Mercury-containing wastewater treatment process---Dusheng mercury removal resins CH-95 & CH-97

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Description of mercury-containing wastewater treatment processes -- DuSheng specialty mercury removal resins Tulsion CH-95 & Tulsion CH-97: In wastewater, mercury exists not only in its inorganic form but also in various organic compound forms. Mercury in any form present in the environment (metallic mercury, inorganic divalent mercury, arylmercury, alkylmercury, etc.) can, under certain conditions, be converted into highly toxic methylmercury. Mercury is a volatile, toxic heavy metal element; it is the only metal that exists in liquid form at normal temperature and pressure. It has a silver-white color, exhibits stable chemical properties, is insoluble in both acids and bases, and can evaporate at room temperature. Mercury possesses characteristics such as a low melting point, high density, high boiling point, good electrical conductivity, and a uniform coefficient of expansion, which enable its wide use in industries, agriculture, science and technology, transportation, medicine and health, as well as national defense. 　　Mercury vapor and mercury compounds are highly toxic, with methylmercury being particularly toxic. Mercury is a chemical with persistence, mobility, and high bioaccumulation potential. All forms of mercury in the environment can be converted into the highly toxic methylmercury under certain conditions. Mercury can also travel over long distances and settle far away, leading to cross-border pollution and becoming a regional issue; the United Nations Environment Programme has listed it as a global pollutant. 　 This presentation covers the sources and forms of mercury in water bodies, its pollution characteristics and hazards, provides an overview of various treatment methods for mercury-containing wastewater, and finally offers recommendations for the control of mercury wastewater pollution. 　　1. Sources, forms of existence, and hazards of mercury in water bodies. 　　Our country has **primary mercury production**; there is a high demand for primary mercury in our country and it is widely used, but the mining of mercury deposits poses significant environmental risks. The current situation regarding mercury production, use, and emissions in our country is far from optimistic. 　　The sources of mercury in water bodies are mainly due to improper handling and use of mercury, as well as the production of mercury mines, gold mines, chlor-alkali plants, facilities for recovering precious metals through amalgamation processes, non-ferrous metal smelters, pesticide factories, batteries, fluorescent lamps, and thermometers. In addition, pharmaceuticals, cosmetics, and hospital laboratories also generate a certain amount of mercury-containing wastewater. Mercury pollutants are primarily found in the sediment and suspended particles near the discharge points. 　　In wastewater, mercury exists not only in its inorganic form but also in various organic compound forms. Mercury in any form present in the environment (metallic mercury, inorganic divalent mercury, arylmercury, alkylmercury, etc.) can, under certain conditions, be converted into highly toxic methylmercury. Methylmercury includes methylmercury (Hg+-CH3) and dimethylmercury (CH3-Hg-CH3). In 1967, Swedish scholars S. Jensen and Jerndov et al. pointed out that anaerobic bacteria in the sediments of freshwater bodies can methylate inorganic mercury, resulting in the formation of methylmercury and dimethylmercury. Japanese researchers have found that when organic compounds such as acetic acid, acetaldehyde, methanol, ethanol, and wood alcohol are present together in water, methyl radicals generated upon exposure to ultraviolet light or sunlight can methylate mercury chloride. 　　2. The hazards of mercury in aquatic environments. 　　In the 1950s, Minamata disease—one of the eight major environmental disasters that shocked the world—occurred because wastewater discharged from an acetaldehyde plant contained methylmercury. This wastewater flowed into Minamata Bay, where methylmercury accumulated in fish. Prolonged consumption of fish containing methylmercury led to damage to the central nervous system in humans. The Minamata disease outbreak in Japan resulted in 5,172 cases and 730 deaths. In the mercury poisoning incident that occurred in 1972 in Iraq when seeds were treated with methylmercury and ethylmercury fungicides, 459 people died. 　　Studies have shown that elemental mercury and organic mercury compounds may cause damage to the kidneys and immune system, while methylmercury can pose a threat to the nervous system as well as the heart and blood vessels. Methylmercury has the ability to accumulate in the food chain and ultimately enter the human body, thereby affecting human health. Therefore, the hazards of mercury pollution in aquatic environments are increasingly causing concern. 　　3. Control technologies for mercury in wastewater 　　Currently, the treatment methods for mercury-containing wastewater include precipitation, electrolysis, ion exchange, activated carbon adsorption, and combined process treatments. 　　(1) Precipitation method: The precipitation method is divided into two types: coagulation precipitation and sulfide precipitation. The principle of coagulation sedimentation is to add coagulants (lime, iron salts, aluminum salts) to mercury-containing wastewater; under weakly alkaline conditions with a pH of 8-10, hydroxide flocs are formed, and these flocs are used to cause mercury to precipitate out together with them. Generally, iron salts are more effective than aluminum salts. The sulfidation precipitation method is a commonly reported precipitation method. This method involves adding sodium sulfide to mercury-containing wastewater; utilizing the strong affinity between Hg2+ and S2-, mercury sulfide with extremely low solubility is formed, thereby removing mercury from the solution. Wu Xiuying et al. conducted pilot and scale-up tests using sodium sulfide to treat mercury-containing wastewater from the Qingdao Battery Factory. The test results showed that the mercury content in the wastewater was below the **standard, indicating good treatment effectiveness; moreover, the chemical properties of the sediment remained stable, making this method suitable for use in small and medium-sized chemical industries. The sulfidation precipitation method is widely used in the control of mercury pollution in chlor-alkali plants in countries such as the United States. This method is suitable for treating mercury salts of different concentrations and types; when the concentration of mercury ions is high, chemical precipitation should be the preferred method. It is reported that the removal rate of mercury by precipitation can reach 95%-99.9%. 　　The disadvantages of this method are: (1) it tends to cause water hardness, fails to treat wastewater containing low concentrations of mercury thoroughly, and can lead to secondary pollution. (2) Affected by precipitants, environmental conditions, and process control parameters, it is difficult for the effluent concentration to meet the discharge standards; therefore, further treatment is required. 　　(2) Electrolysis method The electrolysis method makes use of the electrochemical properties of metals; under the action of direct current, mercury compounds dissociate into mercury ions at the anode and are reduced to metallic mercury at the cathode, thereby removing mercury from wastewater. This method is suitable for treating wastewater containing high concentrations of inorganic mercury. The disadvantages of this method are that the concentration of mercury ions in water cannot be reduced very low, it consumes a large amount of electricity, the investment cost is high, and it easily generates mercury vapor, leading to secondary pollution. 　　(3) Ion exchange method The ion exchange method is carried out in an ion exchanger, where large-pore thiol-based ion exchange resins are used to adsorb mercury ions from mercury-containing wastewater. The thiol groups on the resin have a strong adsorption capacity for mercury ions; the mercury adsorbed on the resin can be eluted using concentrated hydrochloric acid for quantitative recovery. 　　Compared to precipitation and electrolysis methods, the ion exchange method is suitable for treating wastewater containing low concentrations of mercury. Studies show that treating first with primary treatment and then using ion exchange yields the best results for ion exchange. Generally, after treating mercury-containing wastewater using ion exchange methods, the minimum concentration of inorganic mercury in the effluent is 1–5 ug/L. We import the mercury-removal resins CH-95 or CH-97 specifically designed for DuSheng; after treatment, mercury emissions can be reduced to below 5 ppt, which is much lower than the mandated emission standard of 1 ppb. There are many operational cases of chlor-alkali plants both domestically and internationally. 　　(4) Activated carbon adsorption method The activated carbon adsorption method is a relatively mature technique for treating mercury-containing wastewater. It can effectively adsorb mercury from wastewater; some factories in China have used this method to treat mercury-containing wastewater, but it is expensive and only suitable for treating wastewater with low concentrations of mercury. When the wastewater concentration is too high, primary treatment can be carried out first, followed by adsorption treatment using activated carbon. According to relevant information, this method is suitable for wastewater with a mercury content of 1–2 mg·L⁻¹ or less; after treatment using activated carbon adsorption, the mercury concentration in the effluent can be reduced to 0.01–0.05 mg·L⁻¹. 　　There are many factors that affect the efficiency of activated carbon adsorption treatment, including the contact time between the wastewater and the adsorbent, the structure and pore size of the activated carbon, the initial form and concentration of mercury in the wastewater, as well as the amount and form of the activated carbon used. The pH and temperature of wastewater also affect the adsorption by activated carbon. Generally, activated carbon has a higher adsorption capacity under acidic conditions than under alkaline conditions. The adsorption reaction is usually an exothermic reaction; therefore, a low temperature is favorable for it. Activated carbon is more effective in removing organic mercury than inorganic mercury. Treating wastewater with high mercury content using activated carbon yields a treatment efficiency of approximately 85-99%. 　　The disadvantages of this treatment method are: a large amount of activated carbon is required, there are few regeneration facilities, the regeneration costs are high, and the precision of advanced treatment is not very high. 　　(5) Application of combined treatment technologies
Huang Mingrong et al. employed a “combined process consisting of sulfide precipitation, coagulation, ultrafiltration, and activated carbon treatment” to treat mercury-containing wastewater generated in the VCM production step during the calcium carbide-based production of polyvinyl chloride in the chlor-alkali industry. The results showed that the mercury removal rate could reach 99.95%. Ultrafiltration proved to be highly effective in removing mercury from the effluent produced by the sulfide precipitation process; the mercury concentration in the treated water remained stable at around 20 ppb. Additionally, this process effectively prolonged the saturation period of the activated carbon. This combined process is easy to operate, achieves good treatment results, and has certain practical value. In the current chlor-alkali industry, regarding the mercury removal process using ion-exchange membrane caustic soda, an additional stage of mercury removal using resin is usually added after this combined process; it is typically designed to operate in series to ensure that the concentration of mercury in the final wastewater remains below 1 PPB. 　　(6) Other methods Superconducting magnetic separation technology is a newly developed application technique for superconducting magnets. This technology is a method for separating materials with different magnetic properties by utilizing the force of magnetic fields. The superconducting high-gradient magnetic separation technology can be used to purify and separate wastewater containing mercury. Currently, this technology is still in the research phase and has not yet been put into industrial application. 　　3. Conclusions and Recommendations 　　Through research, experimentation, and application, various mature treatment technologies for mercury-containing wastewater have been developed. Depending on the characteristics of different types of mercury-containing wastewater, appropriate treatment methods can be selected. 　　The recommendations are as follows: 1. Control at the source to reduce the emission of mercury pollutants. 2. Reduce the sources of mercury-containing waste discharged into various environmental elements (water, air, sludge, soil), and strengthen the control of mercury pollutants. 3. Increase research on the monitoring and treatment of mercury-containing waste, particularly the degradation of methylmercury, to prevent it from entering the food chain and causing significant impacts on human health. Analysis of mercury-containing wastewater treatment processes——Dusheng specialty mercury removal resins Tulsion CH-95 & Tulsion CH-97. Analysis of mercury-containing wastewater treatment processes——Dusheng specialty mercury removal resins Tulsion CH-95 & Tulsion CH-97. In wastewater, mercury exists not only in its inorganic form but also in various organic compound forms. Mercury in any form present in the environment (metallic mercury, inorganic divalent mercury, arylmercury, alkylmercury, etc.) can, under certain conditions, be converted into highly toxic methylmercury. Mercury is a volatile, toxic heavy metal element; it is the only metal that exists in liquid form at normal temperature and pressure. It has a silver-white color, exhibits stable chemical properties, is insoluble in both acids and bases, and can evaporate at room temperature. Mercury possesses characteristics such as a low melting point, high density, high boiling point, good electrical conductivity, and a uniform coefficient of expansion, which enable its wide use in industries, agriculture, science and technology, transportation, medicine and health, as well as national defense. 　　Mercury vapor and mercury compounds are highly toxic, with methylmercury being particularly toxic. Mercury is a chemical with persistence, mobility, and high bioaccumulation potential. All forms of mercury in the environment can be converted into the highly toxic methylmercury under certain conditions. Mercury can also travel over long distances and settle far away, leading to cross-border pollution and becoming a regional issue; the United Nations Environment Programme has listed it as a global pollutant. 　 This presentation covers the sources and forms of mercury in water bodies, its pollution characteristics and hazards, provides an overview of various treatment methods for mercury-containing wastewater, and finally offers recommendations for the control of mercury wastewater pollution. 　　1. Sources, forms of existence, and hazards of mercury in water bodies. 　　Our country has **primary mercury production**; there is a high demand for primary mercury in our country and it is widely used, but the mining of mercury deposits poses significant environmental risks. The current situation regarding mercury production, use, and emissions in our country is far from optimistic. 　　The sources of mercury in water bodies are mainly due to improper handling and use of mercury, as well as the production of mercury mines, gold mines, chlor-alkali plants, facilities for recovering precious metals through amalgamation processes, non-ferrous metal smelters, pesticide factories, batteries, fluorescent lamps, and thermometers. In addition, pharmaceuticals, cosmetics, and hospital laboratories also generate a certain amount of mercury-containing wastewater. Mercury pollutants are primarily found in the sediment and suspended particles near the discharge points. 　　In wastewater, mercury exists not only in its inorganic form but also in various organic compound forms. Mercury in any form present in the environment (metallic mercury, inorganic divalent mercury, arylmercury, alkylmercury, etc.) can, under certain conditions, be converted into highly toxic methylmercury. Methylmercury includes methylmercury (Hg+-CH3) and dimethylmercury (CH3-Hg-CH3). In 1967, Swedish scholars S. Jensen and Jerndov et al. pointed out that anaerobic bacteria in the sediments of freshwater bodies can methylate inorganic mercury, resulting in the formation of methylmercury and dimethylmercury. Japanese researchers have found that when organic compounds such as acetic acid, acetaldehyde, methanol, ethanol, and wood alcohol are present together in water, methyl radicals generated upon exposure to ultraviolet light or sunlight can methylate mercury chloride. 　　2. The hazards of mercury in aquatic environments. 　　In the 1950s, Minamata disease—one of the eight major environmental disasters that shocked the world—occurred because wastewater discharged from an acetaldehyde plant contained methylmercury. This wastewater flowed into Minamata Bay, where methylmercury accumulated in fish. Prolonged consumption of fish containing methylmercury led to damage to the central nervous system in humans. The Minamata disease outbreak in Japan resulted in 5,172 cases and 730 deaths. In the mercury poisoning incident that occurred in 1972 in Iraq when seeds were treated with methylmercury and ethylmercury fungicides, 459 people died. 　　Studies have shown that elemental mercury and organic mercury compounds may cause damage to the kidneys and immune system, while methylmercury can pose a threat to the nervous system as well as the heart and blood vessels. Methylmercury has the ability to accumulate in the food chain and ultimately enter the human body, thereby affecting human health. Therefore, the hazards of mercury pollution in aquatic environments are increasingly causing concern. 　　3. Control technologies for mercury in wastewater 　　Currently, the treatment methods for mercury-containing wastewater include precipitation, electrolysis, ion exchange, activated carbon adsorption, and combined process treatments. 　　(1) Precipitation method: The precipitation method is divided into two types: coagulation precipitation and sulfide precipitation. The principle of coagulation sedimentation is to add coagulants (lime, iron salts, aluminum salts) to mercury-containing wastewater; under weakly alkaline conditions with a pH of 8-10, hydroxide flocs are formed, and these flocs are used to cause mercury to precipitate out together with them. Generally, iron salts are more effective than aluminum salts. The sulfidation precipitation method is a commonly reported precipitation method. This method involves adding sodium sulfide to mercury-containing wastewater; utilizing the strong affinity between Hg2+ and S2-, mercury sulfide with extremely low solubility is formed, thereby removing mercury from the solution. Wu Xiuying et al. conducted pilot and scale-up tests using sodium sulfide to treat mercury-containing wastewater from the Qingdao Battery Factory. The test results showed that the mercury content in the wastewater was below the **standard, indicating good treatment effectiveness; moreover, the chemical properties of the sediment remained stable, making this method suitable for use in small and medium-sized chemical industries. The sulfidation precipitation method is widely used in the control of mercury pollution in chlor-alkali plants in countries such as the United States. This method is suitable for treating mercury salts of different concentrations and types; when the concentration of mercury ions is high, chemical precipitation should be the preferred method. It is reported that the removal rate of mercury by precipitation can reach 95%-99.9%. 　　The disadvantages of this method are: (1) it tends to cause water hardness, fails to treat wastewater containing low concentrations of mercury thoroughly, and can lead to secondary pollution. (2) Affected by precipitants, environmental conditions, and process control parameters, it is difficult for the effluent concentration to meet the discharge standards; therefore, further treatment is required. 　　(2) Electrolysis method The electrolysis method makes use of the electrochemical properties of metals; under the action of direct current, mercury compounds dissociate into mercury ions at the anode and are reduced to metallic mercury at the cathode, thereby removing mercury from wastewater. This method is suitable for treating wastewater containing high concentrations of inorganic mercury. The disadvantages of this method are that the concentration of mercury ions in water cannot be reduced very low, it consumes a large amount of electricity, the investment cost is high, and it easily generates mercury vapor, leading to secondary pollution. 　　(3) Ion exchange method The ion exchange method is carried out in an ion exchanger, where large-pore thiol-based ion exchange resins are used to adsorb mercury ions from mercury-containing wastewater. The thiol groups on the resin have a strong adsorption capacity for mercury ions; the mercury adsorbed on the resin can be eluted using concentrated hydrochloric acid for quantitative recovery. 　　Compared to precipitation and electrolysis methods, the ion exchange method is suitable for treating wastewater containing low concentrations of mercury. Studies show that treating first with primary treatment and then using ion exchange yields the best results for ion exchange. Generally, after treating mercury-containing wastewater using ion exchange methods, the minimum concentration of inorganic mercury in the effluent is 1–5 ug/L. We import the mercury-removal resins CH-95 or CH-97 specifically designed for DuSheng; after treatment, mercury emissions can be reduced to below 5 ppt, which is much lower than the mandated emission standard of 1 ppb. There are many operational cases of chlor-alkali plants both domestically and internationally. 　　(4) Activated carbon adsorption method The activated carbon adsorption method is a relatively mature technique for treating mercury-containing wastewater. It can effectively adsorb mercury from wastewater; some factories in China have used this method to treat mercury-containing wastewater, but it is expensive and only suitable for treating wastewater with low concentrations of mercury. When the wastewater concentration is too high, primary treatment can be carried out first, followed by adsorption treatment using activated carbon. According to relevant information, this method is suitable for wastewater with a mercury content of 1–2 mg·L⁻¹ or less; after treatment using activated carbon adsorption, the mercury concentration in the effluent can be reduced to 0.01–0.05 mg·L⁻¹. 　　There are many factors that affect the efficiency of activated carbon adsorption treatment, including the contact time between the wastewater and the adsorbent, the structure and pore size of the activated carbon, the initial form and concentration of mercury in the wastewater, as well as the amount and form of the activated carbon used. The pH and temperature of wastewater also affect the adsorption by activated carbon. Generally, activated carbon has a higher adsorption capacity under acidic conditions than under alkaline conditions. The adsorption reaction is usually an exothermic reaction; therefore, a low temperature is favorable for it. Activated carbon is more effective in removing organic mercury than inorganic mercury. Treating wastewater with high mercury content using activated carbon yields a treatment efficiency of approximately 85-99%. 　　The disadvantages of this treatment method are: a large amount of activated carbon is required, there are few regeneration facilities, the regeneration costs are high, and the precision of advanced treatment is not very high. 　　(5) Application of combined treatment technologies
Huang Mingrong et al. employed a “combined process consisting of sulfide precipitation, coagulation, ultrafiltration, and activated carbon treatment” to treat mercury-containing wastewater generated in the VCM production step during the calcium carbide-based production of polyvinyl chloride in the chlor-alkali industry. The results showed that the mercury removal rate could reach 99.95%. Ultrafiltration proved to be highly effective in removing mercury from the effluent produced by the sulfide precipitation process; the mercury concentration in the treated water remained stable at around 20 ppb. Additionally, this process effectively prolonged the saturation period of the activated carbon. This combined process is easy to operate, achieves good treatment results, and has certain practical value. In the current chlor-alkali industry, regarding the mercury removal process using ion-exchange membrane caustic soda, an additional stage of mercury removal using resin is usually added after this combined process; it is typically designed to operate in series to ensure that the concentration of mercury in the final wastewater remains below 1 PPB. 　　(6) Other methods Superconducting magnetic separation technology is a newly developed application technique for superconducting magnets. This technology is a method for separating materials with different magnetic properties by utilizing the force of magnetic fields. The superconducting high-gradient magnetic separation technology can be used to purify and separate wastewater containing mercury. Currently, this technology is still in the research phase and has not yet been put into industrial application. 　　3. Conclusions and Recommendations 　　Through research, experimentation, and application, various mature treatment technologies for mercury-containing wastewater have been developed. Depending on the characteristics of different types of mercury-containing wastewater, appropriate treatment methods can be selected. 　　The recommendations are as follows: 1. Control at the source to reduce the emission of mercury pollutants. 2. Reduce the sources of mercury-containing waste discharged into various environmental elements (water, air, sludge, soil), and strengthen the control of mercury pollutants. 3. Increase research on the monitoring and treatment of mercury-containing waste, particularly the degradation of methylmercury, to prevent it from entering the food chain and causing significant impacts on human health. 【Mobile】17090831380, 13917047856 (same number on WeChat). The DuSheng ion exchange resin is currently available in the CH-95 PH 0-7 grade ； CH-97 is reusable (usable within a pH range of 0-14); feel free to ask if you are interested in mercury-removing resins.