An electrochemical method for spontaneous electricity generation for boron recovery from wastewater

Abstract

The application discloses an electrochemical method for recycling boron in wastewater by self-power generation. The method comprises the following steps: arranging a zinc negative electrode and a carbon felt positive electrode at the left and right ends of an electrolytic cell respectively, arranging a cation exchange membrane, an anion exchange membrane and a bipolar membrane in sequence and at intervals between the zinc negative electrode and the carbon felt positive electrode, connecting the zinc negative electrode and the carbon felt positive electrode by a wire, and forming a boron-containing wastewater treatment unit; the space where the zinc negative electrode is located at the left end of the boron-containing wastewater treatment unit is an anode chamber, the space where the carbon felt positive electrode is located at the right end is a cathode chamber, the space between the cation exchange membrane and the anion exchange membrane is a recovery chamber, and the space between the anion exchange membrane and the bipolar membrane is a wastewater chamber; NaCl solution is added into the anode chamber, the cathode chamber and the recovery chamber as an electrolyte, and a mixed solution of boron-containing wastewater and NaCl is added into the wastewater chamber. The zinc-air battery system is coupled with the bipolar membrane electrodialysis system, the zinc-air battery is used for self-power generation to generate an electric field force, the bipolar membrane electrodialysis is driven to operate, and the boron in water is recycled in the form of zinc borate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, and particularly relates to an electrochemical method for recovering boron from wastewater by self-power generation. BACKGROUND

[0002] Boron is an essential element in industrial manufacturing, such as glass, ceramics, electronics, pharmaceuticals, catalysts, fertilizers, semiconductors and detergent industries, and is an important raw material for manufacturing neodymium iron boron permanent magnets. In addition, isotope B-10 can control the nuclear reaction rate to avoid nuclear explosion, providing a safe guarantee for the development of the nuclear industry. Boron mainly exists in the form of H3BO3 molecules, partially dissociated borate anions, transition metal complexes and borate salts in nature. However, the toxicity effect caused by excessive boron in the environment is also a serious problem currently faced. Due to the increasing demand for boron in global industrial manufacturing and various industries, a large amount of boron-containing wastewater enters the surface water and groundwater system, thereby affecting humans, animals and plants.

[0003] Boron plays an irreplaceable role in plant metabolism, nutrient, ion and hormone transport, tissue meristem growth, etc. Insufficient supply of boron will cause the yield of crops to decrease, root and leaf growth to be slow, tree bark to crack, enzyme reaction and photosynthesis to be slow, and even cause plant death. Therefore, in the field of agricultural planting, farmers will solve the problem of boron deficiency in plants by applying boron-containing fertilizers, and excessive intake of boron will cause plant poisoning (leaf yellow spots, necrosis, and root cell division reduction or even death). For animals and humans, boron is related to the immune function of the organism, and also has an impact on bone metabolism and central nervous system function. Boron deficiency will cause the development of vertebrate embryos to be deformed, and the absorption efficiency of nutrients such as calcium, magnesium and phosphorus is low. Long-term drinking of high-boron drinking water may increase cardiovascular diseases, nervous and reproductive system diseases and other problems.

[0004] In summary, boron plays an important role in animals, plants and humans, and has a wide application in industrial manufacturing, and has great industrial value. However, the environmental toxicity effect caused by excessive boron is also a difficult problem that needs to be solved urgently. Therefore, it is of great significance for environmental protection to develop an effective method for recovering boron from water bodies in nature, reducing the boron content in water bodies to a standard value and recycling boron resources.

[0005] In natural aqueous solutions, boron usually exists in the form of boric acid and various borate salts, which depends on the pH value of the solution and the concentration of boron. Boric acid is a weak acid, and when pH < 9.2, boric acid is dominant, and when pH > 9.2, boric acid anion exists.

[0006] Currently, the methods for removing and recovering boron from natural water bodies mainly include precipitation, adsorption, ion exchange, solvent extraction, electrocoagulation, reverse osmosis and bipolar membrane electrodialysis. The precipitation method refers to a method for converting boric acid or borate in water into a compound with low solubility to separate boron from the solution. Calcium hydroxide, calcium-based minerals, alum and barium salts are often used for chemical precipitation of boron. The chemical precipitation method is suitable for the removal of high-concentration boron, and it is a simple, easy-to-automate and widely used process. However, there are limitations to the removal of boric acid in wastewater by the chemical precipitation method, and a large amount of chemical reagent is required. When using this method, an oxidation step needs to be added, which requires the addition of an additional oxidizing agent, such as KMnO4, H2O2, etc. If a metal hydroxide coprecipitation method is used, it is not environmentally friendly. The adsorption method is an effective method for removing boron from low-concentration solutions, which has high efficiency and is easy to operate, and can effectively remove boron. Boron-specific resin is the most widely used adsorbent at present, but its production process is complex and the cost is high. Other inorganic adsorbents such as activated carbon, fly ash and metal oxides have poor selectivity. Most adsorbents are limited in their application due to their low adsorption performance. Chelating ion exchange resin has a high adsorption rate for boron, but the removal of boron usually shows slow kinetics, and their ion exchange capacity is also low. In addition, the selective ion exchange resin is expensive and the regeneration process is a tedious process, and this method can only handle a small amount of wastewater. The solvent extraction method has the advantages of simple operation, wide application range and high recovery rate, but using solvent extraction for boron requires the use of a large amount of organic solvent, which not only consumes a large amount of chemicals but also may cause organic solvent pollution. Electrocoagulation is simple to operate, uses less chemical than chemical precipitation, and produces less sludge. If it is used to treat solutions with low boron concentration, the energy consumption will be greatly increased. Reverse osmosis (RO) is widely used in boron removal due to its high retention rate and compactness. Reverse osmosis can effectively concentrate boron, but it requires a large operating pressure, which has a high requirement for industrial application. Bipolar membrane electrodialysis is an effective electro-membrane separation technology that can produce acid and alkali without the need for additional chemical reagents. Bipolar membrane electrodialysis can provide an alkaline environment to dissociate H3BO3 molecules into B(OH)4 - , and then migrate B4O7 2- and B(OH)4 - across the membrane for recovery. However, bipolar membrane electrodialysis requires an external power source to promote ion transport across the membrane, resulting in high energy consumption and low current efficiency, and is prone to membrane clogging problems. SUMMARY

[0007] The purpose of the present application is to provide an electrochemical method for recovering boron from wastewater by self-power generation, which uses zinc-air battery coupled with bipolar membrane electrodialysis to recover boron in the form of zinc borate from water.

[0008] In order to achieve the above object, the technical scheme adopted by the present application is as follows:

[0009] An electrochemical method for recovering boron in wastewater by self-power generation, which couples a zinc-air battery system with a bipolar membrane electrodialysis system, utilizes the electric field force generated by the zinc-air battery to drive the operation of the bipolar membrane electrodialysis, and recovers boron in the water body in the form of zinc borate.

[0010] NaCl solution is added to the anode chamber, the cathode chamber and the recovery chamber as an electrolyte, and a mixed solution of boron-containing wastewater and NaCl is added to the wastewater chamber. 2+ When the boron-containing wastewater treatment unit starts to work, the zinc-air battery starts to work, the zinc negative electrode loses electrons to Zn - OH - OH - Under the action of the electric field force, Zn 2+ Na + in the anode chamber migrate to the recovery chamber through the cation exchange membrane, and B(OH)4 - Cl - in the wastewater chamber migrate to the recovery chamber through the anion exchange membrane, so that the recovered Zn 2+ B(OH)4 - recovery liquid is synthesized into zinc borate by a hydrothermal method.

[0011] Further, the electrolytic cell is made of organic glass material.

[0012] Further, the concentration of the NaCl solution is 2.8-3.2 g / L.

[0013] Further, the mixed solution of boron-containing wastewater and NaCl has a final concentration of boron-containing wastewater of 90-110 mg / L and a final concentration of NaCl of 2.8-3.2 g / L.

[0014] The present application has the following beneficial effects:

[0015] A metal-air battery is a primary battery system consisting of an active metal anode, an air cathode, and an electrolyte. Metal-air battery systems can generate their own electricity to power external circuits and are increasingly being used in environmental protection. This invention utilizes a zinc-air battery coupled with bipolar membrane electrodialysis to simultaneously collect the electricity generated by the metal-air battery and provide Zn. 2 + The advantages of bipolar membrane electrodialysis in separating and enriching ions in solution. Applying a zinc-air battery-coupled bipolar membrane electrodialysis system to the recovery of boron from water, the electrical energy generated by the zinc-air battery drives the bipolar membrane electrodialysis, where hydrolysis of the bipolar membrane produces OH-. - Providing an alkaline environment causes the H3BO3 molecule to dissociate into B(OH)4. - Under the action of an electric field, B(OH)4 - Migration through the anion exchange membrane; the zinc anode loses electrons, and the zinc electrode converts Zn into Zn. 2+ Zn detaches into the solution 2+ Zn migrates to the recovery chamber via the cation exchange membrane. 2+ With B(OH)4 - Zinc borate, a flame-retardant material, is synthesized via a hydrothermal method. In this invention, the zinc-air battery not only generates electricity to hydrolyze the bipolar membrane, providing an electric field for ion migration, but also provides a zinc source for the subsequent synthesis of zinc borate. The zinc-air battery, coupled with bipolar membrane electrodialysis, recovers boron from water in the form of zinc borate. This responds to the national dual-carbon target, saves energy through self-generated electricity, and provides a new approach for environmental protection. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the device used in this invention;

[0017] Wherein, 1: electrolytic cell; 2: zinc negative electrode, located at the left end of the electrolytic cell; 3: cation exchange membrane (CEM); 4: anion exchange membrane (AEM); 5: bipolar membrane (BPM); 6: carbon felt positive electrode, located at the right end of the electrolytic cell. Detailed Implementation

[0018] The apparatus used in this invention, an electrochemical method for recovering boron from wastewater through self-generated power, is as follows: Figure 1 As shown, the zinc negative electrode 2, cation exchange membrane 3, anion exchange membrane 4, bipolar membrane 5, and carbon felt positive electrode 6 are arranged sequentially from the negative end to the positive end, forming a boron-containing wastewater treatment unit. The carbon felt positive electrode and the zinc negative electrode are connected by wires. In the boron-containing wastewater treatment unit, the space at the left end where the zinc negative electrode 2 is located is the anode chamber, and the space at the right end where the carbon felt positive electrode 6 is located is the cathode chamber. The space between the cation exchange membrane 3 and the anion exchange membrane 4 on the right side of the anode chamber is the recovery chamber, and the space between the anion exchange membrane 4 and the bipolar membrane 5 on the right side of the recovery chamber is the wastewater chamber.

[0019] Add 50 mL of 3 g / L NaCl solution as electrolyte to the anode chamber, cathode chamber, and recovery chamber. Add 50 mL of a mixed solution of boric acid (simulating boron-containing wastewater) and NaCl to the wastewater chamber. The final concentration of boron is 100 mg / L, and the final concentration of NaCl is 3 g / L.

[0020] At the start of the experiment, when the zinc-air battery was working, the zinc negative electrode lost electrons to produce Zn. 2+ Dissolved oxygen in the anode chamber solution detaches and enters the cathode chamber solution, where it gains electrons at the carbon felt cathode to generate OH-. - The electric field generated by the zinc-air battery causes the bipolar membrane to hydrolyze, producing OH-. - In the wastewater chamber, H3BO3 dissociates into B(OH)4 under alkaline conditions. - Under the influence of an electric field, Zn in the anode chamber 2+ Na + B(OH)4 in the wastewater chamber migrates through the cation exchange membrane into the recovery chamber. - Cl - The Zn-containing ions migrate through the anion exchange membrane to the recovery chamber, thereby recovering the Zn-containing ions. 2+ B(OH)4 - The recovered liquid was used to synthesize zinc borate via a hydrothermal method.

Claims

1. An electrochemical method for recovering boron from wastewater through self-generated power, characterized in that: A zinc-air battery system is coupled with a bipolar membrane electrodialysis system. The self-generated electric field of the zinc-air battery drives the operation of the bipolar membrane electrodialysis to recover boron from the water in the form of zinc borate. This method uses a zinc sheet as the negative electrode and a carbon felt as the positive electrode. The zinc negative electrode and the carbon felt positive electrode are respectively set at the left and right ends of the electrolytic cell. A cation exchange membrane, an anion exchange membrane, and a bipolar membrane are sequentially arranged between the zinc negative electrode and the carbon felt positive electrode. The zinc negative electrode and the carbon felt positive electrode are connected by wires to form a boron-containing wastewater treatment unit. In the boron-containing wastewater treatment unit, the space where the zinc negative electrode is located at the left end is the anode chamber, the space where the carbon felt positive electrode is located at the right end is the cathode chamber, the space between the cation exchange membrane and the anion exchange membrane is the recovery chamber, and the space between the anion exchange membrane and the bipolar membrane is the wastewater chamber. NaCl solution is added to the anode chamber, cathode chamber and recovery chamber as electrolyte, and a mixed solution of boron-containing wastewater and NaCl is added to the wastewater chamber; When the boron-containing wastewater treatment unit starts working, the zinc-air battery begins to operate, and the zinc negative electrode loses electrons to produce Zn. 2+ Dissolved oxygen in the anode chamber solution detaches and enters the cathode chamber solution, where it gains electrons at the carbon felt cathode to generate OH-. - The electric field generated by the zinc-air battery causes the bipolar membrane to hydrolyze, producing OH-. - In the wastewater chamber, H3BO3 dissociates into B(OH)4 under alkaline conditions. - Under the influence of an electric field, Zn in the anode chamber 2+ Na + B(OH)4 in the wastewater chamber migrates through the cation exchange membrane into the recovery chamber. - Cl - The Zn-containing ions migrate through the anion exchange membrane to the recovery chamber, thereby recovering the Zn-containing ions. 2+ B(OH)4 - The recovered liquid was used to synthesize zinc borate via a hydrothermal method.

2. The electrochemical method for recovering boron from wastewater through self-generated power according to claim 1, characterized in that: The electrolytic cell is made of plexiglass.

3. The electrochemical method for recovering boron from wastewater through self-generated power according to claim 1, characterized in that: The concentration of the NaCl solution is 2.8~3.2 g / L.

4. The electrochemical method for recovering boron from wastewater through self-generated power according to claim 1, characterized in that: A mixed solution of boron-containing wastewater and NaCl, with a final concentration of boron-containing wastewater of 90~110 mg / L and a final concentration of NaCl of 2.8~3.2 g / L.

Images