Method for treating chromium-containing wastewater by adopting ion exchange

Abstract

The invention relates to a method for treating chromium-containing wastewater by ion exchange, which comprises the following steps: (1) feeding chromium-containing wastewater into a primary cation exchange carbon fiber column, and sequentially backwashing, regenerating and leaching saturated cation exchange carbon fibers; (2) effluent in the step (1) enters an anion exchange fiber column, the anion exchange fiber column is composed of a second-stage anion exchange fiber column and a third-stage anion exchange fiber column which are connected in series, and saturated anion exchange fibers are sequentially subjected to backwashing, regeneration and leaching; and (3) enabling the anion exchange fiber regenerated eluent to enter a four-stage sulfonic cation exchange resin column. The method is suitable for treating industrial wastewater with relatively complex Cr (VI) pollution conditions, chromium ions in the wastewater are removed by adopting a multi-stage ion exchange coupling method, the chromium content in the treated wastewater can reach 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 chromium-containing wastewater treatment technology, and in particular to a method for treating chromium-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 discharged into wastewater can cause significant harm. 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. Cr(VI), or hexavalent chromium, is a highly toxic, highly mobile, and carcinogenic pollutant widely present due to industrial activities. my country has listed Cr(VI) as a Class I pollutant requiring strict control, and the GB8978 "Integrated Wastewater Discharge Standard" clearly stipulates that the maximum allowable discharge concentration of Cr(VI) is 0.5 mg / L.

[0003] Currently, there are many methods for treating chromium-containing wastewater, including chemical reduction precipitation, adsorption, ion exchange, electrolysis, membrane separation, and biological methods. Ion exchange is essentially the exchange reaction between exchangeable ions on an ion exchanger and other ions of the same charge in the solution; it is a special adsorption process, usually a reversible chemical adsorption process. The most commonly used ion exchanger for treating chromium plating rinsing wastewater is ion exchange resin, which utilizes the exchangeable ions (such as Cl-) on the ion exchange resin. － OH － ), and Cr(VI) ions with the same charge as those in the wastewater (such as CrO4), 2－ HCrO4 － The resin exchanges Cr(VI) from the wastewater onto the resin, thus purifying the wastewater. Ion exchange technology is widely used in industrial water treatment due to its advantages such as small size, simple operation, and stability. However, despite its many advantages, ion exchange technology also has disadvantages such as low exchange efficiency and incomplete regeneration.

[0004] Chinese patent application CN115571948A discloses a method for ion exchange treatment and reuse of chromium-containing electroplating wastewater, comprising the following steps: (1) filtering the chromium-containing electroplating wastewater to remove impurities; (2) adjusting the pH of the chromium-containing electroplating wastewater from step (1) to 2-3, and then sequentially passing it through an anion exchange column and a cation exchange column for ion exchange until the Cr(VI) concentration in the wastewater reaches the standard; the anion exchange column uses a chromium-specific adsorption resin; the cation exchange column uses a strong acid cation exchange resin; (3) stopping the exchange and rinsing and regenerating the anion exchange column and the cation exchange column respectively; (4) using the liquid obtained from rinsing and regenerating the anion exchange column in step (3) as the regenerated liquid, and then evaporating and concentrating the regenerated liquid through a sodium ion exchange column to remove sodium, which is then used in the electroplating process. However, this method does not achieve waste utilization and has relatively high treatment costs.

[0005] Chinese patent application CN109336284A discloses a "method for deep treatment and recycling of chromium-containing electroplating wastewater", including the following steps: (I) Pretreatment: the wastewater is pumped into a precision filter to remove suspended solids and particulate solid impurities; (II) Chromium ion adsorption: the pretreated wastewater is passed into a chromium ion absorption system for adsorption treatment. First, the chromium ion absorption system adsorbs hexavalent chromium ions in the wastewater, and then adsorbs trivalent chromium ions. The chromium ion exchange system includes an adsorption mechanism consisting of a first ion exchange column at the end for adsorbing trivalent chromium ions and multiple second ion exchange columns connected in series before the first ion exchange column for adsorbing hexavalent chromium ions; (III) Circulation desorption and regeneration of the adsorption mechanism: the second ion exchange column at the beginning of the adsorption mechanism... After the first ion exchange column reaches saturation in absorbing hexavalent chromium ions from the wastewater, the connection status of the valves connected between each second ion exchange column is controlled to keep the first ion exchange column disconnected for elution and regeneration. The remaining second ion exchange columns then absorb the hexavalent chromium ions from the wastewater sequentially. After desorption and regeneration, the second ion exchange columns are connected to the end of the adsorption mechanism for use, thus performing cyclic desorption and regeneration of the adsorption mechanism. (IV) Qualified discharge: The wastewater is discharged after passing the test following treatment by the chromium ion exchange system. (V) Chromium ion recovery: After the first ion exchange column reaches saturation, the chromium ion exchange system is desorbed using a sodium hydroxide solution with a mass fraction of 4-6%, and then regenerated using a sodium chloride solution to obtain a sodium chromate solution for recovery. However, this method is relatively cumbersome to operate, uses a large number of reagents, and has high treatment costs.

[0006] Chinese patent application CN104628087A discloses a method for treating vanadium-chromium wastewater using ion exchange fibers. This method employs strongly alkaline anion exchange fibers as the adsorption medium to adsorb pentavalent vanadium and hexavalent chromium ions from the wastewater, recovering both ions. After adsorption, a desorption agent is added to the ion exchange fibers to obtain a desorption solution. An alkaline substance is then added to precipitate vanadium and chromium, recovering both elements. However, this method does not achieve waste utilization and has relatively high treatment costs.

[0007] Chinese patent application CN103663621A discloses a "method for treating hexavalent chromium wastewater using weakly basic ion exchange fibers". The method involves first pretreating the hexavalent chromium wastewater; then packing weakly basic ion exchange fibers into a column and treating it with hydrochloric acid solution to convert it into Cl-. － The process involves using fiber-type ion exchangers to obtain treated ion exchange columns. Two to four of these columns are connected in series to form an ion exchange system. The treated hexavalent chromium wastewater is then passed through this system for adsorption. Wastewater is discharged when the hexavalent chromium concentration in the effluent is less than 0.5 mg / L; otherwise, it continues to be treated in the next ion exchange column until the discharge standard is met. This method involves multiple ion exchange systems, is relatively complex to operate, and is costly.

[0008] The publicly available literature, "Research on Ion Exchange Method for Treating Chromium-Containing Wastewater" (by Zeng Jing, *Jiangxi Chemical Industry*, 2019, No. 3, pp. 108-110), describes the use of ion exchange to treat chromium-containing wastewater. A 201×7 strongly basic anion exchange resin was selected to remove chromium from the wastewater. The resin, having lost its exchange capacity, can be regenerated with sodium hydroxide solution for reuse. However, this study only presents the treatment results for simulated chromium-containing wastewater; its effectiveness in treating chromium-containing wastewater generated in industrial processes remains unknown.

[0009] The publicly available literature, "Research on the Treatment of Chromium-Containing Wastewater with Ion Exchange Resin" (by Xu Ling et al., *Industrial Safety and Environmental Protection*, No. 11, 2007, pp. 12-13), introduces the principle of ion exchange resin treatment of chromium-containing wastewater, discusses the factors affecting the treatment capacity of ion exchange resins, and identifies the optimal reaction conditions through static pH experiments and dynamic flow experiments. The results show that ion exchange resin is feasible for removing hexavalent chromium from wastewater, with good treatment effect. The optimal pH value for the wastewater in this experiment was 3. However, its application is limited to laboratory settings, and its effectiveness in treating chromium-containing wastewater generated in industrial processes remains unknown. Summary of the Invention

[0010] This invention provides a method for treating chromium-containing wastewater using ion exchange, which is suitable for treating industrial wastewater with complex Cr(VI) pollution (such as drastic water quality fluctuations, interference from coexisting pollutants, etc.). The method uses a multi-stage ion exchange coupling approach to remove chromium ions from the wastewater, ensuring that the chromium content in the treated wastewater meets national emission standards, and features 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 chromium-containing wastewater using ion exchange includes the following steps: (1) Chromium-containing wastewater enters the primary cation exchange carbon fiber column and stays for a period of time to remove trivalent chromium; the primary cation exchange carbon fiber column is equipped with cation exchange carbon fibers. After saturation, the cation exchange carbon fibers are first backwashed with municipal wastewater, then regenerated with pickling waste liquid from steel enterprises, and finally rinsed with deionized water. (2) The anion exchange fiber column is composed of a series of secondary anion exchange fiber columns and a tertiary anion exchange fiber column. During normal operation, both are running simultaneously. In step (1), the effluent enters the secondary anion exchange fiber column and the tertiary anion exchange fiber column in sequence to remove hexavalent chromium. Both the secondary and tertiary anion exchange fiber columns are equipped with anion exchange fibers. The secondary and tertiary anion exchange fiber columns are alternately regenerated offline, and the effluent meets the discharge standards. When the saturated anion exchange fiber is regenerated, it is first backwashed with municipal wastewater, then regenerated with sodium hydroxide solution, and finally rinsed with deionized water. (3) The eluent during the regeneration of anion exchange fibers enters the quaternary sulfonic acid cation exchange resin column and remains for a period of time to recover chromium; the quaternary sulfonic acid cation exchange resin column is equipped with sulfonic acid cation exchange resin.

[0012] In step (1), the residence time of chromium-containing wastewater after entering the primary cation exchange carbon fiber column 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 steel enterprises 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 total water consumption for rinsing is 5-10 times the volume of the cation exchange carbon fiber.

[0013] In step (1), the cation exchange carbon fiber is a carboxylic acid-based polyacrylonitrile ion exchange carbon fiber.

[0014] In step (2), the running time of the secondary anion exchange fiber column is set to 40-50 min; the flow rate of urban water during backwashing is 20-30 m / h; the concentration of sodium hydroxide solution used for 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 total rinsing water is 5-10 times the volume of the anion exchange fiber.

[0015] The sodium hydroxide solution is the effluent from the electrodialysis unit in the deep treatment process of coking wastewater.

[0016] In step (2), the anion exchange fiber is a quaternary ammonium-based anion exchange fiber with polystyrene copolymer as the fiber matrix.

[0017] In step (3), the sulfonic acid-based cation exchange resin is a hydrogen-type cation exchange resin.

[0018] In step (3), the residence time of the eluent after entering the quaternary sulfonic acid cation exchange resin column is 30-40 min.

[0019] Compared with the prior art, the beneficial effects of the present invention are: It is suitable for treating industrial wastewater with complex Cr(VI) pollution, and can ensure that the chromium content in the treated wastewater meets the national discharge standards. 1) The anion exchange fiber column consists of a series of secondary and tertiary anion exchange fiber columns, which can be regenerated alternately; it has the characteristics of stable treatment effect and high cost-effectiveness. 2) By adopting the waste-to-waste approach, the resin can be recycled and reused, which is economical and environmentally friendly; at the same time, chromium can be recycled, avoiding the waste of resources. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the principle of a method for treating chromium-containing wastewater using ion exchange as described in this invention. Detailed Implementation

[0021] 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 chromium-containing wastewater using ion exchange according to the present invention includes the following steps: (1) Chromium-containing wastewater enters the primary cation exchange carbon fiber column and stays for a period of time to remove trivalent chromium; the primary cation exchange carbon fiber column is equipped with cation exchange carbon fibers. After saturation, the cation exchange carbon fibers are first backwashed with municipal wastewater, then regenerated with pickling waste liquid from steel enterprises, and finally rinsed with deionized water. (2) The anion exchange fiber column is composed of a series of secondary anion exchange fiber columns and a tertiary anion exchange fiber column. During normal operation, both are running simultaneously. In step (1), the effluent enters the secondary anion exchange fiber column and the tertiary anion exchange fiber column in sequence to remove hexavalent chromium. Both the secondary and tertiary anion exchange fiber columns are equipped with anion exchange fibers. The secondary and tertiary anion exchange fiber columns are alternately regenerated offline, and the effluent meets the discharge standards. When the saturated anion exchange fiber is regenerated, it is first backwashed with municipal wastewater, then regenerated with sodium hydroxide solution, and finally rinsed with deionized water. (3) The eluent during the regeneration of anion exchange fibers enters the quaternary sulfonic acid cation exchange resin column and remains for a period of time to recover chromium; the quaternary sulfonic acid cation exchange resin column is equipped with sulfonic acid cation exchange resin.

[0022] In step (1), the residence time of chromium-containing wastewater after entering the primary cation exchange carbon fiber column 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 steel enterprises 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 total water consumption for rinsing is 5-10 times the volume of the cation exchange carbon fiber.

[0023] In step (1), the cation exchange carbon fiber is a carboxylic acid-based polyacrylonitrile ion exchange carbon fiber.

[0024] In step (2), the running time of the secondary anion exchange fiber column is set to 40-50 min; the flow rate of urban water during backwashing is 20-30 m / h; the concentration of sodium hydroxide solution used for 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 total rinsing water is 5-10 times the volume of the anion exchange fiber.

[0025] The sodium hydroxide solution is the effluent from the electrodialysis unit in the deep treatment process of coking wastewater.

[0026] In step (2), the anion exchange fiber is a quaternary ammonium-based anion exchange fiber with polystyrene copolymer as the fiber matrix.

[0027] In step (3), the sulfonic acid-based cation exchange resin is a hydrogen-type cation exchange resin.

[0028] In step (3), the residence time of the eluent after entering the quaternary sulfonic acid cation exchange resin column is 30-40 min.

[0029] As a preferred embodiment, the method for treating chromium-containing wastewater using ion exchange according to the present invention is as follows: (1) Chromium-containing wastewater enters the primary cation exchange carbon fiber column from top to bottom, with a residence time of 20-30 min. The saturated cation exchange carbon fiber is first backwashed with urban wastewater at a flow rate of 20-30 m / h, then regenerated with pickling wastewater from steel enterprises at 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 amount of rinsing water is 5-10 times the volume of the cation exchange carbon fiber.

[0030] The cation exchange carbon fiber, preferably a carboxylic acid-based polyacrylonitrile ion exchange carbon fiber, uses polyacrylonitrile as the fiber matrix and can remove most of the trivalent chromium and Fe from chromium-containing wastewater. 3+ Ca 2+ It is isocationic. Backwashing is performed using municipal wastewater, and regeneration is achieved using pickling waste liquid from steel enterprises, realizing 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.

[0031] (2) In step (1), the effluent enters the anion exchange fiber column, which consists of a series of secondary and tertiary anion exchange fiber columns. During normal operation, both columns operate simultaneously. The secondary and tertiary anion exchange fiber columns each contain anion exchange fibers to remove hexavalent chromium from the chromium-containing wastewater. The chromium-containing wastewater enters the secondary and tertiary anion exchange fiber columns sequentially from top to bottom. When the concentration of hexavalent chromium in the effluent of one of the anion exchange fiber columns is the same as that in the influent, it indicates that the built-in anion exchange fibers have reached saturation and need regeneration. At this time, the anion exchange fiber column requiring regeneration is taken offline (isolated from the system by valve switching), while the other anion exchange fiber column operates independently, still ensuring that the effluent meets discharge standards. During actual operation, the operating time of the secondary anion exchange fiber column can be set (e.g., 40-50 minutes). After the operating time is exceeded, regeneration is performed. The regeneration time for the tertiary anion exchange fiber column is determined based on the actual operating conditions.

[0032] During the regeneration of anion exchange fibers, backwashing is first performed using municipal wastewater with a flow rate of 20–30 m / h, followed by regeneration using a sodium hydroxide solution with a concentration of 2–3 mol / L, and finally rinsing 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 ion exchange fibers.

[0033] The anion exchange fiber is preferably a quaternary ammonium-based anion exchange fiber, which uses polystyrene copolymer as the fiber matrix and has good chemical stability and exchange adsorption performance.

[0034] The anion exchange fiber column of this invention consists of a secondary anion exchange fiber column and a tertiary anion exchange fiber column connected in series. When one of the anion exchange fiber columns breaks through, it is backwashed and regenerated individually, which can effectively improve the concentration and purity of dichromic acid (H2Cr2O7). The sodium hydroxide solution can be the effluent from the electrodialysis unit in the deep treatment process of coking wastewater, realizing resource utilization.

[0035] (3) The eluent generated during the regeneration of the anion exchange fiber enters a four-stage sulfonic acid-based cation exchange resin column (preferably a hydrogen-type cation exchange resin) to recover chromium (to obtain chromium-containing sludge or crude chromium salts, which are then used as raw materials to prepare chromium anhydride or other chromium products). The eluent enters the four-stage sulfonic acid-based cation exchange resin column from top to bottom, with a residence time of 30–40 min.

[0036] All concentrations mentioned in this invention are mass concentrations.

[0037] 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.

[0038]

Example 1

[0039] (2) The anion exchange fiber column consists of a series of secondary anion exchange fiber columns and a tertiary anion exchange fiber column. During normal operation, both operate simultaneously. In step (1), the effluent enters the secondary anion exchange fiber column and the tertiary anion exchange fiber column sequentially from top to bottom. In this embodiment, the operating time of the secondary anion exchange fiber column is set to 40 minutes. After the operating time is over, the secondary anion exchange fiber column stops working and the anion exchange fibers in it are regenerated. At this time, the tertiary anion exchange fiber column operates alone and ensures that the effluent meets the discharge standards.

[0040] During the regeneration of anion exchange fibers, backwashing is first performed using municipal wastewater with a flow rate of 20 m / h, followed by regeneration using a sodium hydroxide solution with a concentration of 2 mol / L, and finally rinsing with deionized water. During rinsing, the water flow rate is gradually increased from 2 m / h to 4 m / h, and the amount of rinsing water is 5 times the volume of the ion exchange fibers.

[0041] (3) The eluent generated during the regeneration of anion exchange fibers enters the four-stage sulfonic acid cation exchange resin column from top to bottom and stays for 30 minutes.

[0042] After the above process, the concentration of total chromium in the chromium-containing wastewater decreased from 109 mg / L at the influent to 1.2 mg / L at the effluent, with a removal rate of 98.9%.

[0043]

Example 2

[0044] (2) The anion exchange fiber column consists of a series of secondary anion exchange fiber columns and a tertiary anion exchange fiber column. During normal operation, both operate simultaneously. In step (1), the effluent enters the secondary anion exchange fiber column and the tertiary anion exchange fiber column sequentially from top to bottom. In this embodiment, the operating time of the secondary anion exchange fiber column is set to 45 minutes. After the operating time is over, the secondary anion exchange fiber column stops working and the anion exchange fibers in it are regenerated. At this time, the tertiary anion exchange fiber column operates alone and ensures that the effluent meets the discharge standards.

[0045] During the regeneration of anion exchange fibers, backwashing is first performed using municipal wastewater with a flow rate of 25 m / h, followed by regeneration using a sodium hydroxide solution with a concentration of 2 mol / L, and finally rinsing with deionized water. During rinsing, the water flow rate is gradually increased from 2.5 m / h to 4.5 m / h, and the amount of rinsing water is 7 times the volume of the ion exchange fibers.

[0046] (3) The eluent generated during the regeneration of anion exchange fibers enters the quaternary sulfonic acid cation exchange resin column from top to bottom and stays for 35 minutes.

[0047] After the above process, the concentration of total chromium in the chromium-containing wastewater decreased from 109 mg / L at the influent to 0.3 mg / L at the effluent, with a removal rate of 99.7%.

[0048]

Example 3

[0049] (2) The anion exchange fiber column consists of a series of secondary anion exchange fiber columns and a tertiary anion exchange fiber column. During normal operation, both operate simultaneously. In step (1), the effluent enters the secondary anion exchange fiber column and the tertiary anion exchange fiber column sequentially from top to bottom. In this embodiment, the operating time of the secondary anion exchange fiber column is set to 50 minutes. After the operating time is over, the secondary anion exchange fiber column stops working and the anion exchange fibers in it are regenerated. At this time, the tertiary anion exchange fiber column operates alone and ensures that the effluent meets the discharge standards.

[0050] During the regeneration of anion exchange fibers, backwashing is first performed using municipal wastewater with a flow rate of 30 m / h, followed by regeneration using a sodium hydroxide solution with a concentration of 3 mol / L, and finally rinsing with deionized water. During rinsing, the water flow rate is gradually increased from 3 m / h to 5 m / h, and the amount of rinsing water is 10 times the volume of the ion exchange fibers.

[0051] (3) The eluent generated during the regeneration of anion exchange fibers enters the quaternary sulfonic acid cation exchange resin column from top to bottom and stays for 40 minutes.

[0052] After the above process, the concentration of total chromium in the chromium-containing wastewater decreased from 109 mg / L at the influent to 0.87 mg / L at the effluent, with a removal rate of 99.2%.

[0053] 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 wastewater containing chromium by ion exchange, characterized by, The method comprises the following steps: (1) the chromium-containing wastewater enters a first cation exchange carbon fiber column and stays for a period of time to remove trivalent chromium; the first cation exchange carbon fiber column is provided with cation exchange carbon fiber, and the saturated cation exchange carbon fiber is first back-flushed with municipal water, then regenerated with pickling wastewater of a steel enterprise, and finally leached with deionized water; (2) the anion exchange fiber column is composed of a second anion exchange fiber column and a third anion exchange fiber column connected in series, and the two columns are operated simultaneously in normal operation; the effluent of step (1) enters the second anion exchange fiber column and the third anion exchange fiber column in sequence to remove hexavalent chromium; the second anion exchange fiber column and the third anion exchange fiber column are both provided with anion exchange fiber, and the second anion exchange fiber column and the third anion exchange fiber column are regenerated alternately offline, and the effluent is discharged up to the standard; the saturated anion exchange fiber is first back-flushed with municipal water, then regenerated with a sodium hydroxide solution, and finally leached with deionized water; (3) the eluent during regeneration of the anion exchange fiber enters a fourth sulfonic acid group cation exchange resin column and stays for a period of time to recover chromium; the fourth sulfonic acid group cation exchange resin column is provided with sulfonic acid group cation exchange resin.

2. The method for treating wastewater containing chromium by ion exchange according to claim 1, characterized in that, In step (1), the chromium-containing wastewater stays in the first cation exchange carbon fiber column for 20-30 min; the flow rate of the municipal water during back-flushing is 20-30 m / h; the pickling wastewater of the steel enterprise used during regeneration has an acid concentration of 2-3 mol / L; the flow rate of the deionized water during leaching gradually increases from 2-3 m / h to 4-5 m / h, and the total water consumption for leaching is 5-10 times the volume of the cation exchange carbon fiber.

3. The method for treating wastewater containing chromium by ion exchange according to claim 1, wherein In step (1), the cation exchange carbon fiber is carboxylic acid type polyacrylonitrile ion exchange carbon fiber.

4. The method for treating wastewater containing chromium by ion exchange according to claim 1, wherein In step (2), the second anion exchange fiber column is operated for 40-50 min; the flow rate of the municipal water during back-flushing is 20-30 m / h; the concentration of the sodium hydroxide solution used for regeneration is 2-3 mol / L; the flow rate of the deionized water during leaching gradually increases from 2-3 m / h to 4-5 m / h, and the total water consumption for leaching is 5-10 times the volume of the anion exchange fiber.

5. The method for treating wastewater containing chromium by ion exchange according to claim 1 or 4, characterized in that, The sodium hydroxide solution is the effluent of an electrodialysis device in a coking wastewater advanced treatment process.

6. The method for treating wastewater containing chromium by ion exchange according to claim 1, wherein In step (2), the anion exchange fiber is quaternary ammonium group anion exchange fiber with polystyrene copolymer as the fiber matrix.

7. The method for treating wastewater containing chromium by ion exchange according to claim 1, wherein In step (3), the sulfonic acid group cation exchange resin is hydrogen type cation exchange resin.

8. The method for treating wastewater containing chromium by ion exchange according to claim 1, wherein In step (3), the eluent stays in the fourth sulfonic acid group cation exchange resin column for 30-40 min.

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