Electrolytic treatment method for mercury-containing wastewater

Abstract

The invention belongs to the field of environmental protection, and particularly relates to an electrolytic treatment method for mercury-containing wastewater, which comprises the following steps: (1) adjusting the pH value of the mercury-containing wastewater to 7, and adding an electrolytic additive imidazole ionic liquid; (2) introducing the mercury-containing wastewater in the step (1) into an electrolytic bath, and introducing a cathode and an anode; and (3) electrolyzing the mercury-containing wastewater containing the additive by setting the cell voltage, the current intensity and the electrolysis temperature of the electrolytic cell in the step (2). The method has the technical advantages that the mercury removal rate is high, the temperature is stable and easy to control, the process condition is stable, the operation is convenient, the current efficiency is high, and secondary pollution to the environment is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to an electrolytic treatment method for mercury-containing wastewater. Background Art

[0002] Mercury is a naturally occurring heavy metal that is highly toxic and persistent. It is frequently released into the environment through industrial processes, mining activities, and medical waste, causing serious water and soil pollution. Mercury in water and soil enters organisms and is ultimately absorbed through the food chain, posing a health risk. Therefore, developing effective methods for treating mercury-containing wastewater is crucial for protecting the environment and human health.

[0003] In existing technologies, the main methods for treating mercury-containing wastewater are: ① Chemical precipitation, which has the advantage of being the preferred choice for treating high-concentration mercury ion wastewater and is easy to implement. However, it has the disadvantage of not being able to completely treat low-concentration mercury wastewater, which can easily lead to secondary pollution. ② Metal reduction, which has the advantage of being able to treat single-component mercury-containing wastewater and having a high reaction rate. However, it has the disadvantage of incomplete mercury removal.

[0004] ③ Activated carbon adsorption method, its advantage is that it has a high mercury removal efficiency when the mercury content is high, and the efficiency decreases when the mercury content is low. Its disadvantages are complex operation, high cost, and fluctuating water quality, which can easily lead to exceeding the standard; ④ Ion exchange method, its advantage is that it can thoroughly treat low-concentration mercury wastewater, but its disadvantages are that it is easily affected by impurities in the water and has high cost.

[0005] Chinese patent CN1092606C discloses a water electrolysis device capable of removing chlorine and mercury heavy metals. A plurality of concentric negative and positive electrodes and a diaphragm are arranged within a circular body. Alkaline and acidic aqueous solutions are supplied to the device via a cross-shaped diverter plate at the bottom for electrolysis. A cross-shaped separation cover at the top collects the water. The top surface of the cross-shaped diverter plate has a pointed structure for securing the electrodes. The bottom surface is a cross-shaped slot structure with staggered holes corresponding to the electrodes, forming two water inlet and wastewater tanks on either side. The water solution circulates between the water inlet and wastewater tanks on the same side via holes and a barrier plate. This allows electrolyzed water to be generated from the bottom up, removing chlorine, and allowing sediment to be collected due to the cross-shaped diverter plate. This complex structure is costly to manufacture and use.

[0006] Therefore, there is an urgent need to provide a technical solution to the above-mentioned shortcomings of the existing technology. Summary of the Invention

[0007] In order to overcome the deficiencies of the prior art, the present invention provides an electrolytic treatment method for mercury-containing wastewater, which has a simple process, convenient operation, short treatment time, and is suitable for large-scale wastewater treatment.

[0008] In order to achieve the above objectives, the present application provides a method for electrolytic treatment of mercury-containing wastewater using the following technical solutions:

[0009] A method for electrolytic treatment of mercury-containing wastewater comprises the following steps:

[0010] (1) Adjust the pH of mercury-containing wastewater to 7 and add electrolytic additives;

[0011] (2) introducing the mercury-containing wastewater in step (1) into an electrolytic cell, wherein the mercury-containing wastewater containing an additive is used as an electrolyte and introduced into the cathode and anode of the electrolytic cell;

[0012] (3) Setting the cell voltage, current intensity, electrolysis temperature and electrolysis time of the electrolytic cell in step (2) to electrolyze the mercury-containing wastewater containing the additive.

[0013] Furthermore, the mercury content in the mercury-containing wastewater in step (1) is 0.005-0.01 mg / L.

[0014] Furthermore, the acid used to adjust the pH value in step (1) is hydrochloric acid.

[0015] Furthermore, in step (1), the electrolytic additive is an imidazole ionic liquid, and the concentration of the imidazole ionic liquid in the mercury-containing wastewater is 0.02-0.05 g / L.

[0016] Furthermore, the cation of the imidazolium ionic liquid includes 1-butyl-3-methylimidazole or 1-ethyl-3-methylimidazole.

[0017] Furthermore, the imidazolium ionic liquid is a 1-butyl-3-methylimidazolium chloride solution.

[0018] Furthermore, in step (2), the cathode is a stainless steel electrode and the anode is a titanium electrode.

[0019] Furthermore, in step (3), the cell voltage is 5-8V and the current density is 80-120A / m 2 .

[0020] Furthermore, in step (3), the electrolysis time is 5-8 hours and the electrolysis temperature is 20-40°C.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The electrolysis method is based on the unique electrochemical properties of metals. A certain DC voltage is applied to mercury-containing wastewater. Mercury and its compounds form an electrolytic cell in the wastewater under the action of electrolysis. At the cathode of the electrolytic cell, they receive electrons and are reduced to elemental mercury, thereby effectively removing mercury residues.

[0023] (2) The present invention uses imidazole ionic liquid as an additive, which can increase the conductivity and electrochemical stability of the electrolyte and improve the current efficiency of electrolysis;

[0024] (3) Imidazole ionic liquids containing imidazole structures have high ionic conductivity, a wide electrochemical window, good thermal stability and chemical stability. During the electrolysis process, no hydrogen or other gases are produced. They also have certain catalytic activity and catalyze the electrolytic deposition of mercury with high current efficiency.

[0025] (4) Ionic liquids with imidazole structures have large heat capacity, the temperature during electrolysis is stable and easy to control, and the process conditions are relatively stable;

[0026] (5) Ionic liquid mercuric chloride electrolyte solution containing imidazole structure has a saturated vapor pressure of almost zero and is non-volatile. Through electrolysis, mercury ions are reduced to metallic mercury and deposited on the electrode, avoiding the use of chemical agents and reducing the risk of secondary pollution to the environment.

[0027] (6) The electrolysis equipment is simple, easy to operate, and easy to realize automatic control. It is suitable for continuous treatment. The metallic mercury deposited during the electrolysis process can be recycled and reused, which is economical. The electrolysis method is suitable for mercury-containing wastewater of different concentrations and compositions. It has strong adaptability, fast electrolysis reaction speed, short treatment time, and is suitable for large-scale wastewater treatment. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described in further detail below with reference to the examples.

[0029] Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations can be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as part of one embodiment can be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention should fall within the scope of protection of the embodiments of the present invention.

[0030] Example 1

[0031] A method for electrolytic treatment of mercury-containing wastewater, wherein the mercury content is determined to be 0.005 mg / L, the mercury-containing wastewater is adjusted to pH 7 with hydrochloric acid, an electrolytic ionic liquid 1-butyl-3-methylimidazolium chloride is added to prepare an electrolyte solution, the mass fraction of 1-butyl-3-methylimidazolium in the electrolyte solution is 0.02 g / L, the electrolyte solution is introduced into an electrolytic cell, a stainless steel electrode is used as a cathode, a titanium electrode is used as an anode, the cell voltage is set to 5 V, and the current density is set to 80 A / m 2The electrolysis temperature was 20°C. After 5 hours of electrolysis, the mercury content was determined to be 0.0002 mg / L, and the mercury removal rate was 96%.

[0032] Example 2

[0033] A method for electrolytic treatment of mercury-containing wastewater, wherein the mercury content is determined to be 0.01 mg / L, the mercury-containing wastewater is adjusted to pH 7 with hydrochloric acid, an ionic liquid 1-butyl-3-methylimidazole chloride is added to prepare an electrolyte solution, the mass fraction of 1-butyl-3-methylimidazole in the electrolyte solution is 0.05 g / L, the electrolyte solution is introduced into an electrolytic cell, a stainless steel electrode is used as a cathode, a titanium electrode is used as an anode, the cell voltage is set to 8 V, and the current density is set to 120 A / m 2 The electrolysis temperature was 40°C. After 8 hours of electrolysis, the mercury content was determined to be 0.0001 mg / L, and the mercury removal rate was 99%.

[0034] Example 3

[0035] A method for electrolytic treatment of mercury-containing wastewater, wherein the mercury content is determined to be 0.008 mg / L, the mercury-containing wastewater is adjusted to pH 7 with hydrochloric acid, an ionic liquid 1-butyl-3-methylimidazolium chloride is added to prepare an electrolyte solution, the mass fraction of 1-butyl-3-methylimidazolium in the electrolyte solution is 0.04 g / L, the electrolyte solution is introduced into an electrolytic cell, a stainless steel electrode is used as a cathode, a titanium electrode is used as an anode, the cell voltage is set to 7 V, and the current density is set to 100 A / m 2 The electrolysis temperature was 30°C. After 7 hours of electrolysis, the mercury content was determined to be 0.0001 mg / L, and the mercury removal rate was 98.7%.

[0036] Comparative Example 1

[0037] A method for electrolytic treatment of mercury-containing wastewater, wherein the mercury content is determined to be 0.005 mg / L, the mercury-containing wastewater is adjusted to pH=7 with hydrochloric acid, the mercury-containing wastewater electrolyte solution is introduced into an electrolytic cell, a stainless steel electrode is used as the cathode, a titanium electrode is used as the anode, the cell voltage is set to 5V, and the current density is 80A / m 2 The electrolysis temperature was 20°C. After 5 hours of electrolysis, the mercury content was determined to be 0.0008 mg / L, and the mercury removal rate was 84%.

[0038] Comparative Example 2

[0039] A method for electrolytic treatment of mercury-containing wastewater, wherein the mercury content is determined to be 0.01 mg / L, the mercury-containing wastewater is adjusted to pH=7 with hydrochloric acid, the mercury-containing wastewater electrolyte solution is introduced into an electrolytic cell, a stainless steel electrode is used as the cathode, a titanium electrode is used as the anode, the cell voltage is set to 8V, and the current density is 120A / m 2The electrolysis temperature was 40°C. After 8 hours of electrolysis, the mercury content was measured to be 0.004 mg / L, and the mercury removal rate was 60%.

[0040] Comparative Example 3

[0041] A method for electrolytic treatment of mercury-containing wastewater, wherein the mercury content is determined to be 0.008 mg / L, the mercury-containing wastewater is adjusted to pH = 7 with hydrochloric acid, and the mass fraction of mercury in the mercuric chloride electrolyte solution is 0.04 g / L, the electrolyte solution is introduced into an electrolytic cell, a stainless steel electrode is used as the cathode, a titanium electrode is used as the anode, the cell voltage is set to 7 V, and the current density is set to 100 A / m 2 The electrolysis temperature was 30°C. After 7 hours of electrolysis, the mercury content was measured to be 0.002 mg / L, and the mercury removal rate was 75%.

Claims

1. A method for electrolytic treatment of mercury-containing wastewater, characterized in that: The steps include: (1) Adjust the pH of mercury-containing wastewater to 7 and add electrolytic additives; (2) introducing the mercury-containing wastewater in step (1) into an electrolytic cell, wherein the mercury-containing wastewater containing an additive is used as an electrolyte and introduced into the cathode and anode of the electrolytic cell; (3) Setting the cell voltage, current intensity, electrolysis temperature and electrolysis time of the electrolytic cell in step (2) to electrolyze the mercury-containing wastewater containing the additive.

2. The electrolytic treatment method for mercury-containing wastewater according to claim 1, characterized in that: The mercury content in the mercury-containing wastewater in step (1) is 0.005-0.01 mg / L.

3. The electrolytic treatment method for mercury-containing wastewater according to claim 1, characterized in that: The acid used to adjust the pH value in step (1) is hydrochloric acid.

4. The electrolytic treatment method for mercury-containing wastewater according to claim 1, characterized in that: In step (1), the electrolytic additive is an imidazole ionic liquid, and the concentration of the imidazole ionic liquid in the mercury-containing wastewater is 0.02-0.05 g / L.

5. The electrolytic treatment method for mercury-containing wastewater according to claim 4, characterized in that: The cation of the imidazolium ionic liquid includes 1-butyl-3-methylimidazole or 1-ethyl-3-methylimidazole.

6. The electrolytic treatment method for mercury-containing wastewater according to claim 5, characterized in that: The imidazolium ionic liquid is 1-butyl-3-methylimidazolium chloride solution.

7. The electrolytic treatment method for mercury-containing wastewater according to claim 1, characterized in that: In step (2), the cathode is a stainless steel electrode and the anode is a titanium electrode.

8. The electrolytic treatment method for mercury-containing wastewater according to claim 1, characterized in that: In step (3), the cell voltage is 5-8V and the current density is 80-120A / m 2 .

9. The electrolytic treatment method for mercury-containing wastewater according to claim 1, characterized in that: In step (3), the electrolysis time is 5-8 hours and the electrolysis temperature is 20-40°C.