CN1887416A

CN1887416A - Microwave process and application of foamed nickel supported and modified nanometer TiO2

Info

Publication number: CN1887416A
Application number: CN 200610085775
Authority: CN
Inventors: 丁震; 陈晓东; 陈连生; 林萍
Original assignee: JIANGSU DISEASE PREVENTION CONTROL CENTRAL
Current assignee: JIANGSU DISEASE PREVENTION CONTROL CENTRAL
Priority date: 2006-06-30
Filing date: 2006-06-30
Publication date: 2007-01-03

Abstract

The present invention discloses microwave heating process for preparing nanometer TiO2 photocatalyst, and the nanometer TiO2 photocatalyst is modified through mixing metal ion and supported with foamed nickel when used in degrading formaldehyde gas and volatile organic matter. Transparent TiO2 sol is prepared through hydrolyzing organic titanium precursor with alkoxyl titanium or through treating inorganic titanium precursor in a coprecipitation-peptization process, and during the preparation, AgNO3 and La(NO3)3 .nH2O in different ratios are added. After loaded on foamed nickel plate as carrier, the TiO2 sol is calcined at 250 deg.c under air atmosphere inside a muffle furnace for 1 hr to obtain foamed nickel plate with supported modified nanometer TiO2 photocatalyst. The present invention has high photocatalysis efficiency, and may be used in degrading formaldehyde gas and volatile organic matter in the air effectively.

Description

Microwave preparation of foamed nickel loaded modified nano TiO2Method and application of

Technical Field

The invention belongs to the fields of chemistry and chemical engineering and environmental protection, and particularly relates to a method for loading modified nano TiO on metal foam nickel by using microwaves₂The preparation method of the photocatalyst can effectively remove the pollution of formaldehyde and volatile organic pollutants (VOCs) in indoor air.

Background

The discovery of nano TiO in 1972₂Since the photocatalysis phenomenon, the nano photocatalysis technology is developed rapidly, and has the advantages of mild reaction conditions, low energy consumption, less secondary pollution, capability of oxidizing and decomposing organic matters with stable structures at normal temperature and normal pressure, and the like. The heterogeneous photocatalytic oxidation technology has been attracting attention of researchers. Research in recent years shows that many organic pollutants which are difficult to degrade, such as halogenated hydrocarbons, organic phosphorus compounds, pesticides, surfactants, organic dyes and the like, can obtain obvious degradation effect under the photocatalytic oxidation effect. Current research indicates that the compounds are useful as photocatalytic semiconductors (including TiO)₂、ZnO、CdS、PbS、WO₃、MoO₃And SnO₂) The catalytic ability of (2) is related to its energy level structure, and in general, the larger the forbidden band width, the stronger the catalytic oxidation ability. From the viewpoint of forbidden energy level, the photocatalytic activity sequence of these above conventional semiconductor materials is TiO₂＞ZnO＞WO₃Due to TiO₂Has the advantages of strong oxidation-reduction property, good chemical property stability, no secondary pollution, no toxicity, indissolvability, safety, low cost and the like, and is one of green and environment-friendly catalysts with development prospect, so that the TiO is₂The photocatalytic oxidation technology has great application potential.

The current research is focused on the reduction of nano TiO by treatment during the preparation phase₂Grain size of the crystal grains, increasing TiO₂Increasing the degree of lattice distortion and expansion of TiO₂The photocatalytic efficiency of the photocatalyst; on the other hand, nano TiO₂The photocatalyst is supported on different carrier materials to obtain higher photocatalytic efficiency, and the commercial TiO is prepared by Fumihide in Japan₂Loaded on honeycomb ceramic material and matched with activated carbon for useDegradation of Formaldehyde gas (Chem Eng Sci, 2003, 58 (6): 929), Ichiura uses textile printing technology to deposit TiO₂Supported on zeolite flakes degrades organic contaminants (chemisphere, 2003, 50 (5): 673), but these materials act as a support for liability and lower photocatalytic efficiency due to the low amount of photocatalyst that is not highly porous.

Through the search of the prior patent documents, the following results are found: chinese patent: CN 1394675A discloses a flexible substrate material surface loaded with TiO₂A process for preparing the film photocatalyst includes such steps as preparing the sol of active layer from n-butyl titanate or titanium tetrachloride as precursor, adding pore-forming agent, coating the sol of active layer on the cleaned flexible substrate, centrifugal removing excess sol, loading the flexible substrate in hydrothermal reactor, and low-temp preparing nano-class TiO by using water-alcohol as mixed solvent₂A thin film photocatalyst. Chinese patent: CN 1712131A discloses a foam metal loaded TiO₂The preparation method of the nanometer photocatalysis net is characterized in that a foam metal sheet is used as a carrier, before a photocatalysis active component is loaded, an inert material is loaded on the foam metal sheet to be used as a transition intermediate layer, then the foam metal sheet is impregnated with sol which uses tetrabutyl titanate or titanium tetrachloride or titanium trichloride as a precursor, and the supported photocatalysis net is prepared through drying and calcining.

So far, the application of microwave heating technology to nano TiO has not been searched₂Research report on preparation process of photocatalystAnd (4) carrying out the following steps.

Disclosure of Invention

The invention provides a metal foam nickel loaded nanometer TiO₂Method for preparing photocatalyst, and method for preparing metal ion-doped TiO by hydrolysis of alkoxy titanium and chemical coprecipitation₂Sol, heating and calcining at lower temperature by using a microwave muffle furnace to prepare TiO loaded on the surface of the foamed nickel₂The film, the carrier material has high removal efficiency on typical organic pollutants of formaldehyde and Volatile Organic Compounds (VOCs) caused by indoor air decoration, and the specific preparation stepsComprises the following steps:

1.TiO₂preparation of the Sol

TiO of the invention₂The sol is prepared by two methods respectively: a hydrolysis method of alkoxy titanium by taking organic titanium as a precursor and a chemical coprecipitation-peptization method by taking inorganic titanium salt as a precursor.

With tetra-n-butyl titanate [ Ti (OC)₄H₉)₄]Preparing pure TiO by hydrolysis of alkoxy titanium as precursor₂Sol and TiO modified by Fe, Ag and La ions₂And (3) sol. The alkoxy hydrolysis method is characterized in that titanium alkoxide (titanate) is used as a raw material, anhydrous low-carbon alcohol (ethanol, n-butyl alcohol and isopropanol) is used as an organic solvent, and the raw material and a certain amount of acidified water are hydrolyzed together. The method adopts inorganic strong acid for catalysis, and a small amount of titanium alkoxide-alcohol solution is dripped into a large amount of water, so that the titanium alkoxide is fully hydrolyzed in an excessive water medium to generate [ Ti (OH)₆]^2-The ions and the hydrolysate are controlled in an acidic condition, the generated nucleating particles have positive charges, and the dispersed particles are mutually repelled due to the action of an electric double layer, so that stable TiO can be finally formed₂A hydrosol.

The hydrolysis and polycondensation reaction of butyl titanate is as follows:

chemical coprecipitation-peptization method for preparing TiO₂Is characterized in that cheap inorganic titanium source TiCl can beused₄(or titanium disulfide) is used as a starting material, and the reaction condition is mild and is basically carried out under the conditions of normal temperature and normal pressure. TiCl can be inhibited by mainly controlling the reaction temperature and pH value₄And then Ti (OH)₄The precipitation rate of (a), which directly affects the particle size and stability of the sol system; the peptization aging process will directly affect the crystal structure integrity of the sol nanoparticles.

The reaction equation is as follows:

(light yellow solution)

(white precipitate)

(acid clear Sol)

(Sol particles crystallized by oxygen bridge combination)

(neutral transparent Sol)

2. Carrier pretreatment and coating method

Ultrasonically cleaning a foamed nickel plate in ethanol for 15min, drying in a constant-temperature air-blast drying oven, and soaking in the prepared TiO₂In the sol, a soaking-pulling method is adopted to plate a film on the foamed nickel, the film is pulled at the speed of 5mm/s, and after the film is completely pulled, the film is dried in a blast drying oven for 15min at the temperature of 80 ℃, and the process is repeated for 2 times.

3. Putting the dried and coated foam nickel plate into an American PHOENIX microwave muffle furnace, calcining for 1h at the temperature rising rate of 30 ℃/min at the temperature of 250 ℃ in air atmosphere to prepare the supported nano TiO₂A thin film nickel foam sheet.

4. The photocatalysis effect experiment is carried out in the experiment chamber, and the specification of the experiment chamber is as follows: 30cm x 30cm, 27L volume of organic glass cabin lined with polytetrafluoroethylene, photocatalytic reactor placed in the cabin: a cubic glass box with a square cross section, a side length of 8cm and a length of 20cm, wherein one end of the cubic glass box is provided with a fan, and 2 loaded nano TiO chips are obliquely inserted in the middle₂The foamed nickel of the photocatalyst is added with an ultraviolet lamp tube (power 13W, characteristic wavelength 254nm, ultraviolet light intensity 19.85 mw/cm) in the middle of a 2-layer plate²). A certain amount of formaldehyde and volatile organic gases were generated in the chamber, respectively, and the experiment was conducted for 90min, and the change in the concentration of pollutants in the chamber was tested using a uk ppm400 formaldehyde tester and a us PGM-7240 VOCs tester.

Drawings

FIG. 1 shows TiO of the present invention₂Transmission Electron Microscopy (TEM) and electron diffraction patterns of the sol;

FIG. 2 shows the preparation of lanthanum-doped 1.5% TiO using microwave in accordance with the present invention₂Transmission Electron Microscope (TEM) and electron diffraction patterns of the powder;

FIG. 3 shows the preparation of lanthanum-doped 1.5% TiO using microwave in accordance with the present invention₂X-ray diffraction (XRD) pattern of the powder;

FIG. 4 shows the loading of lanthanum-doped 1.5% TiO prepared by microwave according to the invention₂Scanning photographs (SEM) and energy spectrum analysis (XPS) of the foamed nickel surface.

Detailed Description

Example 1:

1. adding 25mL of butyl titanate into 8mL of isopropanol, and fully and uniformly mixing; preparing 200mL deionized water solution containing 2mL and 70 wt% nitric acid, and adding silver nitrate (AgNO) into dilute nitric acid solution₃]Wherein the mass ratio of Ag to Ti is 1.5%, adding 0.5mL of acetylacetone chelating agent and 1.Og of polyethylene glycol (PEG1500) organic polymer; slowly dripping the organic alcohol titanium acid mixed solution into the aqueous solution at the speed of 1 drop per second under the condition of high-speed stirring, and simultaneously controlling the temperature of the reaction solution to be about 70 ℃ by using a constant-temperature water bath until the butyl titanate is completely hydrolyzed. Adjusting the pH value to 3, continuously stirring for 12h, peptizing at room temperature and aging for 24h to finally form transparent TiO₂And (3) sol.

2 pieces of metal foam nickel plates which are ultrasonically cleaned by ethanol are soaked in the prepared TiO₂Pulling the sol at a speed of 5mm/s, taking out, drying in a forced air drying oven at 80 ℃ for 15min, repeating the process for 2 times, putting the dried and coated foam nickel plate into an American PHOENIX microwave muffle furnace, calcining at the temperature of 250 ℃ in air atmosphere at the temperature of 30 ℃/min for 1h to obtain the loaded nano TiO₂A thin film nickel foam sheet.

The prepared loaded nano TiO is used in an experimental cabin₂Photocatalytic degradation of formaldehyde and Volatile Organic Compounds (VOCs) by using foamed nickel plate of photocatalystThe test is carried out for 90min, and the initial concentration of the generated formaldehyde gas is 1.03mg/m³After 90min of reaction, the first part is removedThe aldehyde concentration was 0.14mg/m³The degradation rate is 89%; initial concentration of VOCs 4.05mg/m occurs³The concentration of VOCs after 90min of reaction is 0.76mg/m³And the degradation rate is 85 percent.

Example 2:

with the same TiO as in example 1₂The sol preparation process is characterized by adding lanthanum nitrate La (NO) into dilute nitric acid water solution₃)₃·nH₂O]Wherein the La/Ti mass ratio is 1.0 percent, and the photocatalytic degradation experiment is also carried out to obtain the formaldehyde concentration of 0.12mg/m after the reaction is carried out for 90min³The degradation rate is 89%; initial concentration of VOCs 4.04mg/m occurs³The concentration of VOCs after 90min of reaction is 0.82mg/m³And the degradation rate is 80 percent.

Example 3:

with the same TiO as in example 1₂The sol preparation process is characterized by adding lanthanum nitrate La (NO) into dilute nitric acid water solution₃)₃·nH₂O]Wherein the La/Ti mass ratio is 1.5 percent, and the photocatalytic degradation experiment is also carried out to obtain the formaldehyde concentration of 0.06mg/m after the reaction is carried out for 90min³The degradation rate is 94%; initial concentration of VOCs 4.08mg/m occurs³The concentration of VOCs after 90min of reaction is 0.54mg/m³And the degradation rate is 87 percent.

Example 4:

50mL of TiCl was taken₄Dropwise adding the mixture into 100mL of deionized water at 5 ℃, and adding lanthanum nitrate [ La (NO) into the water₃)₃·nH₂O]Wherein the La/Ti mass ratio is 1.5%, stirring at high speed while adjusting TiCl₄The dropping speed of the liquid is controlled by using an ice water bath to control the temperature of the reaction liquid to be 50-60 ℃ until a light yellow transparent liquid is formed. To ensure TiCl₄The hydrolysis reaction is completed, and 10 percent ammonia water diluted solution is slowly dripped into the TiCl₄Fully stirring the hydrolysate, and finally adjusting the pH value to 10.0 to finally form white precipitate. For removing inorganic salt ammonium ion (NH)₄ ⁺) And chloride ion (Cl)^-) Washing the precipitate with deionized water, suction filtering, and reactionWashing for several times until the pH value of the filtrate is lower than 7.5; dispersing the precipitate in deionized water to form suspension system, regulating pH of water dispersion phase to 1.5 with 10% hydrochloric acid or nitric acid solution, stirring at room temperature for 12 hr, aging for 24 hr to obtain uniform and transparent TiO₂And (4) diluting the sol.

The prepared loaded nano TiO is used in an experimental cabin₂The foam nickel plate of the photocatalyst is subjected to an experiment of photocatalytic degradation of formaldehyde and Volatile Organic Compounds (VOCs) for 90min, and the initial concentration of generated formaldehyde gas is 1.02mg/m³The concentration of formaldehyde after 90min of reaction is 0.08mg/m³The degradation rate is 92 percent; initial concentration of VOCs 4.11mg/m occurs³The concentration of VOCs after 90min of reaction is 0.61mg/m³And the degradation rate is 85 percent.

Claims

1. Metallic foam nickel loaded nano TiO₂The preparation method of the photocatalyst is characterized in that the metal ion-doped TiO is prepared by alkoxy titanium hydrolysis method and chemical coprecipitation method₂Sol is catalyzed by inorganic strong acid, the reaction temperature is controlled at 60-70 ℃, and TiO is loaded by microwave heat treatment₂Foamed nickel plate of photocatalyst.

2. The modified nano TiO for treating formaldehyde gas and Volatile Organic Compounds (VOCs) according to claim 1₂The preparation method of the photocatalyst is characterized in that the optimal doped metal ion is La³⁺The optimum doping ratio is 1.5% (La/Ti mass ratio).

3. The method of claim 1Of nano TiO₂The preparation method of the photocatalyst is characterized in that the supported nano TiO is heated and treated by a microwave muffle furnace₂The temperature rise rate of the foam nickel plate of the photocatalyst is 30 ℃/min, and the foam nickel plate is calcined for 1h at the temperature of 250 ℃ in the air atmosphere.