation method, preferably, in step (3), CO2 gas is introduced into the reaction system to adjust the pH value of the system after the reaction in step (2) to 6-7.

[0014] The second aspect of this application provides a regenerated adsorbent obtained by the regeneration and activation method described above, wherein the regenerated mercury adsorbent uses mercury-removed sulfides as a framework, and elemental selenium active sites are dispersedly attached to its surface and pores.

[0015] A third aspect of this application provides the application of the above-mentioned regenerated adsorbent in capturing gaseous and ionic mercury in smelting flue gas or wastewater.

[0016] Compared with the prior art, this application has the following beneficial effects: (1) In-situ grafting of heterogeneous high-activity sites: This invention breaks through the limitations of traditional regeneration methods that only attempt to repair the original sulfur sites. By constructing a system rich in unsaturated sulfur complexes in the Na2S system, the invention utilizes polysulfide selenide compounds formed by elemental selenium and sodium sulfide under alkaline conditions as precursors. Subsequently, by introducing weakly acidic CO2 gas (pH adjusted to 6-7), the dissolution equilibrium of these complexes is disrupted, promoting the "in-situ nucleation and precipitation" of highly active elemental selenium on the depleted adsorbent framework (such as CuS). This "heterogeneous grafting" mechanism introduces novel selenium-based active sites with ultra-high affinity for mercury into the pores and surface of the adsorbent at the nanoscale, thereby achieving a fundamental reconstruction of the adsorption function.

[0017] (2) Adsorption performance surpasses that of native materials: due to the adsorption capacity of elemental selenium for mercury (especially gaseous Hg) 0 and ionic Hg 2+ The chemical affinity of selenium is significantly stronger than that of sulfur. This invention, by introducing highly dispersed selenium particles, not only effectively compensates for the structural defects and loss of active sites caused by mercury removal treatment, but more importantly, it endows the material with a completely new and powerful mercury adsorption capacity that surpasses that of virgin copper sulfide materials. Experimental results show that the adsorbent regenerated using the method of this invention has an adsorption capacity that is approximately 50% higher than that of virgin CuS adsorbent, achieving "super-regeneration" of waste adsorbents. This is a milestone in the field of environmental functional material regeneration.

[0018] (3) Mild reaction conditions and environmentally friendly: The entire regeneration process of this invention is carried out at room temperature and pressure, avoiding the high energy consumption, severe equipment corrosion, and secondary pollution risks that may be caused by traditional high-temperature treatment or strong acid and strong alkali elution. By introducing CO2 gas to precisely control the pH value of the system to 6-7, the mild precipitation of elemental selenium is achieved, effectively avoiding the secondary heavy metal wastewater or exhaust gas pollution problems caused by the use of strong acids and strong alkalis. This makes the regeneration method of this invention have good industrial promotion value and environmental sustainability. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of an adsorption experiment conducted on a fixed bed using the activated and regenerated waste adsorbent of this invention. Figure 2 SEM and EDS images of the regenerated and activated adsorbent surface in Example 1 of this invention. Detailed Implementation

[0021] To facilitate understanding of this application, the following description will be more comprehensive and detailed in conjunction with the accompanying drawings and preferred embodiments, but the scope of protection of this application is not limited to the following specific embodiments.

[0022] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of this application.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0024] The present invention provides a method for regenerating and reactivating mercury removal waste adsorbents based on a selenium-containing unsaturated sulfur system, comprising the following steps: (1) Preparation of saturated sulfur system: Prepare an alkaline aqueous solution of sodium sulfide (Na2S) with a mass fraction of 20%. Then, add elemental selenium to the Na2S solution according to a precise mass ratio of 1:2 for elemental selenium (Se) to solute in the Na2S solution. Stir thoroughly at room temperature (about 20-25℃) until the elemental selenium is completely dissolved and the system turns dark red. During this process, elemental selenium reacts with Na2S to form unsaturated sulfur ions containing active selenium, mainly including , , , These components, including ions, are key precursors for the subsequent in-situ precipitation of selenium active sites.

[0025] (2) Contact and wetting: Waste metal sulfide adsorbent (preferably waste copper sulfide adsorbent, i.e., CuS), which has undergone mercury removal treatment (such as thermal desorption or chemical elution) and has had its attached mercury removed, is added to the mixed solution prepared in step (1). At room temperature, the mixture is vigorously stirred at 1000 r / min using a high-speed stirrer for 1 hour. The purpose of vigorous stirring is to ensure that the active solution fully wets the adsorbent particles and promotes the full wetting and diffusion of the active components into the micropores of the adsorbent.

[0026] (3) In-situ precipitation and activation: Under continuous stirring, pure CO2 gas at a flow rate of 100 mL / min was introduced into the suspension system after the reaction in step (2). The purpose of introducing CO2 was to adjust the pH value of the system by introducing a weakly acidic gas. When the pH value of the solution steadily dropped to the range of 6-7, the gas was stopped. During this process, due to the change in pH value, the dissolution equilibrium of the unsaturated sulfur system was broken, resulting in the decomposition of precursor ions. Some elemental selenium would undergo in-situ nucleation and precipitation on the surface and inside the pores of the waste copper sulfide adsorbent. These highly dispersed, nanoscale elemental selenium particles formed new selenium active sites. These newly formed selenium sites were uniformly loaded on the CuS framework, achieving deep activation of the adsorbent. Finally, the regenerated and activated mercury adsorbent was obtained by solid-liquid separation (filtration), repeated washing with deionized water until neutral to remove residual salts and unreacted substances, and vacuum drying at 60°C.

[0027] Example 1: A method for regenerating and reactivating mercury removal waste adsorbent based on a selenium-containing unsaturated sulfur system according to the present invention mainly includes the following steps: (1) Preparation of unsaturated sulfur system: Prepare elemental selenium powder with a purity of 99.9%, and simultaneously prepare a 20% (w / w) alkaline aqueous solution of Na2S. Based on a mass ratio of elemental selenium to solute in the Na2S solution of 1:2, add the appropriate amount of elemental selenium to the 20% Na2S solution. After adding the elemental selenium to the Na2S solution, place it in a reaction vessel equipped with a magnetic stirrer and stir continuously at room temperature (25℃) for 2 hours to ensure complete dissolution of the elemental selenium. At this time, the color of the reaction system changes from colorless to a uniform dark red.

[0028] (2) Contact and wetting: Weigh out the waste copper sulfide (CuS) adsorbent (this adsorbent has been used to adsorb mercury-containing flue gas until it penetrates, and has undergone thermal desorption to remove mercury, wherein the thermal desorption conditions are: heating rate of 10℃ / min under inert atmosphere, temperature rises to 450℃, and is kept at this temperature for 1h, rich in high concentration of Hg). 0 The pyrolysis exhaust gas is rapidly introduced into a multi-stage condenser, where gaseous mercury undergoes a phase change at low temperature and is converted into elemental mercury for recovery.

[0029] The weighed waste copper sulfide adsorbent was slowly added to the dark red mixed solution prepared in step (1) at a mass ratio of 1:4. At room temperature (25°C), the mixture was vigorously stirred at a constant speed of 1000 r / min using a high-speed stirrer for 1 hour. This process aims to maximize the contact area between the active solution and the adsorbent particles and promote the full wetting and diffusion of the active ingredients into the micropores of the adsorbent.

[0030] (3) In-situ precipitation and activation: Under continuous stirring in step (2), pure CO2 gas (using N2 as carrier gas) is introduced into the suspension system after reaction at a rate of 100 mL / min through a gas diffuser. During the gas introduction process, the pH value of the system is continuously monitored. When the pH value of the solution gradually decreases from the initial 11.0 and finally stabilizes at around 6.5, the CO2 gas introduction is stopped. During the pH decrease, the selenium species in the unsaturated sulfur system begin to decompose, and nano-sized elemental selenium particles selectively nucleate and precipitate in situ on the surface of the waste copper sulfide adsorbent and inside the damaged or collapsed microporous structure. These newly formed selenium sites are uniformly loaded on the CuS framework in a highly dispersed form, realizing the deep activation of the adsorbent.

[0031] (4) Regeneration: The reaction slurry obtained in step (3) was vacuum filtered using a Buchner funnel. The resulting solid product was repeatedly washed with deionized water until the washing solution was neutral to completely remove residual Na2S and its byproducts. The washed solid was dried in a vacuum drying oven at 60°C for 12 hours to obtain the regenerated mercury adsorbent with newly formed selenium active sites on its surface. Its SEM and EDS spectra are shown below. Figure 2 As shown, elemental selenium was successfully loaded onto the adsorbent surface during the activation and regeneration process.

[0032] The mercury adsorbent obtained in this embodiment was subjected to mercury adsorption performance testing and compared with the original copper sulfide adsorbent and the unactivated mercury-removed waste copper sulfide adsorbent. The original copper sulfide adsorbent was MRCS-1 mercury removal agent from Liaoning Haitai Technology Co., Ltd.

[0033] The Hg content of the adsorbent sample was evaluated using a simulated fixed-bed adsorption apparatus at 220 °C. 0 Adsorption performance Figure 1 As shown. The tubular furnace reactor is controlled to achieve a stable target reaction temperature. By using Hg 0 The osmosis device was immersed in a temperature-controlled 60°C water bath, producing stable Hg. 0 Steam. Hg 0 The vapor was mixed with high-purity N2 (flow rate of 0.2 L / min) to maintain a total gas concentration of 300 μg / m³. 3 and ensure Hg 0 The inlet concentration is stable. The required simulated flue gas includes O2, SO2, HCl, water vapor, and N2 mixed together. The flow rate is precisely adjusted using mass flow control to maintain a constant total flow rate of 0.6 L / min. The Hg at the outlet after the reaction... 0The concentration was monitored and recorded in real time using an online mercury monitor (Lumex RA-915 M). To eliminate the influence of acidic gases (SO2 and HCl), the simulated flue gas first passed through a gas washing bottle containing sodium hydroxide (NaOH, Sinopharm) solution, then through a condenser and a silica gel drying tube, and finally entered the Lumex RA-915M mercury analyzer. Moisture in the simulated flue gas was generated by a steam generator. The steam generator controlled the heating temperature and nitrogen flow rate to change the water vapor concentration. Finally, a purification system was used to purify the exhaust gas. Before each adsorption experiment, the Hg at the inlet was measured. 0 Concentration (C) in The concentration value will be continuously monitored until C in Equilibrium was reached, meaning fluctuations of less than 5% over a period of more than 30 minutes. Subsequently, a certain amount of adsorbent was added to the fixed bed. Then, simulated flue gas was introduced into the adsorption bed reactor, and Hg at the outlet was continuously monitored using an online mercury detector. 0 Concentration (C) out The removal of Hg from adsorbent samples was evaluated using multiple key indicators. 0 The adsorption capacity, namely adsorption efficiency (E, %), adsorption rate (R, μg / g / min) and adsorption capacity (Q, mg / g), is defined by the following equation.

[0034] (1) (2) (3) Comparison of Samples and Results: Under the same simulated smelting flue gas conditions, the specific adsorption capacities of the primary CuS adsorbent, the unactivated waste adsorbent after thermal desorption, and the regenerated and activated adsorbent of Example 1 were measured. Statistical analysis was performed using one-way ANOVA; specific data and significance analysis are shown in Table 1.

[0035] Table 1 Comparison of mercury adsorption efficiency of adsorbent before and after regeneration and activation

[0036] The results showed that the regenerated and activated adsorbent prepared in this embodiment achieved an adsorption capacity of 324.2 mg / g for mercury. This represents an increase of approximately 367.6% compared to the adsorption capacity of approximately 88.2 mg / g for the original copper sulfide adsorbent. In contrast, the adsorption capacity of the unactivated mercury-removing waste adsorbent was only approximately 23.6 mg / g. This demonstrates that the regeneration method of the present invention not only effectively restores the activity of the adsorbent but also achieves "super-standard regeneration" in performance.

[0037] Example 2: This embodiment is based on a method for regenerating and reactivating mercury-removing waste adsorbents using a selenium-containing unsaturated sulfur system. The overall steps are basically the same as in Example 1, except that in step (1), the mass ratio of elemental selenium to the solute in the sodium sulfide solution is adjusted: in step (1), the mass ratio is set to 1:1, 1:2 (i.e., Example 1), 1:3, 1:4, and 1:5, respectively. The remaining preparation methods are consistent with Example 1. The activated and regenerated adsorbents are named Adsorbent 1, Adsorbent 2, Adsorbent 3, Adsorbent 4, and Adsorbent 5, respectively. The specific adsorption capacity is measured using the same mercury adsorption measurement method as in Example 1, as shown in Table 2.

[0038] Table 2 Comparison of Mercury Adsorption Efficiency of Different Adsorbents

[0039] The results showed that the mass ratio of elemental selenium to the solute in the sodium sulfide solution affected the adsorbent's regeneration capacity during the regeneration and activation process. Table 2 shows that when the mass ratio was between 1:2 and 1:4, the adsorption efficiency of the regenerated adsorbent for mercury was above 90.12%. When the mass ratio exceeded this range, the activation and regeneration effect of the adsorbent decreased. A specific mass ratio is beneficial for the regeneration and activation of spent adsorbents.

[0040] Example 3: This embodiment is based on a method for regenerating and reactivating mercury removal waste adsorbents using a selenium-containing unsaturated sulfur system. The overall steps are basically the same as in Example 1, except that the pH value of the solution is controlled during the activation and regeneration process: In step (3), CO2 gas is introduced into the suspension system after the reaction, and the pH value of the solution is adjusted to steadily decrease to 5, 6, 7, and 8, respectively, at which point the introduction of CO2 gas is stopped. The remaining preparation, cleaning, and drying processes are consistent with those in Example 1. The obtained adsorbents are named Adsorbent 6, Adsorbent 7, Adsorbent 8, and Adsorbent 9. The adsorption test results are obtained using the same method as in Example 1, and the specific values ​​are shown in Table 3.

[0041] Table 3 Comparison of adsorption efficiency of adsorbent for mercury at different pH values

[0042] The results are shown in the table above. When the pH value is 8, the average saturated adsorption capacity of the regenerated activated adsorbent obtained in this example is 145.5 mg / g, and when the pH value is 5, the average saturated adsorption capacity is 198.6 mg / g. The results indicate that the regenerated activated adsorbent can effectively promote efficient in-situ nucleation of selenium active sites within a pH range of 6-7, providing a relatively wide process operating window and facilitating engineering applications.

[0043] Comparative Example 1: This embodiment is based on a method for regenerating and reactivating mercury removal waste adsorbents using a selenium-containing unsaturated sulfur system. The overall steps are basically the same as in Example 1, except that the pH adjustment method in step (3) is changed: in step (3), instead of introducing CO2 gas into the suspension system after the reaction, sulfuric acid solution is added dropwise into the suspension system after the reaction. The addition of sulfuric acid solution is stopped when the pH value of the solution steadily drops to 7. The remaining preparation, cleaning, and drying processes are consistent with those in Example 1. The activated and regenerated adsorbent is named Adsorbent 10. The adsorption test was performed using the same method as in Example 1, and the specific values ​​are shown in Table 4.

[0044] Table 4 Comparison of adsorption efficiencies of adsorbents for mercury

[0045] The results showed that during the regeneration and activation of the adsorbent, the mild and stable acidic conditions created by the slow introduction of CO2 were conducive to the precipitation of selenium in the solution. Compared with the adsorbent activated and regenerated by adjusting the pH value with sulfuric acid, the adsorbent activated and regenerated by adjusting the pH value with CO2 had an adsorption capacity increased by 70.0%, thus enhancing the regeneration and activation capacity of the waste adsorbent.

[0046] Comparative Example 2: This comparative example is based on a method for regenerating and reactivating mercury-removing waste adsorbents using a selenium-containing unsaturated sulfur system. The overall steps are basically the same as in Example 1, except that in step (1), elemental selenium is replaced with an equal amount of elemental sulfur. The rest of the preparation methods are consistent with Example 1. The activated and regenerated adsorbent is named Adsorbent 11. The specific adsorption capacity was measured using the same mercury adsorption measurement method as in Example 1, as shown in Table 5.

[0047] Table 5 Comparison of Mercury Adsorption Efficiency of Different Adsorbents

[0048] The results showed that during the regeneration and activation of the adsorbent, the free unsaturated sulfur ions in the sodium sulfide solution replenished the sulfur ions lost by the adsorbent in the mercury removal reaction. In the absence of elemental selenium, the regeneration effect of the adsorbent was reduced, and the addition of elemental selenium promoted the regeneration and activation effect of the waste adsorbent.

[0049] The above are merely preferred embodiments of this application. It should be noted that this application is not limited to the above embodiments. For those skilled in the art, several improvements and modifications can be made without departing from the principles of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should also be considered within the scope of protection of this application.

Claims

1. A method for regenerating and reactivating mercury removal waste adsorbent based on a selenium-containing unsaturated sulfur system, characterized in that, Includes the following steps: (1) Dissolve elemental selenium in Na2S solution and react to form an active mixed solution containing selenium-containing unsaturated sulfur ions; (2) Add the pre-removed mercury waste adsorbent to the mixed solution obtained in step (1) to carry out the reaction; (3) Adjusting the pH value of the system after the reaction in step (2) causes some elemental selenium to nucleate and precipitate in situ on the surface and pores of the waste adsorbent, forming selenium active sites. After solid-liquid separation, the regenerated mercury adsorbent is obtained.

2. The regeneration and revitalization method as described in claim 1, characterized in that, In step (2), the waste adsorbent refers to waste metal sulfide adsorbent, and the method for pre-removing mercury refers to treating the waste metal sulfide adsorbent by thermal desorption or chemical elution.

3. The regeneration and revitalization method according to claim 2, characterized in that, The waste metal sulfide adsorbent is a waste copper sulfide adsorbent.

4. The regeneration and revitalization method as described in claim 1, characterized in that, In step (1), the mass fraction of the Na2S solution is 10%-30%; the mass ratio of elemental selenium to the solute in the Na2S solution is 1:2-1:4; and the reaction is carried out at room temperature.

5. The regeneration and revitalization method as described in claim 1, characterized in that, In step (1), the active mixed solution containing selenium-containing unsaturated sulfide ions includes at least , , , One or more combinations thereof.

6. The regeneration and revitalization method as described in claim 1, characterized in that, The mass ratio of the waste adsorbent from which mercury has been removed to the mass of the mixed solution obtained in step (1) is 1:2-1:

5.

7. The regeneration and revitalization method as described in claim 1, characterized in that, In step (2), the reaction process is stirred at a speed of 800-1200 r / min, a reaction temperature of 10-35℃, and a reaction time of 0.75-1.25 h.

8. The regeneration and revitalization method as described in claim 1, characterized in that, In step (3), CO2 gas is introduced into the reaction system to adjust the pH value of the system after the reaction in step (2) to 6-7.

9. A regenerated adsorbent obtained by the regeneration and activation method according to any one of claims 1-8, wherein the regenerated mercury adsorbent uses mercury-removed sulfides as a framework, and elemental selenium active sites are dispersedly attached to its surface and pores.

10. The application of the regenerated adsorbent as described in claim 9 in capturing gaseous and ionic mercury in smelting flue gas or wastewater.

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