Method for preparing micro-nano calcium carbonate from waste residues

Abstract

The invention discloses a method for preparing micro-nano calcium carbonate from waste residues, which comprises the following steps: (1) soaking calcium-containing waste residues in an acid solution, and carrying out suction filtration to obtain a leachate; (2) adding a microbial catalyst into the leachate obtained in the step (1), and uniformly mixing; (3) introducing CO2 into the mixed solution obtained in the step (2), and adjusting the mixed solution to be alkaline; and (4) carrying out solid-liquid separation on the mixed solution obtained in the step (3), and drying a solid product in a drying oven to obtain a dried solid product. According to the method, calcium ions can be efficiently leached by adopting acid, CO2 is promoted to be mineralized by coupling a microbial catalyst, the micro-nano biological calcium carbonate can be prepared under the conditions of normal temperature and normal pressure, and the energy consumption can be effectively reduced; in addition, the generated micro-nano biological calcium carbonate can be used as a cement / concrete additive, a rubber / plastic filler, a building coating, a papermaking coating and the like.

Description

Technical Field

[0001] The present invention relates to the field of building materials, and particularly to a method for preparing micro-nano calcium carbonate from waste residues. Background Art

[0002] Calcium-containing waste residues (such as steel slag, magnesium slag, carbide slag, phosphogypsum, red mud, etc.) are the main solid wastes in industrial production. A large amount of stacking causes environmental pollution and waste of resources. The global output of calcium-containing waste residues has exceeded 1 billion tons, and the output in China reaches 400 million tons. Therefore, scientifically disposing of calcium-containing waste residues and promoting their resource utilization has become an urgent need to solve the dual dilemmas of environmental load and waste of resources.

[0003] The scientifically treated calcium-containing industrial waste residues show broad application prospects in many fields, providing an important way for the construction of a "waste-free city" and the development of circular economy. They can be widely applied to many fields such as agriculture and building materials to realize the recycling of resources. At present, the method of microbial mineralization is often used to treat waste residues, and this method is also an effective way to achieve CO2 sequestration. Compared with the traditional high-temperature carbonization method, the biological method can effectively reduce energy consumption and improve economic benefits. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing micro-nano calcium carbonate from waste residues, so as to solve the problems of environmental load and waste of resources caused by the large amount of stacking of calcium-containing waste residues, and to prepare micro-nano calcium carbonate with high added value.

[0005] To achieve the above purpose, the present invention adopts the following technical scheme: A method for preparing micro-nano calcium carbonate from waste residues, comprising the following steps: (1) Soaking the calcium-containing waste residue in an acid solution, and performing suction filtration to obtain a leachate; (2) Adding a microbial catalyst to the leachate obtained in step (1), and mixing evenly; (3) Introducing CO2 into the mixture obtained in step (2), and adjusting the mixture to be alkaline; (4) Separating the solid and liquid of the mixture obtained in step (3), and putting the solid product into an oven for drying to obtain a dry solid product.

[0006] Preferably, in step (1), the calcium-containing waste residue is one or more of steel slag, magnesium slag, red mud, etc.

[0007] Preferably, the particle size D of the calcium-containing waste residue 50 is 5 - 50 µm.

[0008] Preferably, in step (1), the concentration of the acid solution is 1 - 3 mol / L.

[0009] Preferably, in step (1), the liquid-solid mass ratio of the acid solution to the calcium-containing waste residue is 5-10.

[0010] Preferably, in step (1), before suction filtration, the mixed solution of the calcium-containing waste residue and the acid solution is first placed on a shaker and oscillated at a temperature of 20-50 °C, a rotation speed of 150-200 rpm, and a reaction time of 8 h; then it is taken out and left to stand for 16 h.

[0011] Preferably, in step (2), the mass ratio of the microbial catalyst to the leaching solution is 1:1.

[0012] Preferably, in step (2), the microorganism is all microorganisms capable of producing carbonic anhydrase.

[0013] Preferably, in step (3), CO2 is introduced into the mixed solution at a rate of 2-3 L / min.

[0014] Preferably, in step (3), CO2 is introduced until the amount of bubbles escaping from the mixed solution = the amount of bubbles introduced.

[0015] Preferably, in step (3), the CO2 comes from industrial flue gas generated by steel mills, cement plants, petrochemical plants, etc.

[0016] Preferably, in step (3), the pH value of the mixed solution is not less than 10.

[0017] Preferably, in step (4), after solid-liquid separation, the suspended solid content < 100 mg / L.

[0018] Preferably, in step (4), the moisture content of the dried solid product ≤ 0.5%.

[0019] Preferably, in step (4), the method of solid-liquid separation is centrifugation.

[0020] Advantageous effects: The comparative advantage of the present invention over the prior art is that acid can be used to efficiently leach calcium ions and coupled with a microbial catalyst to promote CO2 mineralization, and micro-nano bio-calcium carbonate can be prepared under normal temperature and pressure conditions, which can effectively reduce energy consumption; in addition, the generated micro-nano bio-calcium carbonate can be used as cement / concrete additives, rubber / plastic fillers, architectural coatings, paper coatings, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a process schematic diagram of preparing micro-nano calcium carbonate from waste residue according to the present invention; Figure 2 is the morphology of the synthesized calcium carbonate in the example; Figure 3 is the XRD pattern of the synthesized calcium carbonate in the example. DETAILED DESCRIPTION OF THE INVENTION

[0022] Such asFigure 1 The following is a schematic process diagram of a method for preparing micro-nano calcium carbonate using waste residues according to the present invention, including the following steps: (1) Immerse the calcium-containing waste residues in an acid solution, and perform suction filtration to obtain a leachate; In some preferred embodiments of the present invention, the calcium-containing waste residues are one or more of steel slag, magnesium slag, red mud, etc., and more preferably converter steel slag.

[0023] In some preferred embodiments of the present invention, the particle size D of the calcium-containing waste residues 50 is 5 - 50 µm.

[0024] In some preferred embodiments of the present invention, the acid solution is hydrochloric acid, and the solution concentration is 1 - 3 mol / L.

[0025] In some preferred embodiments of the present invention, the liquid-solid mass ratio of the hydrochloric acid solution to the steel slag is 5 - 10.

[0026] In some preferred embodiments of the present invention, before suction filtration, the mixed solution of the steel slag and the hydrochloric acid solution is first placed on a shaker and oscillated at a temperature of 20 - 50 °C, a rotation speed of 150 - 200 rpm, and a reaction time of 8 h; then it is taken out and left to stand for 16 h.

[0027] (2) Add a microbial catalyst to the leachate obtained in step (1) and mix evenly; In some preferred embodiments of the present invention, the mass ratio of the microbial catalyst to the leachate is 1:1.

[0028] In some preferred embodiments of the present invention, the microorganism is all microorganisms capable of producing carbonic anhydrase.

[0029] (3) Introduce CO₂ into the mixed solution obtained in step (2) and adjust the pH value of the mixed solution to alkaline; In some preferred embodiments of the present invention, CO₂ with a volume concentration of 99% is introduced into the mixed solution at a rate of 2 - 3 L / min.

[0030] In some preferred embodiments of the present invention, CO₂ is introduced until the amount of bubbles escaping from the mixed solution = the amount of bubbles introduced.

[0031] In some preferred embodiments of the present invention, the pH value of the mixed solution is not less than 10.

[0032] (4) Perform solid-liquid separation on the mixed solution obtained in step (3), put the solid product into an oven for drying, and obtain a dry solid product, which is mainly the micro-nano calcium carbonate.

[0033] In some preferred embodiments of the present invention, after solid-liquid separation, the suspended solid content < 100 mg / L.

[0034] In some preferred embodiments of the present invention, the moisture content of the dried solid product is ≤ 0.5%.

[0035] In some preferred embodiments of the present invention, the method of solid-liquid separation is centrifugation.

[0036] The following further describes the present invention in conjunction with embodiments, which can help those of ordinary skill in the art better implement the present invention. It should be noted, however, that the present invention is not limited solely to the following embodiments, and any obvious changes or equivalent substitutions based on the inspiration of the present invention should also be considered as falling within the protection scope of the present invention.

[0037] The converter steel slag used in the following examples and comparative examples of the present invention has a particle size D 50 of 5 - 50 µm, and the hydrochloric acid purity is 36% - 38%. Example

[0038] This example includes the following steps: (1) Prepare 50 g of 1 mol / L hydrochloric acid solution, weigh 10 g of steel slag and put it into the hydrochloric acid solution, place it on a shaker and shake for 8 h, keep the temperature at 35 °C, the rotation speed is 170 rpm, take it out and let it stand for 16 h, and filter by suction to obtain the leaching solution.

[0039] (2) According to the mass ratio of the microbial catalyst to the leaching solution of 1:1, add the microbial catalyst to the leaching solution and mix evenly.

[0040] (3) Pass CO₂ with a concentration of 99% into the mixed solution obtained in step (2) at a rate of 2 - 3 L / min for a duration of 0.5 h until the amount of bubbles escaping from the mixed solution = the amount of bubbles introduced; drop in NaOH solution to adjust the pH value to 10.

[0041] (4) Centrifuge the mixed solution obtained in step (3), and the suspended solid content after centrifugation is < 100 mg / L; put the solid product into an oven until it is dried, and the moisture content of the dried solid product is ≤ 0.5%. Example

[0042] This example includes the following steps: (1) Prepare 100 g of 1 mol / L hydrochloric acid solution, weigh 10 g of steel slag and put it into the hydrochloric acid solution, place it on a shaker and shake for 8 h, keep the temperature at 35 °C, the rotation speed is 170 rpm, take it out and let it stand for 16 h, and filter by suction to obtain the leaching solution.

[0043] (2) According to the mass ratio of the microbial catalyst to the leaching solution of 1:1, add the microbial catalyst to the leaching solution and mix evenly.

[0044] (3) Introduce CO2 with a concentration of 99% into the mixed solution obtained in step (2) at a rate of 2 - 3 L / min for a duration of 0.5 h until the amount of bubbles escaping from the mixed solution = the amount of bubbles introduced; drop in NaOH solution to adjust the pH value to 10.

[0045] (4) Centrifuge the mixed solution obtained in step (3), and the suspended solid content after centrifugation < 100 mg / L; put the solid product into an oven until it is dried, and the moisture content of the dried solid product ≤ 0.5%.

[0046] Comparative Example 1 This comparative example includes the following steps: (1) Weigh 50 g of water, weigh 10 g of steel slag and put it into water, place it on a shaker and oscillate for 8 h, maintain the temperature at 35°C, the rotation speed is 170 rpm, take it out and let it stand for 16 h, and filter by suction to obtain the leaching solution.

[0047] (2) Introduce CO2 with a concentration of 99% into the mixed solution at a rate of 2 - 3 L / min for a duration of 0.5 h, and drop in NaOH solution to adjust the pH value to 10.

[0048] (3) After centrifugation, put the solid product into an oven until it is dried.

[0049] Comparative Example 2 This comparative example includes the following steps: (1) Weigh 50 g of water, weigh 10 g of steel slag and put it into water, place it on a shaker and oscillate for 8 h, maintain the temperature at 35°C, the rotation speed is 170 rpm, take it out and let it stand for 16 h, and filter by suction to obtain the leaching solution.

[0050] (2) According to the mass ratio of the microbial catalyst to the leaching solution being 1:1, add the microbial catalyst to the leaching solution and mix evenly.

[0051] (3) Introduce CO2 with a concentration of 99% into the mixed solution at a rate of 2 - 3 L / min for a duration of 0.5 h, and drop in NaOH solution to adjust the pH value to 10. After centrifugation, put the solid product into an oven until it is dried.

[0052] Finally, represent the test conditions and yields of Examples 1 and 2 and Comparative Examples 1 and 2 in the form of a table. As shown in Table 1: Table 1 Test Conditions and Yield Results of Each Case

[0053] The results show that the yields of Examples 1 and 2 using hydrochloric acid as the leaching agent are 0.92 g and 2.03 g respectively, which are much higher than 0.06 g of Comparative Example 1 and 0.32 g of Comparative Example 2. In addition, by comparing Comparative Examples 1 and 2, it can be found that using a microbial catalyst can effectively increase the yield; by comparing Examples 1 and 2, it can be found that using a higher liquid-solid mass ratio can also effectively increase the yield. It shows that more solid products can be obtained when hydrochloric acid is used as the leaching agent, the liquid-solid mass ratio of 10 is used, and a microbial catalyst is used. Figure 2 This is the SEM image of the solid product, and it can be observed that its size is about 700 nm - 10 µm. Figure 3 This is the XRD pattern of the solid product. After comparison with the PDF card data, it is determined to be calcite-type calcium carbonate.

[0054] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing micro-nano calcium carbonate using waste residues, characterized in that: It includes the following steps: (1) Immerse the calcium-containing waste residue in an acid solution, and perform suction filtration to obtain a leaching solution; (2) Add a microbial catalyst to the leaching solution obtained in step (1), and mix evenly; (3) Introduce CO2 into the mixed solution obtained in step (2), and adjust the mixed solution to be alkaline; (4) Perform solid-liquid separation on the mixed solution obtained in step (3), put the solid product into an oven to dry, and obtain a dried solid product.

2. The method for preparing micro-nano calcium carbonate using waste residue according to claim 1, wherein: In step (1), the calcium-containing waste residue is one or more of steel slag, magnesium slag, and red mud, and the particle size D 50 is 5 - 50 µm.

3. The method for preparing micro-nano calcium carbonate by using waste residues according to claim 1, characterized in that: In step (1), the concentration of the acid solution is 1-3 mol / L, and the liquid-solid mass ratio of the acid solution to the calcium-containing waste residue is 5-10.

4. The method for preparing micro-nano calcium carbonate by using waste residues according to claim 1, characterized in that: In step (1), before suction filtration, the mixed solution of the calcium-containing waste residue and the acid solution is first placed on a shaker and oscillated at a temperature of 20-50 °C, a rotation speed of 150-200 rpm, and a reaction time of 8 h; then it is taken out and left to stand for 16 h.

5. The method for preparing micro-nano calcium carbonate using waste residues according to claim 1, characterized in that: In step (2), the mass ratio of the microbial catalyst to the leaching solution is 1:1, and the microorganisms are all microorganisms capable of producing carbonic anhydrase.

6. The method for preparing micro-nano calcium carbonate using waste residues according to claim 1, characterized in that: In step (3), introduce CO2 into the mixed solution at a rate of 2-3 L / min; until the amount of bubbles escaping from the mixed solution = the amount of bubbles introduced; the CO2 comes from industrial flue gases generated by steel mills, cement plants, petrochemical plants, etc.

7. The method for preparing micro-nano calcium carbonate using waste residue according to claim 1, characterized in that: In step (3), the pH value of the mixed solution is not less than 10.

8. The method for preparing micro-nano calcium carbonate using waste residues according to claim 1, characterized in that: In step (4), after solid-liquid separation, the suspended solid content < 100 mg / L.

9. The method for preparing micro-nano calcium carbonate using waste residue according to claim 1, characterized in that: In step (4), the moisture content of the dried solid product ≤ 0.5%.

10. The method for preparing micro-nano calcium carbonate using waste residue according to claim 1, characterized in that: In step (4), the method of solid-liquid separation is centrifugation.

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