CN114122569B - Hydride/air battery for simultaneous treatment of waste acid and waste alkali and generation of electricity - Google Patents

Abstract

A metal hydride/air electrochemical cell device for synchronously treating waste acid and waste alkali and generating electric energy. Comprising the following steps: an air diffusion electrode as a positive electrode, a pre-hydrogen-storage hydride electrode as a negative electrode, and an ion exchange membrane, wherein: the positive electrode and the negative electrode are respectively arranged in a waste acid solution and a waste alkali solution, the positive electrode and the negative electrode are connected with an external circuit, and the ion exchange membrane is arranged between the two electrolytes of acid and alkali and is used as a diaphragm material; when the battery discharges or waste acid and alkali treatment is carried out, the reaction generated by the negative electrode is that hydrogen is separated out and oxidation reaction is carried out between the hydrogen and OH ^‑ ions in the waste alkali, so that water is generated and electrons are produced; meanwhile, electrons are led out from an external circuit and flow to the anode, so that oxygen in the air and H ⁺ ions in the waste acid undergo a reduction reaction to generate water. The invention provides a harmless, reduced and recycling treatment technical path for the environmental pollution problem caused by waste acid and waste alkali generated in industrial production, and has practical significance and good application prospect.

Description

Hydride/air battery for simultaneous treatment of waste acid and waste alkali and generation of electricity

Technical Field

The present invention relates to a technology related to the fields of chemical industry, environment and energy, and specifically to a device and method for a hydride/air battery for safely and simultaneously treating waste acid and waste alkali and generating electricity.

Background Art

Waste acids and alkalis discharged from industrial production have a great impact on our water environment and are a prominent problem restricting my country's sustainable development. Traditional technologies for treating waste acids and alkalis include direct mixing of waste acids and alkalis for neutralization, biotechnology, high-temperature incineration in cement kilns, flotation precipitation and impurity removal, iron-carbon micro-electrolysis, and wet oxidation treatment technology. However, these traditional technical methods have low resource utilization and lack economic benefits. For example, direct mixing and neutralization treatment technology is to mix acidic wastewater and alkaline wastewater for neutralization or to directly neutralize acidic wastewater with solid waste alkali residue. However, the waste heat energy generated in the chemical neutralization process of this technology has not been converted and utilized, resulting in low overall utilization and economic benefits.

Summary of the invention

The present invention aims at the problem that there is a lack of technology for simultaneous treatment of waste acid and waste alkali with high safety and high resource utilization rate at present, and proposes a metal hydride/air electrochemical battery device for simultaneous treatment of waste acid and waste alkali and generation of electric energy. The technical invention utilizes the oxidation reaction of the highly safe hydride consuming ^OH- ions under alkaline conditions as the negative electrode reaction and the reduction reaction of the highly safe air diffusion electrode consuming H ⁺ ions under acidic conditions as the positive electrode reaction, and the acid-base electrolyte is separated by an ion exchange membrane. During the discharge or electrochemical neutralization process, that is, while treating the waste acid and waste alkali, electric energy can be obtained from the waste acid and waste alkali treatment process, thereby realizing efficient, safe and resource-utilized electrochemical neutralization treatment. In the process of treating the waste acid and waste alkali of the present invention, no waste gas and waste liquid are discharged, and the waste acid and waste alkali can be continuously treated. The present invention provides a "harmless, reduced and resource-utilized" treatment technology path for the environmental pollution caused by the waste acid and waste alkali generated in industrial production, which has practical significance and good application prospects.

The present invention is achieved through the following technical solutions:

The invention relates to a metal hydride/air electrochemical battery device for simultaneously treating waste acid and waste alkali and generating electric energy, comprising: an air diffusion electrode as a positive electrode, a hydride electrode for pre-storing hydrogen as a negative electrode, and an ion exchange membrane, wherein: the positive electrode and the negative electrode are respectively placed in a waste acid solution and a waste alkali solution and are connected to an external circuit, and the ion exchange membrane is arranged between the acid and alkali electrolytes as a diaphragm material; when the battery is discharged or the waste acid and waste alkali are treated, the reaction occurring at the negative ^electrode is hydrogen precipitation and oxidation reaction with OH- ions in the waste alkali to generate water and produce electrons; at the same time, the electrons are led out of the external circuit and flow to the positive electrode, so that oxygen in the air and H ⁺ ions in the waste acid undergo reduction reaction to generate water.

During the above-mentioned whole discharge process of the device, H ⁺ ions and ^OH- ions are effectively electrochemically neutralized and release electric energy through corresponding electrochemical reactions.

The waste acid solution and waste alkali solution can be taken from waste acid and waste alkali produced in industry, and directly used as the electrolyte of the electrochemical cell device of the present invention, and electric energy is obtained while being electrochemically neutralized.

The air diffusion electrode is obtained by mixing and grinding a platinum-carbon catalyst, conductive carbon black and a binder solution, applying the mixture on the surface of a hydrophobic carbon cloth and drying the mixture.

The hydride electrode for pre-storing hydrogen is obtained by the following steps:

① The active material is obtained by mixing and grinding the metal hydride (MH) of LaNi ₅ in the nickel-hydrogen battery, conductive carbon black and a binder solution, and then drying;

② After applying the active substance on the nickel foam, fold the nickel foam in half and sandwich the nickel-plated steel strip in the middle to form a sandwich structure with the nickel-plated steel strip partially extending out of the nickel foam.

③ The sandwich structure is dried and compacted before being activated.

The metal hydride is composed of LaNi ₅ lanthanum nickel hydrogen storage alloy.

The activation treatment refers to: charging and discharging with a current of 20 mA (charging time is 2 hours, discharge cut-off voltage is 0.2 volts), a total of four cycles, and finally charging once (cut-off voltage is 1.5 volts) to form a hydride electrode for pre-storing hydrogen.

The waste acid solution preferably has a pH value of less than 1 before treatment, and after treatment, the concentration of hydrogen ions in the waste acid is reduced, specifically, for every 87.5 mAh of electricity produced, the hydrogen ion concentration decreases by at least 0.15-0.21 M. The increase in the pH value of the waste acid solution after treatment means that the acidity is significantly weakened.

The waste alkali solution preferably has a pH value greater than 13 before treatment, and after treatment, the concentration of hydroxide ions in the waste alkali is reduced, specifically, for every 87.5 mAh of electricity produced, the concentration of hydroxide ions decreases by at least 0.15-0.21 M. The decrease in the pH value of the waste alkali solution after treatment means that the alkalinity is significantly weakened.

The battery discharges, and the total reaction is 1 mole of oxygen, 4 moles of hydrogen ions, 4 moles of hydride pre-stored with hydrogen and 4 moles of hydroxide ions to generate 4 moles of hydride after hydrogen is released and 6 moles of water, and no waste gas or waste liquid is generated in the reaction products.

The discharge reaction mechanism of the hydride/air battery for simultaneously treating waste acid and waste alkali and generating electricity specifically includes:

Positive electrode reaction:

Negative electrode reaction:

Overall reaction:

Technical Effects

The present invention utilizes the oxidation reaction of the highly safe hydride hydrogen storage material under alkaline conditions to consume ^OH- ions as the negative electrode reaction and the reduction reaction of the highly safe air diffusion electrode under acidic conditions to consume H ⁺ ions as the positive electrode reaction, and uses an ion exchange membrane to separate the acid-base electrolyte to prevent direct mixing of chemical neutralization reactions. The total electrochemical reaction of the electrochemical battery device formed can electrochemically neutralize H ⁺ ions and ^OH- ions and produce water and electricity. Compared with the prior art, the negative electrode adopts a highly safe room-temperature metal hydride hydrogen storage material, which greatly improves the safety of actual industrial production operations; the liquid product is only water, and no waste gas or waste liquid is discharged, which is green and environmentally friendly; the battery structure design based on the two chambers and acid-base electrode pairing can be used to treat waste liquids with different pH values; the synchronous electrochemical neutralization treatment of waste acid and waste alkali liquids and the generation of electricity are achieved through a new electrochemical reaction method, which improves the resource utilization rate.

Based on the standard electrode potential of the positive and negative electrodes, when the concentrations of hydrogen ions and hydroxide ions are 1M each, the battery of the invention can theoretically produce a voltage of 2.03 volts under standard conditions. The actual open circuit voltage measurement value of the electrochemical battery device formed by the present invention is higher than 1.6 volts. In addition, the hydrogen ions in the waste acid and the hydroxide ions in the waste alkali are effectively neutralized and produce electricity during the discharge process. Therefore, the battery device of the invention has the advantages of efficiently and simultaneously treating waste acid and waste alkali and utilizing the electricity generated during the treatment process. The typical technical effect is: the electrochemical battery device simultaneously treats hydrogen ion concentrations and hydroxide ions of 0.15-0.21M each, which can generate 87.5 mAh of electricity, and the acidity and alkalinity of the two waste liquids are significantly weakened.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a diagram showing the discharge reaction mechanism of a hydride/air battery;

FIG2 is a comparison diagram of voltage changes over time in battery current tests in Example 1 and Example 2;

FIG3 is a polarization curve diagram of a battery in Example 3 at 5-100 mA current test;

FIG4 is a polarization curve diagram of a battery in Example 4 under a current test of 5-70 mA;

FIG5 is a structural diagram of a hydride/air battery that simultaneously treats waste acid and waste alkali and generates electricity;

In the figure: air diffusion electrode 1, gas diffusion layer 101, catalyst layer 102, ion exchange membrane 2, metal hydride 3, external circuit 4;

Fig. 6 is a diagram of the actual working device of the embodiment;

In the figure: an air diffusion electrode 1, a gas diffusion layer 101, a catalyst layer 102, an ion exchange membrane 2, a metal hydride electrode 3 with a nickel-plated steel strip and immersed in an alkaline solution, a Teflon cavity 4 filled with an acidic solution in contact with the catalyst layer of the air diffusion electrode, a Teflon cavity 5 allowing air to contact the gas diffusion layer of the air diffusion electrode, and a stainless steel strip current collector 6 in contact with the catalyst layer of the air diffusion electrode and conducting electricity.

DETAILED DESCRIPTION

Example 1

This embodiment includes the following process and testing steps:

1) Preparation of electrolyte: Prepare 35 mL of 0.5 M sulfuric acid as the simulated spent acid positive electrolyte and 35 mL of 1 M KOH solution as the simulated spent alkali negative electrolyte.

2) Preparation of positive electrode: 30 mg of platinum-carbon catalyst was mixed with 0.4 mL of 50 wt% polytetrafluoroethylene (PTFE) adhesive solution, ground and coated on the surface of hydrophobic carbon cloth, and placed in an oven at 80° C. for 2 h.

3) Preparation of negative electrode: Take out metal hydride (MH) from a fully discharged rechargeable battery, mix and grind 1g MH, 50mg carbon black (Cabot), and 1mL 50wt% PTFE solution, put it in an oven and dry it to cement, to obtain an active material, apply the active material on the upper half of a 3*6cm, 0.5mm thick nickel foam, cut a 6cm long, 0.15*8mm thick nickel-plated steel strip, fold the nickel foam in half, sandwich the active material and the nickel-plated steel strip in the middle, and partially extend the nickel-plated steel strip outside the nickel foam as a conductor current collector, thereby preparing a negative electrode. The electrode was placed in an oven at 80°C for 2h, and after being taken out, it was pressed with a press at a pressure of 45KPa for 20min.

4) Activation of the negative electrode: Take out the positive electrode (whose component is nickel hydroxide) from the fully discharged rechargeable battery, use 1M KOH solution as electrolyte, and form a secondary battery together with the negative electrode prepared in step 3), charge and discharge at a current of 20mA, cycle four times, and finally charge to 1.5V at a current of 20mA to obtain an activated and fully charged negative electrode.

5) Diaphragm material processing and battery assembly: Take out the cation exchange membrane soaked in 5wt% NaCl solution for more than 12 hours and wash it with deionized water. The positive electrode chamber is filled with positive electrode electrolyte; the negative electrode chamber is filled with negative electrode electrolyte and is in a static state; the two sides of the positive electrode chamber are the negative electrode chamber and the air chamber respectively. The positive and negative electrode electrolytes are separated by an ion exchange membrane to avoid direct contact and chemical neutralization. The key materials obtained in steps 1), 2), 4) and 5) are assembled into batteries for testing. The positive and negative electrode current collectors are stainless steel strips and nickel-plated steel strips respectively.

Current test: Use Wuhan Blue Electric Battery Test System to discharge the battery continuously at a constant current of 5 mA from 5 mA to 35 mA for 5 minutes, and measure the open circuit voltage every 10 seconds. Use a digital pH meter to directly measure the pH value of the electrolyte after the test.

In this embodiment, the pH value changes as shown in Table 1 below. The pH changes significantly, with specific values as follows: the pH value of the acidic solution rises from 0.63 to 1.14, while the pH value of the alkaline solution drops from 13.65 to 12.89, with pH change values of 0.51 and 0.76, respectively. Therefore, hydrogen ions/hydroxyl ions are consumed to a certain extent, indicating that the battery can discharge and neutralize the corresponding portion of the waste acid and waste alkali solution. The electrochemical battery device in this embodiment produces about 12 milliampere hours of electricity.

Example 2

This embodiment includes the following process and testing steps:

1) Preparation of electrolyte: 35 mL of 1M sulfuric acid was prepared as a simulated waste acid positive electrode electrolyte. 35 mL of 1M KOH solution was prepared as a simulated waste alkali negative electrode electrolyte. Different from Example 1, this example uses a more acidic waste acid solution to further demonstrate the practicality of the battery.

2) Preparation of positive electrode: 30 mg of platinum-carbon catalyst was mixed with 0.4 mL of 50 wt% PTFE adhesive solution, ground and coated on the surface of hydrophobic carbon cloth, and placed in an oven at 80° C. for 2 h.

3) Preparation of negative electrode: Take out metal hydride (MH) from a fully discharged rechargeable battery, mix and grind 1g MH, 50mg carbon black (Cabot), and 1mL 50wt% PTFE solution, put it in an oven and dry it to cement to obtain an active material, apply the active material on the upper half of a 3*6cm, 0.5mm thick nickel foam, cut a 6cm long, 0.15*8mm thick nickel-plated steel strip, fold the nickel foam in half, sandwich the active material and the nickel-plated steel strip in the middle, and partially extend the nickel-plated steel strip out of the nickel foam, thereby preparing a negative electrode as a conductor current collector. The electrode was placed in an oven at 80°C for 2h, and after being taken out, it was pressed with a press at a pressure of 45MPa for 20min. Different from Example 1, this embodiment uses a higher pressure to prepare the electrode to further improve the electrode performance.

4) Activation of the negative electrode: Take out the positive electrode (composed of nickel hydroxide) from the fully discharged rechargeable battery, use 1M KOH solution as the electrolyte, and form a secondary battery together with the negative electrode prepared in step 3), charge and discharge at a current of 20mA, cycle four times, and finally charge to 1.5V at a current of 20mA to obtain an activated and fully charged negative electrode.

5) Diaphragm material processing and battery assembly: Take out the cation exchange membrane soaked in 5wt% NaCl solution for more than 12 hours and wash it with deionized water. The positive electrode chamber is filled with positive electrode electrolyte; the negative electrode chamber is filled with negative electrode electrolyte and is in a static state; the two sides of the positive electrode chamber are the negative electrode chamber and the air chamber respectively. The positive and negative electrode electrolytes are isolated by an ion exchange membrane to avoid direct contact. The key materials obtained in steps 1), 2), 4) and 5) are assembled into batteries for testing, and the positive and negative electrode current collectors are stainless steel strips and nickel-plated steel strips respectively.

Current test: Use Wuhan Blue Electric Battery Test System to discharge the battery continuously at a constant current of 5 mA from 5 mA to 35 mA for 5 minutes, and measure the open circuit voltage every 10 seconds. Use a digital pH meter to directly measure the pH value of the electrolyte after the test.

In this embodiment, the pH changes are shown in Table 2 below. The pH changes significantly, with specific values as follows: the pH value of the acidic solution increases from 0.34 to 0.73, while the pH value of the alkaline solution decreases from 13.46 to 12.89, with pH change values of 0.39 and 0.57, respectively. Therefore, both hydrogen ions and hydroxide ions are consumed to a certain extent, indicating that the battery can discharge and neutralize the corresponding portion of the acid and alkaline solution. The electrochemical battery device in this embodiment produces about 12 mAh of electricity.

The voltage variation curves of Examples 1 and 2 over time are shown in FIG2 , where the experimental data of Voltage 1 are obtained in Example 1, and the experimental data of Voltage 2 are obtained in Example 2. In Example 2, the increased pressure used to press the negative electrode makes the material structure more compact and less likely to fall off, and the battery performance is more stable, which is specifically manifested in that the discharge platform is higher than 1.4 volts within the tested current range.

Example 3

This embodiment includes the following process and testing steps:

1) Preparation of electrolyte: 17 mL of 1M sulfuric acid was prepared as a simulated waste acid positive electrolyte. 17 mL of 1M KOH solution was prepared as a simulated waste alkali negative electrolyte. This example uses less electrolyte to explore the practicality of the battery device.

2) Preparation of positive electrode: 30 mg of platinum-carbon catalyst was mixed with 0.4 mL of 50 wt% PTFE adhesive solution, ground and coated on the surface of carbon cloth, and placed in an oven at 80° C. for 2 h.

3) Preparation of negative electrode: Take out metal hydride (MH) from a fully discharged rechargeable battery, mix and grind 1g MH, 50mg carbon black (Cabot), and 1mL 50wt% PTFE solution, put it in an oven and dry it to cement to obtain an active material, apply the active material on the upper half of a 3*6cm, 2mm thick nickel foam, cut a 6cm long, 0.15*8mm thick nickel-plated steel strip, fold the nickel foam in half, sandwich the active material and the nickel-plated steel strip in the middle, and partially extend the nickel-plated steel strip outside the nickel foam as a conductor current collector, thereby preparing a negative electrode. Place the electrode in an oven at 80°C for 2h, take it out and press it with a press at a pressure of 45MPa for 20min. Different from Examples 1 and 2, this embodiment uses thicker nickel foam to prepare the electrode, so as to further improve the electrode performance.

4) Activation of the negative electrode: Take out the positive electrode (whose component is nickel hydroxide) from the fully discharged rechargeable battery, use 1M KOH solution as electrolyte, and form a secondary battery together with the negative electrode prepared in step 3), charge and discharge at a current of 20mA, cycle four times, and finally charge to 1.6V at a current of 20mA to obtain an activated and fully charged electrode negative electrode.

5) Diaphragm material processing and battery assembly: Take out the anion exchange membrane soaked in 5wt% NaCl solution for more than 12 hours and wash it with deionized water. The positive electrode chamber is filled with positive electrode electrolyte; the negative electrode chamber is filled with negative electrode electrolyte and is in a static state; the two sides of the positive electrode chamber are the negative electrode chamber and the air chamber respectively. The positive and negative electrode electrolytes are isolated by the ion exchange membrane to avoid direct contact. The key materials obtained in steps 1), 2), 4) and 5) are assembled into a battery for testing, and the positive and negative electrode current collectors are stainless steel strips and nickel-plated steel strips, respectively. Different from Examples 1 and 2, this embodiment uses anion exchange membrane as a diaphragm material to slow down the diffusion of H ⁺ ions, thereby further improving battery performance.

Current test: Use Wuhan Blue Battery Test System to discharge the battery from 5mA to 100mA at a constant current of 5mA for 5 minutes, and measure the open circuit voltage every 10s. Use a digital pH meter and conductivity meter to measure the pH value and conductivity of the electrolyte after the test.

In this embodiment, the formed hydride/air battery discharges stably. Among them, the pH of the acidic solution before discharge is 0.13, the conductivity S is 83.75mS/cm, the pH of the alkaline solution is 13.56, and the conductivity S is 42.26mS/cm. After discharge, the pH of the acidic solution is 0.24, the conductivity S is 62.26mS/cm, and the pH of the alkaline solution is 13.30, and the conductivity S is 22.61mS/cm. The above data all indicate that the acidic solution and the alkaline solution are subjected to corresponding electrochemical neutralization treatment, the acidity and alkalinity are significantly weakened, and the output power is 87.5 mAh.

According to the polarization curve in Figure 3, when the output current is stabilized at 90mA, the output power of the battery is the maximum, reaching 93mW. According to Faraday's law, the efficiency of the battery is as high as 94%. This means that 94% of the waste acid and alkali that have been electrochemically neutralized have produced corresponding electricity in the process.

Example 4

This embodiment includes the following process and testing steps:

1) Preparation of electrolyte: 17 mL of waste acid simulation solution was prepared as the positive electrode electrolyte, and its composition was 17 wt% H ₂ SO ₄ , 5 wt% FeSO ₄ , 1.5 wt% Al ₂ (SO ₄ ) ₃ , 1 wt% Ti(SO ₄ ) ₂ ; 80 mL of waste alkali simulation solution was prepared as the negative electrode electrolyte, and its composition was 3 wt% Na ₂ CO ₃ , 0.5 wt% NaHCO ₃ , 0.1 wt% NaOH, 0.5 wt% NaClO.

Different from Examples 1, 2 and 3, this example verifies the continuous processing capability and feasibility of quantitative processing of the present invention through a circulation electrochemical neutralization test of single-side spent alkali.

2) Preparation of positive electrode: 20 mg of platinum-carbon catalyst, 0.15 g of conductive carbon black (Cabot) and 0.4 mL of 50 wt% PTFE adhesive solution were mixed and ground, then applied to the surface of the carbon cloth and placed in an oven at 80°C for 2 h.

3) Preparation of negative electrode: Take out metal hydride (MH) from a fully discharged rechargeable battery, mix and grind 1g MH, 50mg conductive carbon black (Cabot), and 1mL 50wt% PTFE solution, put it in an oven and dry it to cement, to obtain an active material, apply the active material on the upper half of a 3*6cm, 2mm thick nickel foam, cut a 6cm long, 0.15*8mm thick nickel-plated steel strip, fold the nickel foam in half, sandwich the active material and the nickel-plated steel strip in the middle, and partially extend the nickel-plated steel strip outside the nickel foam as a conductor current collector, thereby preparing a negative electrode. The electrode was placed in an oven at 80°C for 2h, and after being taken out, it was pressed with a press at a pressure of 45MPa for 20min.

4) Activation of the negative electrode: Take out the positive electrode (whose component is nickel hydroxide) from the fully discharged rechargeable battery, use 1M KOH solution as electrolyte, and form a secondary battery together with the negative electrode prepared in step 3), charge and discharge at a current of 20mA, cycle four times, and finally charge to 1.5V at a current of 20mA to obtain an activated and fully charged negative electrode.

5) Diaphragm material processing and battery assembly: Take out the anion exchange membrane soaked for more than 12 hours from the 5wt% NaCl solution and wash it with deionized water. The positive electrode chamber is filled with positive electrode electrolyte; the negative electrode chamber is filled with negative electrode electrolyte, and a peristaltic pump is used through a silicone tube pipeline connected to the inlet and outlet of the negative electrode chamber of the battery, and connected to an external beaker containing negative electrode electrolyte, so that the negative electrode electrolyte is in a flow circulation state; the two sides of the positive electrode chamber are the negative electrode chamber and the air chamber respectively. The positive and negative electrode electrolytes are isolated by an ion exchange membrane to avoid direct contact. The key materials obtained in steps 1), 2), 4), and 5) are assembled into a battery for testing, and the positive and negative electrode current collectors are stainless steel strips and nickel-plated steel strips respectively.

Current test: Use Wuhan Blue Electric Battery Test System to discharge continuously at a constant current of 5 mA to 70 mA for 10 seconds, and measure the open circuit voltage every 2 seconds.

In this embodiment, the battery system formed can stably treat waste acid and waste alkali solutions simulating actual industrial production. From the polarization curve in Figure 4, it can be seen that when the output current is stabilized at 40mA, the output power of the battery is the maximum, reaching 22mW.

pH(before test) pH(after test) ΔpH 0.5MH ₂ SO ₄ 0.63 1.14 0.51 1M KOH 13.65 12.89 0.76

Table 1

pH(before test) pH(after test) ΔpH 1M H ₂ SO ₄ 0.34 0.73 0.39 1M KOH 13.46 12.89 0.57

Table 2

The catalyst of the air electrode is a platinum-carbon mixture.

The negative electrode hydride active material is LaNi5 in the AB5 type lanthanum (La) nickel (Ni) alloy system.

The membrane material is an anion exchange membrane or a cation exchange membrane.

After specific practical experiments, the actual open circuit voltage measurement value of the electrochemical battery device formed by the present invention is higher than 1.6 volts. For every 87.5 milliampere-hours of electricity produced by the device, there is at least a 0.15-0.21M drop in the concentration of hydrogen ions or hydroxide ions, and the acidity and alkalinity of the treated waste liquid are significantly weakened. It can be seen that the present invention has a new function of efficiently and simultaneously treating waste acid and waste alkali and utilizing the electricity generated during the treatment process, which is beneficial to improving resource utilization. In addition, the electricity recovery rate when treating acidic waste liquid and alkaline waste liquid can be as high as 94%, and when the maximum power is reached (i.e. 93mW), the voltage can still be maintained at about 1 volt. No waste gas or waste liquid is generated during the reaction, indicating that the target reaction has high selectivity, is green and pollution-free, and improves resource utilization.

Compared with the prior art, the technical effects of the present invention include: First, the introduction of metal hydride as the negative electrode greatly improves the safety and stability of the actual simultaneous processing of the battery. Second, the battery can obtain a power recovery rate of up to 94% from the electrochemically neutralized waste acid and waste alkali. Third, based on the improvement of the battery structure design of two chambers and acid-base electrode pairing, the battery device can specifically treat a variety of waste liquids with different pH values, providing a "harmless, reduced and resource-based" waste acid and waste alkali simultaneous treatment technology path.

The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims (4)

1. A metal hydride/air electrochemical cell device for extracting and converting the neutralization energy of spent acid and spent caustic, comprising: an air diffusion electrode as a positive electrode, a pre-hydrogen-storage hydride electrode as a negative electrode, and an ion exchange membrane, wherein: the positive electrode and the negative electrode are respectively arranged in a waste acid solution and a waste alkali solution, the positive electrode and the negative electrode are connected with an external circuit, and the ion exchange membrane is arranged between the two electrolytes of acid and alkali and is used as a diaphragm material; when the battery discharges or waste acid and alkali treatment is carried out, the oxidation reaction of the negative electrode is to separate out hydrogen and carry out oxidation reaction with OH ^- ions in the waste alkali to generate water and generate electrons; meanwhile, electrons are led out from an external circuit and flow to the positive electrode, so that oxygen in the air and H ⁺ ions in waste acid undergo a reduction reaction at the positive electrode to generate water;

The waste acid solution and the waste alkali solution are taken from waste acid and waste alkali generated in industry and are directly used as electrolyte, and electric energy is obtained while electrochemical neutralization treatment is carried out;

The metal hydride is LaNi ₅ lanthanum nickel hydrogen storage alloy;

The waste acid solution and the waste alkali solution are arranged in the battery device and separated by an ion exchange membrane;

The pH value of the waste acid solution before treatment is less than 1, the concentration of hydrogen ions in the waste acid is reduced after treatment, and particularly, the electric quantity is generated at each time of 87.5 milliampere hours, and the hydrogen ion concentration is reduced by at least 0.15-0.21M; the pH value of the treated waste acid solution rises;

The pH value of the waste alkali solution before treatment is more than 13, and the concentration of hydroxide ions in the waste alkali is reduced after treatment, specifically, the concentration of hydroxide ions is reduced by at least 0.15-0.21M when the electric quantity of 87.5 milliampere hours is generated; the pH value of the treated waste alkali solution is reduced;

The battery discharges, the total reaction is that 1 mole of oxygen, 4 moles of hydrogen ions, 4 moles of pre-stored hydrogen hydride and 4 moles of hydroxide ions generate 4 moles of hydrogen released hydride and 6 moles of water, no waste gas and waste liquid are generated in the reaction product, and the specific reaction formula comprises:

positive electrode reaction:

Negative electrode reaction:

Total reaction:

2. The metal hydride/air electrochemical cell device of claim 1, wherein the air diffusion electrode is obtained by grinding a platinum carbon catalyst, conductive carbon black and a binder solution, and then coating the mixture on the surface of a hydrophobic carbon cloth and drying the mixture.

3. The metal hydride/air electrochemical cell device of claim 1, wherein said pre-hydrogen storage hydride electrode is obtained by:

① Mixing, grinding and drying metal hydride, conductive carbon black and binder solution in the nickel-hydrogen battery to obtain an active substance;

② After the active substances are coated on the foam nickel, folding the foam nickel in half and sandwiching a nickel-plated steel belt to form a sandwich structure, wherein a nickel-plated steel belt part extends out of the foam nickel;

③ And drying and compacting the sandwich structure, and then performing activation treatment.

4.A metal hydride/air electrochemical cell device as claimed in claim 3, wherein said activation treatment is: charging and discharging are carried out at 20mA current, the total cycle is four times, and finally, one-time charging is carried out to form the hydride electrode for pre-storing hydrogen.