METHOD OF ELECTRODEPOSITION IN SEAWATER FOR THE GROWTH OF CONSTRUCTION MATERIALS

Abstract

The present invention relates to a method to produce calcium rich-based aggregates by electrodeposition in salty aqueous CO.sub.2 enriched solutions, that can be used in the construction industry. The method includes filtering an aqueous salty solution to produce an aqueous salty solution free of organic debris or pollutants, adjusting a temperature and pH in a conditioning reactor CR1 to produce an aqueous salty solution, bringing the aqueous salty solution from CR1 to a continuous reactor CR2 equipped with an electroactive substrate comprising at least one cathode and at least one anode connected to an electrical DC supply, injecting in CR2 a flux of a gas mixture containing CO.sub.2 (C-gas) in contact with the flux of the aqueous solution, applying to the flux of the CO.sub.2-enriched aqueous solution a constant DC current, and recovering the calcium rich-based aggregates deposited on the electroactive substrate and/or on the bottom of CR2.

Claims

1. Method to produce calcium rich-based aggregates, said method comprising the following steps: a) Filter an aqueous salty solution AS1 to produce an aqueous salty solution AS2 free of organic debris or pollutants; b) Bring the aqueous salty solution AS2 at a temperature from 18 to 29 C. and at a pH from 7.1 to 9, in a conditioning reactor CR1 to produce an aqueous salty solution AS3; c) Bring the aqueous salty solution AS3 from CR1 to a continuous reactor CR2 equipped with an electroactive substrate comprising at least one cathode and at least one anode connected to an electrical DC supply, wherein the flux of AS3 (FRAS3) in CR2 is kept at a velocity or displacement speed VAS3 located from 0.01 m/s to 5 m/s; d) Inject in CR2 a flux of a gas mixture containing CO.sub.2 (C-gas) in contact with the flux of the aqueous solution AS3; e) Apply to the flux of the CO.sub.2-enriched aqueous solution AS3 a constant DC current ranging from 1 A/m.sup.2 to 5000 A/m.sup.2, the m.sup.2 representing the deployed surface of the electrodes in contact with AS3, or a voltage ranging from 0.5 V to 20.0 V, to the electrodes; f) Recover the calcium rich-based aggregates deposited on the electroactive substrate and/or on the bottom of CR2.

2. Method according to claim 1, wherein the aqueous salty solution AS2 is brought in step b) at a temperature from 20 C. to 25 C. and at a pH from 8.0 to 8.4, in CR1.

3. Method according to claim 1, wherein the continuous reactor CR2 of step c) comprises at least two compartments each comprising at least one cathode or at least one anode.

4. Method according to claim 1, wherein the C-gas of step d) is re-circulated to be re-injected into CR2.

5. Method according to claim 1, wherein the volume % of CO.sub.2 injected in the continuous reactor CR2 in step d) is 0.05-10 volume % per hour.

6. Method according to claim 1, wherein the DC current ranges from 5 A/m.sup.2 to 1000 A/m.sup.2.

7. Method according to claim 1, wherein the voltage ranges from 0.8 V to 10.0 V volts.

8. Method according to claim 1, wherein the calcium rich-based aggregates are produced with a CaCO.sub.3 content from 20% to 90%.

9. Method according to claim 1; wherein the calcium rich-based aggregates are produced with an average size from 0.1 mm to 15 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0124] FIG. 1 shows a general view of the methodology/process according to the invention.

[0125] FIG. 2A and FIG. 2B show an alternative for reactor CR2 using multiple chambers for respectively the anodes and the cathodes (2a) example of a second preferred embodiment according to the invention where the reactor CR2 has 2 chambers (or compartments) arranged in series (2b) example of a second preferred embodiment according to the invention where the reactor CR2 has 2 chambers (or compartments) arranged in parallel.

[0126] FIG. 3 shows the macroscopic view of the dried electrodeposited solid minerals produced at or near the stainless-steel cathode from laboratory experiments of a 2-liter vessel without and with CO.sub.2 injection. The macroscopic size of the aggregates varies between 0.01-5 mm depending upon the magnitude of applied current or voltage and white/pale white in color.

[0127] FIG. 4 shows the macroscopic view of the dried electrodeposited aggregates (A) at constant current (B) at constant voltage, produced at or near the stainless-steel cathode from laboratory experiments of a 2-liter vessel. The macroscopic size of the aggregates varies between 0.01-5 mm depending upon the magnitude of applied current or voltage and white/pale white in color.

[0128] FIGS. 5A-5C shows by scanning electronic microscopy (SEM) of the morphological features of the dried electrodeposited aggregates on microscopic scale that resemble brucite, aragonite and calcite polymorphs ranging from numerous small petals forming a fibrous interwoven structure of brucite particles appearing as flower petals, to elongated needle-like columnar structures of aragonite, to cubic subhedral microcrystals of calcite appearing as small cubes.

[0129] FIGS. 6A and 6B shows the relationship between the total mass of electrodeposited aggregates and the injected CO.sub.2 flow rate at an applied electrochemical current (240 mA or 840 A/m.sup.2, FIG. 6A) and voltage (2 V vs Ag/AgCl, FIG. 6B).

[0130] FIGS. 7A-7D illustrates the percentage weight of (7A) polymorphs determined by XRD (7B) CaCO.sub.3 and Mg(OH).sub.2 estimated from TGA at an applied current of 240 mA or 840 mA/cm.sup.2 (7C) polymorphs determined by XRD (7D) CaCO.sub.3 and Mg(OH).sub.2 estimated from TGA at an applied voltage of 2 V (vs Ag/AgCl).

[0131] FIG. 8A and FIG. 8B shows the normalized production rate and energy consumption (8A) at an applied current of 240 mA or 840 mA/cm.sup.2 (8B) at an applied voltage of 2 V (vs Ag/AgCl).

EXAMPLES

Example 1: Materials and Methods

Synthesis of Artificial Seawater

[0132] Artificial saltwater was synthesized using sea salt (ASTM D1141-98) from Lake Products Company LLC and Type 1 ultrapure water (18.2 Mwcm of resistivity at 25 C.) from Millipore Sigma. As a result, 41.953 g of sea salt was completely dissolved in 1 liter of water to meet the ASTM D1141-98 requirement. Instant mixed seawater was found to have a pH that ranged from 8.3 to 8.4 at ambient temperatures.

CO.SUB.2 .Injection Pathway

[0133] A mass flow controller of range 0.01-300 sccm (standard cubic centimeter per minute) from Alicat Scientific Inc. was used for CO.sub.2 injection.

[0134] CO.sub.2 injected from a gaseous stream of 0.01% to 100% CO.sub.2 at a flowrate so that the concentration of CO.sub.2 in cathodic chamber injected in the range 30-100 mM in seawater. For a reactor vessel of 2-liter, the flowrate between 0.15-0.45 sccm (standard cubic centimeter per minute) from a 99.9% concentrated CO.sub.2 stream can maintain the required concentration.

Electrochemical Treatment

[0135] All the experiments have been performed on a batch scale on a 2-liter artificial seawater in a controlled laboratory setting. Initially, the system is allowed to equilibrate for 1 hour as the open circuit potential is measured. Electrodeposits are created by applying a constant current or voltage for a time 24 or 72 or 120 or 168 h (i.e., 1 day-7 days) using a DC power source. The working current range is 1-5000 A/m.sup.2 including 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 3000, 4000, 5000 A/m.sup.2. The working potential range is 0.1-10 V including voltages of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2, 3, 4, 5, 6, 7, 8-, 9, 10 V (vs Ag/AgCl i.e. silver-silver chloride) corresponding to 0.803, 1.003, 1.203, and 1.403, 1.603, 1.803, 2.803, 3.803, 4.803, 5.803, 6.803, 7.803, 8.803, 8.803, 9.803 V (vs SHE i.e. standard hydrogen electrode).

Removing Solid Deposits:

[0136] Shutdown the reactor: Before performing any maintenance, ensure that the electrochemical reactor is safely shut down, and power to the anode and cathode is disconnected. Removal of solid deposits involves removal from the cathode surface as well as removal from the reactor surface. [0137] Mechanical removal of solid aggregates: Depending on the location of the solid deposits on the cathode at the bottom of the reactor, the use of mechanical means to scrape or brush them off the cathode and the reactor's surface can be employed. Firstly, application of a voltage higher than operational voltage or ultrasonic waves can be used to dislodge aggregates from the electrode surface. Then, empty the reactor by filtering out the aqueous solution from the reactor using a filtration unit at the outlet followed using electrically operated scrappers to remove the aggregates from the bottom of the reactor through aggregates outlet. [0138] Or in another configuration, dislodge the aggregates from the electrodes by applying higher voltage as operational voltage and resulting in falling down all the solids at the bottom of the reactor. Then all the aqueous solution from the reactor containing aggregates and aqueous stream can be subjected to a vacuum filtration bed where aggregates can be filtered out using gravity or rotational filtration bed and sent for drying and aqueous filtrate can be discharged upon environmental testing. [0139] Cleaning of electrodes and reactor: [0140] Scraping and Brushing: Tools like metal or polymer scrapers and brushes can be used to physically dislodge deposits from the cathode and reactor surfaces. [0141] Ultrasonic Cleaning of cathode: Ultrasonic cleaning involves the use of high-frequency sound waves to create tiny, high-energy bubbles in a cleaning solution. These bubbles can dislodge and remove deposits from surfaces. This method is effective for cleaning intricate or hard-to-reach areas and can be gentle on materials. The cleaning solution can be filtered out from the outlet and solids can be obtained on filtration unit.

[0142] High-Pressure water Jet Cleaning: High-pressure water jet cleaning utilizes pressurized water to dislodge and remove deposits. This method is effective for removing tough, adherent deposits. It's important to adjust the water pressure to a level that can remove deposits without damaging the stainless steel and titanium. Abrasive Cleaning: Abrasive methods involve using abrasive materials, such as sandpaper, wire brushes, or abrasive compounds, to physically scrub away deposits.

[0143] Sanding and Polishing: In some cases, light sanding and polishing may be used to remove deposits and restore the smooth surface of the cathode and reactor components. This can be particularly effective if deposits have caused surface irregularities.

[0144] Automated Cleaning Systems: For larger industrial setups, automated cleaning systems that involve cleaning with rotating brushes or mechanical arms can be employed for more efficient and consistent cleaning. These systems can be programmed to clean on a regular schedule or in response to deposit buildup.

Characterizations:

[0145] Electrodeposits are collected for upcoming physicochemical characterizations after each test is finished. The deposits are removed from the reactor and dried in a desiccator for 48 hours at room temperature. Scanning electron microscopy (SEM) is used to photograph the electrodeposits' surface and morphological characteristics. X-Ray diffraction (XRD) spectra are obtained at room temperature to determine the crystalline phases of the electrodeposits. The thermal stability of the electrodeposits and corresponding carbon content is investigated using thermogravimetric analysis (TGA).

Example 2: Results and Advantages

[0146] Working example 1: In a method for electrodeposition in seawater for the purpose of obtaining aggregates in the form of electrodeposits, an electric current with a density of 840 A/m.sup.2 is applied to the cathode, where the cathode and anode have a surface area ratio of 1.5. The cathode and anode are positioned at a separation distance equal to the length of the anode. Simultaneously, CO.sub.2 gas is introduced at a rate of 0.15 sccm (standard cubic centimeter per minute) at the bottom of a batch reactor with a volume of 2 liters, the reactor employing artificial seawater with an initial pH in the range of 8.3-8.5. The cathode's surface area is nearly 1.5 cm.sup.2 per unit volume of the reactor. The electrodeposition process is sustained for a duration of 72 hours. The resulting electrodeposit has a mass of 355.67 mg/cm.sup.2 and comprises aragonite (93.05%), calcite (6.81%), and brucite (0.11%), yielding a composite with 45.43% CaCO.sub.3 and 54.57% Mg(OH).sub.2. The electrodeposit exhibits a density of 2.91 g/cc, and its aggregate size ranges from 0.01 to 5 mm. (FIG. 4A, 840 A/m.sup.2; 0.15 sccm CO.sub.2).

[0147] Working example 2: In a method for electrodeposition in seawater for the purpose of obtaining aggregates in the form of electrodeposits, an electric current with a density of 840 A/m.sup.2 is applied to the cathode, where the cathode and anode have a surface area ratio of 1.5. The cathode and anode are positioned at a separation distance equal to the length of the anode. Simultaneously, CO.sub.2 gas is introduced at a rate of 0.30 sccm (standard cubic centimeter per minute) at the bottom of a batch reactor with a volume of 2 liters, the reactor employing artificial seawater with an initial pH in the range of 8.3-8.5. The cathode's surface area is nearly 1.5 cm.sup.2 per unit volume of the reactor. The electrodeposition process is sustained for a duration of 72 hours. The resulting electrodeposit has a mass of 685.78 mg/cm.sup.2 and comprises aragonite (65.89%), calcite (9.31%), and brucite (24.79%), yielding a composite with 52.01% CaCO.sub.3 and 47.99% Mg(OH).sub.2. The electrodeposit exhibits a density of 2.75 g/cc, and its aggregate size ranges from 0.01 to 5 mm. (FIG. 4A, 840 A/m.sup.2; 0.30 sccm CO.sub.2).

[0148] Working example 3: In a method for electrodeposition in seawater for the purpose of obtaining aggregates in the form of electrodeposits, an electric current with a density of 840 A/m.sup.2 is applied to the cathode, where the cathode and anode have a surface area ratio of 1.5. The cathode and anode are positioned at a separation distance equal to the length of the anode. Simultaneously, CO.sub.2 gas is introduced at a rate of 0.45 sccm (standard cubic centimeter per minute) at the bottom of a batch reactor with a volume of 2 liters, the reactor employing artificial seawater with an initial pH in the range of 8.3-8.5. The cathode's surface area is nearly 1.5 cm.sup.2 per unit volume of the reactor. The electrodeposition process is sustained for a duration of 72 hours. The resulting electrodeposit has a mass of 430.70 mg/cm.sup.2 and comprises aragonite (64.4%), calcite (26.41%), and brucite (9.18%), yielding a composite with 62.91% CaCO.sub.3 and 37.09% Mg(OH).sub.2. The electrodeposit exhibits a density of 2.81 g/cc, and its aggregate size ranges from 0.01 to 5 mm. (FIG. 4A, 840 A/m.sup.2; 0.45 sccm CO.sub.2).

[0149] Working Example 4: In a method for electrodeposition in seawater for the purpose of obtaining aggregates in the form of electrodeposits, an electric potential vs Ag/AgCl reference electrode of 2 V is applied to the cathode, where the cathode and anode have a surface area ratio of 1.5. The cathode and anode are positioned at a separation distance equal to the length of the anode. Simultaneously, CO.sub.2 gas is introduced at a rate of 0.15 sccm (standard cubic centimeter per minute) at the bottom of a batch reactor with a volume of 2 liters, the reactor employing artificial seawater with an initial pH in the range of 8.3-8.5. The cathode's surface area is nearly 1.5 cm.sup.2 per unit volume of the reactor. The electrodeposition process is sustained for a duration of 72 hours. The resulting electrodeposit has a mass of 637.43 mg/cm.sup.2 and comprises aragonite (69.01%), calcite (3.93%), and brucite (27.06%), yielding a composite with 69.28% CaCO.sub.3 and 30.71% Mg(OH).sub.2. The electrodeposit exhibits a density of 2.75 g/cc, and its aggregate size ranges from 0.01 to 5 mm. (FIG. 4B, 2V; 0.15 sccm CO.sub.2)

[0150] Working Example 5: In a method for electrodeposition in seawater for the purpose of obtaining aggregates in the form of electrodeposits, an electric potential vs Ag/AgCl reference electrode of 2 V is applied to the cathode, where the cathode and anode have a surface area ratio of 1.5. The cathode and anode are positioned at a separation distance equal to the length of the anode. Simultaneously, CO.sub.2 gas is introduced at a rate of 0.30 sccm (standard cubic centimeter per minute) at the bottom of a batch reactor with a volume of 2 liters, the reactor employing artificial seawater with an initial pH in the range of 8.3-8.5. The cathode's surface area is nearly 1.5 cm.sup.2 per unit volume of the reactor. The electrodeposition process is sustained for a duration of 72 hours. The resulting electrodeposit has a mass of 654.68 mg/cm.sup.2 and comprises aragonite (62.25%), calcite (20.93%), and brucite (16.81%), yielding a composite with 67.58% CaCO.sub.3 and 32.41% Mg(OH).sub.2. The electrodeposit exhibits a density of 2.78 g/cc, and its aggregate size ranges from 0.01 to 5 mm. (FIG. 4B, 2V; 0.30 sccm CO.sub.2)

[0151] Working Example 6: In a method for electrodeposition in seawater for the purpose of obtaining aggregates in the form of electrodeposits, an electric potential vs Ag/AgCl reference electrode of 2 V is applied to the cathode, where the cathode and anode have a surface area ratio of 1.5. The cathode and anode are positioned at a separation distance equal to the length of the anode. Simultaneously, CO.sub.2 gas is introduced at a rate of 0.15 sccm (standard cubic centimeter per minute) at the bottom of a batch reactor with a volume of 2 liters, the reactor employing artificial seawater with an initial pH in the range of 8.3-8.5. The cathode's surface area is nearly 1.5 cm.sup.2 per unit volume of the reactor. The electrodeposition process is sustained for a duration of 72 hours. The resulting electrodeposit has a mass of 589.30 mg/cm.sup.2 and comprises aragonite (41.95%), calcite (7.64%), and brucite (50.41%), yielding a composite with 43.92% CaCO.sub.3 and 56.08% Mg(OH).sub.2. The electrodeposit exhibits a density of 2.61 g/cc, and its aggregate size ranges from 0.01 to 5 mm. (FIG. 4B, 2V; 0.45 sccm CO.sub.2)

TABLE-US-00002 TABLE 1 Summary of working examples with experimental conditions and results Working Working Working Working Working Working example 1 example 2 example 3 example 4 example 5 example 6 Experimental parameters: Cathode Cylinder, Cylinder, Cylinder, Cylinder, Cylinder, Cylinder, geometry Outer Outer Outer Outer Outer Outer diameter diameter diameter diameter diameter diameter 2 mm, active 2 mm, active 2 mm, active 2 mm, active 2 mm, active 2 mm, active length 4.5 cm length 4.5 cm length 4.5 cm length 4.5 cm length 4.5 cm length 4.5 cm Anode geometry Cylinder, Cylinder, Cylinder, Cylinder, Cylinder, Cylinder, outer outer outer outer outer outer diameter diameter diameter diameter diameter diameter 0.78 mm, active 0.78 mm, active 0.78 mm, active 0.78 mm, active 0.78 mm, active 0.78 mm, active length 7.5 cm length 7.5 cm length 7.5 cm length 7.5 cm length 7.5 cm length 7.5 cm Cathode/anode 1.5 1.5 1.5 1.5 1.5 1.5 surface area ratio Active surface 0.14 m.sup.2 0.14 m.sup.2 0.14 m.sup.2 0.14 m.sup.2 0.14 m.sup.2 0.14 m.sup.2 of cathode per m.sup.3 of AS3 Reactor volume 2.5 liters 2.5 liters 2.5 liters 2.5 liters 2.5 liters 2.5 liters Volume of AS3 2 liters 2 liters 2 liters 2 liters 2 liters 2 liters Seawater Artificial Artificial Artificial Artificial Artificial Artificial composition seawater seawater seawater seawater seawater seawater CO.sub.2 Carbon Carbon Carbon Carbon Carbon Carbon composition dioxide dioxide dioxide dioxide dioxide dioxide research research research research research research 99.999% 99.999% 99.999% 99.999% 99.999% 99.999% CO.sub.2 flowrate 0.15 sccm 0.30 sccm 0.45 sccm 0.15 sccm 0.30 sccm 0.45 sccm (standard (standard (standard (standard (standard (standard cubic cubic cubic cubic cubic cubic centimeter centimeter centimeter centimeter centimeter centimeter per minute) per minute) per minute) per minute) per minute) per minute) in 2 liters of in 2 liters of in 2 liters of in 2 liters of in 2 liters of in 2 liters of AS3 AS3 AS3 AS3 AS3 AS3 Applied current 840 A/m2 840 A/m2 840 A/m2 Applied voltage 2 V 2 V 2 V Time of electric 3 days per 2 3 days per 2 3 days per 2 3 days per 3 days per 3 days per treatment liters of AS3 liters of AS3 liters of AS3 2 liters of 2 liters of 2 liters of AS3 AS3 AS3 pH of AS3 8.3-8.5 8.3-8.5 8.3-8.5 8.3-8.5 8.3-8.5 8.3-8.5 Temperature 21-25 C. 21-25 C. 21-25 C. 21-25 C. 21-25 C. 21-25 C. Results: Total mass of 355.67 685.78 430.70 637.43 654.68 589.30 the Or Or Or Or Or Or electrodeposits 3.56 6.86 4.31 6.37 6.55 5.89 [mg cm.sup.2] Or [kg m.sup.2] Composition of Aragonite Aragonite Aragonite Aragonite Aragonite Aragonite electrodeposits 93.05%, 65.89%, 64.4%, 69.01%, 62.25%, 41.95%, Calcite Calcite Calcite Calcite Calcite Calcite 6.81%, 9.31%, 26.41%, 3.93%, 20.93%, 7.64%, Brucite Brucite Brucite Brucite Brucite Brucite 0.11% 24.79% 9.18% 27.06% 16.81% 50.41% CaCO.sub.3% 45.43% 52.01% 62.91% 69.28% 67.58% 43.92% Mg(OH).sub.2% 54.57% 47.99% 37.09% 30.71% 32.41% 56.08% Size of the 0.01-5 mm 0.01-5 mm 0.01-5 mm 0.01-5 mm 0.01-5 mm 0.01-5 mm electrodeposits Density of 2.91 g/cc 2.75 g/cc 2.81 g/cc 2.75 g/cc 2.78 g/cc 2.61 g/cc electrodeposits mixture Energy 127.79 125.18 123.37 113.84 87.75 96.41 consumption [kJ]

Non-working Example 1

[0152] Applying a current density of 840 mA/cm.sup.2 without injecting any external CO.sub.2 produces lesser yield (170.84 mg/cm.sup.2) with higher energy consumption (311.63 kJ) as compared to the product yield achieved with CO.sub.2 injection (>350 mg/cm.sup.2) with similar experimental parameters and conditions and lower energy (127.79 kJ). The magnitude of current density described leads to an elevated production rate of OH-ions, resulting in a high interfacial pH near the cathode. However, due to the limited availability of carbonate and bicarbonate ions in seawater (in case of absence of external CO.sub.2 injection) compared to calcium and magnesium, coupled with the concurrent generation of H.sup.+ at the anode, both OH and H.sup.+ ions can engage in neutralization reactions independently of OH-participation in precipitation reactions results in lower production yield. This underscores the significance of carbonate ion concentrations in achieving the solubility precipitation index of CaCO.sub.3 and increase the yield as well as CO.sub.2 sequestration in CaCO.sub.3. (FIG. 4A, 840 A/m.sup.2; No CO.sub.2).

Non-Working Example 2

[0153] Applying a voltage of 2 V vs Ag/AgCl reference electrode without injecting any external CO.sub.2 produces lesser yield (217.47 mg/cm.sup.2) with equal energy consumption (139.63 kJ) as compared to the product yield achieved with CO.sub.2 injection (>550 mg/cm.sup.2) with similar experimental parameters and conditions and energy consumption (100 kJ). This is again due to the reason of sufficient production of OH ions but limited availability of carbonate ions. Moreover, as the electrochemical reactions that produce OH-ions are voltage dependent, a lower electrochemical voltage can provide a higher yield with less energy consumption when there is no CO.sub.2 injection. Applying a voltage of 2 V (vs Ag/AgCl reference electrode) without introducing external CO.sub.2 results in a lower yield (217.47 mg/cm.sup.2) with equivalent energy consumption (139.63 kJ) compared to the product yield achieved through CO.sub.2 injection (>550 mg/cm.sup.2) under similar experimental parameters and conditions, with energy consumption approximately around 100 kJ. This disparity arises from the ample production of OH-ions at this voltage but limited availability of carbonate ions in the absence of CO.sub.2 injection. Furthermore, given that the electrochemical reactions generating OH-ions are voltage-dependent, a lower electrochemical voltage (e.g., 1.4 V) can yield higher outputs with reduced energy consumption as compared to 2 V when external CO.sub.2 is not introduced. (FIG. 4B, 2V; No CO.sub.2).

Non-Working Example 3

[0154] Applying a current density of 1680 A/m.sup.2 and injecting a CO.sub.2 concentration of 0.30 scm CO.sub.2 results in a lower product yield (332.9 mg/cm.sup.2) compared to 840 mA/cm.sup.2 (685.58 mg/cm.sup.2) while consuming significantly more energy. This outcome underscores the insight that merely augmenting the rate of OH-generation at the cathode, coupled with the availability of calcium and carbonates, does not necessarily enhance the precipitation rate. The observed limitation arises from the dynamics of a membrane-free, one-pot batch reactor, where increasing current density leads to heightened mass transfer of ions, cross talk of ions, and side reactions, thereby impeding precipitation. This observation suggests the utilization of membranes in the reactor design.

[0155] Non-working example 4: Applying a less negative potential such as-1.4 V vs Ag/AgCl and injecting a concentration of CO.sub.2 (0.15 sccm CO.sub.2) produces lesser yield of the product after CO.sub.2 injection (195.05 mg/cm.sup.2 as compared to 322.86 mg/cm.sup.2) due to decrease in pH and insufficient availability of OH ions to participate in precipitation reactions. The result directs towards a shift in potential required to produce a higher yield with CO.sub.2 injection as there needs extra moles of OH-ions to neutralize the acidity introduced by CO.sub.2. Hence, achieving an optimal equilibrium between the rate of OH-ion production at the cathode and the concentration of carbonates/CO.sub.2 is essential for achieving a higher product yield and enhanced CO.sub.2 sequestration.

TABLE-US-00003 TABLE 2 Summary of non-working examples Non-Working Non-Working Non-Working Non-Working example 1 example 2 example 3 example 4 Experimental parameters: Cathode geometry Cylinder, Outer Cylinder, Outer Cylinder, Outer Cylinder, Outer diameter 2 mm, diameter 2 mm, diameter 2 mm, diameter 2 mm, active length active length active length active length 4.5 cm 4.5 cm 4.5 cm 4.5 cm Anode geometry Cylinder, outer Cylinder, outer Cylinder, outer Cylinder, outer diameter 0.78 mm, diameter 0.78 mm, diameter 0.78 mm, diameter 0.78 mm, active length 7.5 cm active length 7.5 cm active length 7.5 cm active length 7.5 cm Cathode/anode surface 1.5 1.5 1.5 1.5 area ratio [SAR] Active surface of 0.14 m.sup.2 0.14 m.sup.2 0.14 m.sup.2 0.14 m.sup.2 cathode per m.sup.3 of AS3 Reactor volume [CR2V] 2.5 liters 2.5 liters 2.5 liters 2.5 liters Volume of AS3 2 liters 2 liters 2 liters 2 liters Seawater composition Artificial seawater Artificial seawater Artificial seawater Artificial seawater [AS3] CO.sub.2 composition [C- Carbon dioxide Carbon dioxide Carbon dioxide Carbon dioxide Gas] research 99.999% research 99.999% research 99.999% research 99.999% CO.sub.2 inlet flowrate, [CGI] 0, No CO.sub.2 0, No CO.sub.2 0.30 sccm 0.15 sccm (standard cubic (standard cubic centimeter per centimeter per minute) in 2 minute) in 2 liters of AS3 liters of AS3 Applied current [mA] 240 mA 240 mA Current density [A/m.sup.2] 840 A/m.sup.2 1680 A/m.sup.2 Applied voltage [V] 2 V 1.4 V Time of electric 3 days per 2 3 days per 2 3 days per 2 3 days per 2 treatment liters of AS3 liters of AS3 liters of AS3 liters of AS3 pH of AS3 8.3-8.5 8.3-8.5 8.3-8.5 8.3-8.5 Temperature 21-25 C. 21-25 C. 21-25 C. 21-25 C. Total mass of the 170.84 217.47 332.9 195.05 electrodeposits Or Or Or Or [mg cm.sup.2] Or 1.70 2.17 3.33 1.95 [kg m.sup.2] Energy consumption 311.63 139.63 308.49 1.74 [kJ]

[0156] FIG. 6 shows the relationship between the total mass of electrodeposited aggregates and the injected CO.sub.2 flow rate at an applied electrochemical current (840 A/m.sup.2, FIG. 6A) and voltage (2 V vs Ag/AgCl, FIG. 6B). As the volume (concentration) of injected CO.sub.2 rises from no CO.sub.2 to a flow rate of 0.45 sccm (standard cubic centimeters per minute) in 2-liter seawater (equivalent to 1944 scc or 86.78 mmol per 2-liter), FIG. 6A and B indicates an increase in the total yield of aggregates after external CO.sub.2 injection. This growth is attributed to the higher availability of carbonate ions following CO.sub.2 injection and an increased precipitation rate under these specific current and potential conditions.

[0157] FIG. 7A illustrates the percentage weight of polymorphs determined by XRD, while FIG. 7B depicts the percentage weight of CaCO.sub.3 and Mg(OH).sub.2 estimated from TGA at an applied current of 240 mA or 840 mA/cm.sup.2. These figures represent the impact of injected CO.sub.2 flow rate in a 2-liter vessel. In FIG. 7A, at a current of 840 A/m.sup.2, there is a substantial increase in the weight percentage of aragonite and calcite, along with a decrease in brucite growth. This suggests that the injected CO.sub.2 is stored as CaCO.sub.3.

[0158] FIG. 7B, utilizing TGA, reveals an increased percentage of CaCO.sub.3 and as well as the presence of undetectable amorphous Mg(OH).sub.2 by XRD. It also indicates that a higher CO.sub.2 flow rate, allowing a greater CO.sub.2 concentration near the cathode, is unfavorable to precipitation of solids. This is due to a pH drop caused by the elevated CO.sub.2 concentration, hindering aggregate growth. The figures highlight the interdependence between the OH.sup. ion production rate near the cathode (linked to magnitude of applied current) and the CO.sub.2 injection flow rate or concentration over time.

[0159] Similarly, FIG. 7C illustrates the percentage weight of polymorphs determined by XRD, while FIG. 7D depicts the percentage weight of CaCO.sub.3 and Mg(OH).sub.2 estimated from TGA at an applied voltage of 2 V (vs Ag/AgCl). These figures again represent the impact of injected CO.sub.2 flow rate in a 2-liter vessel. In FIG. 7C, at a voltage of 2 V, there's a substantial increase in the weight percentage of aragonite and calcite, along with a decrease in brucite growth. This suggests that the injected CO.sub.2 is stored as CaCO.sub.3. FIG. 7D, utilizing TGA, reveals an increased percentage of CaCO.sub.3 and decreased Mg(OH).sub.2. It also indicates that a higher CO.sub.2 flow rate, allowing a greater CO.sub.2 concentration near the cathode, is unfavorable to CaCO.sub.3 formation. This is due to a pH drop caused by the elevated CO.sub.2 concentration, hindering aggregate growth. The figures highlight the interdependence between the OH-ion production rate near the cathode (linked to magnitude of applied voltage) and the CO.sub.2 injection flow rate or concentration over time.

[0160] FIGS. 8A and 8B illustrate the production rate (left y-axis) and energy consumption (right y-axis) in relation to the flow rate of injected CO.sub.2, with a constant current of 840 mA/cm.sup.2 and an applied voltage of 2.0 V (vs Ag/AgCl). The normalized production rate is quantified in kg.Math.m.sup.2.Math.m.sup.3 per day, denoting the mass of electrodeposits achievable from processing 1 m.sup.2 of cathode surface area using 1 m.sup.3 of seawater daily. Similarly, the normalized energy consumption is expressed in MJ.Math.kg.sup.1, reflecting the energy required to produce 1 kg of electrodeposits. The laboratory findings highlight an optimal balance between energy consumption (attributed to electric current and voltage application) and production rate in response to CO.sub.2 injection. Moreover, the observed increase in production rate resulting from carbon sequestration through injected CO.sub.2 contributes to a reduction in energy consumption per unit of the produced aggregates.

Discussion of the Results and Advantages

[0161] An optimum yield at a higher volume of injected CO.sub.2 requires a balance in pH because of simultaneous generation of alkalinity (due to voltage/current) and acidity (due to CO.sub.2). It is evident that CO.sub.2 injection leads to an increase in the total electrodeposits yield, however, needs a higher overpotential to fulfill the upraised requirement of OH.sup. raised due to drop in pH caused by CO.sub.2.

[0162] pH trend depicts that the generation or consumption of both H.sup.+ and OH-during the electrochemical conversion process of CO.sub.2 is influenced by the voltage/current, which in turn impacts the precipitation reactions taking place at the cathode. On the other hand, the applied voltage helps generate protons (H.sup.+) at the anode, where oxidation events occur. The pH of the seawater solution near the anode may decrease because of these protons' additional contribution to the acidification of the solution. Controlling the pH facilitates the subsequent mineral precipitation process and improves the electrochemical system's overall stability.

[0163] The electrodeposition process allows tailoring an electrodeposit mixture of CaCO.sub.3 and Mg(OH).sub.2 in a range of percentage weight of 50:50, 30:70 and 10:90. The carbonates content in mixture of electrodeposits highlights the efficacy of the carbon-negative electrodeposition approach in sequestering carbon dioxide from the atmosphere.

[0164] It is possible to fine-tune variables including carbon dioxide input, applied electrochemical potential, and reactor design to regulate crucial electrodeposited mineral properties. Aspects including morphology, size, content, mineral structure, yield, and carbon sequestration capability are included in this.

[0165] The type of polymorph is a function of the Mg: Ca ratio in AS1 and temperature. The possible polymorphs of CaCO.sub.3 to precipitate are calcite, aragonite, and vaterite in order of their decreasing thermodynamic stability. We have not observed vaterite formation on a lab scale so far. It is possible to form vaterite under certain conditions (low temperature, pH>9) but even if it forms, it can transform aragonite within 60 minutes when exposed to a temperature of 60 C. or more and it can change into calcite over 24 hours when kept at room temperature. (Geochimica et Cosmochimica Acta, Vol. 67, No. 9, pp. 1659-1666, 2003, Geology; January 1997; v. 25; no. 1; p. 85-87) [9].

[0166] To ensure and maintain a high calcium content in precipitated aggregates results show that maintaining the pH within the range of 9.5 to 10 is advisable, as exceeding a pH of 10 may induce preferential precipitation of magnesium hydroxide (Mg(OH).sub.2). Calcium hydroxide (Ca(OH).sub.2) does not precipitate under these conditions as it remains undersaturated in the pH range below 12.

Core Advantages of the Invention:

[0167] Carbon sequestration through electrodeposition: One of the primary advantages is the substantial reduction of carbon emissions in the cement and concrete industries. The proposed technique actively absorbs the dissolved carbon dioxide during the electrodeposition process, contributing to carbon sequestration. By harnessing ocean and sea waters to electrodeposit calcium and magnesium-based minerals while injecting carbon dioxide gas, the process actively absorbs carbon dioxide in the form of mineral carbonates. This dual functionality addresses both the production of construction materials and the removal of carbon dioxide from the atmosphere. This addresses a pressing global challenge of mitigating climate change by directly reducing the carbon footprint associated with construction materials.

[0168] Utilization of abundant oceanic mineral resources: By capitalizing on the substantial mineral resources found in ocean and sea waters, the invention taps into an abundant and naturally available source of calcium, magnesium, and bicarbonate ions. Electrodeposition allows the conversion of calcium present in seawater into calcium carbonates and magnesium in the form of hydroxides which can also be converted into magnesium carbonates later step by reacting with more carbon-dioxide. This approach reduces the environmental impact linked to conventional mining for cement and concrete production raw materials, offering a sustainable alternative for aggregates production that can substitute traditional mined resources in the industry.

[0169] Sustainable construction materials: The electrodeposition technique offers a sustainable alternative for manufacturing construction materials. By cultivating minerals from oceanic resources, the approach minimizes the ecological footprint of the cement and concrete industries. This aligns with the growing demand for environmentally friendly and sustainable practices in the construction sector. The technique leverages the interaction of hydroxide ions generated in the water-splitting electrode with the naturally occurring calcium and magnesium ions in ocean and sea waters and externally injected carbon-dioxide allows the availability of sufficient carbonate ions. This enhances mineral deposition rates, making the manufacturing process more efficient and potentially cost-effective.

[0170] Customization of mineral attributes: The innovation allows for the tailoring of central attributes of electrodeposited minerals, including their morphology, size, composition, mineral form, yield, and carbon sequestration potential. This level of customization provides flexibility in adapting the construction materials to specific requirements, ensuring their suitability for various applications in the cement and concrete industries.

[0171] Laboratory-validated feasibility: The experimental laboratory tests conducted in custom-designed electrochemical cells confirm the feasibility of the proposed approach. This scientific validation establishes a foundation for further development and implementation, assuring that the technique is not just theoretical but can be practically applied on a larger scale.

[0172] Scalable implementation: The findings pave the way for scalable implementation of the proposed approach, indicating that it has the potential to be adopted on a larger, industrial scale. This scalability is crucial for addressing the significant demands of the construction industry while maintaining sustainability.

[0173] Comprehensive solution to industry challenges: The proposed innovation offers a comprehensive solution to the pressing global challenges faced by the cement and concrete industries. By addressing both carbon emissions and the sustainable sourcing of construction materials, it represents a holistic approach that aligns with the broader goals of sustainable development and environmental stewardship.

LIST OF REFERENCES

[0174] 1. U.S. Pat. No. 11,413,578 [0175] 2. WO 2022/178125 [0176] 3. WO 2007/140544 [0177] 4. US20100084283 [0178] 5. EP 1 830 945 [0179] 6. U.S. Pat. No. 11,465,925 [0180] 7. Zhang et al., Direct Electrochemical Seawater Splitting for Green Hydrogen and Artificial Reefs, ACS Applied Energy Materials, 6 (14): 7636-7642, 2023 [0181] 8. Carre et al., Electrochemical calcareous deposition in seawater. A review, Environmental Chemistry Letters, 18:1193-1208, 2020 [0182] 9. Geochimica et Cosmochimica Acta, Vol. 67, No. 9, pp. 1659-1666, 2003, Geology; January 1997; v. 25; no. 1; p. 85-87