Method for treating mercury-containing wastewater by adopting ion exchange

Abstract

The invention relates to a method for treating mercury-containing wastewater by adopting ion exchange. The method comprises the following steps: (1) adding a NaHCO3 solution and sodium sulfide into the mercury-containing wastewater; (2) effluent in the step (1) enters a first-stage sulfydryl cation exchange fiber column, and saturated sulfydryl cation exchange fibers are sequentially subjected to backwashing, regeneration and leaching; (3) effluent in the step (2) enters a secondary carboxyl type amphoteric ion exchange fiber column, and saturated amphoteric ion exchange fibers are sequentially subjected to backwashing, regeneration and leaching; and (4) the effluent in the step (3) enters a three-stage mixed ion exchange resin column, saturated ion exchange resin is sequentially subjected to backwashing, regeneration and leaching, and the effluent is discharged after reaching the standard. By adopting a chemical precipitation and multi-stage ion exchange coupling method, the method has a good removal effect on mercury ions in various valence states, the mercury content in the treated wastewater reaches the national discharge standard, and the method has the characteristics of stable treatment effect, economy and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of mercury-containing wastewater treatment technology, and in particular to a method for treating mercury-containing wastewater using ion exchange. Background Technology

[0002] With the continuous development of my country's industry, especially the rapid development of metallurgy and chemical industries, the content of toxic heavy metals in the environment has been increasing. Even small concentrations of toxic heavy metals can cause harm once discharged into wastewater. Wastewater containing heavy metals is characterized by its long-term persistent toxicity, ability to accumulate in large quantities, and inability to be degraded by microorganisms, making it one of the most potentially hazardous pollution sources. Mercury, a silvery-white heavy metal that is liquid at room temperature, is commonly known as "quicksilver." It is persistent, bioaccumulative, and highly toxic in the environment. Mercury-containing wastewater is a particularly hazardous type of industrial wastewater. my country stipulates that the primary discharge limit for total mercury in wastewater is 0.05 mg / L.

[0003] Currently, there are three main conventional methods for treating mercury-containing wastewater: The first involves removing heavy metal ions through chemical reactions, including neutralization precipitation, sulfide precipitation, ferrite co-precipitation, chemical reduction, electrochemical reduction, and polymeric heavy metal scavenging agents. The second method involves adsorption, concentration, and separation of heavy metals in wastewater without altering their chemical form, including adsorption, solvent extraction, and ion exchange. The third method utilizes the flocculation, absorption, accumulation, and enrichment of heavy metals by microorganisms or plants, including bioflocculation and bioadsorption. Each of these methods has its advantages and disadvantages. Some methods, such as neutralization precipitation and sulfide precipitation, have been gradually phased out due to their potential for secondary pollution. Membrane methods (which rely on pressure or concentration to mechanically sieve, dissolve, diffuse, or repel pollutants through semi-permeable membranes with specific pore sizes or selective permeability) and ion exchange methods (which utilize the reversible exchange reaction between exchangeable ions on ion exchange resins and like ions in solution to remove target ions from water) are increasingly valued and are currently a focus of research because they can recover effective components from wastewater, avoid "secondary pollution," and achieve resource recycling.

[0004] Chinese patent application CN107445278A discloses a "method for treating laboratory mercury-containing wastewater". After adding EDTA to the wastewater, under acidic conditions (pH 3-6), EDTA reacts as H3Y- and H2Y-. 2- The form of Hg 2+A positive complex is formed and adsorbed by a cation exchange resin, eliminating interference from chloride ions and removing mercury ions from wastewater. The addition of EDTA, in an acidic medium, fixes mercury ions into stable cations, unaffected by chloride ions, enabling effective ion exchange with the cation exchange resin. The total mercury removal rate can reach 99%, achieving effective removal of mercury from wastewater. However, the removal efficiency for different mercury valence states is not specified, and the acidic conditions (pH 3–6) result in high treatment costs.

[0005] Chinese patent application CN116693115A discloses a "method for treating mercury-containing wastewater," which includes the following steps: adjusting the pH value of the mercury-containing wastewater to a preset range, adding a sulfiding agent, a composite additive, and a flocculant to form HgS precipitate, separating the HgS precipitate and collecting the supernatant; filtering the supernatant to separate particulate matter and water, and collecting the filtered water; and treating the water by adsorption to obtain standard discharge water. However, this method uses a large number of reagents, is costly, and has cumbersome operation steps.

[0006] Chinese patent application CN115028304A discloses a "mercury-containing wastewater treatment system for an acetylene-based vinyl chloride plant," which includes a neutralization tank for collecting mercury-containing wastewater. Hydrochloric acid and / or sodium hydroxide are added to the neutralization tank, followed by sodium hydrosulfide. The outlet of the neutralization tank is sequentially connected to a precipitation filter unit and a physical adsorption filter unit. The other end of the physical adsorption filter unit is connected to a stripping tower, into which a steam stream is introduced. The liquid phase outlet of the stripping tower is connected via a pipeline to an activated carbon adsorber and an ion exchange resin adsorption tower. However, this system is relatively complex, has high equipment costs, and is cumbersome to operate.

[0007] Chinese patent application CN107226572A discloses a "zero-discharge system and method for deep treatment of mercury-containing wastewater." This method involves sequentially performing distillation, oxidation, ultrafiltration, nanofiltration, electrodialysis, reverse osmosis, and acoustic distillation to remove small-molecule organic matter, large-molecule organic matter, divalent ions, and sodium chloride molecules from mercury-containing wastewater. The resulting concentrated brine is used for salt desalination, and the purified water is used for other process water applications. However, this method involves numerous steps and is relatively complex to operate.

[0008] The published literature “Research on the Treatment of Laboratory Mercury-Containing Wastewater by Ion Exchange Method” (by Lin Jianqing et al., Journal of Quanzhou Normal University, 2018, No. 2, pp. 45-49) uses ion exchange resins (strong acid cation exchange resin and strong base anion exchange resin) to treat laboratory mercury-containing wastewater. It studies the effects of wastewater pH, chloride ions, and EDTA coexistence on the removal of ionic mercury and concludes that: (1) the presence of chloride ions will inhibit the adsorption of mercury ions in wastewater by strong acid cation exchange resin and improve the adsorption of mercury ions by strong base anion exchange resin; (2) EDTA can combine with mercury ions to form a stable (2) When EDTA and chloride ions coexist in simulated wastewater, EDTA can preferentially combine with mercury ions to form a complex, which can be completely adsorbed by a strong acid cation exchange resin, and the total mercury concentration in the effluent is far below the emission standard limit for mercury in wastewater; (3) When EDTA and chloride ions coexist in simulated wastewater, EDTA can preferentially combine with mercury ions to form a complex, which can be completely adsorbed by a strong acid cation exchange resin, and the total mercury concentration in the effluent is far below the emission standard limit for mercury in wastewater; (4) The best method for removing mercury from wastewater is to adjust the pH of the wastewater to 6-10, and in the presence of sufficient EDTA, a strong acid cation exchange resin can be used to completely remove mercury from the wastewater, thereby achieving the standard discharge of the effluent. However, this literature only focuses on the treatment of wastewater containing low concentrations of mercury and does not involve the resin desorption process.

[0009] The publicly available literature, "Engineering Application of Coagulation-Sedimentation-Ultrafiltration-Ion Exchange Process in Mercury-Containing Wastewater Treatment" (by Huang Dezhi, *Guangdong Chemical Industry*, 2015, No. 8, pp. 142-143), employs an "ultrafiltration + two-stage ADS (resin)" process. A single-stage UF filtration removes suspended mercury from the wastewater, followed by a two-stage ADS adsorption process to remove dissolved mercury. The two-stage resin adsorption removes mercury ions of various configurations from the wastewater. After the first-stage resin becomes saturated, industrial pure water / steam condensate + hydrochloric acid / liquid alkali is used as a desorbent to desorb the resin. The high-concentration mercury desorbed is combined with the mercury-containing wastewater from the workshop and returned to the sodium sulfide sedimentation tank. This scheme utilizes ultrafiltration, resulting in high maintenance costs. Summary of the Invention

[0010] This invention provides a method for treating mercury-containing wastewater using ion exchange. The method employs a combination of chemical precipitation and multi-stage ion exchange, which effectively removes mercury ions of various valence states. After treatment, the mercury content in the wastewater meets national emission standards, and the method is characterized by stable treatment effect and high cost-effectiveness.

[0011] To achieve the above objectives, the present invention employs the following technical solution: A method for treating mercury-containing wastewater using ion exchange includes the following steps: (1) Add NaHCO3 solution to mercury-containing wastewater to adjust the pH value of mercury-containing wastewater to 8-10, then add sodium sulfide to mercury-containing wastewater, stir thoroughly, and precipitate and separate the supernatant to initially remove divalent mercury ions; (2) In step (1), the effluent enters the primary mercapto-type cation exchange fiber column and remains there for a period of time to treat Hg. 2+ Hg2 2+ The removal process is as follows: The primary mercapto-type cation exchange fiber column contains mercapto-type cation exchange fibers; the saturated mercapto-type cation exchange fibers are first backwashed with municipal wastewater, then regenerated with pickling waste liquid from steel enterprises, and finally rinsed with deionized water. (3) The effluent from step (2) enters the secondary carboxyl type zwitterionic ion exchange fiber column and stays for a period of time to remove the cation mercury and the mercury anion complex; the secondary carboxyl type zwitterionic ion exchange fiber column is equipped with zwitterionic ion exchange fibers composed of carboxyl type cation exchange fibers and carboxyl type anion exchange fibers; the saturated zwitterionic ion exchange fibers are first backwashed with municipal wastewater, then the carboxyl type cation exchange fibers are desorbed and regenerated with pickling waste liquid from steel enterprises, then the carboxyl type anion exchange fibers are desorbed and regenerated with sodium hydroxide solution, and finally the regenerated zwitterionic ion exchange fibers are rinsed with deionized water; (4) The effluent from step (3) enters the three-stage mixed ion exchange resin column and stays for a period of time to remove the residual mercury ions in various forms. The effluent meets the discharge standards. The three-stage mixed ion exchange resin column is equipped with modified macroporous resin and quaternary ammonium salt strong base anion exchange resin as ion exchange resin. The saturated ion exchange resin is first backwashed with municipal wastewater, then regenerated with sodium hydroxide solution, and finally rinsed with deionized water.

[0012] In step (1), the mass concentration of the added NaHCO3 solution is 5% to 8%; the stirring time is 30 to 40 minutes.

[0013] In step (1), 3-5g of sodium sulfide is added for every 1L of mercury-containing wastewater treated.

[0014] In step (2), the primary thiol-type cation exchange fiber column uses polythiostyrene-polyvinyl alcohol cation exchange fiber as the thiol-type cation exchange fiber.

[0015] In step (2), the residence time of the mercury-containing wastewater is 20-30 min; the flow rate of urban water during backwashing is 20-30 m / h; the acid concentration of the pickling waste liquid from the steel enterprise used during regeneration is 2-3 mol / L; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of the cation exchange fiber.

[0016] In step (3), the secondary carboxyl type zwitterionic ion exchange fiber column uses formic acid-polyacrylonitrile zwitterionic ion exchange fiber as the zwitterionic ion exchange fiber.

[0017] In step (3), the residence time of mercury-containing wastewater is 30-40 min; the flow rate of urban water during backwashing is 20-30 m / h; the acid concentration of the pickling waste liquid from steel enterprises used for desorption and regeneration of carboxyl-type cation exchange fibers is 1-2 mol / L; the concentration of sodium hydroxide solution used for desorption and regeneration of carboxyl-type anion exchange fibers is 1-2 mol / L; the sodium hydroxide solution is the effluent from the electrodialysis device in the deep treatment process of coking wastewater; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of the zwitterionic exchange fibers.

[0018] In step (4), the bottom of the three-stage mixed ion exchange resin column is filled with modified macroporous resin, which accounts for 1 / 3 to 1 / 2 of the total volume, and the remaining volume is filled with quaternary ammonium salt strong basic anion exchange resin.

[0019] In step (4), the residence time of mercury-containing wastewater is 20-30 min; the flow rate of urban water during backwashing gradually decreases from 20-30 m / h to 5-10 m / h; the concentration of sodium hydroxide solution used during regeneration is 2-3 mol / L; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of ion exchange resin.

[0020] In step (4), the modified macroporous resin is obtained by modifying macroporous resin. Coke powder, coconut shell charcoal and macroporous resin are mixed and placed in a muffle furnace. After high-temperature activation at 400-500℃, the modified macroporous resin is obtained. The mass ratio of macroporous resin, coke powder and coconut shell charcoal is 1:1:3 to 1:1:5. The average pore size of macroporous resin is 30-60 nm, and the average pore size of modified macroporous resin is 70-90 nm.

[0021] Compared with the prior art, the beneficial effects of the present invention are: 1) The method of chemical precipitation and multi-stage ion exchange coupling has a good removal effect on mercury ions of various valence states, and the mercury content in the treated wastewater meets the national emission standards. 2) It features stable treatment results and high cost-effectiveness; 3) It achieves waste treatment with waste, and the resin can be recycled and reused, which is economical and environmentally friendly. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a method for treating mercury-containing wastewater using ion exchange, as described in this invention. Detailed Implementation

[0023] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: like Figure 1 As shown, the method for treating mercury-containing wastewater using ion exchange according to the present invention includes the following steps: (1) Add NaHCO3 solution to mercury-containing wastewater to adjust the pH value of mercury-containing wastewater to 8-10, then add sodium sulfide to mercury-containing wastewater, stir thoroughly, and precipitate and separate the supernatant to initially remove divalent mercury ions; (2) In step (1), the effluent enters the primary mercapto-type cation exchange fiber column and remains there for a period of time to treat Hg. 2+ Hg2 2+ The removal process is as follows: The primary mercapto-type cation exchange fiber column contains mercapto-type cation exchange fibers; the saturated mercapto-type cation exchange fibers are first backwashed with municipal wastewater, then regenerated with pickling waste liquid from steel enterprises, and finally rinsed with deionized water. (3) The effluent from step (2) enters the secondary carboxyl type zwitterionic ion exchange fiber column and stays for a period of time to remove the cation mercury and the mercury anion complex; the secondary carboxyl type zwitterionic ion exchange fiber column is equipped with zwitterionic ion exchange fibers composed of carboxyl type cation exchange fibers and carboxyl type anion exchange fibers; the saturated zwitterionic ion exchange fibers are first backwashed with municipal wastewater, then the carboxyl type cation exchange fibers are desorbed and regenerated with pickling waste liquid from steel enterprises, then the carboxyl type anion exchange fibers are desorbed and regenerated with sodium hydroxide solution, and finally the regenerated zwitterionic ion exchange fibers are rinsed with deionized water; (4) The effluent from step (3) enters the three-stage mixed ion exchange resin column and stays for a period of time to remove the residual mercury ions in various forms. The effluent meets the discharge standards. The three-stage mixed ion exchange resin column is equipped with modified macroporous resin and quaternary ammonium salt strong base anion exchange resin as ion exchange resin. The saturated ion exchange resin is first backwashed with municipal wastewater, then regenerated with sodium hydroxide solution, and finally rinsed with deionized water.

[0024] In step (1), the mass concentration of the added NaHCO3 solution is 5% to 8%; the stirring time is 30 to 40 minutes.

[0025] In step (1), 3-5g of sodium sulfide is added for every 1L of mercury-containing wastewater treated.

[0026] In step (2), the primary thiol-type cation exchange fiber column uses polythiostyrene-polyvinyl alcohol cation exchange fiber as the thiol-type cation exchange fiber.

[0027] In step (2), the residence time of the mercury-containing wastewater is 20-30 min; the flow rate of urban water during backwashing is 20-30 m / h; the acid concentration of the pickling waste liquid from the steel enterprise used during regeneration is 2-3 mol / L; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of the cation exchange fiber.

[0028] In step (3), the secondary carboxyl type zwitterionic ion exchange fiber column uses formic acid-polyacrylonitrile zwitterionic ion exchange fiber as the zwitterionic ion exchange fiber.

[0029] In step (3), the residence time of mercury-containing wastewater is 30-40 min; the flow rate of urban water during backwashing is 20-30 m / h; the acid concentration of the pickling waste liquid from steel enterprises used for desorption and regeneration of carboxyl-type cation exchange fibers is 1-2 mol / L; the concentration of sodium hydroxide solution used for desorption and regeneration of carboxyl-type anion exchange fibers is 1-2 mol / L; the sodium hydroxide solution is the effluent from the electrodialysis device in the deep treatment process of coking wastewater; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of the zwitterionic exchange fibers.

[0030] In step (4), the bottom of the three-stage mixed ion exchange resin column is filled with modified macroporous resin, which accounts for 1 / 3 to 1 / 2 of the total volume, and the remaining volume is filled with quaternary ammonium salt strong basic anion exchange resin.

[0031] In step (4), the residence time of mercury-containing wastewater is 20-30 min; the flow rate of urban water during backwashing gradually decreases from 20-30 m / h to 5-10 m / h; the concentration of sodium hydroxide solution used during regeneration is 2-3 mol / L; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of ion exchange resin.

[0032] In step (4), the modified macroporous resin is obtained by modifying macroporous resin. Coke powder, coconut shell charcoal and macroporous resin are mixed and placed in a muffle furnace. After high-temperature activation at 400-500℃, the modified macroporous resin is obtained. The mass ratio of macroporous resin, coke powder and coconut shell charcoal is 1:1:3 to 1:1:5. The average pore size of macroporous resin is 30-60 nm, and the average pore size of modified macroporous resin is 70-90 nm.

[0033] like Figure 1 As shown, as a preferred embodiment, the method for treating mercury-containing wastewater using ion exchange according to the present invention is as follows: (1) Add a 5% to 8% NaHCO3 solution to the mercury-containing wastewater to adjust the pH value of the mercury-containing wastewater to 8 to 10. Then add sodium sulfide to the mercury-containing wastewater and stir thoroughly for 30 to 40 minutes before precipitating and separating the supernatant. The NaHCO3 solution added in step (1) has a dual function: it can both adjust the pH value of the mercury-containing wastewater and react with the mercury in the wastewater to form basic mercuric carbonate precipitate, thereby removing some of the mercury from the wastewater. The amount of sodium sulfide added is proportional to the amount of mercury-containing wastewater, that is, 3-5g of sodium sulfide is added for every 1L of mercury-containing wastewater treated.

[0034] (2) In step (1), the effluent enters the first-stage mercapto-type cation exchange fiber column from bottom to top (preferably polysulfide-polyvinyl alcohol cation exchange fiber), and the residence time is 20-30 min. After saturation, the mercapto-type cation exchange fiber is first backwashed with urban wastewater at a flow rate of 20-30 m / h, then regenerated with pickling wastewater from steel enterprises with an acid concentration of 2-3 mol / L, and finally rinsed with deionized water. During rinsing, the water flow rate gradually increases from 2-3 m / h to 4-5 m / h, and the rinsing water volume is 5-10 times the volume of the mercapto-type cation exchange fiber.

[0035] The polystyrene-sulfopolyvinyl alcohol cation exchange fiber, using polyvinyl alcohol as the chemical fiber matrix, possesses excellent chemical stability and exchange adsorption performance. It utilizes municipal wastewater for backwashing and steel mill pickling wastewater for regeneration, achieving waste-to-waste treatment, saving costs, and avoiding resource waste. The water flow rate during rinsing is initially low and gradually increases to better remove residual regenerated liquid.

[0036] (3) In step (2), the effluent enters the secondary carboxyl type zwitterionic exchange fiber column (preferably formic acid-polyacrylonitrile zwitterionic exchange fiber) from bottom to top, and the residence time is 30-40 min. After saturation, the zwitterionic exchange fibers are first backwashed with urban wastewater at a flow rate of 20-30 m / h, then the carboxyl type cation exchange fibers are desorbed and regenerated with pickling waste liquid from steel enterprises at a concentration of 1-2 mol / L, then the carboxyl type anion exchange fibers are desorbed and regenerated with sodium hydroxide solution at a concentration of 1-2 mol / L, and finally the regenerated zwitterionic exchange fibers are rinsed with deionized water. During rinsing, the water flow rate is gradually increased from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of the zwitterionic exchange fibers.

[0037] The zwitterionic exchange fiber, formed by grafting formic acid onto polyacrylonitrile as the chemical fiber matrix, exhibits excellent removal effects on mercury ions and mercury compounds in mercury-containing wastewater. The sodium hydroxide solution is preferably obtained from the effluent of the electrodialysis unit in the advanced treatment process of coking wastewater, to achieve resource utilization.

[0038] (4) In step (3), the effluent enters the three-stage mixed ion exchange resin column from bottom to top (the ion exchange resin is preferably a modified macroporous resin + quaternary ammonium salt strong base anion exchange resin), with a residence time of 20-30 minutes, and the effluent meets the discharge standards. After saturation, the ion exchange resin is first backwashed with municipal wastewater (the flow rate is gradually reduced from 20-30 m / h to 5-10 m / h), then regenerated with a sodium hydroxide solution with a concentration of 2-3 mol / L, and finally rinsed with deionized water (the water flow rate is gradually increased from 2-3 m / h to 4-5 m / h). The amount of rinsing water is 5-10 times the volume of the ion exchange resin.

[0039] Modified macroporous resin is obtained by modifying macroporous resin. Coke powder, coconut shell charcoal and macroporous resin are mixed and placed in a muffle furnace and activated at high temperature of 400-500℃ to obtain modified macroporous resin. The mass ratio of macroporous resin, coke powder and coconut shell charcoal is 1:1:3 to 1:1:5. The average pore size of macroporous resin is 30-60 nm, and the average pore size of modified macroporous resin is 70-90 nm.

[0040] In the preparation of a three-stage mixed ion exchange resin column, a modified macroporous resin (accounting for 1 / 3 to 1 / 2 of the total column volume) is first added to the column, followed by a quaternary ammonium salt strong basic anion exchange resin (accounting for 1 / 2 to 2 / 3 of the total column volume).

[0041] All concentrations mentioned in this invention are mass concentrations.

[0042] To more intuitively illustrate the present invention, the embodiments of the present invention will be further described in conjunction with the examples. The following examples are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technical solutions that can be obviously obtained by those skilled in the art within the scope of the technology disclosed in the present invention, including simple variations or equivalent substitutions, are all within the scope of protection of the present invention.

[0043]

Example 1

[0044] (3) In step (2), the effluent enters the secondary carboxyl type zwitterionic ion exchange fiber column (using formic acid-polyacrylonitrile zwitterionic ion exchange fiber) from bottom to top and stays for 30 minutes. After saturation, the zwitterionic ion exchange fiber is first backwashed with urban wastewater at a flow rate of 20 m / h, then the carboxyl type cation exchange fiber is desorbed and regenerated with pickling waste liquid from steel enterprises at an acid concentration of 1 mol / L, then the carboxyl type anion exchange fiber is desorbed and regenerated with sodium hydroxide at a concentration of 1 mol / L, and finally the regenerated zwitterionic ion exchange fiber is rinsed with deionized water (the water flow rate gradually increases from 2 m / h to 4 m / h), and the rinsing water volume is 5 times the volume of the zwitterionic ion exchange fiber.

[0045] (4) In step (3), the effluent enters the three-stage mixed ion exchange resin column (using modified macroporous resin + quaternary ammonium salt strong base anion exchange resin) from bottom to top, stays for 20 minutes, and is discharged after meeting the standards. The average pore size of the modified macroporous resin in the three-stage mixed ion exchange resin column is 70 nm, and the filling amount is 1 / 3 of the total volume. The filling amount of the quaternary ammonium salt strong base anion exchange resin accounts for 2 / 3 of the total volume. After saturation, the ion exchange resin is first backwashed with municipal wastewater (the flow rate is gradually reduced from 20 m / h to 5 m / h), then regenerated with a sodium hydroxide solution with a concentration of 2 mol / L, and finally rinsed with deionized water (the water flow rate is gradually increased from 2 m / h to 4 m / h). The amount of rinsing water is 5 times the volume of the ion exchange resin.

[0046] After the above process, the concentration of total mercury in the mercury-containing wastewater decreased from 5 mg / L at the influent to 0.32 mg / L at the effluent, with a removal rate of 93.6%.

[0047]

Example 2

[0048] (3) In step (2), the effluent enters the secondary carboxyl type zwitterionic ion exchange fiber column (using formic acid-polyacrylonitrile zwitterionic ion exchange fiber) from bottom to top and stays for 35 minutes. After saturation, the zwitterionic ion exchange fiber is first backwashed with urban wastewater at a flow rate of 25 m / h, then the carboxyl type cation exchange fiber is desorbed and regenerated with pickling waste liquid from steel enterprises at an acid concentration of 1.5 mol / L, then the carboxyl type anion exchange fiber is desorbed and regenerated with sodium hydroxide at a concentration of 1.5 mol / L, and finally the regenerated zwitterionic ion exchange fiber is rinsed with deionized water (the water flow rate gradually increases from 2 m / h to 5 m / h), and the rinsing water volume is 7 times the volume of the zwitterionic ion exchange fiber.

[0049] (4) In step (3), the effluent enters the three-stage mixed ion exchange resin column (using modified macroporous resin + quaternary ammonium salt strong base anion exchange resin) from bottom to top, stays for 20 minutes, and is discharged after meeting the standards. The average pore size of the modified macroporous resin in the three-stage mixed ion exchange resin column is 80 nm, and the filling amount is 1 / 2 of the total volume. The filling amount of the quaternary ammonium salt strong base anion exchange resin is 1 / 2 of the total volume. After saturation, the ion exchange resin is first backwashed with municipal wastewater (the flow rate is gradually reduced from 25 m / h to 8 m / h), then regenerated with a sodium hydroxide solution with a concentration of 2 mol / L, and finally rinsed with deionized water (the water flow rate is gradually increased from 2.5 m / h to 4.5 m / h). The amount of rinsing water is 9 times the volume of the ion exchange resin.

[0050] After the above process, the concentration of total mercury in the mercury-containing wastewater decreased from 5 mg / L at the influent to 0.025 mg / L at the effluent, with a removal rate of 99.5%.

[0051]

Example 3

[0052] (3) In step (2), the effluent enters the secondary carboxyl type zwitterionic ion exchange fiber column (using formic acid-polyacrylonitrile zwitterionic ion exchange fiber) from bottom to top and stays for 40 minutes. After saturation, the zwitterionic ion exchange fiber is first backwashed with urban wastewater at a flow rate of 30 m / h, then the carboxyl type cation exchange fiber is desorbed and regenerated with pickling waste liquid from steel enterprises at an acid concentration of 2 mol / L, then the carboxyl type anion exchange fiber is desorbed and regenerated with sodium hydroxide at a concentration of 2 mol / L, and finally the regenerated zwitterionic ion exchange fiber is rinsed with deionized water (the water flow rate gradually increases from 3 m / h to 5 m / h), and the amount of rinsing water is 10 times the volume of the zwitterionic ion exchange fiber.

[0053] (4) In step (3), the effluent enters the three-stage mixed ion exchange resin column (using modified macroporous resin + quaternary ammonium salt strong base anion exchange resin) from bottom to top, stays for 30 minutes, and is discharged after meeting the standards. The average pore size of the modified macroporous resin in the three-stage mixed ion exchange resin column is 90 nm, and the filling amount is 2 / 3 of the total volume. The filling amount of the quaternary ammonium salt strong base anion exchange resin accounts for 1 / 3 of the total volume. After saturation, the ion exchange resin is first backwashed with municipal wastewater (the flow rate is gradually reduced from 30 m / h to 10 m / h), then regenerated with a sodium hydroxide solution with a concentration of 3 mol / L, and finally rinsed with deionized water (the water flow rate is gradually increased from 3 m / h to 5 m / h). The amount of rinsing water is 10 times the volume of the ion exchange resin.

[0054] After the above process, the concentration of total mercury in the mercury-containing wastewater decreased from 5 mg / L at the influent to 0.085 mg / L at the effluent, with a removal rate of 98.3%.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for treating mercury-containing wastewater using ion exchange, characterized in that, Includes the following steps: (1) Add NaHCO3 solution to mercury-containing wastewater to adjust the pH value of mercury-containing wastewater to 8-10, then add sodium sulfide to mercury-containing wastewater, stir thoroughly, and precipitate and separate the supernatant to initially remove divalent mercury ions; (2) In step (1), the effluent enters the primary mercapto-type cation exchange fiber column and remains there for a period of time to treat Hg. 2+ Hg2 2+ The removal process is as follows: The primary mercapto-type cation exchange fiber column contains mercapto-type cation exchange fibers; the saturated mercapto-type cation exchange fibers are first backwashed with municipal wastewater, then regenerated with pickling waste liquid from steel enterprises, and finally rinsed with deionized water. (3) The effluent from step (2) enters the secondary carboxyl type zwitterionic ion exchange fiber column and stays for a period of time to remove the cation mercury and the mercury anion complex; the secondary carboxyl type zwitterionic ion exchange fiber column is equipped with zwitterionic ion exchange fibers composed of carboxyl type cation exchange fibers and carboxyl type anion exchange fibers; the saturated zwitterionic ion exchange fibers are first backwashed with municipal wastewater, then the carboxyl type cation exchange fibers are desorbed and regenerated with pickling waste liquid from steel enterprises, then the carboxyl type anion exchange fibers are desorbed and regenerated with sodium hydroxide solution, and finally the regenerated zwitterionic ion exchange fibers are rinsed with deionized water; (4) The effluent from step (3) enters the three-stage mixed ion exchange resin column and stays for a period of time to remove the residual mercury ions in various forms. The effluent meets the discharge standards. The three-stage mixed ion exchange resin column is equipped with modified macroporous resin and quaternary ammonium salt strong base anion exchange resin as ion exchange resin. The saturated ion exchange resin is first backwashed with municipal wastewater, then regenerated with sodium hydroxide solution, and finally rinsed with deionized water.

2. The method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (1), the mass concentration of the added NaHCO3 solution is 5% to 8%; the stirring time is 30 to 40 minutes.

3. The method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (1), 3-5g of sodium sulfide is added for every 1L of mercury-containing wastewater treated.

4. The method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (2), the primary thiol-type cation exchange fiber column uses polythiostyrene-polyvinyl alcohol cation exchange fiber as the thiol-type cation exchange fiber.

5. The method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (2), the residence time of the mercury-containing wastewater is 20-30 min; the flow rate of urban water during backwashing is 20-30 m / h; the acid concentration of the pickling waste liquid from the steel enterprise used during regeneration is 2-3 mol / L; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of the cation exchange fiber.

6. The method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (3), the secondary carboxyl type zwitterionic ion exchange fiber column uses formic acid-polyacrylonitrile zwitterionic ion exchange fiber as the zwitterionic ion exchange fiber.

7. The method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (3), the residence time of mercury-containing wastewater is 30-40 min; the flow rate of urban water during backwashing is 20-30 m / h; the acid concentration of the pickling waste liquid from steel enterprises used for desorption and regeneration of carboxyl-type cation exchange fibers is 1-2 mol / L; the concentration of sodium hydroxide solution used for desorption and regeneration of carboxyl-type anion exchange fibers is 1-2 mol / L; the sodium hydroxide solution is the effluent from the electrodialysis device in the deep treatment process of coking wastewater; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of the zwitterionic exchange fibers.

8. A method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (4), the bottom of the three-stage mixed ion exchange resin column is filled with modified macroporous resin, which accounts for 1 / 3 to 1 / 2 of the total volume, and the remaining volume is filled with quaternary ammonium salt strong basic anion exchange resin.

9. A method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (4), the residence time of mercury-containing wastewater is 20-30 min; the flow rate of urban water during backwashing gradually decreases from 20-30 m / h to 5-10 m / h; the concentration of sodium hydroxide solution used during regeneration is 2-3 mol / L; the flow rate of deionized water during rinsing gradually increases from 2-3 m / h to 4-5 m / h, and the amount of rinsing water is 5-10 times the volume of ion exchange resin.

10. A method for treating mercury-containing wastewater by ion exchange according to claim 1, characterized in that, In step (4), the modified macroporous resin is obtained by modifying macroporous resin. Coke powder, coconut shell charcoal and macroporous resin are mixed and placed in a muffle furnace. After high-temperature activation at 400-500℃, the modified macroporous resin is obtained. The mass ratio of macroporous resin, coke powder and coconut shell charcoal is 1:1:3 to 1:1:

5. The average pore size of macroporous resin is 30-60 nm, and the average pore size of modified macroporous resin is 70-90 nm.

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