Immobilization method of carbon dioxide in atmosphere by utilizing 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 ocean's carbon dioxide absorption capacity by adjusting the carbon dioxide content in the ocean components and the atmosphere, thereby maintaining the ocean's carbon dioxide recovery capacity as constant as possible on average at all times, thereby reducing fluctuations in global warming. [Background technology]

[0002] In general, carbon dioxide is exchanged between the atmosphere and oceans surrounding the Earth, with the oceans absorbing carbon dioxide from the atmosphere. There are also areas in the ocean 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 oceans and the atmosphere varies greatly depending on the season and year, as well as the ocean areas and the amount of carbon dioxide absorbed or released. Therefore, as global warming progresses in the future, it is predicted that the oceans' ability to absorb carbon dioxide may begin to decline, and it is therefore necessary to constantly monitor this irregular absorption and release of carbon dioxide by the oceans.

[0003] Here, when we look at the main factors that change the absorption and release of carbon dioxide by the ocean, we find that they are related to the difference between the partial pressure of carbon dioxide in the atmosphere and the partial pressure of carbon dioxide in the ocean surface, as well as fluctuations in wind speed. In other words, when the partial pressure of carbon dioxide in the ocean surface is higher than that of the atmosphere, the ocean will release carbon dioxide to the atmosphere, and conversely, when the partial pressure of carbon dioxide in the ocean surface is lower than that of the atmosphere, the ocean will absorb carbon dioxide from the atmosphere. In this case, the faster the wind speed, the more carbon dioxide will be absorbed or released.

[0004] In this case, the partial pressure of carbon dioxide in surface seawater, for example, decreases as the water temperature increases, and the carbon dioxide that does not completely dissolve increases the partial pressure of carbon dioxide in the surface seawater. Furthermore, the partial pressure of carbon dioxide in the surface seawater increases when it mixes with the lower water, which contains more carbon dioxide, due to vertical mixing and upwelling of seawater. In addition, when biological activity becomes active, phytoplankton consumes carbon dioxide, lowering the partial pressure of carbon dioxide in the surface seawater. Thus, the partial pressure of carbon dioxide in the surface seawater fluctuates greatly due to various influences such as water temperature, vertical mixing and upwelling of seawater, and biological activity.

[0005] Regarding the distribution of carbon dioxide absorption or release and the characteristics of seasonal fluctuations, the seasonal distribution and seasonal fluctuations of carbon dioxide exchange volume are shown below, divided into the equatorial region, subtropical zone, and subpolar zone. First, in the equatorial region, the partial pressure of carbon dioxide in the surface seawater is high due to the influence of upwelling, and although seasonal fluctuations are said to be relatively small in the equatorial Pacific Ocean in particular, the amount of carbon dioxide released is the largest in the entire ocean, and carbon dioxide release areas are widely distributed around this area, with carbon dioxide being released throughout the year.

[0006] On the other hand, in the subtropics, carbon dioxide sinks are widely distributed, and the partial pressure of carbon dioxide in the surface seawater fluctuates seasonally due to the influence of sea surface temperature, generally with more absorption in winter and less in summer. Furthermore, in the subarctic zone, seasonal fluctuations occur due to the combined influence of not only sea surface temperature but also vertical mixing of seawater and biological activity, so the annual amount of carbon dioxide exchange is not uniform. Generally, in winter, strong winds cool the sea surface, causing strong vertical mixing, which turns it into a carbon dioxide release area, and from spring to autumn, biological activity consumes carbon dioxide in the surface seawater, turning it into a sink area, repeating seasonal fluctuations.

[0007] Furthermore, looking at variations over a 10-year period, the equatorial Pacific Ocean is an area where carbon dioxide emissions are particularly high, as mentioned above, and because the amount of emissions also varies greatly between the occurrence of El Niño and La Niña phenomena and other times, the amount of carbon dioxide absorbed by the entire ocean on a global scale tends to vary significantly from year to year. Conversely, during the occurrence of the La Niña phenomenon, there is a tendency for carbon dioxide emissions to increase due to stronger upwelling.

[0008] As mentioned above, it is predicted that the average carbon dioxide absorption capacity of the ocean as a whole may begin to decline if global warming continues in the future, and therefore there is a strong desire to realize a technology to regulate such irregular absorption and release of carbon dioxide by the ocean. One method has been known to date that includes the steps of (1) electrolyzing saturated salt water to obtain sodium hydroxide, (2) adding sodium hydroxide to seawater to convert the magnesium chloride and calcium chloride in the seawater to magnesium hydroxide and calcium hydroxide, and (3) introducing carbon dioxide into water containing magnesium hydroxide and calcium hydroxide to convert them back to magnesium carbonate and calcium carbonate. (JP Patent Publication No. 2010-125354)

[0009] Also known is a method for recovering and removing carbon dioxide from seawater, which comprises combining calcium and magnesium coexisting in seawater with carbon dioxide (JP 2005-21870 A). Furthermore, in order to increase the carbon dioxide reduction capacity while taking into account the amount of carbon dioxide emissions, a carbon dioxide fixation method is also known that includes a process for obtaining alkaline earth metal oxide from brine containing alkaline earth metal, and a carbon dioxide reaction process for reacting the alkaline earth metal oxide with a gas containing carbon dioxide (JP 2020-175344 A).

[0010] Furthermore, an artificial global warming prevention system is also known that utilizes natural conditions in which high-pressure steam generated by a steam generator such as a ship or a boiler is sprayed into the sky under certain conditions, thereby generating an updraft, which causes water vapor in the air to rise and form clouds in the sky, partially covering a certain area of ​​the Earth, blocking solar heat and causing rain to fall (JP 2010-155957 A).

[0011] Furthermore, a method of preventing global warming is also known in which deep-sea water is utilized by moving it to the surface using a water-passing pipe that is nearly horizontal on the inlet side and curves upward toward the outlet, and is moored in seawater, and by mixing the deep-sea water, which is a cold heat source, with seawater in the surface layer, thereby lowering the air temperature above the sea surface in the surface layer (JP Patent Publication No. 2009-046973). [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2010-125354 A [Patent Document 2] JP 2005-21870 A [Patent Document 3] JP 2020-175344 A [Patent Document 4] JP 2010-155957 A [Patent Document 5] JP 2009-046973 A Summary of the Invention [Problem to be solved by the invention]

[0013] However, the technology described in the above Patent Document 1 has technical difficulties in that it uses a method of electrolyzing saturated salt water to obtain sodium hydroxide. That is, as a result of many repeated experiments and research into the method of electrolyzing saturated salt water to obtain sodium hydroxide together with chlorine and hydrogen, it is not realistic to approach this on a quasi-global scale, assuming a unique global-scale exchange of carbon dioxide, which is the key to maintaining the carbon dioxide capture capacity in the ocean as constant as possible on average at all times and reducing the fluctuation of global warming.

[0014] In addition, in this case, the statements "saturated salt water is electrolyzed to obtain sodium hydroxide" and "sodium hydroxide is added to seawater to convert the magnesium chloride and calcium chloride in the seawater into magnesium hydroxide and calcium hydroxide" are unclear, since seawater contains dissolved cations such as sodium ions, magnesium ions, calcium ions, potassium ions, etc., and complex ions such as chloride ions, sulfate ions, bicarbonate ions, etc., as anions.

[0015] In addition, in the case of combining calcium and magnesium coexisting in seawater with carbonic acid as described in Patent Document 2, it is presumed that calcium is combined as carbonate, but for magnesium, only hydroxide is formed, and there is no practical basis for the formation of carbonate. Also, it is said that "decarbonated seawater, which has had the carbon dioxide contained in deep ocean water removed, absorbs carbon dioxide from the atmosphere by coming into contact with the atmosphere," but although it is possible that decarbonated seawater absorbs carbon dioxide from the atmosphere, whether or not it actually does so is related to the balance of parameters such as the pH, temperature, pressure, and alkalinity of the seawater, and it cannot be said that seawater necessarily has a superior ability to absorb carbon dioxide.

[0016] Furthermore, it is written that "the hydrogen ion concentration of seawater after electrolysis is lower than that before treatment, and therefore the carbon dioxide absorption capacity is further increased," but this statement forgets that when the hydrogen ion concentration is lower, 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 cations and anions are not balanced. Furthermore, the bittern mentioned there is a license related to the production of sodium hydroxide and has nothing to do with the carbon dioxide capture method.

[0017] The carbon dioxide fixation method described in Patent Document 3 includes a step of obtaining alkaline earth metal oxide from alkaline earth metal-containing brine, and a carbon dioxide reaction step of reacting the alkaline earth metal oxide with a gas containing carbon dioxide, in order to increase the carbon dioxide reduction capacity while taking into account the amount of carbon dioxide emissions. Since an evaporation and concentration step is incorporated, a large amount of thermal energy is used, and even if carbon dioxide can be fixed in some steps, the overall process including all the steps will result in more carbon dioxide being emitted.

[0018] In addition, as described in Patent Document 4, a system for preventing global warming is artificially developed by injecting high-pressure steam generated by steam generators such as ships and boilers into the sky under certain conditions, which generates an updraft, causing water vapor in the air to rise and form clouds in the sky, partially covering a certain area of ​​the earth and blocking solar heat, resulting in rain. However, if clouds are to be generated using high-pressure steam, a huge amount of thermal energy is required, and more carbon dioxide is generated in order to obtain this energy source. Moreover, the generation of steam not only generates clouds, but also increases the concentration of water vapor in the atmosphere. Since water vapor is a more powerful greenhouse gas than carbon dioxide, this system actually promotes global warming.

[0019] In addition, the method for preventing global warming in Patent Document 5, which uses "a water pipe with an inlet facing the upstream of the flow of deep sea water, through which deep sea water flows, and an outlet curved or inclined upward, said water pipe having fins and an inlet facing the upstream side of the flow of deep sea water" to move deep sea water, which is a cold heat source, to the surface, and to fuse the deep sea water with the original sea water in the surface to lower the sea water temperature in the surface, and to lower the air temperature above the sea surface in the surface by gas-liquid heat transport between the deep sea water and the atmosphere in contact with the sea surface, is merely a water pipe through which deep sea water flows and an outlet curved or inclined upward, and is naturally not practical for stabilizing the carbon dioxide absorption capacity of deep sea water on a global scale. [Means for solving the problem]

[0020] Therefore, the inventors have been working on CO2 fixation technology using seawater components, as a relatively small-scale plant that can be expanded in the future, and as a result, they have succeeded in developing a groundbreaking plant that can absorb CO2 into the bittern component in seawater. In order to complete the plant, the inventors established reliable technology and, with a strong desire to contribute to the creation of an advanced society, conducted research activities to realize environmental technology, particularly efforts aimed at reducing CO2 in the atmosphere, in order to realize the rich lives and dreams of people around the world. At the same time, in October 2020, Japan declared "carbon neutral by 2050," and in April 2021, a new government policy was announced, aiming for a 46% reduction from 2013 as a new target for greenhouse gas reduction in 2030, and continuing to challenge itself to reach a higher target of 50%.

[0021] Meanwhile, according to our research, the current amount of CO2 in the atmosphere is 750Gt (as C), and is increasing by about 3.3GtC per year. In addition, an analysis of seawater components showed that the amount of carbon in the form of dissolved carbonate (HCO3) is 3.8×10 4The amount of dissolved bittern in seawater is about 50 times that of the atmosphere. Seawater is like "salty sodium bicarbonate water." The amount of bittern is about 2×10 in sediments, mainly limestone. 7 GtC is believed to be present. This is estimated to be approximately 27,000 times the amount of CO2 in the atmosphere.

[0022] In addition, fossil fuel reserves have a 1.2×10 4 GtC, land biomass 2 x 10 3 GtC and the like are thought to be the main locations of carbon dioxide on Earth. The project organized by the inventors attempts to develop technology to fix the increase in atmospheric CO2 (hereinafter simply referred to as "1") as part of sediments, specifically carbonates (limestone), via marine components (12,000 times), i.e., as part of 6 million times. Incidentally, calcification (fixation of carbon dioxide) is a phenomenon that occurs universally in nature.

[0023] In a project planned by the present inventors, the main dissolved components per kg of seawater were investigated, and it was found that 0.413 g of calcium and 0.142 g of carbon dioxide were dissolved as HCO3. In seawater, calcium and carbon dioxide are 3 to 6 times supersaturated as calcium carbonate, but they do not precipitate because the coexisting magnesium ions hinder the precipitation of both. In addition, according to extensive repeated research by the present 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 high alkaline range of around 10.5 or more.

[0024] When magnesium ions are removed from seawater, carbon dioxide and calcium ions combine to form calcium carbonate precipitates, and the chemical balance in this case is such that of the two equivalents of CO2 dissolved in seawater, one equivalent of CO2 is released into limestone and the other equivalent of CO2 is released back into the atmosphere.

[0025] The existence of the above phenomenon is verified below. For the verification, seawater that constitutes the actual ocean is used, and it is revealed that by adding sodium hydroxide to the seawater to raise the pH to a high alkaline range, precipitating and removing Mg(OH)2, and then injecting CO2 gas into the seawater, the partial pressure of CO2 is increased and the pH is 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 fixation of CO2 as limestone will be explained and confirmed below. Effect of the Invention

[0026] As is clear from the above research results, the increase in atmospheric carbon dioxide (assumed to be 1) was fixed as part of the carbonates in sediments (6 million times) via marine components (12,000 times). Although calcium carbonate in surface seawater is dissolved in a supersaturated state, it does not form a precipitate due to the coexisting dissolved magnesium ions. Therefore, subsequent research revealed that adding a saturated sodium hydroxide solution to seawater to bring the pH to a highly alkaline range of 10.5 to 12 makes it possible to precipitate and remove the magnesium ions as magnesium hydroxide.

[0027] In other words, because calcium ions are dissolved in this alkaline supernatant, blowing carbon dioxide into it causes a neutralization reaction, which causes calcium carbonate to precipitate, and calcium and carbon dioxide are removed from the solution as crystals and fixed. Also, by blowing carbon dioxide into magnesium hydroxide slurry generated from seawater, the magnesium hydroxide is converted into magnesium carbonate, allowing carbon dioxide to be fixed. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a perspective view showing an outline of an experimental apparatus for sediment recovery using a closed batch test. [Diagram 2] A graph showing the hydroxide formation zone due to pH adjustment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of the entire experimental apparatus used to demonstrate that injecting CO2 gas into the above seawater in the present invention neutralizes the pH, resulting in the crystallization of calcium carbonate CaCO3 (limestone). In Fig. 1, 1 and 2 respectively denote flexible tanks for storing raw seawater (sample seawater). 1a and 2b denote valves provided on the upper surface of each flexible tank. 3 denotes a large-capacity water tank, which is connected to flexible tank 1 via hose 4 with pump P interposed in the middle, and is also connected to flexible tank 2 via hose 5 with pump P interposed in the middle.

[0030] Hoses 4 and 5 join midway and are introduced into water tank 3. Reference numeral 6 denotes a solution container for supplying NaOH saturated solution into flexible tanks 1 and 2. Reference numeral 7 denotes an air supply pipe for purging water tank 3, and reference numeral 8 denotes a pipe for supplying CO2 gas from Tedlar bag 8a into water tank 3, with valve 9 provided midway. Reference numeral 10 denotes a pipe for supplying phosphoric acid to generate CO2 gas in gas container 11, with valve 12 provided midway. Reference numeral 13 denotes a container for holding NaOH saturated solution. Reference numeral 14 denotes a supply pipe for supplying NaOH saturated solution from container 13 into water tank 3.

[0031] In the present invention, a closed seawater area is set up like a huge water tank, and a saturated sodium hydroxide solution is added to the alkaline supernatant in the water area to adjust the pH to a high alkaline range of pH 10.5 or more, desirably pH 11 to pH 12, and more preferably pH 11.1 to pH 11.6, thereby separating the precipitate of magnesium hydroxide. Even in a supersaturated state, calcium carbonate, which was inhibited from precipitating by magnesium ions, is neutralized by reaction and calcium carbonate precipitates, and calcium and carbon dioxide are fixed as crystals from the solution and can be easily removed. By expanding this on a large scale, 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 present inventors, the main dissolved components per kg of seawater were investigated, and it was found that 0.413 g of calcium and 0.142 g of carbon dioxide were dissolved as HCO3. In seawater, calcium and carbon dioxide are 3 to 6 times supersaturated as calcium carbonate, but they do not precipitate because the coexisting magnesium ions hinder the precipitation of both. Furthermore, according to the present inventors' research, it was found that magnesium, among the dissolved compounds, can be most efficiently removed as Mg(OH)2 at a pH of around 11.4.

[0033] When magnesium ions are removed from seawater, carbon dioxide and calcium ions combine to form calcium carbonate, which precipitates. In this case, the chemical amount of two equivalents of CO2 is one equivalent of CO2 that is released into limestone and the other equivalent of CO2 is released back into the atmosphere.

[0034] The existence of the above phenomenon will be verified while explaining it below. For the verification, seawater that constitutes the actual ocean was used, and it was revealed that by adding sodium hydroxide to the seawater to raise the pH to a high alkaline range, precipitating and removing Mg(OH)2, and then injecting CO2 gas into the seawater with an increased CO2 partial pressure, the pH is neutralized, and calcium carbonate CaCO3 (limestone) can be crystallized. The mass balance of CO2 in the series of processes described above will be grasped to confirm the fixation of CO2 as limestone.

[0035] As mentioned above, Ca in the ocean surface water 2+ According to the latest research results, it is calculated that the calcium carbonate CaCO3 (limestone) is 3 to 6 times supersaturated (Ω value), but it does not usually form inorganic precipitation. This is because the coexisting Mg 2+ This is thought to be the effect of the change in pH value. 2+ , Ca 2+ The relationship between the formation of hydroxides and the solubility product of Mg(OH)2 was shown. A saturated NaOH solution was added to the filtered seawater, and Mg(OH)2 was precipitated and separated with high efficiency at a high pH of 11.4. In this case, almost no precipitation of Ca(OH)2 was observed at pH 11.4, and most of the Ca 2+ remains in the supernatant water (some Ca 2+ co-precipitates as CaCO3).

[0036] After separation, the supernatant water was neutralized by blowing in CO2 gas, which caused it to precipitate and be fixed as CaCO3. By blowing in CO2 gas into the precipitate of Mg(OH)2, it was also possible to convert it to magnesium carbonate. By the above method, it was possible to fix carbon dioxide as carbonate using seawater components. The experiment in Figure 1 was 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 mentioned above, seawater collected from a clean coastline was used, filtered (equivalent to 0.45 μm) to measure the practical salinity, and then 19 kg of the water was weighed into two 20-liter flexible tanks 1 and 2, and the pH value was tentatively set to pH 11.4 to precipitate Mg(OH)2, and the tank was left overnight. The supernatant liquid in the flexible tank was transferred to a 25-liter glass tank 3 by a peristaltic pump P, and CaCO3 was precipitated in the glass tank 3 by blowing CO2 gas generated in a gas container 11 into the tank 3 through a pipe 10. The CO2 gas was generated by accurately weighing 10 to 50 g of NaHCO3 (sodium bicarbonate) in a plastic bottle and dropping phosphoric acid (1+1) into the bottle.

[0038] The aeration gas was circulated using a pump. After neutralizing the pH to about 7, the solution was again made alkaline with saturated NaOH solution, neutralized with CO2 gas, and CaCO3 (limestone) precipitation was repeated. Finally, the supernatant liquid in glass tank 3 was poured off and the precipitate was collected. The Mg(OH)2 precipitates in tanks 1 and 2 were weighed together with one of the tanks. CO2 gas was blown in as above, and circulating aeration was continued for more than 48 hours. After aeration, the increase in tank weight was weighed and recorded as the fixed amount of CO2 gas. The following water quality analysis was carried out 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 precipitate collected in the experiment was washed with pH-adjusted purified water, desalted, dried, and then used as an analytical sample. The precipitate was subjected to qualitative analysis by X-ray analysis, and quantitative analysis of Ca and Mg was carried out. The precipitate in tank 3 was considered to be CaCO3, and the amount of fixed CO2 was calculated and added to the amount fixed in tanks 1 and 2. The amount of fixed CO2 in the above experiment was calculated to be 105g. This amount was slightly excessive when compared to the theoretical value calculated from the practical salinity of the 38kg filtered seawater used (corrected for analytical sampling amount, 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 precipitates in 1 and 2 as brucite, Mg(OH)2, and the compound that was transformed 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] In the present invention, a closed seawater area is set up like a huge tank as shown in FIG. 1, and the alkaline supernatant in the seawater area is adjusted to pH 10.5 to pH 12, preferably pH 11 to 12, and more preferably pH 11.1 to pH 11.6 by adding saturated sodium hydroxide solution. Furthermore, calcium ions, which were inhibited from precipitating by magnesium ions even in a supersaturated state, are reacted and neutralized to precipitate calcium carbonate, and calcium and carbon dioxide are fixed as crystals from the solution, making it easy to remove. By expanding this to a large scale, it is possible to promote the absorption of CO2 in the atmosphere, which can greatly contribute to global warming. In addition, the diffusion of alkaline water into the sea can also contribute to the prevention of seawater acidification, which is another carbon dioxide problem. Subsequent experiments showed that the best results were obtained efficiently when the pH was 11.4.

[0042] The seawater used in the experiment is filtered in a seawater filtration device prepared in advance, then stored in a flexible tank (1 and 2 in the drawing). When the pH is adjusted to a high alkaline range of 11 (pH 11.0 to less than pH 12) with sodium hydroxide, magnesium hydroxide is precipitated and separated. As a result of various experiments, magnesium hydroxide is precipitated and separated even at about pH 10.5, but the efficiency is somewhat reduced. The preferable pH range is pH 11.0 to pH 12, and even better results were obtained at pH 11.1 to pH 11.6, and even more preferably pH 11.4. Furthermore, the supernatant seawater from which magnesium ions, which are a substance that hinders calcium ion precipitation, have been removed is transferred to a separate water tank 3, and when CO2 gas is blown into it, calcium carbonate precipitates due to a neutralization reaction, and calcium and carbon dioxide are fixed as crystals from the solution, making it possible to easily remove them.

[0043] It was also found that magnesium carbonate produced by blowing carbon dioxide into a magnesium hydroxide slurry has better sedimentation properties and is easier to recover than magnesium hydroxide slurry. As is clear from the above experimental results, the increase in atmospheric carbon dioxide (assumed to be 1) was fixed as part of the carbonates in sediments (6 million times) via marine components (12,000 times). Although calcium carbonate in surface seawater is dissolved in a supersaturated state, it does not form a precipitate due to the coexisting dissolved magnesium ions. Therefore, by adding a saturated sodium hydroxide solution to seawater and raising the pH to the 11 range (above pH11 and below pH12), the magnesium ions can be precipitated and removed as magnesium hydroxide. [Explanation of symbols]

[0044] 1 Flexible Tank 2 Flexible Tank 3. Aquarium 4 Hose 5 Hose 6 Solution vessel 7 Air supply pipe 8. Pipes 9 Valve 10 Pipes 11 Gas bottles 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, comprising the steps of adding a saturated solution of sodium hydroxide to seawater to make it highly alkaline at pH 10.5 to pH 12, and separating the magnesium from most of the calcium in the seawater, and reacting hydrogen carbonate ions and calcium ions dissolved in the seawater to precipitate and co-precipitate calcium carbonate.

2. 2. A method for fixation of carbon dioxide in the atmosphere utilizing marine components according to claim 1, wherein the highly alkaline region obtained by adding a saturated sodium hydroxide solution to seawater has a pH range of 11.0 to 12.

3. 2. A method for fixation of carbon dioxide in the atmosphere utilizing marine components according to claim 1, wherein the highly alkaline region obtained by adding a saturated sodium hydroxide solution to seawater has a pH range of 11.1 to 11.

6.

4. 2. The method for fixing carbon dioxide according to claim 1, further comprising the step of: adding a saturated solution of sodium hydroxide to 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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