KR102032948B1 - A method for separating of metal ions in seawater-based industrial wastewater by ph control and a method for manufacturing high purity carbonate by using thereof - Google Patents

Abstract

An embodiment of the present invention provides a method for manufacturing carbonate comprising following steps of: (a) mixing sodium hydroxide with industrial wastewater generated in a salt purification process to precipitate and separate metal salts; (b) conducting a reaction of the metal salts with carbon dioxide; and (c) separating and purifying carbonate in a product of the step (b).

Description

METHODS FOR SEPARATING OF METAL IONS IN SEAWATER-BASED INDUSTRIAL WASTEWATER BY PH CONTROL AND A METHOD FOR MANUFACTURING HIGH PURITY CARBONATE BY USING THEREOF}

The present invention relates to a method for producing high purity carbonate, and more particularly, to a method for producing high purity carbonate using seawater based industrial wastewater.

CO ₂ is the most common greenhouse gas emissions in the atmosphere is the main reason for intensifying global warming. Therefore, a global effort is needed to prevent this. One such effort, "Paris Convention" will be on CO ₂ emissions of the Convention Bureau, Convention, each State was decided in consultation with the mandatory reduction of CO ₂ emissions.

Carbon capture and storage (CCS) technology, one of the means to do this, is the most widely known technology to reduce CO ₂ emissions. CCS has the advantage that it can be applied to existing industrial facilities, but it requires a high temperature-high pressure condition, has a high energy consumption, and requires a safe place for long-term storage of CO ₂ .

Carbon Capture and Utilization (CCU) technology, on the other hand, is a technology that converts the captured carbon dioxide into a valuable material. In particular, the inorganic carbonation process has the advantage of fast reaction and low cost, the prepared metal carbonate is an advantage that can be reused for industrial and medical use does not need a separate place for storing CO ₂ . However, in order to apply the CCU technology, there is a problem that stable supply and demand of metal ions and CO ₂ ions is required.

Since salt is an essential ingredient for human survival, the process of producing refined salt from seawater is also ongoing. Industrial wastewater from salt refining processes can cause fatal damage to the environment, especially the coastal environment, without further treatment. Therefore, there is also a need for an economical and efficient method of treating salt refinery industrial wastewater.

The present invention is to solve the above-mentioned problems of the prior art, an object of the present invention is to provide a method for supplying the essential metal ions to the CCU from the industrial wastewater generated in the salt purification process and a method for producing a carbonate comprising a CO ₂ capture process To provide.

Another object of the present invention is to provide a method for producing a high purity carbonate.

Still another object of the present invention is to provide a method for producing a carbonate having a high reuse rate of used raw materials.

One aspect of the present invention comprises the steps of (a) mixing sodium hydroxide in the industrial wastewater generated in the salt purification process to precipitate and separate the metal salt; (b) reacting the metal salt with carbon dioxide; And (c) separating and purifying the carbonate in the product of step (b).

In one embodiment, the metal salt may be a magnesium salt.

In one embodiment, the step (a) may be to add the sodium hydroxide to the industrial wastewater to precipitate by separating the metal salt in a condition of pH 11 or less.

In one embodiment, the step (b) may be to react the slurry of the mixed metal salt and sodium hydroxide with carbon dioxide in the gas state.

In one embodiment, the metal salt may be a calcium salt.

In one embodiment, the step (a) may be to add the sodium hydroxide to the industrial wastewater to precipitate by separating the metal salt at a pH of more than 11 conditions.

In one embodiment, the step (b) may be the reaction by mixing the metal salt with an aqueous solution of alkanolamine collected carbon dioxide.

In one embodiment, the filtrate from which the carbonate of step (c) is separated may be nitrogen treated at 330 to 380 K to regenerate the alkanolamine.

In one embodiment, the carbon dioxide adsorption rate of the regenerated alkanolamine may be at least 70% of the carbon dioxide adsorption rate of the alkanolamine before regeneration.

In one embodiment, the purity of the carbonate may be 90% or more.

In one embodiment, the step (c) may be to separate and purify the carbonate by drying the product of the step (b) for 1 to 48 hours at 330 ~ 380K after filtration.

In an embodiment, sodium bicarbonate is separated by adding an aqueous alkanolamine solution adsorbed with carbon dioxide to the filtrate from which the metal salt of step (a) is separated, and the filtrate from which the sodium bicarbonate is separated is generated in a salt refining process. It can be added to industrial wastewater to regenerate sodium hydroxide.

According to one aspect of the present invention, it is possible to provide a method for supplying the essential metal ions to the CCU from the industrial wastewater generated in the salt purification process and a method for producing a carbonate comprising a CO ₂ capture process.

According to another aspect of the present invention, a high purity carbonate can be produced from industrial wastewater generated in the salt purification process.

According to another aspect of the present invention, it is possible to increase the reuse rate of the raw materials used during the carbonate manufacturing process.

It is to be understood that the effects of the present invention are not limited to the above effects, and include all effects deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 shows a schematic diagram of a salt purification process in which industrial wastewater used in the present invention is generated.
2 shows a schematic diagram of an embodiment of the invention.
Figure 3 shows a schematic of the CO ₂ capture process of the present invention.
Figure 4 shows the result of measuring the metal ion separation efficiency (M / K ratio) according to the pH.
FIG. 5 shows the XRD curve of Mg precipitate prepared by adding each wet absorbent to Mg metal salt.
6 shows the XRD curve of Mg carbonate prepared by the direct carbonation method.
7 shows an SEM image of Mg carbonate prepared by the direct carbonation method.
8 shows the TG / DTG curve of Mg carbonate prepared by the direct carbonation method.
9 shows the adsorption and desorption CO ₂ loading curves for each wet absorbent.
FIG. 10 shows resorption CO ₂ loading curves for each wet absorbent.
FIG. 11 shows XRD curves of Ca precipitates prepared by adding respective wet absorbers to Ca metal salts.
12 shows SEM images of Ca precipitates prepared by adding respective wet absorbers to Ca metal salts.
FIG. 13 shows TG / DTG curves of Ca precipitates prepared by adding respective wet absorbers to Ca metal salts.

Hereinafter, with reference to the accompanying drawings will be described the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, it includes not only "directly connected" but also "indirectly connected" with another member in between. . In addition, when a part is said to "include" a certain component, this means that it may further include other components, without excluding the other components unless otherwise stated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to Figure 1, it is a schematic diagram of a salt refining process for generating seawater-based industrial wastewater used in the present invention. Due to the nature of the salt refining process that separates salt from seawater, large amounts of metal ions may be present in industrial wastewater. Therefore, it is possible to obtain metal ions such as Ca ²⁺ , Mg ²⁺ , Na ⁺ from the industrial wastewater. Due to the supersaturated Ca ²⁺ in sea water, the metal ion concentration may be different according to the temperature change, and thus it may be used after filtering at least once at low temperature below room temperature.

Method for producing a carbonate according to an aspect of the present invention, (a) mixing the sodium hydroxide in the industrial wastewater generated in the salt purification process to precipitate the metal salt to separate; (b) reacting the metal salt with carbon dioxide; And (c) separating and purifying the carbonate in the product of step (b).

In the step (a), the metal ions such as Ca ²⁺ , Mg ²⁺ and Na ⁺ present in the industrial wastewater may be precipitated and separated by precipitation of a metal salt in hydroxide form.

The step (b) may be a carbonation reaction of the metal salt and carbon dioxide.

In the step (c), the mixture of step (b) may be filtered to separate the carbonate and the filtrate, and the carbonate may be dried at 330 to 380 K for 1 to 48 hours to improve the purity of the carbonate.

Purity of the carbonate may be at least 90%. The metal salt and gaseous carbon dioxide may be directly reacted, or may be reacted with carbon dioxide collected using an alkanolamine as an absorbent to obtain high purity carbonate.

When an aqueous carbon dioxide adsorbed alkanolamine solution is added to the filtrate from which the metal salt of step (a) is separated, sodium bicarbonate may precipitate and be separated. When the sodium bicarbonate separated filtrate is added to the industrial wastewater generated in the salt purification process, sodium hydroxide may be regenerated.

Specifically, the metal salt of step (a) may be a magnesium salt.

If the metal salt is a magnesium salt, in step (a), sodium hydroxide may be added to the industrial wastewater until the pH is 11 to precipitate and separate the magnesium salt. If the pH is less than 11, the yield of the magnesium salt may be reduced, and if the pH is more than 11, the purity of the magnesium salt may be reduced.

The magnesium salt may be washed with distilled water and dried at 330 to 380 K for 1 to 48 hours to remove impurities to improve purity.

In the step (b), the magnesium salt may be mixed with an aqueous sodium hydroxide solution having a concentration of 0.1 to 10% by weight to prepare a slurry, and then reacted with carbon dioxide gas to prepare a carbonate.

In addition, the metal salt of step (a) may be a calcium salt.

If the metal salt is a calcium salt, sodium hydroxide may be added to industrial wastewater having a pH greater than 11 in step (a) to precipitate and separate the calcium salt. If the pH is 11 or less, calcium salt may not precipitate. Precipitating and removing the magnesium salt before obtaining the calcium salt can increase the purity of the calcium salt.

In the step (b), the calcium salt may be carbonized by mixing with an aqueous solution of alkanolamine in which carbon dioxide is collected.

The alkanolamine solution may be used as a carbon dioxide absorbent for trapping carbon dioxide in exhaust gas containing a large amount of carbon dioxide.

Alkanolamines are compounds containing an amine group (-NH ₄ ) and a hydroxyl group (-OH) simultaneously. For example, primary amines such as monoethanolamine, secondary amines such as diethanolamine, methyldi Tertiary amines such as ethylamine and the like. The amine group may increase the basicity to promote absorption of carbon dioxide, which is an acidic gas. The hydroxyl group may increase the water-soluble property to reduce the vapor pressure of the material. The binding mechanism of the alkanolamine and carbon dioxide may be represented according to the following formulas (1) to (4).

[Equation 1]

[Equation 2]

[Equation 3]

[Equation 4]

Formulas 1 to 3 are reaction schemes of primary and secondary amines, and Formula 4 is reaction schemes of tertiary amines. In Formulas 1 to 4, CO ₂ gas is converted into carbonate ions, and the carbonate ions may react with metal ions to form a precipitate.

Ammonia (NH ₃ ) can also be used to raise the basicity to capture carbon dioxide, but using alkanolamines other than ammonia can yield higher purity carbonates with a purity of 90% or more.

After the step (c), the filtrate from which the carbonate is separated may be nitrogen-treated at 330 to 380 K to recover alkanolamine. The carbon dioxide adsorption rate of the regenerated alkanolamine may be 70% or more of the carbon dioxide adsorption rate of the alkanolamine before regeneration.

Hereinafter, embodiments of the present invention will be described in more detail. However, the following experimental results are described only representative experimental results of the above embodiments, the scope and content of the present invention by the examples and the like can not be interpreted to be reduced or limited. The effects of each of the various embodiments of the invention, which are not explicitly set forth below, will be described in detail in that section.

Raw material

NaOH (sodium hydroxide, purity more than 97% by weight, CAS No. 1310-73-2, Sigma-Aldrich)

MEA (monoethanolamine, purity more than 99% by weight, CAS No. 141-43-5, Sigma-Aldrich)

DEA (diethanolamine, purity 98% by weight or more, CAS No. 111-42-2, Sigma-Aldrich)

MDEA (methyldiethanolamine, purity more than 99% by weight, CAS No. 105-59-9, Sigma-Aldrich)

Industrial wastewater (provided by Hanju, Ulsan, Korea)

Example

A schematic diagram of one embodiment of the present invention is shown in FIG. Referring to FIG. ₂ , the following embodiments may include four steps including i) a metal salt production process, ii) a CO ₂ capture process, iii) a carbonate production process, and iv) a NaOH regeneration process.

i) metal salt manufacturing process

Filtration at 283.15 K for removal of supersaturated ions in industrial wastewater. A 4M NaOH aqueous solution was added to the industrial wastewater to separate Mg metal salts. The pH of the industrial wastewater to which NaOH was added was adjusted to 7, 8, 9, 10, 11, 12, 12.5 and 13, and extracted to measure the pH at which Mg ²⁺ ions were completely separated by precipitation, and the Mg ²⁺ ions were The pH of Ca ²⁺ ions precipitated and separated from the filtrate was measured.

The Mg metal salt was washed with distilled water and dried at 353.15 K for 24 hours to remove impurities such as NaCl. The reduction of the impurities was confirmed through weight changes before and after washing. In addition, NaOH was added to the filtrate containing Ca ²⁺ ions to separate the Ca metal salt. The Ca metal salt was washed with distilled water and dried at 353.15 K for 24 hours to remove impurities.

ii) CO ₂  Capture process

400 ml of MEA, DEA, and MDEA aqueous solutions each having a concentration of 30% by weight were used as a wet absorbent for CO ₂ capture. The CO ₂ capture process using a wet absorbent is shown in FIG. 3. Referring to FIG. 3, the absorber was injected and stirred while maintaining a reactor treated with high purity N ₂ gas for 10 minutes to remove impurities and CO ₂ residue at a temperature of 298.15K. After confirming that the CO ₂ concentration measured by a gas analyzer is maintained at 0% by volume for 30 minutes, the simulated flue gas whose CO ₂ concentration is adjusted to 15% by volume is the same as a general industrial flue gas ( simulated flue gas) was injected into the bottom of the reactor. The injection was continued until CO ₂ was saturated in the absorbent and then the amount of CO ₂ absorbed was measured.

In order to control the CO ₂ concentration of the simulated flue gas, a mass flow controller and a mass flow management system are installed between the gas tank and the gas mixer, and the standard temperature and pressure , STP), and the flow rates of N ₂ and CO ₂ were set to 1,602 ml / min and 300 ml / min, respectively. A condenser and a freezer were connected to the top of the reactor to maintain the concentration of the absorbent and the coolant temperature inside the condenser was maintained at 273.15 K.

iii) carbonate manufacturing process

The Mg or Ca metal salt was injected into a CO ₂ saturated absorbent. The mixed solution was stirred at 300 rpm for 12 hours. The solution was filtered and dried at 353.15 K for 24 hours to give a precipitate. The precipitate was XRD (X-ray diffraction, Ultima Iv, Rigaku), FE-SEM (Field Emission-Scanning Electron Microscope, JSM-7001F, JEOL, Ltd.), TG / DTG (Thermogravimetry / Derivative Thermogravimetry, SDT Q600, TA Instruments) to determine the crystal structure and purity. The Ca precipitate was Ca carbonate while the Mg precipitate was Mg hydroxide.

In addition, Mg metal salt was mixed with a 5% by weight aqueous NaOH solution to prepare a slurry, and then a direct carbonation method of mixing it with CO ₂ was performed to obtain Mg carbonate.

iv) NaOH regeneration process

The Mg and Ca precipitate was filtered off and the wet absorbent was added to the remaining solution to give NaHCO ₃ . After that, the industrial wastewater was re-added to check whether NaOH was generated.

Furthermore, by exposing the sorbent to check the reusability of the absorbents in the high temperature N ₂ gas at 343.15K then remove the CO ₂ and reviewed the reusability of the CO ₂ to repeat the collection process.

Experimental Example

The industrial wastewater was filtered by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES, OPTIMA 8300, Perkin Elmer) and the filtered metal ion concentrations are shown in Table 1 below.

Metal ions Concentration (mg / L) Molarity (mol / L) Ca ²⁺ 25,934.3 0.6484 Mg ²⁺ 50,634.3 2.0837 Na ⁺ 23,324.3 1.0141 K ⁺ 29,752.8 0.7609

Referring to Table 1, it was confirmed that Ca ²⁺ and Mg ²⁺ ions exist in an amount capable of capturing up to 2.732 mol of CO ₂ per liter of industrial wastewater. ⁺ Ions did not precipitate. It was shown in Figure 4 by measuring the metal ion separation efficiency by the M / K ratio (metal ion concentration / K ⁺ ion concentration) using this.

^Referring to FIG. 4, it was confirmed that Mg ²⁺ was completely precipitated at pH 11 and Ca ²⁺ was not precipitated at pH 12 or below. Thus, pH 11 may be a suitable pH for obtaining a well separated solution.

The conversion rate was calculated and compared to confirm the amount of the absorbent reacted with the metal salt in the CO ₂ collected. In case of Mg, the reactivity of Mg (OH) ₂ and CO ₂ was lower than that of amine and CO ₂ , so that CO ₂ combined with the absorbent did not react with the metal salt. Thus, Mg carbonate was prepared by direct carbonation. The conversion rate was calculated. On the other hand, Ca has a higher reactivity between Ca (OH) ₂ and CO ₂ than the binding force between amine and CO ₂ , which enables the preparation of Ca carbonate by simple mixing. Thus, Ca carbonate is prepared by indirect carbonation and the conversion rate is calculated. It was.

The molar flow rate of the mixed gas introduced / outflowed by the mass flow meter was measured, and the CO ₂ volume concentration of the reactor outlet pipe was measured by a gas analyzer. The molar flow rate and the CO ₂ volume concentration were substituted into the following equation to calculate the CO ₂ uptake.

[Equation 5]

Wherein, n _absorbed (mol) is the amount of absorbed CO _2, n _CO2 (mol / min) is the molar flow rate of CO _2, C _{CO2, set} (% by volume) is set CO ₂ volume concentration (15% by volume )ego, C _{CO 2, analyzer} (vol.%) Is the concentration measured with a gas analyzer, and Δt (min) is the measurement time.

400 ml of a 30% by weight amine solution was prepared, and the measured data was substituted into the following formula to calculate the CO ₂ loading. The molar number of each of the amine solutions was 1.988 mol of MEA, 1.242 mol of DEA, and 1.0295 mol of MDEA.

[Equation 6]

Where n _amine is the mole number of the amine.

Mg and Ca carbonate were obtained by separating and purifying each precipitate. After measuring the weight and purity of the precipitates, the molar yield was calculated and confirmed to be consistent with the CO ₂ loading data. This means that the number of moles of CO ₂ removed by forming a precipitate is equal to the number of moles of Mg and Ca carbonates produced.

The number of moles of CO ₂ converted to Mg or Ca carbonate was calculated by the following formula.

[Equation 7]

Where m _product is the weight of the product, MW _{metal carbonate} is the molar weight of the metal carbonate, and purity of carbonate was measured by TG / DTG analysis.

The number of moles of CO ₂ converted to Mg and Ca carbonate per 500 ml of industrial wastewater is shown in Table 2 below.

division Mg CONV _CO2 (mol CO ₂ ) Ca CONV _CO2 (mol CO ₂ ) Total CONV _CO2 (mol CO ₂ ) MEA 0.757 0.1976 0.9546 DEA 0.757 0.1990 0.9560 MDEA 0.757 0.1928 0.9498

It was confirmed that the purity of Ca carbonate was the highest when using MEA, and the total mole number of precipitated CO ₂ was 0.9546 mol, referring to Table 2. The Mg metal salt was obtained by mixing with a CO ₂ rich amine absorbent solution. It was confirmed that the Mg precipitate was not carbonate. XRD was measured to confirm the composition of the Mg precipitate, the results are shown in FIG.

Referring to FIG. 5, in all three cases, there was no MgCO ₃ peak in the XRD pattern, and only Mg (OH) ₂ peak was present. This is because CO ₂ did not migrate to Mg (OH) ₂ in the amine molecule. The energy stability of MgCO ₃ is higher than Mg (OH) ₂ , and the difference is larger than the energy gap of CaCO ₃ and Ca (OH) ₂ . This is because the binding force between the amine molecule and the CO ₂ molecule is greater than the reactivity between Mg (OH) ₂ and CO ₂ . Therefore, the direct carbonation method is applied instead of indirect carbonation using an amine absorbent.

In the case of using MEA, the result of calculating n _absorbed , which is an _absorbed amount of CO ₂ , according to Equation 5 was 1.1917 mol. The weight of the product produced by the direct carbonation method is 110.035 g. The data and calculated purity were substituted into Equation 7 to confirm that 0.757 mol of CO ₂ was converted.

Mg carbonate has the form of nesquehonite (MgCO _{3 ·} 3H ₂ O), hydromagnesite (Mg ₅ (CO ₃ ) ₄ (OH) _{2 ·} 4H ₂ O) and magnesite (MgCO ₃ ). Nesquehonite is rod-shaped, hydromagnesite is rectangular lamellar or spherical, and magnesite is cubic.

Figure 6 shows the XRD pattern of the Mg carbonate prepared by the direct carbonation method, Figure 7 is an SEM image.

Referring to FIG. 6, it was confirmed that the majority of Mg carbonate peaks coincide with the majority of Nesquehonite and some of the brucite (Mg (OH) ₂ ). The addition of NaOH is believed to contribute to the production of brucite. In addition, Ca ions were hardly extracted in the absence of Ca (OH) ₂ or CaCO ₃ , and it was confirmed that the purity of MgCO ₃ was high.

8 shows the results of TG / DTG analysis of Mg carbonate. Crystallographic analysis shows that the vast majority of Mg carbonate is Nesquehonite. The thermal decomposition of Nesque Honite occurred in five stages. Ness kweho night is 1, in step 2, to lose H ₂ O of 1mol, in step 3, it lost the H ₂ O of 0.5 to 0.7mol. Decarbonation occurred in step 4 and the remaining 0.3 to 0.5 mol of H ₂ O was lost in step 5. Since the product includes not only Nesquehonite but also brucite, FIG. 8 also shows pyrolysis of brucite. Pyrolysis of brucite occurred in one step at about 573-623K.

To calculate purity, the mole loss following decarbonated was calculated as the mole loss of Nesquehonite, and the mole loss due to dehydration of about 573 to 623 K was calculated as the molar loss of Brucite. The calculation is as follows.

[Equation 8]

[Equation 9]

The purity of Mg carbonate calculated according to the above formulas 8 to 9 was found to be 95.150% or more.

In the case of Ca precipitates, CaCO ₃ was formed when mixed with CO ₂ rich amine absorbents. This is expected because the CO ₂ combined with the amine migrated to calcium ions to form a precipitate.

The CO ₂ loading curves for absorption and desorption in the Ca ²⁺ separation step with the respective absorbents are shown in FIG. 9. CONV _CO2 values were calculated using Equations 5 and 6 above to compare the CO ₂ loading amounts. For each kind of the amine but some differences in CONV _CO2 value, the CO ₂ has been reduced to approximately 0.195mol. In addition, the resorption rate was measured to confirm the reusability of the absorbent. Resorption rate was calculated by dividing the amount of loading at the time of resorption by the amount of primary CO ₂ loading. The resorption CO ₂ loading curve is shown in FIG. 10, and the calculation results are shown in Tables 3 and 4.

division Absorption CO ₂ Loading
(mol CO ₂ / mol amine) Desorption CO ₂ Loading
(mol CO ₂ / mol amine) CONV _CO2
(mol CO ₂ ) MEA 0.5242 0.144 0.1976 DEA 0.4480 0.273 0.1990 MDEA 0.4864 0.1887 0.1928

division Resorption CO2 Loading (mol CO ₂ / mol amine) Resorption Rate (%) MEA 0.4265 81.37 DEA 0.3722 83.09 MDEA 0.3514 72.13

The XRD pattern of Ca precipitate prepared by adding each wet absorbent to Ca metal salt is shown in FIG. 11 and the SEM image is shown in FIG. 12. CaCO ₃ shows three crystal structures of calsite, batite and aragonite. Among the three crystal structures, calsite is the most stable, and vaterite and aragonite are unstable and can be converted to calsite. Calsite generally has a rhombic structure, batiterite and aragonite have a spherical and needle-like structure, respectively, and Ca (OH) ₂ has a hexagonal structure.

Referring to FIG. 11, Ca precipitates generally comprise calsite. The only exceptions when using MEA as absorbent include batelite and aragonite. When DEA and MDEA were used as absorbents, Ca (OH) ₂ peaks were weak.

Referring to FIG. 12, when DEA and MDEA were used, Ca precipitates formed a lozenge and hexagonal structure of calcite and Ca (OH) ₂ . On the other hand, in the case of using MEA, the majority are lozenge structures, and some spherical and needle-like structures exist.

FIG. 13 shows the TG / DTG curve of Ca precipitates. The TG / DTG data was substituted into Equations 8 and 9 to calculate the purity of the Ca precipitate. In general, the decomposition temperature range of CaCO ₃ is 873.15 to 1073.15K, and the decomposition temperature range of Ca (OH) ₂ is 603.15 to 723.15K. Referring to Figure 13, it was confirmed that the agreement with the XRD and SEM results. Referring to FIG. 13 (a), it was confirmed that CaCO ₃ was the main component when MEA was used as the absorbent. Referring to Figure 13 (b) and (c), it was confirmed that the presence of Ca (OH) _{2 in} addition to CaCO ₃ when using DEA and MDEA as the absorbent. The purity of the CaCO ₃ corresponding to the temperature range of 873.15 to 1073.15K is shown in Table 5 below.

division Carbonate Purity (%) MEA 96.51 DEA 91.55 MDEA 91.69

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the invention is indicated by the following claims, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the invention.

Claims (12)

(a) precipitating and separating metal salts by mixing sodium hydroxide with industrial wastewater generated in the salt refining process;
(b) reacting the metal salt with carbon dioxide; And
(c) separating and purifying the carbonate in the product of step (b);
The sodium bicarbonate was separated by adding an aqueous alkanolamine solution in which carbon dioxide was adsorbed to the filtrate from which the metal salt of step (a) was separated, and the filtrate from which the sodium bicarbonate was separated was added to the industrial wastewater generated in the salt refining process to obtain hydroxide. A method for producing carbonate, which regenerates sodium. The method of claim 1,
The metal salt is a magnesium salt, a method for producing a carbonate. The method of claim 2,
In the step (a), by adding sodium hydroxide to the industrial wastewater, the metal salt is precipitated and separated under the conditions of pH 11 or less. The method of claim 2,
The step (b) is a method for producing a carbonate, the reaction mixture of the metal salt and sodium hydroxide with a carbon dioxide in the gas state. The method of claim 1,
The metal salt is a calcium salt, a method for producing a carbonate. The method of claim 5,
In the step (a), by adding sodium hydroxide to the industrial wastewater, the metal salt is precipitated and separated under a condition of pH 11 or higher. The method of claim 5,
In the step (b), the metal salt is mixed with an aqueous alkanolamine solution in which carbon dioxide is absorbed and reacted. The method of claim 7, wherein
Nitrogen treatment of the filtrate separated from the carbonate of step (c) at 330 ~ 380K to regenerate the alkanolamine, carbonate production method. The method of claim 8,
The carbon dioxide adsorption rate of the regenerated alkanolamine is 70% or more of the carbon dioxide adsorption rate of the alkanolamine before regeneration, carbonate production method. The method of claim 1,
Purity of the carbonate is 90% or more, the production method of the carbonate. The method of claim 1,
In the step (c), the product of step (b) is filtered and then dried for 1 to 48 hours at 330 to 380 K to separate and purify the carbonate. delete

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