A method for fixing carbon dioxide in the atmosphere using marine components.

Abstract

To provide a technique of adjusting irregular absorption and emission of carbon dioxide by ocean in order to prevent warming.SOLUTION: An immobilization technique of carbon dioxide in seawater consists of: a step of adding sodium hydroxide saturated solution to seawater to bring it to a high alkaline region of pH 11.1 to 11.6, and separating magnesium and almost all calcium in seawater; and a step of allowing hydrogencarbonate ion and calcium ion dissolved in seawater to react with each other to sediment and co-precipitate calcium carbonate. Increase of CO2 in the global environment can be prevented by making an immobilization plant much larger by using the technique.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention aims to stabilize the carbon dioxide absorption capacity of the ocean by adjusting the carbon dioxide content in the ocean and the atmosphere, thereby maintaining the carbon dioxide capture capacity of the ocean as consistently and on average as possible, and reducing fluctuations in global warming. [Background technology]

[0002] Generally, carbon dioxide is exchanged between the Earth's atmosphere and oceans, with the oceans absorbing carbon dioxide from the atmosphere. Furthermore, the oceans consist of areas that absorb carbon dioxide from the atmosphere and areas that release carbon dioxide into the atmosphere. It is also known that the exchange of carbon dioxide between the ocean and the atmosphere, as well as the areas of absorption and release, fluctuate significantly depending on the season and year. Therefore, as global warming progresses in the future, it is predicted that the ocean's carbon dioxide absorption capacity will decline. Thus, it is necessary to constantly monitor these irregular absorption and release of carbon dioxide by the ocean.

[0003] When examining the main factors that influence the absorption and release of carbon dioxide by the ocean, it can be found that the difference between the partial pressure of carbon dioxide in the atmosphere and the partial pressure of carbon dioxide in the seawater surface, as well as fluctuations in wind speed, are related. In other words, when the partial pressure of carbon dioxide in the surface seawater is higher than that of the atmosphere, the ocean releases carbon dioxide into the atmosphere, and conversely, when the partial pressure of carbon dioxide in the surface seawater is lower than that of the atmosphere, the ocean absorbs carbon dioxide from the atmosphere. In this case, the greater the wind speed, the greater the absorption or release of carbon dioxide.

[0004] In this case, the partial pressure of carbon dioxide in surface seawater fluctuates significantly due to various influences such as water temperature, vertical mixing and upwelling of seawater, and biological activity. For example, when the water temperature rises, the solubility of carbon dioxide in water decreases, and the undissolved carbon dioxide increases the partial pressure of carbon dioxide in surface seawater. Also, vertical mixing and upwelling of seawater cause the surface seawater to mix with the lower layers of water which contain more carbon dioxide, increasing the partial pressure of carbon dioxide in surface seawater. Furthermore, when biological activity is vigorous, phytoplankton consume carbon dioxide, which lowers the partial pressure of carbon dioxide in surface seawater.

[0005] Incidentally, regarding the distribution and seasonal variations of carbon dioxide absorption or release, if we divide the region into equatorial, subtropical, and subpolar zones and show the seasonal distribution and seasonal variations of carbon dioxide exchange, first, in the equatorial region, the partial pressure of carbon dioxide in surface seawater is high due to the effect of upwelling, and although seasonal variations are said to be relatively small, the amount of carbon dioxide released is the largest in the entire ocean, and the area of ​​carbon dioxide release is widely distributed around this point, releasing carbon dioxide throughout the year.

[0006] On the other hand, in the subtropical region, carbon dioxide absorption zones are widely distributed, and the partial pressure of carbon dioxide in surface seawater fluctuates seasonally due to the influence of sea surface temperature. Generally, absorption is higher in winter and lower in summer. Furthermore, in the subpolar region, seasonal fluctuations occur due to a combination of factors including not only sea surface temperature but also vertical mixing of seawater and biological activity. As a result, the annual exchange rate of carbon dioxide is not uniform. Generally, in winter, strong winds and cooling of the sea surface lead to strong vertical mixing, creating a region that releases carbon dioxide, while from spring to autumn, increased biological activity consumes carbon dioxide in surface seawater, creating an absorption zone. These seasonal fluctuations repeat.

[0007] Furthermore, looking at fluctuations over a decade, the equatorial Pacific Ocean, as mentioned earlier, is an area with particularly high carbon dioxide emissions, and these emissions also fluctuate significantly between periods of El Niño and La Niña and other periods. Therefore, the total amount of carbon dioxide absorbed by the oceans globally tends to fluctuate significantly from year to year. Conversely, during La Niña events, carbon dioxide emissions tend to increase due to stronger upwelling.

[0008] As mentioned above, it is predicted that as global warming progresses in the future, the average carbon dioxide absorption capacity of the ocean as a whole may begin to decline. Therefore, there is a strong desire for the concretization of technologies to regulate such irregular absorption and release of carbon dioxide by the ocean. One method known so far involves (1) electrolyzing saturated saline solution to obtain sodium hydroxide, (2) adding sodium hydroxide to seawater to convert magnesium chloride and calcium chloride in the seawater into magnesium hydroxide and calcium hydroxide, and (3) introducing carbon dioxide into water containing magnesium hydroxide and calcium hydroxide and converting it back into magnesium carbonate and calcium carbonate. (Japanese Patent Publication No. 2010-125354)

[0009] Furthermore, a method for recovering and removing carbon dioxide from seawater is also known, which involves combining calcium and magnesium, which coexist in seawater, with carbon dioxide (Japanese Patent Publication No. 2005-21870). Furthermore, in order to enhance carbon dioxide reduction capacity while taking into account carbon dioxide emissions, a carbon dioxide fixation method is also known that includes a step of obtaining alkaline earth metal oxides from brine containing alkaline earth metals, and a carbon dioxide reaction step of reacting the alkaline earth metal oxides with a gas containing carbon dioxide (Japanese Patent Publication No. 2020-175344).

[0010] Furthermore, there are also artificial global warming prevention systems that utilize natural conditions, such as injecting high-pressure steam generated by steam generators like ships or boilers into the upper atmosphere under certain conditions, thereby generating updrafts that cause water vapor in the air to rise and create clouds in the upper atmosphere, partially covering a certain area of ​​the Earth to block solar heat and induce rainfall (Japanese Patent Publication No. 2010-155957).

[0011] Furthermore, there is a known method for preventing global warming that utilizes deep-sea water by using a water-conducting pipe that is nearly horizontal at the inlet end and curves upward toward the outlet end, with seawater moored to it, to move the deep-sea water to the surface, and by mixing the deep-sea water, which is a source of cold energy, with the surface seawater, thereby lowering the atmospheric temperature above the sea surface in the surface layer (Japanese Patent Publication No. 2009-046973). [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2010-125354 [Patent Document 2] Japanese Patent Publication No. 2005-21870 [Patent Document 3] Japanese Patent Publication No. 2020-175344 [Patent Document 4] Japanese Patent Publication No. 2010-155957 [Patent Document 5] Japanese Patent Publication No. 2009-046973 [Overview of the project] [Problems that the invention aims to solve]

[0013] However, the technology described in Patent Document 1 above has technical difficulties because it uses a method of obtaining sodium hydroxide by electrolyzing saturated saline solution. In other words, regarding the method of obtaining sodium hydroxide along with chlorine and hydrogen by electrolyzing saturated saline solution, after many experiments and studies, it has been found that it is not realistic to bring this method, which presupposes the unique global carbon dioxide exchange that is key to maintaining the carbon dioxide capture capacity of the ocean as constant as possible on average and reducing fluctuations in global warming, down to a quasi-global scale.

[0014] Furthermore, regarding the statements in this case, "electrolyze saturated saline solution to obtain sodium hydroxide" and "add sodium hydroxide to seawater to convert magnesium chloride and calcium chloride in the seawater into magnesium hydroxide and calcium hydroxide," the statement "magnesium chloride and calcium chloride in seawater" is unclear, as seawater contains dissolved cations such as sodium ions, magnesium ions, calcium ions, and potassium ions, and complex ions such as chloride ions, sulfate ions, and bicarbonate ions as anions.

[0015] Furthermore, regarding the case described in Patent Document 2, where calcium and magnesium coexisting in seawater are combined with carbonic acid, it is presumed that calcium is combined as a carbonate, but only hydroxide is formed for magnesium, and there is no practical basis for claiming that a carbonate is formed. Also, it states that "decarbonized seawater, from which carbonic acid contained in deep-sea water has been removed, absorbs carbon dioxide from the atmosphere when it comes into contact with the atmosphere," but while it is possible that decarbonized seawater can absorb carbon dioxide from the atmosphere, whether or not it actually absorbs it depends on the balance of parameters such as the pH, temperature, pressure, and alkalinity of the seawater, and it cannot necessarily be said that seawater has a superior carbon dioxide absorption capacity.

[0016] Furthermore, there is a description that "the hydrogen ion concentration of seawater after electrolysis becomes lower than that of seawater before treatment, and therefore the carbon dioxide absorption capacity further increases", but this description overlooks the fact that when the hydrogen ion concentration decreases, the carbon dioxide absorption capacity decreases. Also, regarding the description of "Ca(Mg)CO3↓" in Chemical Formula (2), it is clear that this compound does not exist because the balance between cations and anions is not achieved. Incidentally, the bittern described there is a royalty related to the production of sodium hydroxide and has nothing to do with the carbon dioxide capture method.

[0017] Regarding the carbon dioxide immobilization method described in Patent Document 3, which includes a step of obtaining an alkaline earth metal oxide from seawater containing an alkaline earth metal and a carbon dioxide reaction step of reacting the alkaline earth metal oxide with a gas containing carbon dioxide in order to enhance the carbon dioxide reduction ability while considering the carbon dioxide emission amount, since an evaporation concentration step or the like is incorporated, a large amount of thermal energy is used. Even if carbon dioxide can be fixed in some steps, overall including all steps, more carbon dioxide will be emitted.

[0018] Also, regarding the artificial global warming prevention system described in Patent Document 4, which utilizes natural conditions to generate an updraft by injecting high-pressure steam generated by a steam generation device such as a ship or a boiler into the sky under certain conditions, thereby raising the water vapor in the air to generate clouds in the sky, covering a certain area of the earth partially to block solar heat and cause rainfall, generating clouds with high-pressure steam requires a huge amount of thermal energy, and to obtain the energy source, more carbon dioxide will be generated instead. Also, the generation of steam not only generates clouds but also increases the water vapor concentration in the atmosphere. Since water vapor is a greenhouse gas superior to carbon dioxide, it will actually promote global warming.

[0019] In addition, regarding the method for preventing global warming, which uses the water pipe described in Patent Document 5, "a water pipe with an inlet facing upstream of the flow of deep ocean water, allowing deep ocean water to flow in, and having an outlet curved or inclined upward, with fins provided on the water pipe and the inlet of the water pipe facing the upstream side of the flow of deep ocean water", to move deep ocean water, which is a cold heat source, to the surface layer, fuse the deep ocean water with the original seawater in the surface layer to lower the seawater temperature in the surface layer, and reduce the atmospheric temperature above the sea surface in the surface layer through heat transfer between the gas and liquid phases with the atmosphere in contact with the sea surface, it is merely a water pipe that allows deep ocean water to flow in and has an outlet curved or inclined upward. Naturally, it is not practical to stabilize the carbon dioxide absorption capacity in the global-scale deep ocean water.

Means for Solving the Problems

[0020] Therefore, as a result of the inventors' efforts in carbon dioxide fixation technology using seawater components as a plant that can be scaled up in the future even if it is relatively small in scale, they have successfully developed a revolutionary plant capable of absorbing carbon dioxide into the bitter salt component in seawater. To complete the plant, the inventors established reliable technologies and conducted research activities to realize environmental technologies, particularly efforts aimed at reducing carbon dioxide in the atmosphere, with a strong enthusiasm to contribute to the creation of an advanced society and to realize the rich lives and dreams of people around the world. At the same time, in October 2020, Japan declared "carbon neutrality by 2050", and in April 2021, it also announced a new government policy to aim for a 46% reduction from fiscal year 2013 as a new target for reducing greenhouse gas emissions in fiscal year 2030 and to continue to challenge towards a higher goal of 50%.

[0021] Among these, according to our research, looking at the current amount of carbon dioxide in the atmosphere, the current amount continues to increase by about 3.3 GtC per year for 750 Gt (as C). Also, when analyzing the seawater components, carbon exists as dissolved carbonate (HCO3) at 3.8×10 4It contains dissolved GtC to a degree that is estimated to be about 50 times the amount found in the atmosphere. Seawater can be described as having a bittern component to the extent that it is like "salty baking soda water." This bittern component is mainly found in limestone sediments at a concentration of 2 × 10⁻⁶ 7 It appears that GtC exists. This is estimated to be equivalent to approximately 27,000 times the amount of CO2 in the atmosphere.

[0022] In addition, the amount of fossil fuels in the buried reserves is 1.2 × 10 4 GtC, onshore biomass 2 x 10 3 GtC and similar deposits are considered to be the main locations of carbon dioxide on Earth. The project organized by the inventors of this invention attempts to develop a technology to fix the increase in CO2 in the atmosphere (hereinafter simply referred to as "1") as part of sediments, specifically carbonates (limestone), that is, as part of a 6 million-fold increase, via marine components (12,000 times). Incidentally, calcification (fixation of carbon dioxide) is a phenomenon that occurs universally in nature.

[0023] In a project planned by the inventors, an investigation into the main dissolved components per kilogram of seawater revealed that 0.413 g of calcium and 0.142 g of carbon dioxide (HCO3) were dissolved. In seawater, calcium and carbon dioxide are supersaturated 3 to 6 times as calcium carbonate, but coexisting magnesium ions prevent both from precipitation. Furthermore, through extensive repeated research by the inventors, it was found that magnesium, one of the dissolved compounds, can be removed as Mg(OH)2 by raising the pH value to a highly alkaline range of around 10.5 or higher.

[0024] When magnesium ions are removed from seawater, carbon dioxide and calcium ions combine, causing calcium carbonate to precipitate. In this case, chemically, of the two equivalents of CO2 dissolved in seawater, one equivalent of CO2 is converted into limestone, and the other equivalent of CO2 is re-released into the atmosphere.

[0025] The existence of the phenomenon described above will be verified below. The verification will use seawater, which is an actual component of the ocean. By adding sodium hydroxide to the seawater to raise the pH to a highly alkaline range, Mg(OH)2 will precipitate and be removed. Then, by injecting CO2 gas into the seawater, the partial pressure of CO2 will be increased and the pH will be neutralized, resulting in the crystallization of calcium carbonate CaCO3 (limestone). After understanding the mass balance of CO2 in the series of processes described above, the CO2 fixation process by limestone will be explained and confirmed below. [Effects of the Invention]

[0026] As is clear from the research results above, the increase in atmospheric carbon dioxide (assumed to be 1) was fixed as part of the carbonate sediment (6 million times) via the ocean component (12,000 times). Calcium carbonate in surface seawater is supersaturated but does not form precipitates due to the coexisting dissolved magnesium ions. Therefore, subsequent research revealed that by adding a saturated sodium hydroxide solution to seawater and raising the pH to a highly alkaline range of 10.5-12, it is possible to precipitate and remove magnesium ions as magnesium hydroxide.

[0027] In other words, since calcium ions are dissolved in this alkaline supernatant, a neutralization reaction occurs when carbon dioxide is blown into it. This neutralization reaction causes calcium carbonate to precipitate, and the calcium and carbon dioxide are removed and fixed from the solution as crystals. Alternatively, by blowing carbon dioxide into a slurry of magnesium hydroxide produced from seawater, the magnesium hydroxide is converted into magnesium carbonate, which can fix carbon dioxide. [Brief explanation of the drawing]

[0028] [Figure 1] A perspective view illustrating the schematic of a sediment recovery experimental apparatus using a closed-system batch test. [Figure 2] A graph showing the hydroxide formation range due to pH adjustment. [Modes for carrying out the invention]

[0029] The embodiments of the present invention will be described below with reference to the figures. Figure 1 shows a schematic diagram of the entire experimental apparatus used to demonstrate that injecting CO2 gas into seawater as described above neutralizes the pH and causes calcium carbonate CaCO3 (limestone) to crystallize. In Figure 1, 1 and 2 represent flexible tanks for storing raw seawater (sample seawater), respectively. 1a and 2b represent valves located on the top surface of each flexible tank. 3 represents a large-capacity tank, which is connected to flexible tank 1 by a hose 4 with a pump P in between, and to flexible tank 2 by a hose 5 with a pump P in between.

[0030] Hoses 4 and 5 merge partway and are introduced into tank 3. 6 is a solution dispenser for supplying saturated NaOH solution into flexible tanks 1 and 2. 7 is an air supply pipe for air purging into tank 3, and 8 is a pipe for supplying CO2 gas from Tedlar bag 8a into tank 3, with a valve 9 in the middle. Furthermore, 10 is a pipe for supplying phosphoric acid to generate CO2 gas in gas container 11, with a valve 12 in the middle. 13 is a container for holding saturated NaOH solution. 14 represents a supply pipe for supplying saturated NaOH solution from container 13 into tank 3.

[0031] This invention involves setting up a closed seawater area resembling a giant tank, and adjusting the pH of the alkaline supernatant liquid in this area by adding a saturated sodium hydroxide solution to bring it to a highly alkaline range of pH 10.5 or higher, preferably pH 11 to pH 12, and more preferably pH 11.1 to pH 11.6, thereby separating the precipitate of magnesium hydroxide. Calcium carbonate, whose precipitation was inhibited by magnesium ions even in a supersaturated state, is neutralized by the reaction, causing calcium carbonate to precipitate. Calcium and carbon dioxide are then fixed as crystals from the solution, making them easily removable. By scaling this up, it is possible to promote the absorption of CO2 from the atmosphere, thereby contributing to the prevention of global warming.

[0032] In a project planned by the inventors, an investigation into the main dissolved components per kilogram of seawater revealed that 0.413 g of calcium and 0.142 g of carbon dioxide (HCO3) were dissolved. In seawater, calcium and carbon dioxide are supersaturated 3 to 6 times as calcium carbonate, but coexisting magnesium ions prevent both from precipitation. Furthermore, the inventors' research indicates that magnesium, among the dissolved compounds, can be most efficiently removed as Mg(OH)2 at around pH 11.4.

[0033] When magnesium ions are removed from seawater, carbon dioxide and calcium ions combine to precipitate calcium carbonate. In this case, chemically, of the two equivalents of CO2, one equivalent is converted into limestone, and the other equivalent is re-released into the atmosphere.

[0034] The existence of the phenomenon described above will be explained and verified below. The verification will use seawater, which is a component of the actual ocean. By adding sodium hydroxide to the seawater to raise the pH to a highly alkaline range, Mg(OH)2 will precipitate and be removed, and then by injecting CO2 gas into the seawater with an increased CO2 partial pressure, it was found that the pH was neutralized, resulting in the crystallization of calcium carbonate CaCO3 (limestone). Understand the CO₂ mass balance in the above-described series of processes and confirm CO₂ fixation as limestone.

[0035] As described above, Ca in the surface seawater of the ocean 2+ is calculated (Ω value) to be supersaturated by 3 to 6 times as calcium carbonate CaCO₃ (limestone) according to the latest research results, but usually does not generate precipitation inorganically. This is considered to be due to the influence of coexisting Mg 2+ . Figure 2 shows the relationship between the formation of hydroxides according to the solubility products of Mg 2+ , Ca 2+ and the change in pH value. By adding a saturated NaOH solution to the filtered seawater, Mg(OH)₂ can be precipitated and separated with high efficiency at a high pH range of pH 11.4. In this case, almost no precipitation of Ca(OH)₂ is observed at pH 11.4, and most of the Ca 2+ remains in the supernatant (a part of Ca 2+ coprecipitates as CaCO₃).

[0036] After separation, the supernatant was neutralized by blowing CO₂ gas and precipitated and fixed as CaCO₃. By blowing CO₂ gas into the precipitate of Mg(OH)₂, it could be converted into magnesium carbonate. By the above method, carbon dioxide could be fixed as carbonate by seawater components. The experiment in Figure 1 was carried out as a closed system, and the pH of the solution and the CO₂ gas concentration of the gas were monitored with an NDIR meter.

[0037] As repeatedly stated, seawater collected from a clean coastline was used, filtered (to a thickness of approximately 0.45 μm), and the practical salinity was measured. Then, 19 kg of this water was weighed into two 20-liter flexible tanks, 1 and 2, and the pH value was adjusted to 11.4 to allow Mg(OH)2 to precipitate. The mixture was then left overnight. The supernatant liquid from the flexible tanks was transferred to a 25-liter glass tank 3 using a peristaltic pump P. CO2 gas generated in a gas container 11 was then blown into the glass tank 3 via a pipe 10 to precipitate CaCO3. The CO2 gas was generated by accurately weighing 10-50 g of constant-weight NaHCO3 (baking soda) into a PET bottle and adding phosphoric acid (1+1) dropwise.

[0038] The aeration gas was circulated by a pump. After neutralizing the pH to approximately 7, the solution was made alkaline again with saturated NaOH solution, and then neutralized with CO2 gas, repeating the precipitation of CaCO3 (limestone). Finally, the supernatant liquid in glass tank 3 was drained and the precipitate was collected. The Mg(OH)2 precipitate in tanks 1 and 2 was weighed to match the amount in one of the tanks. As described above, CO2 gas was blown in and circulating aeration was continued for more than 48 hours. After aeration, the weight increase of the tank was weighed and used as the amount of CO2 gas fixed. The following water quality analysis was performed on the filtered water and supernatant water.

[0039] Analysis items: pH, Na + , K + Mg 2+ Ca 2+ Cl - SO4 2- , Alkalinity, total carbon dioxide, HCO3 - The precipitates collected in the experiment were washed with pH-adjusted purified water, desalted, and dried before being used as analytical samples. Qualitative analysis of the precipitates was performed by X-ray diffraction, and quantitative analysis of Ca and Mg was also conducted. The precipitate in tank 3 was considered to be CaCO3, and the amount of CO2 fixed was calculated and added to the amounts fixed in tanks 1 and 2. The amount of CO2 fixed in the above experiment was calculated to be 105g. This amount was slightly excessive compared to the theoretical value obtained from the practical salinity of 38kg of filtered seawater used (corrected for analytical sampling amounts, etc.).

[0040] The cause of this was thought to be the influence of water vapor in the experimental system. X-ray analysis identified the initial precipitate in tanks 1 and 2 as Brucite,Mg(OH)2, and the compound converted after CO2 gas injection as Dypingite,Mg5(CO3)4(OH)2·8H2O. The precipitate in glass tank 3 was identified as a mixture of Aragonite,CaCO3 and Calcite,CaCO3.

[0041] This invention sets up a closed seawater area resembling a giant tank, as shown in Figure 1, and adjusts the pH of the alkaline supernatant liquid in this area by adding a saturated sodium hydroxide solution to adjust the pH to 10.5 to 12, preferably 11 to 12, and more preferably 11.1 to 11.6, thereby precipitating and removing magnesium ions. Furthermore, even in a supersaturated state, calcium ions, whose precipitation was inhibited by magnesium ions, are reacted and neutralized, causing calcium carbonate to precipitate. Calcium and carbon dioxide are then fixed as crystals from the solution, making them easily removable. By scaling this up, it is possible to promote the absorption of CO2 from the atmosphere, thereby significantly contributing to combating global warming. In addition, the diffusion of alkaline water into the sea can contribute to preventing seawater acidification, another carbon dioxide problem. Subsequent experiments showed that the best results were obtained efficiently at a pH of 11.4.

[0042] The seawater used in the experiment is filtered in a pre-prepared seawater filtration system and then stored in flexible tanks (1 and 2 in the diagram). When the pH is adjusted to a highly alkaline range of around 11 (pH 11.0 to less than pH 12) with sodium hydroxide, magnesium hydroxide precipitates and separates. In this case, various experiments have shown that magnesium hydroxide precipitates and separates even at a pH of around 10.5, but the efficiency is slightly lower. Preferably, the pH is in the range of 11.0 to 12, and even better results were obtained at pH 11.1 to 11.6, and even more preferably at pH 11.4. Furthermore, the supernatant seawater, from which magnesium ions that interfere with calcium ion precipitation have been removed, is transferred to a separate tank 3, and CO2 gas is blown into it. A neutralization reaction causes calcium carbonate to precipitate, and calcium and carbon dioxide are fixed as crystals from the solution, making them easily removable.

[0043] It was also revealed that magnesium carbonate produced by blowing carbon dioxide into a magnesium hydroxide slurry has better settling properties and is easier to recover than the magnesium hydroxide slurry. As is clear from the experimental results above, the increase in atmospheric carbon dioxide (assumed to be 1) was fixed as part of the carbonate sediment (6 million times) via the ocean components (12,000 times). Calcium carbonate in surface seawater is supersaturated but does not form precipitates due to the coexisting dissolved magnesium ions. Therefore, by adding a saturated sodium hydroxide solution to seawater and adjusting the pH to around 11 (pH 11 or higher but less than pH 12), the magnesium ions can be precipitated and removed as magnesium hydroxide. [Explanation of symbols]

[0044] 1 Flexible Tank 2 Flexible Tank 3 Aquariums 4 hoses 5 hoses 6 Solution vessel 7. Air supply pipe 8 pipes 9 valves 10 pipes 11 Gas containers 12 valves 13. Container for holding saturated NaOH solution 14 Supply pipe

Claims

1. A method for fixing carbon dioxide in the atmosphere using marine components, carried out in a seawater area, The process involves adding a saturated sodium hydroxide solution to surface seawater to create a highly alkaline pH range of 10.5 to 12, thereby precipitating magnesium hydroxide and separating magnesium from most of the calcium in the surface seawater, while simultaneously reacting the bicarbonate ions and calcium ions dissolved in the surface seawater to coprecipitate calcium carbonate. A method for fixing carbon dioxide in the atmosphere using marine components, characterized by comprising the step of reacting atmospheric carbon dioxide with calcium ions dissolved in surface seawater to precipitate calcium carbonate.

2. The method for fixing carbon dioxide in the atmosphere using marine components according to Claim 1, characterized in that the high-alkaline range is within the range of pH 11.0 to pH 12.

3. The method for fixing carbon dioxide in the atmosphere using marine components according to Claim 1, characterized in that the high-alkaline range is within the range of pH 11.1 to pH 11.

6.

4. A method for fixing carbon dioxide in the atmosphere using marine components according to Claim 1, characterized by comprising the step of adding a saturated sodium hydroxide solution to surface seawater to precipitate magnesium hydroxide, and then blowing carbon dioxide gas into the precipitated magnesium hydroxide to convert it into magnesium carbonate.

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