CN102618932B - Method for preparing basic ammonium aluminum carbonate hydroxide whisker and aluminum oxide whisker co-production liquid sodium silicate from bentonite - Google Patents

Abstract

The invention discloses a method for preparing basic ammonium aluminum carbonate hydroxide whisker and aluminum oxide whisker co-production liquid sodium silicate from bentonite, which comprises the following steps of: adding sulfuric acid solution to bentonite mineral powder which is taken as an initial raw material; reacting; then performing filtering separation; collecting an acid-leached filtrate and acid-leached filter cakes; adding salpeter solution and isoamyl alcohol to the acid-leached filtrate; performing liquid separation and collecting an aqueous phase to obtain aluminum salt solution; adding urea and a surface active agent to the aluminum salt solution; reacting; then, separating, washing and drying to obtain basic ammonium aluminum carbonate hydroxide whiskers; and calcining the basic ammonium aluminum carbonate hydroxide whiskers to obtain aluminum oxide whiskers. Aluminum oxide and silicon dioxide which are required by the method disclosed by the invention respectively come from bentonite ore, and other industrial raw materials do not need to be adopted, so that the production cost can be effectively reduced. The method disclosed by the invention has the advantages that the recovery rate is high; the yield of the aluminum oxide in the bentonite can reach at least 90 percent; and the yield of the amorphous silicon dioxide can reach at least 95 percent.

Description

A method for producing basic ammonium aluminum carbonate whiskers and aluminum oxide whiskers to co-produce liquid sodium silicate from bentonite

1. Technical field

The invention relates to a method for preparing basic ammonium aluminum carbonate whiskers and aluminum oxide whiskers to co-produce liquid sodium silicate from bentonite, which belongs to the deep processing and comprehensive reuse of bentonite.

2. Background technology

Bentonite is an important non-metallic mineral, and its main valuable elements are aluminum and silicon. my country's bentonite resources are very rich, with good quality and wide distribution, and have great comprehensive utilization value. In recent years, many literatures have reported its comprehensive development and utilization, such as using silicon in it to produce daily chemical additives instant sodium metasilicate, rubber reinforcing agent white carbon black, etc.; using aluminum in it to produce aluminum series Water purifiers (such as polyaluminum chloride, polyaluminum sulfate, polyaluminum silicate sulfate), chemical additives such as ultra-fine aluminum silicate, and are expected to obtain good economic benefits.

Whisker is a kind of fiber material with a certain length-to-diameter ratio grown in the form of a single crystal. Its diameter is small, its atoms are highly ordered, and its strength is close to the theoretical value of a complete crystal. Therefore, it has excellent high temperature resistance, high heat resistance, and Corrosion performance, good mechanical strength, electrical insulation, light weight, high strength, high elastic modulus, high hardness and other characteristics. Flame retardant is an additive that can improve the flame retardancy, self-extinguishing or smoke suppression of flammable or combustible materials. It is one of the main additives for important fine chemical products and synthetic materials. Aluminum ammonium basic carbonate whisker is a new type of aluminum-based flame retardant, which has excellent properties of large gas release, better smoke suppression effect, and large length/diameter ratio. Alumina whisker is a kind of ceramic whisker. It has superior mechanical properties such as high strength and high elastic modulus. It has good compatibility with ceramic matrix materials and has broad application prospects. It is considered to be a very promising inorganic crystal. beard material. At present, basic aluminum ammonium carbonate whiskers are mainly synthesized by hydrothermal method using aluminum nitrate and ammonium alum as raw materials; aluminum oxide whiskers are mostly made of aluminum powder, aluminum nitrate, aluminum sulfate, etc. It is produced by methods such as thermal method, melting method and fluxing method. The raw materials used in the above-mentioned methods are all industrial grade or even reagent grade, and the price of raw materials is relatively expensive, resulting in higher production costs.

So far, there has been no relevant report on the method of preparing basic aluminum ammonium carbonate whiskers and alumina whiskers using bentonite as a raw material.

3. Contents of the invention

The invention aims to provide a method for producing basic ammonium aluminum carbonate whiskers and alumina whiskers to co-produce liquid sodium silicate from bentonite, which has the characteristics of low production cost, easy process control, and high recovery rate of useful components. At the same time, in order to improve the comprehensive utilization value of bentonite, the silicon in it is used to prepare liquid sodium silicate.

The present invention solves technical problem and adopts following technical scheme:

The method for producing basic ammonium aluminum carbonate whiskers and alumina whiskers to co-produce liquid sodium silicate from bentonite in the present invention uses bentonite mineral powder as the initial raw material, including acid leaching, purification, synthesis, calcination and alkali leaching units process, characterized by:

The acid leaching is to add a sulfuric acid solution with a concentration of 15-60wt% of 2.5-5.5 times the mass of the bentonite powder to the bentonite powder with a particle size of less than 200 μm, react at 80-105°C for 2-6 hours, and then filter, separate and collect acid leaching filtrate and acid leaching filter cake, the acid leaching filter cake is washed to neutrality with clear water;

The purification is to add a nitric acid solution with a mass concentration of 60-70% of the volume of the acid leach filtrate of 0.5-1% to the acid leach filtrate, stir and react for 10 minutes, and then add isoamyl alcohol of 0.5-2.0 times the volume of the acid leach filtrate , and the aqueous phase is collected by liquid separation, which is the aluminum salt solution;

The synthesis is to add urea and surfactant to the aluminum salt solution, react at 100-140°C for 18-36 hours, and then obtain basic ammonium aluminum carbonate whiskers after separation, washing and drying; wherein the aluminum salt solution The ratio of the molar weight of aluminum to the molar weight of urea is 1: 1.5-2.5; the surfactant is selected from polyethylene glycol (PEG, number average molecular weight is 200-6000), hexadecyl trimethyl bromide Ammonium chloride (CTAB) or sodium dodecyl sulfate (SDS), added in an amount of 0.1-1.8% of the mass of aluminum in the aluminum salt solution;

The calcination is to calcine the basic ammonium aluminum carbonate whiskers at 800-1200°C for 2-5 hours to obtain alumina whiskers;

The alkali leaching is to add a sodium hydroxide solution with a concentration of 6-25wt% of 2.5-4.5 times the mass of the acid leaching filter cake to the acid leaching filter cake, react at 60-95° C. for 0.5-2 hours, and then filter to obtain The filtrate is liquid sodium silicate.

Each step reaction equation of the inventive method is:

1. Acid leaching of bentonite

Al ₂ O ₃ 4SiO ₂ 3H ₂ O+3H ₂ SO ₄ +(4n-6)H ₂ O→4SiO ₂ nH ₂ O+Al ₂ (SO ₄ ) ₃

Fe ₂ O ₃ +3H ₂ SO ₄ →Fe ₂ (SO ₄ ) ₃ +3H ₂ O

2. Preparation of Basic Aluminum Ammonium Carbonate Whiskers

Al ₂ (SO ₄ ) ₃ +8CO(NH ₂ ) ₂ +4H ₂ O→2NH ₄ [Al(OH) ₂ CO ₃ ]↓+3(NH ₄ ) ₂ SO ₄ +8NH ₄ HCO ₃

3. Preparation of alumina whiskers

2NH ₄ [Al(OH) ₂ CO ₃ ]→Al ₂ O ₃ +2CO ₂ ↑+2NH ₃ ↑+3H ₂ O

4. Alkali leaching of bentonite acid leaching filter cake

m(SiO ₂ nH ₂ O)+2NaOH→Na ₂ O mSiO ₂ +(nm+1)H ₂ O

The concrete steps that the present invention prepares are as follows:

Step 1: Acid Leaching of Bentonite

Add a sulfuric acid solution with a concentration of 15-60wt% of 2.5-5.5 times the mass of the bentonite powder to the bentonite powder with a particle size of less than 200 μm, react at 80-105° C. for 2-6 hours, and then filter to obtain acid leaching filter cake and acid filter cake. The acid leaching filter cake is washed with clear water until neutral, and the acid leaching filter cake, acid leaching filtrate and washing liquid are collected respectively.

Step 2: Purification of pickling solution

Mix the acid leaching filtrate obtained in step 1 with the lotion to obtain a mixed solution, add 0.5-1% of the volume of the mixed solution to the mixed solution and a nitric acid solution with a mass concentration of 60-70%, stir and react for 5-10 minutes, and then add the mixed solution 0.5-2.0 times the volume of isoamyl alcohol, shake repeatedly at room temperature for 10-20min, after static phase separation, the obtained aqueous phase is aluminum salt solution.

Step 3: Preparation of Basic Aluminum Ammonium Carbonate Whiskers

Add urea and surfactant to the aluminum salt solution prepared in step 2, react at 100-140°C for 18-36 hours, and then obtain basic ammonium aluminum carbonate whiskers after separation, washing and drying; wherein aluminum salt solution The ratio of the molar amount of urea to the molar amount of urea is 1:1.5-2.5; the surfactant is selected from PEG, CTAB or SDS, and the added amount is 0.1-1.8% of the mass of aluminum in the aluminum salt solution.

Step 4: Preparation of alumina whiskers

Calcining the basic ammonium aluminum carbonate whiskers obtained in step 3 at 800-1200° C. for 2-5 hours to obtain alumina whiskers.

Step 5: Alkaline leaching of bentonite acid leached filter cake

Add a sodium hydroxide solution with a concentration of 6-25wt% of 2.5-4.5 times the mass of the acid-leached filter cake to the acid-leached filter cake obtained in step 1, react at 60-95° C. for 0.5-2 hours and filter, and the obtained filtrate is a liquid sodium silicate.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1, the inventive method produces basic ammonium aluminum carbonate whisker, aluminum oxide whisker and liquid sodium silicate, has fully utilized the alumina in the bentonite and the useful ingredient of silicon dioxide, and the production process is a closed circuit, basically without the discharge of three wastes.

2, the required aluminum oxide and silicon dioxide of the present invention's method basic formula ammonium aluminum carbonate whisker, aluminum oxide whisker and liquid sodium silicate all come from bentonite ore, need not adopt other industrial raw materials, can make its production cost obtain effective reduction.

3. The present invention utilizes isoamyl alcohol extraction to remove iron to purify the aluminum salt solution, with high iron removal efficiency and almost no loss of aluminum salt.

4. The recovery rate of the present invention is high, the yield of alumina in bentonite can reach more than 90%, and the yield of amorphous silicon dioxide can reach more than 95%.

The present invention will be further illustrated below by specific examples.

4. Description of drawings

Fig. 1 is the SEM figure of the basic ammonium aluminum carbonate whisker prepared in Example 1 of the present invention.

Fig. 2 is an SEM image of the alumina whiskers prepared in Example 1 of the present invention.

Fig. 3 is the SEM image of the basic ammonium aluminum carbonate whisker prepared in Example 2 of the present invention.

Fig. 4 is an SEM image of the alumina whiskers prepared in Example 2 of the present invention.

Fig. 5 is the SEM image of the basic ammonium aluminum carbonate whisker prepared in Example 3 of the present invention.

Fig. 6 is a SEM image of the alumina whiskers prepared in Example 3 of the present invention.

5. Specific implementation

Example 1:

1, add the sulfuric acid solution that concentration is 20wt% to the bentonite mineral powder of particle diameter≤75 μ m, the mass ratio of bentonite mineral powder and sulfuric acid solution is 1: 5, react at 100 ℃ of temperature after 3h and filter to obtain acid leaching filter cake and Acid leaching filtrate, washing the acid leaching filter cake with clear water to neutrality, collecting acid leaching filter cake, acid leaching filtrate and lotion respectively;

2. Mix the acid leaching filtrate obtained in step 1 and the lotion evenly to obtain a mixed solution, add 0.5% of the volume of the mixed solution to the mixed solution and have a mass concentration of 66% nitric acid solution, stir for 10 minutes, and then add the same volume of the mixed solution Isoamyl alcohol, shaken for 15min, let stand to separate layers, and collect the water phase to be the aluminum sulfate solution;

3. Add 45mL of the aluminum sulfate solution obtained in step 2 into a 75mL reactor, add urea according to the ratio of the molar weight of aluminum in the aluminum sulfate solution to the molar weight of urea in a ratio of 1:1.5, and then add 1/2 of the aluminum weight in the aluminum sulfate solution after dissolving. 0.5% CTAB was dissolved and reacted at 120°C for 24 hours, filtered, washed, and dried at 105°C for 2 hours to obtain basic aluminum ammonium carbonate whiskers.

The aluminum ammonium basic carbonate whisker product was identified as a pure phase by X-ray diffraction. The SEM image of basic ammonium aluminum carbonate whiskers is shown in Figure 1. Fig. 1 shows: whisker length is about 12 μm, and diameter is about 0.8 μm; Basic ammonium aluminum carbonate yield is 91.2%.

4. Put the basic ammonium aluminum carbonate whiskers obtained in step 3 in a muffle furnace, and calcinate at 900° C. for 5 hours to obtain alumina whiskers.

The alumina whisker product was identified as a pure phase by XRD. The SEM images of alumina whiskers are shown in Figure 2. It can be seen from the figure that the diameter of the whiskers is about 0.5 μm, and the average length is about 8 μm; the yield of alumina is 91.0%.

5. Add 8% sodium hydroxide solution with a mass concentration of 4.5 times the mass of the acid leaching filter cake to the acid leaching filter cake collected in step 1, heat and stir for 1 hour at a temperature of 90° C., and filter to obtain a liquid filtrate sodium silicate.

The analysis results show that the modulus of the liquid sodium silicate is about 3.50, which meets the requirements of the liquid-1 product standard. The obtained filter cake mainly contains unreacted bentonite, which can be returned to the acid leaching reaction after washing. The yield of amorphous silica was 95.5%.

Example 2:

1. Adding a sulfuric acid solution with a concentration of 40wt% to bentonite slag with a particle size of ≤100 μm, the mass ratio of bentonite slag and sulfuric acid solution is 1:4, react at a temperature of 95° C. for 4 hours and then filter to obtain acid leaching filter cake and For the acid leaching filtrate, the acid leaching filter cake is washed with clear water until neutral, and the acid leaching filter cake, acid leaching filtrate and washing liquid are collected respectively.

2. Mix the acid leaching filtrate and lotion obtained in step 1 evenly to obtain a mixed solution, add a nitric acid solution with a mass concentration of 0.8% of the mixed solution volume to the mixed solution, stir and react for 8 minutes, and then add 0.5 times the mixed solution volume Isoamyl alcohol, shaken for 20min, let stand to separate layers, and collect the water phase, which is the aluminum sulfate solution.

3. Add 45mL of the aluminum sulfate solution obtained in step 2 into a 75mL reaction kettle, add urea according to the ratio of the molar mass of aluminum in the aluminum sulfate solution to the molar mass of urea in a ratio of 1:2.0, and then add 1/2 of the mass of aluminum in the aluminum sulfate solution after dissolving. 1.0% SDS was dissolved and reacted at 140°C for 18 hours, filtered, washed, and dried at 105°C for 2 hours to obtain basic aluminum ammonium carbonate whiskers.

The aluminum ammonium basic carbonate whisker product was identified as a pure phase by X-ray diffraction. The SEM image of basic ammonium aluminum carbonate whiskers is shown in Figure 3. Figure 3 shows that: the whiskers have an average length of about 15 μm and a diameter of about 1 μm; the yield of basic aluminum ammonium carbonate is 91.6%.

4. Put the basic ammonium aluminum carbonate whiskers obtained in step 3 in a muffle furnace, and calcinate at 1100° C. for 3 hours to obtain alumina whiskers.

The alumina whisker product was identified as a pure phase by X-ray diffraction. The SEM images of alumina whiskers are shown in Figure 4. It can be seen from the figure that the diameter of the whiskers is about 0.6 μm, and the average length is about 8 μm; the yield of alumina is 91.5%.

5. Adding 3.3 times the mass concentration of the acid leaching filter cake to the acid leaching filter cake collected in step 1 is a 13% sodium hydroxide solution, heating and stirring for 1.5 hours at a temperature of 80° C., and filtering. The resulting filtrate is Liquid Sodium Silicate.

The analysis results show that the modulus of the liquid sodium silicate is about 2.75, which meets the requirements of the liquid-3 product standard. The obtained filter cake mainly contains unreacted bentonite, which can be returned to the acid leaching reaction after washing. The yield of amorphous silica is 96.0%;

Example 3:

1. Adding a sulfuric acid solution with a concentration of 50wt% to the bentonite slag with a particle size of ≤125 μm, the mass ratio of the bentonite slag and the sulfuric acid solution is 1:3, reacting at a temperature of 85° C. for 5 hours and then filtering to obtain acid leaching filter cake and For the acid leaching filtrate, the acid leaching filter cake is washed with clear water until neutral, and the acid leaching filter cake, acid leaching filtrate and washing liquid are collected respectively.

2. Mix the acid leaching filtrate and washing liquid obtained in step 1 to obtain a mixed solution, add a nitric acid solution with a mass concentration of 1% of the volume of the mixed solution to the mixed solution, and stir for 5 minutes, then add 2 times the volume of the mixed solution Isoamyl alcohol, shaken for 10 minutes, let stand to separate layers, and collect the water phase, which is the aluminum sulfate solution.

3. Add 45mL of the aluminum sulfate solution obtained in step 2 into a 75mL reactor, add urea according to the ratio of the molar weight of aluminum in the aluminum sulfate solution to the molar weight of urea in a ratio of 1:2.5, and then add 1/2 of the aluminum weight in the aluminum sulfate solution after dissolving. 1.5% PEG2000 was dissolved and reacted at 100°C for 36 hours, filtered, washed, and dried at 105°C for 2 hours to obtain basic ammonium aluminum carbonate whiskers.

The aluminum ammonium basic carbonate whisker product was identified as a pure phase by X-ray diffraction. The SEM image of basic ammonium aluminum carbonate whiskers is shown in Figure 5. Figure 5 shows that the whisker length is about 18 μm and the diameter is about 1.1 μm; the yield of ammonium basic aluminum carbonate is 92.1%.

4. Put the basic ammonium aluminum carbonate whiskers obtained in step 3 in a muffle furnace, and calcinate at 1000° C. for 4 hours to obtain alumina whiskers.

The alumina whisker product was identified as a pure phase by X-ray diffraction. The SEM image of alumina whiskers is shown in Figure 6. It can be seen from the figure that the diameter of the whiskers is about 0.5 μm, and the average length is about 10 μm; the yield of alumina is 92.0%.

5. Add 18% sodium hydroxide solution with a mass concentration of 2.5 times the mass of the acid leaching filter cake to the acid leaching filter cake collected in step 1, heat and stir for 2 hours at a temperature of 70° C., and filter to obtain a liquid filtrate sodium silicate.

The analysis results show that the modulus of the liquid sodium silicate is about 2.40, which meets the requirements of the liquid-4 product standard. The obtained filter cake mainly contains unreacted bentonite, which can be returned to the acid leaching reaction after washing. The yield of amorphous silica was 98.0%.

Claims (1)

1. produced a method for Aluminum Carbonate Basic ammonium whisker and alumina whisker coproduction liquid sodium silicate by wilkinite, detailed process is as follows:

1) in the bentonite of particle diameter≤125 μm, the sulphuric acid soln that concentration is 50wt% is added, the mass ratio of bentonite and sulphuric acid soln is 1:3, acidleach filter cake and acidleach filtrate is filtered to obtain react 5h at 85 DEG C of temperature after, by described acidleach filter cake clear water washing to neutral, collect acidleach filter cake, acidleach filtrate and washing lotion respectively;

2) step 1) gained acidleach filtrate and washing lotion are mixed to obtain mixed solution, the mass concentration adding mixeding liquid volume 1% in mixed solution is the salpeter solution of 66%, stirring reaction 5min, add the primary isoamyl alcohol of mixeding liquid volume 2 times again, shake 10min, stratification, collects aqueous phase and is alum liquor;

3) in 75mL reactor, 45mL step 2 is added) gained alum liquor, urea is added in the molar weight of aluminium in alum liquor and the ratio of the ratio 1: 2.5 of urea molar weight, the PEG2000 of 1.5% of aluminium quality in alum liquor is added again after dissolving, at 100 DEG C of reaction 36h after dissolving, filter, washing, at 105 DEG C of dry 2h, obtain Aluminum Carbonate Basic ammonium whisker, Aluminum Carbonate Basic ammonium yield is 92.1%;

4) step 3) gained Aluminum Carbonate Basic ammonium whisker is placed in retort furnace, in 1000 DEG C of calcining 4h, obtain alumina whisker product, aluminum oxide yield is 92.0%;

5) mass concentration adding acidleach filter cake quality 2.5 times in the acidleach filter cake of step 1) collection is the sodium hydroxide solution of 18%, heated and stirred reaction 2h under the temperature condition of 70 DEG C, and filter, gained filtrate is liquid sodium silicate; The modulus of liquid sodium silicate is 2.40, and the yield of amorphous silica is 98.0%.