METHOD FOR RECOVERING MAGNESIUM BY USING SEDIMENT AND SULFURIC ACID GENERATED IN ELECTROLYTIC CHLORINE GENERATION SYSTEM USING SEAWATER AND BRACKISH WATER

Abstract

The present invention relates to a method for recovering magnesium from sediment generated in an electrolytic chlorine generation system using seawater or brackish water, the method comprising the steps of: eluting magnesium by using sulfuric acid in magnesium hydroxide, which is sediment generated in an electrolytic chlorine generation system using seawater and brackish water; precipitating magnesium sulfate by adding an organic solvent to a magnesium-eluted solution; and after the precipitation of the magnesium sulfate, separating the organic solvent and sulfuric acid by using a vacuum evaporation method, and reusing the organic solvent.

Claims

1. A method for recovering magnesium from sediment generated in an electrolytic chlorine generation system using seawater or brackish water, comprising: eluting magnesium using sulfuric acid in magnesium hydroxide, a sediment generated in an electrolytic chlorine generation system using seawater and brackish water; precipitating magnesium sulfate (MgSO.sub.4.Math.xH.sub.2O(s)) by adding an organic solvent to the magnesium elution solution; and, after precipitating the magnesium sulfate, the organic solvent and sulfuric acid are separated using reduced pressure evaporation and reusing the organic solvent.

2. The method of claim 1, wherein the sulfuric acid is waste sulfuric acid.

3. The method of claim 2, wherein the waste sulfuric acid was generated at industrial sites.

4. The method of claim 1, wherein the method comprises the step of treating sediment generated from an electrolytic chlorine generation system using seawater and brackish water with sulfuric acid (H.sub.2SO.sub.4) to extract high concentration of magnesium, and then separating the magnesium sulfate using an organic solvent.

5. The method of claim 1, wherein the seawater is seawater concentrate.

6. The method of claim 1, wherein the organic solvent is ethanol or acetone.

7. (canceled)

8. The method of claim 1, wherein the method comprises eluting magnesium using 0.5 to 1 M sulfuric acid in magnesium hydroxide, a sediment generated in an electrolytic chlorine generation system and mixing the eluent with the sulfuric acid to ethanol or acetone in a ratio of 1:1.5 to 1:2 (v:v) to precipitate magnesium.

9. The method of claim 8, wherein the method comprises eluting magnesium using 0.5 M sulfuric acid in magnesium hydroxide, a sediment generated in an electrolytic chlorine generation system and mixing the eluent with the sulfuric acid to acetone in a ratio of 1:2 (v:v) to precipitate magnesium.

10. A magnesium compound recovered by the method of claim 1.

11. The magnesium compound according to claim 10, wherein the magnesium compound is magnesium sulfate.

12. The magnesium compound according to claim 10, wherein the sulfuric acid is waste sulfuric acid.

13. The magnesium compound according to claim 12, wherein the waste sulfuric acid was generated at industrial sites.

14. The magnesium compound according to claim 10, wherein the seawater is seawater concentrate.

15. The magnesium compound according to claim 10, wherein the organic solvent is ethanol or acetone.

Description

DESCRIPTION OF DRAWINGS

[0028] FIG. 1 schematically shows a method of recovering magnesium using sulfuric acid and sediment generated in the electrolytic chlorine generation system using seawater and brackish water of the present invention comprising: [0029] a) obtaining sediment generated from an electrolytic chlorine generation system using seawater and brackish water, [0030] b) separating the sediment into dissolved Mg.sup.2+ and SO4.sup.2 using waste sulfuric acid or a sulfuric acid solution, [0031] c) precipitating MgSO.sub.4.Math.xH.sub.2O(s) using an organic solvent (acetone, ethanol, methanol, acetonitrile, isopropyl alcohol, etc.), and [0032] d) after precipitation of MgSO.sub.4.Math.xH.sub.2O(s), separating the organic solvent and sulfuric acid and reusing the separated organic solvent.

[0033] FIG. 2 shows the FE-SEM/EDX analysis results of magnesium hydroxide (Mg(OH).sub.2), a chlorine generation system sediment.

[0034] FIG. 3 is a diagram showing the results of XPS analysis of sediment generated in an electrolytic chlorine generation system.

[0035] FIGS. 4 and 5 show GC-MS analysis results of the recovered solvents, ethanol (FIG. 4) and acetone (FIG. 5).

MODE FOR INVENTION

[0036] Hereinafter, the present invention will be described in more detail through examples, but these are merely illustrative and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that the embodiments described below can be modified without departing from the essential gist of the invention.

Overview of the Present Invention: MgSO.sub.4.Math.xH.sub.2O(s) Precipitation Method

[0037] The method for recovering magnesium from sediment generated in the electrolytic chlorine generation system using seawater and brackish water of the present invention was carried out in the same order as FIG. 1. In the present invention, the following processes were continuously performed to recover magnesium from sediment generated in an electrolytic chlorine generation system using seawater and brackish water: [0038] 1) Step of eluting magnesium from magnesium hydroxide (Mg(OH).sub.2), a precipitate generated in an electrolytic chlorine generation system using seawater and brackish water, using waste sulfuric acid or sulfuric acid; [0039] 2) Precipitating magnesium sulfate (MgSO.sub.4.Math.xH.sub.2O(s)) by adding an organic solvent (99.9% ethanol, 99.9% acetone, 99.9% acetonitrile, 99.9% methanol, 99.9% isopropyl alcohol) to the magnesium elution solution; After the magnesium elution solution and the above five types of organic solvents were mixed in ratios of 1:1, 1:1.5, and 1:2, the optimal organic solvent was selected by comparing the precipitation amount and precipitation efficiency of magnesium sulfate. For precipitation from the mixed solution, it was refrigerated at 3 C. for 12 hours and the precipitated magnesium sulfate and the mixed solution were filtered through GF/F (Glass fiber filter) to separate the magnesium sulfate and the mixed solution, and then magnesium sulfate was dried at 70 C. for 24 hours, and the mass of the dried magnesium sulfate was measured. [0040] 3) After precipitation of magnesium sulfate (MgSO.sub.4.Math.xH.sub.2O(s)), the organic solvent and sulfuric acid were separated using reduced pressure evaporation and the organic solvent was reused.

[0041] This is detailed below.

Example 1: Eluting Magnesium

[0042] The sediment generated from the electrolytic chlorine generation system using seawater and brackish water was dried at 105 C. for 24 hours, made into powder, and used in a magnesium elution test. The mass of each powder sample was 1.00 g. 50 mL of different concentrations of sulfuric acid (0.5, 1.0, 1.5, 2.0, 2.5 M) were added into each of the five solid samples, and then stirred at 150 rpm for 20 minutes. The reason for using sulfuric acid is to prevent calcium, which interferes with the recovery of magnesium, from eluting together with magnesium by precipitating it as calcium sulfate (CaSO.sub.4). The magnesium eluate using sulfuric acid was filtered using a GF/F filter.

Example 2: Magnesium Sulfate Precipitation

[0043] The magnesium eluate using sulfuric acid filtered in Example 1 and one of five organic solvents (99.9% ethanol, 99.9% acetone, 99.9% acetonitrile, 99.9% methanol, 99.9% isopropyl alcohol) were mixed 1:1. (v:v), 1:1.5 (v:v), and 1:2 (v:v) ratios. For example, 50 mL, 100 mL, and 150 mL of ethanol or acetone were added into 50 mL of magnesium eluate using 0.5 M sulfuric acid. Seventy-five solutions with five different sulfuric acid concentrations, different organic solvent types, and mixing ratios were refrigerated at 3 C. for 12 hours. The resulting solid was filtered using a GF/F filter and then dried at 70 C. The mass of the dry solid was measured and analyzed by FE-SEM/EDX and XPS.

Example 3: Recovery of Used Organic Solvent

[0044] After the solid was precipitated in Example 2, the remaining solution (ethanol and acetone) was placed in a round flask and connected to a vacuum fractionation distillation tube and a condenser. When the solution was boiled in water at 40-47 C., some of the liquid vaporized and separated. The solution separated by vaporization was analyzed by GC-MS.

[0045] The results of the above examples are as follows.

X-Ray Fluorescence (XRF) Spectroscopy Analysis Results (Analysis of Sediment Constituent Elements)

[0046] Table 1 below shows the XRF analysis results of sediment generated in the electrolytic chlorine generation system using seawater and brackish water of the present invention.

[0047] Referring to Table 1, the main constituent of the sediment is composed of magnesium (Mg, 69.5 wt %), and additionally calcium (Ca, 5.1 wt %), silicon (Si, 0.6 wt %), sodium (Na, 0.3 wt %), chlorine (Cl, 4.2 wt %) and sulfur (S, 0.5 wt %), indicating that these elements can coprecipitate when producing chlorine using seawater or brackish water.

[0048] In addition, Mg comprised in the sediment has a relatively lower solubility constant than calcium hydroxide (Ca(OH).sub.2, solubility constant=5.510.sup.6), and exists in the form of magnesium hydroxide (Mg(OH).sub.2, solubility constant=5.6110.sup.12) (Zheng, L.; Xuehua, C.; Mingshu, T. Hydration and setting time of MgO-type expansive cement. Cem. Concr. Res. 1992, 22, 1-5).

TABLE-US-00001 TABLE 1 Element Na Mg Si Ca S Cl wt % 0.3 69.5 0.6 5.1 0.5 4.2

[0049] Table 1 shows the results of analysis of the constituent elements of sediment generated in an electrolytic chlorine generation system using seawater and brackish water using XRF.

FE-SEM/EDX Analysis Results of Sediment

[0050] FIG. 2 is a Field emission-scanning electron microscope (FE-SEM) image and Energy dispersive X-ray (EDX) spectrum analysis results of sediment generated in the electrolytic chlorine generation system using seawater and brackish water of the present invention.

[0051] Referring to FIG. 2, the surface of the sediment showed an irregular mineral shape, and EDX results showed that the main elements are composed of oxygen (45.99%) and magnesium (44.38%). This is consistent with the results of XRF and indicates that magnesium hydroxide is the dominant component of the sediment.

XPS Analysis Results of Sediment

[0052] FIG. 3 shows the results of X-ray Photoelectron Spectroscopy (XPS) analysis of sediment generated in the electrolytic chlorine generation system using seawater and brackish water of the present invention.

[0053] Referring to FIG. 3, the main elements of the sediment were found to be composed of magnesium and oxygen. This is consistent with the results in Table 1 and FIG. 2 and indicates that magnesium hydroxide (Mg(OH).sub.2) is the dominant component of the sediment.

Magnesium Sulfate Precipitation

[0054] The results of precipitation experiments conducted by varying the sulfuric acid concentration of the eluate and the type of organic solvent are summarized in Table 2.

[0055] Referring to Table 2 below, when looking at the amount of magnesium sulfate (MgSO.sub.4) precipitated according to the change in sulfuric acid concentration (0.5-2.5M) of the eluate obtained by dissolving 1 g of the precipitate in sulfuric acid and the changing conditions of the mixing ratio (1:1; 1:1.5; 1:2) with five types of organic solvents, under 0.5 M sulfuric acid conditions, a 1:1.5 mixing ratio of ethanol and acetone (precipitation efficiency: ethanol=68%; acetone=97%) and a 1:2 mixing ratio (precipitation efficiency: ethanol=150%; acetone=170%) and under 1.0 M sulfuric acid conditions, a 1:2 mixing ratio (precipitation efficiency: ethanol=108%; acetone=127%).

[0056] The optimal conditions for precipitating magnesium sulfate from sediment generated in an electrolytic chlorine generation system using seawater and brackish water are as follows. It is preferable to elute the precipitate using 0.51.0 M sulfuric acid and mix the eluate with one of two organic solvents (ethanol and acetone) at a ratio of 1:1.5-1:2 (v:v) to precipitate magnesium sulfate. Most preferably, elution is performed using 0.5M sulfuric acid and mixing with acetone in a ratio of 1:2 (v:v) to precipitate magnesium sulfate.

TABLE-US-00002 TABLE 2 Precipitation Mass of precipitated efficiency per material (g) gram of extract (%) Sulfuric Sulfuric Sulfuric acid(vol.):organic acid(vol.):organic Organic acid Conc. solvent (Vol) solvent (Vol) solvent (M) 1:1 1:1.5 1:2 1:1 1:1.5 1:2 Ethanol 0.5 0.08 0.68 1.50 8 68 150 1.0 0.08 0.08 1.08 8 8 108 1.5 0.09 0.08 0.08 9 8 8 2.0 0.09 0.09 0.09 9 9 9 2.5 0.09 0.09 0.08 9 9 8 Acetone 0.5 0.09 0.97 1.70 9 97 170 1.0 0.09 0.1 1.27 9 10 127 1.5 0.09 0.04 0.27 9 4 27 2.0 0.10 0.08 0.40 10 8 40 2.5 0.09 0.10 0.08 9 10 8 Acetonitrile 0.5 0.07 0.07 0.07 7 7 7 1.0 0.08 0.08 0.08 8 8 8 1.5 0.09 0.09 0.08 9 9 8 2.0 0.08 0.09 0.08 8 9 8 2.5 0.09 0.09 0.08 9 9 8 Methanol 0.5 0.07 0.11 0.06 7 11 6 1.0 0.09 0.08 0.06 9 8 6 1.5 0.09 0.08 0.08 9 8 8 2.0 0.09 0.08 0.08 9 8 8 2.5 0.08 0.09 0.09 8 9 9 Isopropyl 0.5 0.08 0.10 0.16 8 10 16 alcohol 1.0 0.08 0.11 0.10 8 11 10 1.5 0.09 0.10 0.16 9 10 16 2.0 0.11 0.10 0.12 11 10 12 2.5 0.10 0.21 0.09 10 21 9

[0057] Table 2 is a table comparing precipitation amount and precipitation efficiency according to sulfuric acid concentration and organic solvent mixing ratio.

XPS Analysis Results after Magnesium Sulfate Precipitation

[0058] As a result of XPS analysis after magnesium sulfate precipitation, the qualitative analysis of the precipitate showed that magnesium sulfate (MgSO.sub.4) was the main component and was consistent with the SEM-EDX results.

GC-MS Analysis Results of Recovered Solvent

[0059] FIGS. 4 and 5 show GC-MS analysis results of the recovered solvents, (a) ethanol and (b) acetone. After precipitation of magnesium sulfate as described above, the filtered solution was separated by distillation under reduced pressure. It was recovered at a reduced pressure of less than 100 hpa and a water bath temperature of 40-47 C. The recovered solvent was analyzed using GC-MS, and the results showed that both ethanol and acetone were 99.9%, which is consistent with the purity of the solvent before use. Additionally, the volume of the recovered solvent was maintained at more than 99.5% of the volume of the solvent used for precipitation. It is believed that recovering and reusing the ethanol and acetone used to precipitate magnesium sulfate will greatly help improve economic efficiency.