CN104131308A - Preparation method for bismuth tungstate - Google Patents

Abstract

The invention discloses a preparation method of bismuth tungstate. The production of bismuth tungstate is completed through an electrochemical process, which specifically includes the following steps: 1) bismuth material is used as an anode, and a platinum sheet is used as a cathode, which is inserted into a tungsten source electrolyte; 2) The electrolyte is energized until there is a continuous electric spark on the surface of the bismuth material, and the energization is maintained for at least 30s, and the current intensity is at least 0.01A. The precipitation in the electrolyte or the bismuth material with a deposited layer is washed and dried to obtain bismuth tungstate powder or film . The preparation method disclosed by the invention has the advantages of simple process, low cost, environmental friendliness, and can effectively control the phase composition of the product.

Description

The preparation method of bismuth tungstate

technical field

The invention relates to a preparation method of bismuth tungstate, belonging to the field of inorganic non-metallic materials.

Background technique

Bismuth tungstate is a kind of environment-friendly functional material, mainly including Bi ₂ WO ₆ , Bi _3.84 W _0.16 O _6.24 , Bi ₁₄ W ₂ O ₂₇ and other phases _. Its photoelectric, fluorescent and piezoelectric properties, its powder or thin film materials have broad application prospects in the field of optoelectronics, especially photocatalytic materials.

At present, the preparation methods of bismuth tungstate mainly include the following types:

1. The solid-phase synthesis method, which is used for the preparation of bismuth tungstate powder, requires a complicated synthesis process. The synthesis temperature of the whole process is high and the energy consumption is large, so it is no longer commonly used.

2. The hydrothermal/solvothermal synthesis method is used for the preparation of bismuth tungstate powder, but it cannot be used for the preparation of thin films. Compared with the traditional solid-phase synthesis method, the synthesis temperature (80-230°C) is lowered, but the synthesis time is longer, requiring high-temperature annealing treatment, and the preparation process can be completed in nearly 20 hours, and the preparation efficiency is very low.

3. For the preparation of bismuth tungstate thin films, sol-gel method (sol-gel), metal-organic decomposition method (MOD) and chemical solution decomposition method (CSD) are mainly used. The thin film process of these methods is complex, including steps such as the preparation of the precursor solution, spin coating method membrane, annealing treatment, need to use special equipment such as spin coater, muffle furnace, increased production cost; also involve a large amount of organic reagents in the preparation process The use and removal of the preparation process is cumbersome, and if the intermediate product is not treated, it will have an adverse impact on the environment, which is not conducive to popularization and application. In the above process, there are various influencing factors such as raw material preparation, precursor solution concentration, homogenization speed, annealing condition (400-600°C), etc., and it also involves the use and removal of a large amount of organic matter, which complicates the preparation process and cannot be effectively Control the quality of the product.

Therefore, there is no preparation process that can be used for bismuth tungstate powder and film at the same time in the prior art, and more critically, there is no preparation process with high preparation efficiency and mild process conditions in the prior art.

Contents of the invention

Aiming at the defects of the prior art, the present invention discloses a preparation method of bismuth tungstate. Based on the electrochemical process, the preparation of powder or film is realized through the anode spark discharge technology, which has the advantages of low synthesis temperature, short reaction time, and synthesis process Simple, controllable phase composition of the product and other advantages.

To achieve the above object, the present invention is achieved through the following technical solutions:

The preparation method of bismuth tungstate comprises the following steps: 1) the bismuth material is used as the anode, and the platinum sheet is used as the cathode, and inserted into the tungsten source electrolyte; At least 30s, the current intensity is at least 0.01A, wash and dry the precipitate in the electrolyte or the bismuth material with the deposited layer, and then obtain the bismuth tungstate powder or film.

Through the above-mentioned process, the preparation of bismuth tungstate is usually completed within 5 to 10 minutes of electrification. At the same time, the above-mentioned process can be used to prepare bismuth tungstate powder and film at the same time. conduct.

Wherein, the size of the electrodes used above is a common specification in the field of electrochemistry, generally 8 cm×4 cm×0.1 cm, and other sizes can also be reasonably adjusted according to the scale of industrial production.

Among them, the current intensity can be adjusted according to needs, and in actual industrial production, it is usually 0.5A or even greater current, but the current intensity is limited by the type of power supply.

Among them, in order to prevent impurities, the anode and the cathode can be cleaned in advance, such as grinding the bismuth material sequentially with sandpaper of different meshes. Cleaning with ethanol to remove oil, etc.; in addition, simple cleaning with organic solvents is also acceptable. The need for pretreatment depends on the electrode used.

Wherein, the electrolytic cell used to accommodate the electrolyte can be any available electrolytic cell in the field of electrochemistry, such as a double-layer glass type electrolytic cell.

In the present invention, the bismuth material used in step 1) is elemental bismuth or bismuth-tungsten alloy or other alloy materials containing bismuth elements; the tungsten source electrolyte used is that the tungsten source is added to water, and the tungsten source used is sodium tungstate, tungsten Ammonium Oxide or Tungstic Acid.

In order to ensure that the electrolyte has a certain pH, it also includes the step of adding an inorganic alkali solution to the tungsten source electrolyte to adjust the acidity and alkalinity, adjusting the concentration of tungstate to 0.01-0.80mol/L, and the concentration of OH ^- to 0.1-2.0mol/L .

Wherein, the above-mentioned inorganic bases include but not limited to sodium hydroxide, potassium hydroxide and the like.

In order to adjust the composition of bismuth tungstate, it also includes the step of adding small molecule organic alcohol (including but not limited to methanol, ethanol, ethylene glycol, propanol, etc.) to the tungsten source electrolyte to adjust the dielectric constant of the electrolyte, usually The dielectric constant is adjusted to 52.4~74.8.

In the present invention, the distance between the anode and the cathode is 0.5-5 cm, and the depth of immersion in the electrolyte is 1-6 cm; preferably, the distance between the anode and the cathode is 1-3 cm, and the depth of immersion in the electrolyte is 2-6 cm. 4cm.

In order to speed up the reaction speed and obtain powder, step 2) also includes the step of stirring or ultrasonicating the tungsten source electrolyte during the electrification process.

Wherein, if magnetic stirring is used, the stirring intensity is preferably 600-800 rpm; if ultrasonic is selected, the ultrasonic intensity is preferably 1-1.2 W/cm ² .

If it is only necessary to prepare a thin film, the above-mentioned stirring or ultrasonic process is not required, and a bismuth tungstate deposition layer can be formed on the surface of the bismuth material through the reaction.

In the present invention, the energy required for the generation of bismuth tungstate comes from the electric spark in the tiny area on the surface of the anode, the overall temperature of the electrolyte is lower than 100°C, and the electrolyte can be kept at room temperature under the condition of circulating water cooling, effectively reducing the At the same time, the entire preparation process does not use complex organic solvents in traditional processes, which avoids environmental pollution and simplifies the synthesis process; the entire electrification process can be completed within 5-10 minutes at the longest, greatly shortening The preparation time is shortened and the production efficiency is improved.

Detailed ways

In the following implementations, the shapes of the anode and cathode are not limited, and conventional shapes such as plates, rods, foils, sheets, tubes, and nets or special-shaped pieces are all available.

Example 1

The elemental bismuth sheet was used as the anode and the cathode was kept at a distance of 1.2cm, vertically immersed in the electrolyte solution for 2cm, and a constant current I=3A was passed and maintained for 5min. During this process, electric sparks continued to appear on the surface of the bismuth material. Stir the electrolyte with strong magnetic force or ultrasonic, and precipitates will form in the solution. Wash the precipitated or deposited bismuth material with deionized water, dry at 60°C, and set aside.

Among them, the electrolyte is sodium tungstate dissolved in deionized water, and NaOH solution is added to adjust the alkalinity. After ultrasonication for 5 minutes, the electrolyte is obtained, wherein the concentration of tungstate is 0.2mol/L, and the concentration of OH ^- is 0.15mol/L.

If magnetic stirring is used, the intensity of stirring is preferably 600-800 rpm; if ultrasound is selected, the intensity of ultrasound is preferably 1-1.2 W/cm ² .

In this case, irregular granular nanoscale powder can be prepared, and its composition is mixed phase: Bi ₂ WO ₆ +Bi _3.84 W _0.16 O _6.24 , with an average particle size of 20-60nm

Example 2

Keep a distance of 2cm between the anode and the cathode, vertically immerse in the electrolyte (the electrolyte contains alcohol substances) for 3cm, pass a constant current I=5A and maintain it for 3min, during which electric sparks continue to appear on the surface of the bismuth material. Stir the electrolyte with strong magnetic force or ultrasonic, and precipitates will form in the solution. Wash the precipitated or deposited bismuth material with deionized water, dry at 60°C, and set aside.

Among them, the electrolyte is to dissolve ammonium tungstate in deionized water, and add KOH solution to adjust the alkalinity. After ultrasonication for 10 minutes, the electrolyte is obtained, in which the concentration of tungstate is 0.45mol/L, and the concentration of OH ^- is 0.8mol/L. Then add ethanol to adjust the dielectric constant to 63.6.

In this case, granular pure-phase nanoscale powder can be prepared, the composition of which is: Bi _3.84 W _0.16 O _6.24 , and the average particle diameter is 20-30nm.

Example 3

Keep a distance of 3cm between the anode and the cathode, vertically immerse in the electrolyte solution for 4.7cm, pass a constant current I=0.5A and maintain it for 3min, during which electric sparks continue to appear on the surface of the bismuth material. When the electrolyte is stirred weakly or without stirring (preferably without stirring), deposits are formed on the surface of the bismuth material. The bismuth material with the deposited layer was washed with deionized water, dried at 60°C, and set aside.

Among them, the electrolyte is to dissolve tungstic acid in deionized water, and add KOH solution to adjust the alkalinity. After ultrasonication for 10 minutes, the electrolyte is obtained, in which the concentration of tungstate is 0.75mol/L, and the concentration of OH ^- is 1.8mol/L.

In this case, a light yellow bismuth tungstate coating can be prepared, and its composition is a mixed phase, namely: Bi ₂ WO ₆ +Bi _3.84 W _0.16 O _6.24 . The surface of the coating is found to be composed of nano-sized particles (average 30nm) And micropores (100 ~ 400nm).

Example 4

Keep a distance of 3 cm between the anode and the cathode, vertically immerse in the electrolyte (the electrolyte contains alcohol substances) for 4 cm, pass a constant current I=4A and maintain it for 3 minutes, during which electric sparks continue to appear on the surface of the bismuth material. Ultrasonic is performed on the electrolyte solution with an ultrasonic intensity of 1.2 W/cm ² , and precipitates are formed in the solution. The precipitate was washed with deionized water and dried at 70°C.

Among them, the electrolyte is to dissolve ammonium tungstate in deionized water, and add KOH solution to adjust the alkalinity. After ultrasonication for 8 minutes, the electrolyte is obtained, wherein the concentration of tungstate is 0.5mol/L, and the concentration of OH ^- is 0.7mol/L; Then add ethanol to adjust the dielectric constant to 55.3.

In this case, granular pure-phase nanoscale powder can be prepared, the composition of which is: Bi _3.84 W _0.16 O _6.24 , and the average particle diameter is about 20nm.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention within.

Claims (7)

1. the preparation method of bismuth tungstate, is characterized in that comprising the steps: 1) bismuth material, is inserted in the electrolytic solution of tungsten source as negative electrode as anode, platinized platinum; 2) tungsten source electrolytic solution is energized to bismuth material surface and continues there is electrical spark, maintains at least 30s that switches on, and strength of current is at least 0.01A, by the precipitation in electrolytic solution or with the bismuth material washing of settled layer, dry, obtains bismuth tungstate powder or film.

2. according to the preparation method of claim 1, it is characterized in that step 1) bismuth material used is bismuth with elementary or bismuth-tungstenalloy or other alloy material that contains bismuth element; Tungsten used source electrolytic solution is that tungsten source is added to the water, and tungsten used source is sodium wolframate, ammonium tungstate or wolframic acid.

3. according to the preparation method of claim 2, characterized by further comprising to tungsten source electrolytic solution and add inorganic alkali solution to adjust the step of acid-basicity, being adjusted to wolframate radical concentration is 0.01～0.80mol/L, OH ^-concentration is 0.1～2.0mol/L.

4. according to the preparation method of claim 2, characterized by further comprising to tungsten source electrolytic solution and add small molecules Organic Alcohol to regulate the step of the specific inductivity of electrolytic solution, adjust specific inductivity and be adjusted to 52.4～74.8.

5. according to the preparation method of claim 1, it is characterized in that the distance between anode and negative electrode is 0.5～5cm, the degree of depth that immerses electrolytic solution is 1～6cm.

6. according to the preparation method of claim 1, it is characterized in that the distance between anode and negative electrode is 1～3cm, the degree of depth that immerses electrolytic solution is 2～4cm.

7. according to the preparation method of claim 1, it is characterized in that step 2) in galvanization, tungsten source electrolytic solution is stirred or ultrasonic step.