CN205085146U - Use bipolar membrane technology and get rid of electrolysis trough of chromium in soil - Google Patents

Abstract

The utility model relates to a bipolar film electrolytic cell which can simultaneously remove trivalent chromium and hexavalent chromium in soil. The bipolar membrane electrolytic cell involved in the utility model is a rectangular parallelepiped cell structure, and the electrolytic cell is formed by anodes, anion exchange membranes and cathodes arranged in sequence, and is naturally separated into an anode chamber and a cathode chamber, and the anode and the cathode are respectively connected with the The positive and negative poles of the DC power supply are connected, and it is characterized in that a soil treatment unit composed of anion exchange membrane, bipolar membrane and cation exchange membrane is arranged between the anode and the anion exchange membrane, thereby separating the electrolytic cell into an anode chamber, Two parallel soil chambers, metal ion chambers and cathode chambers, and a soil chamber between the bipolar membrane and the anion exchange membrane. The electrolytic cell constructed by the utility model does not need to add acid or other anions, which saves costs; it can remove trivalent chromium and hexavalent chromium at the same time; it can be connected in series, and multiple soil chambers can be processed through a pair of cathode and anode electrodes, thereby improving the current efficiency and cell space utilization, reducing energy consumption and cost.

Description

An electrolytic cell for removing chromium in soil using bipolar membrane technology

technical field

The utility model relates to the technical field of environmental pollution control equipment, in particular to an electrolytic cell for simultaneously removing trivalent chromium and hexavalent chromium in soil by applying bipolar membrane technology.

Background technique

With the acceleration of urbanization and the rapid development of the chromium industry, urban sewage, garbage, sludge and various industrial chromium residues have become a major source of soil chromium. Chromium usually exists in soil in two stable valence states of Cr ³⁺ and Cr ⁶⁺ . Cr ³⁺ can be adsorbed and fixed, and is easily adsorbed by soil colloids or precipitated; Cr ⁶⁺ mainly exists in the form of HCrO ^- and CrO ₄ ^2- , which are soluble in water, highly chemically active, and highly toxic. The main pollutant in chromium pollution.

At present, the domestic and foreign methods for dealing with chromium-contaminated soil mainly include: 1) solidification and stabilization method: fully mix chromium-contaminated soil with a binder, embed chromium in a solid matrix, and reduce the ability of chromium to migrate. 2) Chemical reduction method: use a reducing agent to reduce Cr(Ⅵ) and form insoluble compound precipitation, but the reduction effect is not thorough enough, and it is difficult for Cr(Ⅵ) inside the particles Contact and reduction; 2) Eluting method: Commonly used eluting agents include inorganic acids, organic acids, surfactants, artificial chelating agents or water, which will produce a large amount of sewage and easily cause groundwater pollution; 3) Electrochemical method: Chromium Under the action of an external electric field, the metal migrates to the vicinity of the electrode, and then removed by other methods, which consumes a lot of energy; 4) Phytoremediation method: the plant is small, the processing speed is slow, and the plant is tall and poor in tolerance to heavy metals; 5) Microbial remediation method : slow aging, harsh culture conditions, difficult for microorganisms to survive. A single technology has its limitations and cannot be promoted in practical applications.

Bipolar membrane is a new type of ion-exchange composite membrane, which uses bipolar membrane technology to repair chromium-contaminated soil. It has high current efficiency and cell space utilization, less side reactions on the electrode surface, low energy consumption, and no need to add a large amount of acid solution. No secondary pollution and other advantages. The basic principle of bipolar membrane technology to remove chromium from soil is that under the action of a direct current electric field, the water in the intermediate interface layer of the bipolar membrane will dissociate, and hydrogen ions will be continuously generated (so no external acid solution is needed, and a large amount of sewage will not be generated) and hydrogen Oxygen ions and hydrogen ions enter the soil chamber through the positive membrane layer of the bipolar membrane to elute the trivalent chromium cations in the soil, and the eluted chromium ions enter the metal ion chamber under the action of an electric field; The hydroxide ions produced by the dissociation of water in the middle interface layer of the polar membrane, the hydroxide ions enter another soil chamber through the negative membrane layer of the bipolar membrane, and at the same time, the hexavalent chromium anions in the soil chamber move to the anode, and the anion The exchange membrane enters the metal ion chamber, so as to achieve the purpose of simultaneously removing trivalent chromium ions and hexavalent chromium ions in the soil. Heavy metal ions are easily eluted, migrated and removed from the soil under the action of hydrogen ion elution and electric field. The method of applying bipolar membrane technology to remove chromium in soil is to organically combine the leaching method and the electrochemical method. Advantages, overcome its disadvantages. The utility model can also be used for removing chromium in sludge, chromium slag and other solid wastes.

Contents of the invention

The utility model provides a safe and effective electrolytic cell for removing chromium in different valence states in soil by applying bipolar membrane technology. The electrolytic cell uses bipolar membrane technology to simultaneously remove trivalent chromium and hexavalent chromium in the soil, and organically combines the leaching method with the electrochemical method. After treatment, the chromium content in the soil is greatly reduced without secondary pollution.

The utility model relates to an electrolytic cell capable of removing trivalent chromium and hexavalent chromium in soil at the same time, which is a cuboid cell-like structure, and the electrolytic cell is composed of anodes, anion exchange membranes and cathodes arranged in sequence and separated naturally It is an anode chamber and a cathode chamber, and the anode and cathode are respectively connected to the positive and negative poles of the DC power supply. It is characterized in that 1 to 3 groups of anion exchange membrane, bipolar membrane and cation exchange membrane are arranged between the anode and the anion exchange membrane. A soil treatment unit is formed, thereby separating the electrolytic cell into an anode chamber (metal ion chamber), a soil treatment unit and a cathode chamber, and the soil chamber is between the bipolar membrane and the anion exchange membrane. The soil treatment unit described therein comprises two parallel soil chambers and metal ion chambers.

The bipolar membrane is a special ion exchange membrane, which is an anion-cation composite membrane made by compounding an anion membrane layer and an anion membrane layer.

The bipolar membrane is also provided with a microporous ceramic plate on the side surface facing the soil chamber.

The cation exchange membrane and the anion exchange membrane are also provided with microporous ceramic plates on the side facing the soil chamber.

The plurality of soil treatment units composed of anion exchange membranes, bipolar membranes and cation exchange membranes, such as 1 to 3, form an anode chamber (or metal ion chamber) and a cathode chamber at both ends, and a series type in the middle. Soil chamber, soil chamber, metal ion chamber... soil chamber, soil chamber, metal ion chamber... sub-chamber structure.

The bipolar membrane in the above-mentioned electrolytic cell is under the action of a direct current electric field, and the water in the middle interface layer dissociates, and the generated hydrogen ions enter the soil chamber through the positive membrane layer of the bipolar membrane, and the trivalent chromium cations in the soil are washed away. The eluted trivalent chromium cations enter the metal ion chamber under the action of the electric field; at the same time, the hydroxide ions generated by the water dissociation in the middle interface layer of the bipolar membrane enter the other soil chamber through the negative membrane layer of the bipolar membrane In the process, the replacement of hexavalent chromium anions moves to the anode and enters the metal ion chamber through the anion exchange membrane, so that the trivalent chromium ions and hexavalent chromium ions in the soil are simultaneously removed.

The advantages and positive effects of the utility model are: 1. Under the action of a DC electric field, the water in the middle interface layer of the bipolar membrane dissociates to produce hydrogen ions and hydroxide ions, without adding acid or other anions, which saves the cost , to reduce the generation of sewage. 2. The eluted trivalent chromium cations are easily eluted, migrated and removed from the soil under the action of hydrogen ion elution and electric field. 3. At the same time, hexavalent chromium anions are easily eluted, migrated and removed from the soil under the action of hydroxide ion replacement and electric field. 4. It can be connected in series, thereby improving the current efficiency and cell space utilization, reducing the occurrence of side reactions on the electrode surface, reducing energy consumption and cost.

Description of drawings

Fig. 1 is a schematic diagram of the structure of an electrolytic cell using bipolar membrane technology to remove chromium in soil according to the utility model.

Fig. 2 is a structural schematic diagram of an electrolytic cell for removing chromium in soil with multiple soil treatment units and using bipolar membrane technology according to the utility model.

detailed description

In order to further understand the content, features and effects of the present utility model, it will be described in detail in the form of an embodiment in conjunction with the accompanying drawings.

Among Fig. 1 and Fig. 2: 1 is an electrolytic cell; 2 is an anode; 3 is a bipolar membrane; 4 is a microporous ceramic plate; 5 is an anion exchange membrane; 6 is a cation exchange membrane; II is the soil chamber; III is the metal ion chamber; IV is the cathode chamber.

Example 1

As shown in Figure 1, an electrolytic cell using bipolar membrane technology to remove chromium in soil is adopted. The two soil chambers are separated by a bipolar membrane, and the soil chamber and the metal ion chamber are separated by an ion exchange membrane. In addition, the soil and membrane separated by microporous ceramic plates. The anode and the cathode are respectively connected to the positive and negative poles of the DC power supply.

The soil treated in this example contains total Cr, Pb, Fe, Mn, Mg, Ca and other heavy metals, the voltage gradient is 1.0V/m, the electrode distance is 18cm, and the system runs continuously for 5 days. Both the anode chamber and the cathode chamber were added with 0.5mol/L Na ₂ SO ₄ solution as supporting electrolyte, and its liquid level was level with the soil. See Table 1 for the chromium content before and after soil treatment.

Table 1: Chromium content before and after soil treatment (mg/Kg)

Note: From the anode to the cathode are the soil chambers 1 and 2.

Example 2

As shown in Figure 2, an electrolytic cell that uses bipolar membrane technology to remove chromium in soil with multiple soil treatment units is adopted. The adjacent soil chambers are separated by bipolar membranes, and the soil chamber and the metal ion chamber are separated by ion exchange membranes. In addition, the soil and the membrane are separated by a microporous ceramic plate, and two soil treatment units are alternately connected in series. The anode and the cathode are respectively connected to the positive and negative poles of the DC power supply.

The soil treated in this example contains total Cr, Pb, Fe, Mn, Mg, Ca and other heavy metals, the voltage gradient is 1.0V/m, the electrode distance is 36cm, and the system runs continuously for 5 days. Both the anode chamber and the cathode chamber were added with 0.5mol/L Na ₂ SO ₄ solution as supporting electrolyte, and its liquid level was level with the soil. See Table 2 for the chromium content before and after soil treatment.

Table 2: Chromium content before and after soil treatment (mg/Kg)

Note: From the anode to the cathode, there are soil chambers 1, 2, 3, and 4.

Example 3

As shown in Figure 2, an electrolytic cell that uses bipolar membrane technology to remove chromium in soil with multiple soil treatment units is adopted. The adjacent soil chambers are separated by bipolar membranes, and the soil chamber and the metal ion chamber are separated by ion exchange membranes. In addition, the soil and the membrane are separated by a microporous ceramic plate, and two soil treatment units are alternately connected in series. The anode and the cathode are respectively connected to the positive and negative poles of the DC power supply.

The soil treated in this example contains total Cr, Pb, Fe, Mn, Mg, Ca and other heavy metals, the voltage gradient is 1.0V/m, the electrode distance is 36cm, and the system runs continuously for 4 days. Both the anode chamber and the cathode chamber were added with 0.5mol/L Na ₂ SO ₄ solution as supporting electrolyte, and its liquid level was level with the soil. See Table 3 for the chromium content before and after soil treatment.

Table 3: Chromium content before and after soil treatment (mg/Kg)

Note: From the anode to the cathode, there are soil chambers 1, 2, 3, and 4.

Example 4

As shown in Figure 2, an electrolytic cell that uses bipolar membrane technology to remove chromium in soil with multiple soil treatment units is adopted. The adjacent soil chambers are separated by bipolar membranes, and the soil chamber and the metal ion chamber are separated by ion exchange membranes. In addition, the soil and the membrane are separated by a microporous ceramic plate, and two soil treatment units are alternately connected in series. The anode and the cathode are respectively connected to the positive and negative poles of the DC power supply.

The soil treated in this example contains total Cr, Pb, Fe, Mn, Mg, Ca and other heavy metals, the voltage gradient is 1.0V/m, the electrode distance is 36cm, and the system runs continuously for 6 days. Both the anode chamber and the cathode chamber were added with 0.5mol/L Na ₂ SO ₄ solution as supporting electrolyte, and its liquid level was level with the soil. See Table 4 for the chromium content before and after soil treatment.

Table 4: Chromium content (mg/Kg) before and after soil treatment

Note: From the anode to the cathode, there are soil chambers 1, 2, 3, and 4.

Claims (4)

1. the electrolytic cell of an applying double pole membrane technology removal Chromium in Soil, for cuboid channel-shaped structure, by anode in electrolytic cell, anion-exchange membrane and negative electrode sequential form, and be naturally divided into anode chamber and cathode chamber, anode and negative electrode are connected with the positive and negative polarities of dc source respectively, it is characterized in that between anode and anion-exchange membrane, being provided with 1 ~ 3 group by anion-exchange membrane, the soil treatment unit that Bipolar Membrane and cation-exchange membrane are formed, thus electrolytic cell is divided into anode chamber, soil treatment unit and cathode chamber, it is soil chamber between Bipolar Membrane and anion-exchange membrane, wherein said soil treatment unit includes two soil chamber arranged side by side and metal ion room.

2. a kind of applying double pole membrane technology according to claim 1 removes the electrolytic cell of Chromium in Soil, and it is characterized in that described Bipolar Membrane is specific ion exchange membrane, it is by anode membrane layer and the compounded yin, yang composite membrane of cavity block layer.

3. a kind of applying double pole membrane technology according to claim 1 removes the electrolytic cell of Chromium in Soil, it is characterized in that described Bipolar Membrane, is also provided with capillary ceramic plate at the side surface towards soil chamber.

4. a kind of applying double pole membrane technology according to claim 1 removes the electrolytic cell of Chromium in Soil, it is characterized in that described anion-exchange membrane, is also provided with capillary ceramic plate in the side towards soil chamber.