Salt regulation and control type single-chamber electrolytic dechlorination method

Abstract

The invention discloses a salt regulation type single-chamber electrolytic dechlorination method, which belongs to the technical field of wastewater treatment, and comprises the following steps: S1, detecting chloride ions and endogenous buffer cations in wastewater to be treated, and calculating the environment matching characteristic ratio of the chloride ions to the endogenous buffer cations; s2, according to the environment matching characteristic ratio obtained in the S1, the wastewater types are judged, and the wastewater types comprise self-balancing wastewater and unbalanced wastewater; if the wastewater is unbalanced wastewater, adding an electrolytic environment regulating agent to enable the concentrations of chloride ions and metal cations in the wastewater to meet an efficient dechlorination interval, so as to obtain regulated wastewater; and S3, introducing the self-balancing wastewater or the adjusting wastewater obtained in the S2 into a single-chamber electrolysis reactor, and carrying out an electrolytic reaction to remove chlorine in the wastewater. The method has the advantages of high dechlorination efficiency, simple process and low electrolysis device cost, and is suitable for industrial scale application.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, and relates to a method for dechlorinating wastewater with high concentration of chlorine, and more particularly to a salt-controlled single-chamber electrolytic dechlorination method. Background Technology

[0002] Currently, mainstream dechlorination technologies all suffer from significant economic or technical bottlenecks. For example, chemical precipitation methods suffer from high reagent costs and large sludge volumes; ion exchange methods suffer from resin poisoning and frequent regeneration; and electrodialysis methods suffer from expensive membrane modules and susceptibility to clogging. Electrochemical oxidation methods have attracted attention due to their cleanliness and controllability, but they also face significant challenges in practical engineering applications. On the one hand, the ionic composition of industrial wastewater is extremely complex and fluctuates dramatically. Conventional electrolysis often uses fixed voltages or currents, neglecting the decisive influence of the relative abundance of key coexisting metal ions and chloride ions on the selectivity of the electrode reaction. On the other hand, strong hydrogen evolution side reactions lead to electrode scaling or a sharp drop in reaction efficiency. Existing improvement methods mostly focus on modifying electrode materials, lacking a proactive approach to controlling the solution chemical environment, making it difficult to maintain stable dechlorination efficiency in dynamically changing water quality. Therefore, there is an urgent need to develop a new dechlorination process that can respond in real-time to changes in water quality characteristics and lock in the optimal range of the electrolysis reaction through simple exogenous media control. Summary of the Invention

[0003] This invention provides a salt-controlled single-compartment electrolytic dechlorination method to overcome the shortcomings of the prior art.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A salt-regulated single-compartment electrolytic dechlorination method includes the following steps: S1, detecting chloride ions and endogenous buffer cations in the wastewater to be treated, and calculating the environmental matching characteristic ratio of chloride ions to endogenous buffer cations; S2, determining the wastewater type based on the environmental matching characteristic ratio obtained in S1, including self-balancing wastewater and unbalanced wastewater; if it is unbalanced wastewater, adding an electrolytic environmental regulator to make the concentrations of chloride ions and metal cations in the wastewater meet the high-efficiency dechlorination range, thus obtaining regulated wastewater; S3, introducing the self-balancing wastewater or regulated wastewater from S2 into a single-compartment electrolytic reactor for electrolytic reaction to remove chloride from the wastewater.

[0005] To optimize the above technical solution, the specific measures also include: Further, in S1, the endogenous buffer cations include magnesium, zinc, calcium, and sodium; the environmental matching characteristic ratio is the molar ratio of chloride ions to endogenous buffer cations.

[0006] Furthermore, in step S2, the method for determining the wastewater type is: if 2∶1≤R ClIf R ≤ 3∶1, then the wastewater type is self-balancing wastewater; Cl <2∶1 or R Cl If the ratio is greater than 3:1, then the wastewater type is unbalanced wastewater; where R... Cl The environmental matching feature ratio.

[0007] Further, in step S2, the electrolysis environment regulator is divided into a first electrolysis environment regulator and a second electrolysis environment regulator; the first electrolysis environment regulator includes one or more of magnesium salts and sodium salts that are chloride-free and soluble; the second electrolysis environment regulator includes one or more of zinc salts and calcium salts that are chloride-free and soluble; if the endogenous buffer cation in the unbalanced wastewater is magnesium or sodium, then the first electrolysis environment regulator is added; if the endogenous buffer cation in the unbalanced wastewater is zinc or calcium, then the second electrolysis environment regulator is added.

[0008] Furthermore, the first and second electrolytic environment regulators also include auxiliary components, which are one or more of pH buffers and dispersants. The pH buffer is used to construct the complexation-dissociation balance at the cathode interface to prevent excessive local alkalinity from causing precipitation densification. The dispersant is used to optimize the dispersion uniformity of the electrolytic environment regulator in wastewater and the porosity of the electrode surface film.

[0009] Further, the pH buffer is one or more of sodium citrate and sodium gluconate; the dispersant is one or more of polyethylene glycol (PEG) and modified cellulose; and the auxiliary component has a mass fraction of 0.1-5.0% in the electrolytic environment regulator.

[0010] Furthermore, in S2, the high-efficiency dechlorination range is: 2∶1≤R Cl1 ≤3∶1; or, 2.5∶1≤R Cl2 ≤3.5∶1; where R Cl1 R is the molar ratio of chloride ions to magnesium ions / sodium ions in the wastewater. Cl2 This represents the molar ratio of chloride ions to zinc ions / calcium ions in the wastewater.

[0011] Furthermore, in the single-chamber electrolytic reactor, the anode is a titanium plate, the cathode is an iron plate, and the power supply is a DC power supply. After the wastewater enters the electrolytic cell, the electrochemical reaction between the titanium plate at the anode and the iron plate at the cathode achieves efficient removal of chloride ions from the wastewater. During electrolysis, the anode mainly produces chlorine gas and a small portion produces hypochlorous acid; the cathode produces hydrogen gas and hydroxide ions, the latter reacting with a regulator to precipitate and prevent interference from cathode side reactions.

[0012] Furthermore, during the electrolysis process of S3, the power supply voltage is 6.5 to 8.0V, preferably 7.5V; the pH value of the electrolysis system is dynamically maintained between 1.3 and 5.6 using the electrolysis environment regulator.

[0013] Furthermore, the single-chamber electrolytic reactor is equipped with a perforated plate and an aeration disc inside the electrolytic cell; the perforated plate is fixed to the lower part of the electrolytic cell, and the anode and the cathode are installed on the perforated plate; the aeration disc is installed below the perforated plate, and during electrolysis, gas is introduced through the aeration disc for aeration to promote the escape of chlorine gas; the top of the electrolytic cell is also equipped with a gas collection hood for recovering the gas generated during electrolysis.

[0014] The beneficial effects of this invention are as follows: This invention provides a salt-regulated single-compartment electrolytic dechlorination method that can significantly reduce chloride ion concentration in wastewater under conditions of excessively high chloride ion concentration or ion imbalance. This is achieved through the synergistic effect of an electrolytic environment regulator and electrolysis. Specifically, this invention is based on a single-compartment electrolysis system with a titanium anode and an iron cathode. By adding an appropriate amount of electrolytic environment regulator, the content of key metal ions in the reaction system is adjusted to avoid interference with the anodic reaction and maintain a stable reaction environment. This ensures rapid chlorine precipitation from the wastewater under acidic aeration conditions, thereby improving dechlorination efficiency and electrolysis efficiency. This invention achieves efficient directional migration and conversion of chloride ions by constructing an adaptive electrode interface microenvironment, making it particularly suitable for high-chlorine wastewater systems with drastic fluctuations in water quality components, such as desulfurization wastewater from thermal power plants.

[0015] Compared with existing electrochemical dechlorination methods, this invention adopts a single-chamber structure design, simplifying system configuration and reducing equipment complexity and operating costs. Simultaneously, it introduces magnesium-based or zinc-based electrolysis environment regulators as the core adjustment method, improving reaction efficiency. This allows for significant improvement in dechlorination efficiency even when the original wastewater composition does not meet dechlorination requirements (such as high chlorine and low magnesium or high chlorine and low zinc), by adjusting and stabilizing the electrolysis environment. Furthermore, this invention does not require the addition of other complex chemical agents or expensive ion exchange membranes, relying solely on electrical energy and the synergistic effect of the regulators. This saves operating costs and has good environmental compatibility, making it particularly suitable for the large-scale treatment of high-chlorine wastewater from thermal power plants.

[0016] This invention has the advantages of high dechlorination efficiency, simple process, and low cost of electrolysis equipment, and is suitable for industrial-scale applications. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the single-chamber electrolysis reactor in the salt-controlled single-chamber electrolytic dechlorination method of the present invention; The labels in the attached diagram are: 1. Anode; 2. Anode; 3. Power supply box; 4. Circulation inlet; 5. Circulation outlet; 6. Screen plate; 7. Aeration disc; 8. Aeration pump; 9. Air collection hood. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments.

[0019] Example 1 This embodiment provides a salt-controlled single-compartment electrolytic dechlorination method, specifically an electrolytic dechlorination method for water with low chlorine and relatively balanced metal ions.

[0020] like Figure 1 As shown, the structure of the gas-collecting single-chamber electrolytic reaction tank used is as follows: three aeration discs are set at the bottom, and bubbles rise from the bottom; a plate groove is provided every 5.00 mm in the vertical direction at the center for fixing the electrode; a sieve plate is set between the aeration port and the plate to prevent large particles of sediment from flowing into the plate area; and a gas collection hood is installed at the top to collect the reaction gas.

[0021] During the experiment, 13L of pretreated desulfurization wastewater was added to the electrolytic cell. Testing revealed that this batch of wastewater was of "low-chlorine, low-magnesium self-balancing" quality, with an initial chloride ion concentration of 15000ppm and a magnesium ion concentration of 5000ppm. The environmental matching characteristic ratio was R... Cl The electrolysis ratio is 2.06:1, which falls within the suitable electrolysis range of 2:1 to 3:1, therefore no electrolysis environment conditioner is added. Titanium plates (anodes) and iron plates (cathodes) are arranged alternately and perpendicularly, with an electrode spacing of 20.00 mm. The anode and cathode are connected by wires, and the voltage is stably controlled at 7.5V. An aeration pump is connected to an aeration disc to ensure sufficient aeration of the reaction solution, and a perforated sieve plate is used to intercept large precipitates.

[0022] During the 0-0.5h period, the dechlorination rate increased slowly, and the solution pH value decreased from weak acid to strong acid, indicating that the hydrogen ions released from the anode dominated the acidification of the system.

[0023] During the 0.5-6h period, the dechlorination rate continued to rise and then stabilized, with the pH value remaining stable at about 1.6. This indicates that the hydroxide ions generated at the cathode were continuously consumed by magnesium ions in the solution, resulting in magnesium hydroxide precipitate. Meanwhile, in a stable acidic environment, the chlorine evolution reaction at the anode became dominant.

[0024] Experimental results showed that after 6 hours of electrolysis, the chloride ion removal rate reached 84.33%. The original chloride ion concentration was 15,000 ppm, which was reduced to 3,851 ppm after the reaction. At the same time, almost all of the 5,000 ppm magnesium ions in the wastewater were precipitated out as magnesium hydroxide.

[0025] Example 2 This embodiment provides a salt-controlled single-chamber electrolytic dechlorination method, specifically an electrolytic dechlorination method for water with a high chlorine-to-magnesium ratio.

[0026] The structure of the gas-collecting single-chamber electrolytic reactor used is the same as that in Example 1.

[0027] During the experiment, 13L of pretreated desulfurization wastewater was added to the electrolytic cell. The anode was a titanium plate, and the cathode was an iron plate, arranged alternately and vertically with a spacing of 20.00mm. The voltage was maintained at 7.5V, and the aeration system remained operational. Testing revealed that the chloride ion concentration in this batch of wastewater was as high as 40,000ppm, while the magnesium ion concentration was only 6,100ppm, indicating a high environmental matching characteristic ratio (R). Cl The ratio was 4.49:1, indicating a high chlorine, low magnesium imbalance in the wastewater. Therefore, 359g of a first electrolysis environmental conditioner was added to the wastewater. This first electrolysis environmental conditioner consisted of 95wt% magnesium sulfate, 3.0wt% anhydrous sodium sulfate, 1.5wt% sodium citrate (pH buffer), and 0.5wt% polyethylene glycol (dispersant). After thorough stirring and dissolution, the effective magnesium and sodium source concentration in the system was increased to approximately 12000~13000ppm. Cl1 The ratio is 2.19:1, thus restoring the ion balance.

[0028] During the 0-2h period, the pH value dropped from neutral to 1.3, indicating that the hydrogen ions generated at the anode established a strongly acidic environment, while the magnesium ions effectively reacted with the hydroxide ions generated at the cathode to form a precipitate.

[0029] During the 2-6h period, the dechlorination rate steadily increased, the pH value stabilized at 1.3, and the chlorine evolution reaction continued. At 6h, the dechlorination rate reached 57.3%.

[0030] During the 6-12h period, the dechlorination growth slowed down, the pH gradually rose to about 5.6, and the dechlorination rate increased to 71.6% after 12h. The final chloride ion concentration dropped to 11360ppm, and the residual magnesium ion concentration was below 500ppm.

[0031] Although chloride ions were not completely eliminated, experiments showed that by adding a magnesium-based regulator to correct the ionic environment of the high-chlorine wastewater, acidic chlorine precipitation conditions could be effectively maintained, and magnesium ions could be further recovered as magnesium hydroxide byproducts. This method, combined with the background of using magnesium oxide as a desulfurizing agent in the original power plant desulfurization process, can further reduce the cost of replenishing the regulator and improve the system's economic efficiency.

[0032] Example 3 This embodiment provides a salt-controlled single-chamber electrolytic dechlorination method, specifically a dechlorination method for water with high chlorine and scarce zinc and calcium sources.

[0033] The structure of the gas-collecting single-chamber electrolytic reactor used is the same as that in Example 1.

[0034] During the experiment, 13L of pretreated desulfurization wastewater was added to the electrolytic cell. Testing revealed that the chloride ion concentration in the original wastewater was 42,000 ppm, and the zinc ion concentration was 4,700 ppm. The environmental matching characteristic ratio R... Cl The ratio was 16.47:1, indicating a high-chlorine, low-zinc imbalance in the water quality. To create a stable electrolytic microenvironment, 1100g of a second electrolytic environment regulator was added to the wastewater. This regulator consisted of 95wt% zinc sulfate, 3.0wt% anhydrous calcium sulfate, 1.5wt% sodium citrate (pH buffer), and 0.5wt% polyethylene glycol (dispersant). After thorough stirring and dissolution, the effective zinc source concentration in the system was increased to approximately 24500ppm. Cl2 The ratio is 3.16:1.

[0035] During the 0-2h period, the pH rapidly decreased from neutral to 1.2, indicating that the hydrogen ions generated at the anode dominated the acidification process. At the same time, the zinc ions in the regulator reacted with the hydroxide ions generated at the cathode to form zinc hydroxide precipitate, which effectively inhibited the expansion of the alkaline region.

[0036] During the 2-6 hour period: the pH remained within the range of 1.2-1.4, the electrolysis efficiency was stable, chlorine gas continued to be released, and the chloride ion concentration gradually decreased. The dechlorination rate reached 61.8% after 6 hours.

[0037] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0038] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A salt-controlled single-compartment electrolytic dechlorination method, characterized in that: Includes the following steps: S1. Detect chloride ions and endogenous buffer cations in the wastewater to be treated, and calculate the environmental matching characteristic ratio of chloride ions to endogenous buffer cations. S2. Based on the environmental matching characteristic ratio obtained in S1, determine the wastewater type, which includes self-balancing wastewater and unbalanced wastewater. If it is unbalanced wastewater, add an electrolytic environmental regulator to make the concentration of chloride ions and metal cations in the wastewater meet the high-efficiency dechlorination range, and obtain regulated wastewater. S3. The self-balancing wastewater or adjusted wastewater from S2 is introduced into a single-chamber electrolysis reactor to carry out an electrolysis reaction and remove chlorine from the wastewater.

2. The salt-controlled single-compartment electrolytic dechlorination method according to claim 1, characterized in that: In S1, the endogenous buffer cations include magnesium, zinc, calcium, and sodium; The environmental matching characteristic ratio is the molar ratio of chloride ions to endogenous buffer cations.

3. The salt-controlled single-compartment electrolytic dechlorination method according to claim 2, characterized in that: In step S2, the method for determining the type of wastewater is as follows: If 2∶1≤R Cl If the ratio is ≤3:1, then the wastewater type is self-balancing wastewater; If R Cl <2∶1 or R Cl If the ratio is greater than 3:1, then the wastewater type is unbalanced wastewater; In the formula, R Cl The environmental matching feature ratio.

4. The salt-controlled single-compartment electrolytic dechlorination method according to claim 3, characterized in that: In step S2, the electrolysis environment regulator is divided into a first electrolysis environment regulator and a second electrolysis environment regulator; the first electrolysis environment regulator includes one or more of magnesium salts and sodium salts that are soluble and do not contain chloride ions; the second electrolysis environment regulator includes one or more of zinc salts and calcium salts that are soluble and do not contain chloride ions. If the endogenous buffer cation in the unbalanced wastewater is magnesium or sodium, then the first electrolytic environment regulator is added; if the endogenous buffer cation in the unbalanced wastewater is zinc or calcium, then the second electrolytic environment regulator is added.

5. The salt-controlled single-compartment electrolytic dechlorination method according to claim 4, characterized in that: The first and second electrolytic environment regulators also include auxiliary components, which are one or more of pH buffers and dispersants.

6. The salt-controlled single-compartment electrolytic dechlorination method according to claim 5, characterized in that: The pH buffer is one or more of sodium citrate and sodium gluconate; The dispersant is one or more of polyethylene glycol and modified cellulose; The auxiliary component has a mass fraction of 0.1-5.0% in the electrolytic environment regulator.

7. The salt-controlled single-compartment electrolytic dechlorination method according to claim 1, characterized in that: In S2, the high-efficiency chlorine removal zone is: 2∶1≤R Cl1 ≤3∶1； Alternatively, 2.5∶1≤R Cl2 ≤3.5∶1; In the formula, R Cl1 R is the molar ratio of chloride ions to magnesium ions / sodium ions in the wastewater. Cl2 This represents the molar ratio of chloride ions to zinc ions / calcium ions in the wastewater.

8. The salt-controlled single-compartment electrolytic dechlorination method according to claim 1, characterized in that: In the single-chamber electrolysis reactor, the anode is a titanium plate, the cathode is an iron plate, and the power supply is a DC power supply.

9. The salt-controlled single-compartment electrolytic dechlorination method according to claim 8, characterized in that: During the electrolysis process of S3, the power supply voltage is 6.5 to 8.0V; the pH value of the electrolysis system is dynamically maintained between 1.3 and 5.6 using the electrolysis environment regulator.

10. The salt-controlled single-compartment electrolytic dechlorination method according to claim 8, characterized in that: The single-chamber electrolytic reactor is equipped with a perforated sieve plate and an aeration disc inside the electrolytic cell; the perforated sieve plate is fixed at the lower part of the electrolytic cell, and the anode and the cathode are installed on the perforated sieve plate; the aeration disc is installed below the perforated sieve plate, and gas is introduced through the aeration disc for aeration during the electrolysis process; The top of the electrolytic cell is also equipped with a gas collection hood for recovering the gas generated during electrolysis.

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