CN109847735B

CN109847735B - A kind of nano-catalyst for efficiently degrading ammonia pollutants and its application

Info

Publication number: CN109847735B
Application number: CN201910048301.4A
Authority: CN
Inventors: 柳丽芬; 闫彩
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2019-01-18
Filing date: 2019-01-18
Publication date: 2021-05-18
Anticipated expiration: 2039-01-18
Also published as: CN109847735A

Abstract

The invention provides a nano-catalyst for efficiently degrading ammonia gas pollutants and an application thereof, belonging to the technical field of gas-phase pollutant purification treatment and removal of malodorous ammonia gas and other air pollutants. The nano-catalyst Sn-V ₂ O ₅ was fixed and coated with silica sol on the stainless steel mesh, as the conductive cathode, the anode was formed by the corrosion of copper rods in K ₂ SO ₄ electrolyte solution or the metabolic activity of electricity-generating microorganisms, and the two poles were connected by alligator clips. And the wire and the external resistance form a closed circuit loop, the visible light source is provided by the lamp, and a stainless steel reactor is constructed to simulate the ammonia pollution purification system, which can realize the efficient removal of ammonia gas. In the experiment, even a small amount of nano-catalysts can degrade ammonia quickly, and in the presence of the three excitation elements of light, electricity and microorganisms, the performance of degrading ammonia is improved. In the case of electricity generation as the cathode, the effect of degrading ammonia gas is the best.

Description

Nano-catalyst for efficiently degrading ammonia pollutants and application thereof

Technical Field

The invention belongs to the technical field of gas-phase pollutant purification treatment and removal of air pollutants such as stink ammonia gas and the like, and mainly relates to Sn-V₂O₅The preparation of the nano catalyst and the membrane component with the photoelectric catalytic function and the system for controlling and eliminating the ammonia pollution in the stainless steel reactor realize the high-efficiency removal of the ammonia by using the new catalyst, have stable effect, provide reference for further developing high-efficiency degradation catalysts of other air pollutants and provide scientific basis for the aspects of treating odor pollution and purifying air.

Background

The problem caused by the emission of malodorous gas is one of seven environmental public hazards. Gaseous ammonia (NH)₃) Is a common main stink pollutant with wide source, mainly comes from the agricultural large-amount application of nitrogen fertilizer and the continuously expanded livestock and poultry breeding industry. NH (NH)₃As a toxic atmospheric pollution gas, it has irritation and corrosion effects on upper respiratory tract of animal or human body, and can enter blood via alveolus to combine with hemoglobin to destroy red bloodThe oxygen transport function of the protein leads the organism to generate hypoxia, thereby reducing the resistance of the organism and harming the health and the life of animals and human bodies. In addition, ammonia gas can be attached to dust and migrate to farther places, and acidification of soil and water bodies can be caused after sedimentation, so that eutrophication of an ecological system is caused, the ecological environment is damaged, and the environment is seriously polluted. Recent studies have shown that ammonia is also one of the important causes of haze and particulate formation. However, most of the previous researches are directed to sulfur dioxide, nitrogen oxide, formaldehyde, volatile organic compounds and the like, and the researches on photocatalytic degradation of toxic ammonia gas are ignored by most people.

Conventional treatment techniques, such as adsorption and aeration, do not completely eliminate NH₃. Selective catalytic technology (SCO) can be used with various catalyst metals, metal oxides to completely remove oxidized NH₃However, they do not achieve efficient removal of gaseous NH at room temperature₃. In recent years, photocatalytic technology has been used in the air purification field, which can degrade various pollutants such as formaldehyde, volatile organic compounds, etc. into harmless end products such as CO at ambient temperature by using nano-structured photocatalytic materials having unique properties as catalysts using light energy₂Or H₂O and other small molecule species, etc., and without significant energy consumption. Therefore, photocatalytic oxidation (PCO) is considered to be a promising air purification technology. The process is that under the action of light, active species are formed on the surface of the photocatalyst and are degraded into harmless end products through oxidation-reduction reaction with pollutants. At present, the innovation front edge of air purification introduces an electric field into photocatalysis, and researches on enhancing photocatalysis effects are gradually increased. However, the coupling of photocatalysis and electrocatalysis has not been much studied for the treatment of ammonia degradation.

Recently, layered vanadium oxide (V)₂O₅) Materials are of interest because of their excellent physicochemical properties. V₂O₅The n-type semiconductor has infrared reflectivity and transmissivity, a band gap of 2.38eV at room temperature, higher specific capacity and energy density, magnetic susceptibility, variable oxidation state and other properties. Due to these advantagesDifferent properties, V₂O₅Are widely used as cathode materials in batteries, storage media, sensors, catalysts, and the like. Nano-sized materials have various interesting properties such as larger specific surface area, shorter diffusion distance, high crystallinity, better conductivity, etc. These properties of nanomaterials directly affect the properties of the material. V is caused to be present due to the variable oxidation state of the vanadium ion₂O₅The nano material forms a layer of oxide surface, which can improve the defect of gas chemisorption, thereby promoting the rapid degradation of pollutants at room temperature.

Most of the research results show that the cation doping is improved V₂O₅Efficient method of material properties, mainly due to the introduction of V by foreign ions₂O₅The crystal lattice can regulate the ion occupancy and electronic structure of the host material. Wherein tin ion doping has also been shown to be a good cation for improving the performance of metal oxide materials.

Microbial Fuel Cells (MFCs) are devices that convert chemical energy in organic compounds into electrical energy using electricity-producing microorganisms. At present, Sn-V is₂O₅Reports of the introduction of a photocatalytic material into a photoelectricity-cooperated microbial fuel cell system to remove ammonia in air have not yet appeared.

This application takes Sn-V as₂O₅As a catalyst, the catalyst can rapidly remove toxic ammonia gas and achieve the effects of air purification and odor pollution elimination in the process of coupling the microbial fuel cell.

Disclosure of Invention

The invention prepares the semiconductor catalytic material with high ammonia gas removal efficiency, simple preparation process and high stability, and successfully constructs Sn-V₂O₅A photoelectrocatalysis membrane component and an air pollution simulation and purification system. The system has the advantages of high overall treatment and purification efficiency and low energy consumption, and greatly reduces the concentration of toxic ammonia gas in a short time.

The technical scheme of the invention is as follows:

a nanometer catalyst for efficiently degrading ammonia pollutants comprises the following steps:

preparation of sodiumRice catalyst x% Sn-V₂O₅: synthesis of Sn doped V by sol-gel method at low temperature₂O₅A nanoparticle; the synthesis process is as follows: firstly, V is mixed under stirring₂O₅The powder was charged with deionized water and 30 wt% H₂O₂In the resulting mixed solution, wherein H₂O₂And V₂O₅At a molar ratio of 10:1 to form 0.3M V₂O₅A solution; the obtained V₂O₅Stirring the solution at room temperature for 20min, and then carrying out ultrasonic treatment for a period of time; subsequently, V is₂O₅Further diluting the solution until the concentration of the solution is not lower than 0.07M, and further performing ultrasonic treatment for 90min at the treatment temperature of 60-45 ℃; after ultrasonic treatment, brownish red V is obtained₂O₅Diluting the gel; the concentration of the diluted solution is kept between 0.037 and 0.027M, and then the solution is stirred until the color of the solution is changed into transparent brick red; adding solid SnCl₄·5H₂Dissolving O in a small amount of deionized water to form a solution, and reacting with the obtained V₂O₅Mixing the brick red transparent solution; heating and stirring in a water bath kettle for 3h to make the solution become gel until the gel is dried; then drying at room temperature, grinding and sieving to obtain the nano Sn-V₂O₅The compound is the nano catalyst; wherein x% is Sn and V₂O₅The mass ratio of (1) to (6).

The application of the nano catalyst for efficiently degrading ammonia pollutants comprises the following steps:

(1) preparing a photoelectric catalytic membrane component: to the prepared nano Sn-V₂O₅Adding silica sol into the composite, controlling the concentration of the silica sol to be 4 mu L/mg, stirring uniformly, coating the mixture on a pretreated stainless steel conductive carrier, and adding the nano catalyst Sn-V on the area of each square centimeter of a stainless steel mesh in an experiment₂O₅The loading capacity of the membrane is about 1-1.5 mg, the membrane is placed in an oven for drying at constant temperature for 10min, and the membrane is taken out and fixed on the assembled membrane component;

(2) constructing an atmospheric pollution environment simulation system of stainless steel: the photoelectrocatalysis membrane component is divided into two chambers by a proton exchange membrane, and 0.5mol/L K is placed in one chamber₂SO₄The solution is used as electrolyte, and the copper wire is inserted into the electrolyte; the other chamber is fixedly provided with a stainless steel mesh coated with a nano catalyst, so that the nano catalytic material is directly exposed to gas-phase pollutants and is in contact with the pollutants, a visible light source is arranged at a distance of 6-8 cm from the membrane component, the two poles of the chamber are connected with an external resistor through a lead by using crocodile clips to form a closed loop, and the lamp is used for simulating sunlight; when the microbial fuel cell is coupled, the electrolyte solution is replaced by a solution containing electrogenic microbes, and the carbon rod replaces a copper wire to lead out the electricity generated by the electrogenic microbes.

The gas-phase pollutant is ammonia pollutant in the odor pollution.

The invention has the beneficial effects that: the system integrates the synergistic effects of electrocatalysis, photocatalysis and coupling microorganisms, and toxic ammonia gas in the air is degraded and removed; the nano catalyst can quickly adsorb and catalytically degrade ammonia in the air, and the system has obvious purification effect and good stability in a catalytic system and provides scientific support for controlling pollution of other gases such as later catalytically degraded ammonia.

Drawings

FIG. 1 is a graph comparing the degradation effects of ammonia gas measured in five different systems, dark adsorption, Photocatalysis (PC), Electrocatalysis (EC), Photoelectrocatalysis (PEC) and photoelectrocatalysis coupled microorganism (PMFC). In the figure, the abscissa represents time (min) and the ordinate represents degradation rate c/c₀。

FIG. 2 is 100ppm (2 μ LNH)₃·H₂O) comparison graph of photocatalytic degradation effect of ammonia gas on different conductive substrates. In the figure, the abscissa represents time (min) and the ordinate represents degradation rate c/c₀。

FIG. 3 is a comparison chart of the effect of the system in degrading and purifying ammonia gas under the action of different applied voltages, wherein the abscissa represents time (min) and the ordinate represents degradation rate c/c₀。

Detailed Description

The following further describes the specific embodiments of the present invention with reference to the technical solutions and the accompanying drawings.

The first embodiment is as follows: removal of ammonia gas under different systems

Putting the membrane module into a stainless steel reactor system, and injecting 2 mu LNH into the membrane module₃·H₂O(100ppm NH₃) And a small fan fixed in the system is opened before reaction, so that ammonia gas can be quickly volatilized and fully mixed in the system, and membrane modules of different systems are exposed in an ammonia gas atmosphere to treat and degrade the ammonia gas. And detecting the ammonia concentration in the system by using an ammonia portable detector every 10min in the treatment process, wherein the reaction time is 65min, and calculating the ammonia removal efficiency. Under different systems, the membrane module and the external circuit are different in connection and illumination control:

dark adsorption system: 2 percent of Sn-V with a nano catalyst₂O₅The membrane is fixed on the membrane component and placed in a stainless steel reaction system without illumination, and an external resistor is not connected by a lead;

a photocatalytic system: the light irradiation is carried out, and other conditions are the same as those of a dark adsorption system;

electrocatalytic system: the catalytic membrane component is divided into two chambers by a proton exchange membrane, and a copper bar is inserted into one chamber to connect with the electrolyte of 0.5mol/L K₂SO₄An anode of the solution; the other chamber is fixedly provided with a stainless steel mesh coated with a catalyst, and is respectively connected with two stages of a copper wire and the stainless steel mesh by using a crocodile clip, and the two electrodes are connected with an external resistor through a lead to form a closed circuit without illumination;

a photoelectrocatalysis system: the treatment of the photoelectrocatalysis membrane component is the same as that of an electrocatalysis system, and illumination is applied;

a photoelectrocatalysis coupling microbial fuel cell system: one chamber of the photoelectrocatalysis membrane component uses nutrient solution containing electrogenesis microorganism to replace electrolyte solution, and simultaneously uses carbon rod to replace copper rod to conduct electricity to the other electrode, and other conditions are the same as those of a photoelectrocatalysis system.

In FIG. 1, the EC system removal effect is best at 94.58%, indicating that the nano photocatalytic material Sn-V₂O₅The performance is superior under the electric excitation and is far higher than that of a photocatalytic system (the removal efficiency is 82.2%); and the PC-MFC system has higher overall degradation efficiency compared with the PEC system.

Example two: photocatalytic degradation of ammonia on different conductive substrates

2% Sn-V of 8 mg nanometer catalyst₂O₅Dispersing in 30uL of silica sol solution, mixing, coating on different conductive substrates to form photocatalytic membrane electrodes, placing photocatalytic membrane electrodes and natural light lamps in a stainless steel reaction system, sealing the system, and injecting 2.0uL ammonia (100ppm NH)₃) And opening a fan in the system before reaction to enable the ammonia water to be quickly volatilized and continuously and uniformly mixed, opening a light source during reaction, detecting the concentration of the ammonia gas in the system by using an ammonia gas portable detector every 10min after the reaction is started, wherein the reaction time is 65min, and calculating the removal efficiency of the ammonia gas.

In fig. 2, the conductive substrate includes carbon felt, carbon fiber cloth, stainless steel mesh and conductive glass, and the carbon felt in the four conductive substrates has too strong adsorbability to clearly determine the photocatalytic degradation effect of the nanomaterial on ammonia; the degradation effects of the rest three are also different, and the degradation rate is as follows: carbon fiber cloth > stainless steel net > conductive glass, compare carbon fiber cloth, the electrically conductive respond well of stainless steel net, and convenient to use.

Example three: removing ammonia gas under the action of different applied electric forces

In a stainless steel reaction system, a membrane component is placed in the system, a copper rod in an electro-catalysis system is replaced by a carbon rod, the carbon rod is placed in an electrolyte anode separated by a proton exchange membrane, a stainless steel mesh membrane coated with a photocatalyst contacts ammonia gas, two stages of external resistors and an external direct current power supply are connected by alligator clips respectively, gas in the system is mixed by a small fan, a light source is closed during reaction, after the reaction begins, an ammonia gas portable detector is used for detecting the concentration of the ammonia gas every 10min, the reaction is carried out for 65min totally, and the removal rate of the ammonia gas is calculated.

In fig. 3, under different applied voltages, the efficiency (> 94%) of the applied power for removing ammonia gas in the enclosed space is not greatly related to the voltage value (0.5V-2.0V). The degradation efficiency of the nano-catalyst is also shown to be remarkably improved under the excitation of an electric field.

Claims

1. the application of the nano-catalyst of a kind of efficient degrading ammonia pollutant, is characterized in that,

Preparation of nanocatalyst x% Sn-V ₂ O ₅ : Synthesis of Sn-doped V ₂ O ₅ nanoparticles by sol-gel method at low temperature; the synthesis process is as follows: First, under stirring condition, the V ₂ O ₅ powder Add deionized water and 30wt% H ₂ O ₂ into a mixed solution, wherein the molar ratio of H ₂ O ₂ and V ₂ O ₅ is 10:1 to form a 0.3MV ₂ O ₅ solution; the obtained V ₂ O _5. The solution was stirred at room temperature for 20min, and then ultrasonically treated for a period of time; then, the _V2O5 solution was further diluted to a solution concentration of not less _than 0.07M, and then further ultrasonicated for 90min at a temperature of 60-45°C; after ultrasonication , the obtained brown-red V ₂ O ₅ gel was diluted; the concentration of the diluted solution was kept between 0.037 and 0.027 M, and then the solution was stirred until the color became transparent brick red; the solid SnCl ₄ ·5H ₂ O was dissolved in a small amount of deionized water to form a solution, which was mixed with the obtained V ₂ O ₅ brick red transparent solution; then heated and stirred in a water bath for 3 hours to make the solution gel until it dried; then dried at room temperature, ground, Sieve to obtain nano-Sn-V ₂ O ₅ composite, which is a nano-catalyst; wherein, x% is the mass ratio of Sn to V ₂ O ₅ , and x takes 1 to 6;

The application of the nanocatalyst is:

(1) Preparation of photoelectric catalytic membrane module: Add silica sol to the prepared nano-Sn-V ₂ O ₅ composite, control the concentration of silica sol to be 4 μL/㎎, stir evenly, and apply it to the pretreated stainless steel conductive carrier In the experiment, the nano-catalyst Sn-V ₂ O ₅ loading amount per square centimeter of the stainless steel mesh was 1-1.5 mg, put it in an oven to dry at a constant temperature for 10 min, and then take out and fix the membrane on the assembled membrane module;

(2) Construction of a stainless steel atmospheric pollution environment simulation system: the photoelectric catalytic membrane module is divided into two chambers through a proton exchange membrane, one chamber is filled with 0.5mol/LK ₂ SO ₄ solution as the electrolyte, and the copper wire is inserted into the electrolyte; the other chamber A stainless steel mesh coated with nano-catalyst is fixed, so that the nano-catalyst material is directly exposed to gas-phase pollutants and contacts with pollutants. A visible light source is placed at a distance of 6-8 cm from the membrane module. The resistance is connected to form a closed loop, and the lamp is used to simulate sunlight; when the microbial fuel cell is coupled, the electrolyte solution is replaced with a solution containing electricity-producing microorganisms, and the electricity generated by the electricity-producing microorganisms is exported by carbon rods instead of copper wires.

2 . The application according to claim 1 , wherein the gas-phase pollutants are ammonia gas pollutants in odor pollution. 3 .