Abstract: A solvent formulation for the direct air capture of carbon dioxide is provided. The solvent formulation includes an amino acid salt, a polar solvent and an antifreeze agent. A direct air capture system for the direct air capture of carbon dioxide is further provided. The direct air capture system incudes a desorption column, a gas separator, and an air contactor. The desorption column, gas-liquid separator, and air contactor are in fluid communication. The air contactor includes the solvent formulation.

Abstract: A method for regenerating a carbon dioxide (CO2) sorbent material, the method comprising: (i) contacting a sorbent-CO2 complex in an aqueous solution containing a reversible photoacid, wherein the CO2 in the sorbent-CO2 complex is in the form of bicarbonate, carbonate, or carbamate; and (ii) exposing the aqueous solution to electromagnetic radiation having a wavelength that induces proton release from the photoacid and subsequent protonation of the bicarbonate, carbonate, or carbamate in the sorbent-CO2 complex to result in release of CO2 and water and regeneration of the sorbent material. The method may also include re-using the regenerated sorbent to capture carbon dioxide. The sorbent may be, for example, an amino acid (e.g., glycine), alkylamine, alkanolamine, or alkali hydroxide. The reversible photoacid may more particularly be a metastable-state photoacid.

Abstract: A method for regenerating a bis(iminoguanidine) (BIG) carbon dioxide sorbent, the method comprising: (i) providing a carbonate or bicarbonate salt of the BIG carbon dioxide sorbent, and (ii) directly contacting the carbonate or bicarbonate salt of the BIG carbon dioxide sorbent with steam heated to a temperature within a range of 80° C.-130° C. to result in regeneration of the BIG carbon dioxide sorbent with simultaneous conversion of the carbonate or bicarbonate anions into carbon dioxide, wherein the regenerated BIG carbon dioxide sorbent is substantially removed of carbonate or bicarbonate and may optionally contain one or more adduct water molecules. In some processes, the regenerated BIG carbon dioxide sorbent is dissolved in water condensing from the steam during the contacting step to form an aqueous solution of the regenerated BIG carbon dioxide sorbent.

Abstract: A high-flux direct air capture (DAC) contactor is provided. The contactor includes stainless steel mesh elements interlaced into a structured packing to increase the effective surface area for a suitable solvent. In laboratory testing, the contactor demonstrated significant potential in driving down the cost of solvent absorption-based DAC due to its high specific surface area and CO2 uptake efficiency, resistance to corrosion, optimal wettability, smaller relative size, and low manufacturing cost. As a potential breakthrough strategy, the highly efficient CO2 capture contactor can be employed to significantly reduce capital costs in a compact DAC system.

Abstract: Method for removing toxic oxyanions (e.g., selenate) from an aqueous source as follows: (i) dissolving an oxyanion precipitating compound (OPC) in the aqueous source to result in precipitation of a salt containing sulfate, toxic oxyanion, and the OPC, wherein the sulfate in the aqueous source is in a molar concentration at least equal to the total molar concentration of the toxic oxyanion, and the OPC is included in the aqueous source in a molar concentration equal to or greater than the total molar concentration of sulfate and toxic oxyanion; and (ii) removing the precipitated salt from the aqueous source to result in a supernatant containing a substantially lower concentration of the toxic oxyanion compared to the aqueous source.

Abstract: A method for regenerating an amine-containing sorbent material useful in CO2 capture, the method comprising exposing an amine-containing sorbent-CO2 complex to microwave radiation to result in release of CO2 and regenerated amine-containing sorbent that is uncomplexed with CO2, wherein the amine-containing sorbent-CO2 complex contains either: (i) a carbamate bond; or (ii) an ion pair bond of the formula wherein Ra, Rb, and Rc are selected from H and hydrocarbon groups containing at least one carbon atom, wherein at least one of Ra, Rb, and Rc is H; Xm? is a carbonate or bicarbonate anion, with m being 1 for bicarbonate and 2 for carbonate; and n is an integer of 1 or 2, provided that n×m=2. The method may also include re-using the regenerated amine-containing sorbent to capture carbon dioxide.

Abstract: A compound having the following structure: wherein: R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10 are independently selected from (i) hydrogen atom, (ii) hydrocarbon groups (R) containing 1-30 carbon atoms and optionally substituted with one or more fluorine atoms, (iii) —OR? groups, (iv) —NR?2 groups, (v) —C(O)R? groups, and (vi) halogen atoms, wherein R? groups are independently selected from R groups and hydrogen atoms, and wherein the R group optionally includes a C(O), ether, or amino linkage; Xm? is an anionic species with a magnitude of charge m, where m is an integer of at least 1; and n is a number, provided that n×m=1. Also described herein are methods for removing one or more oxyanions from a liquid source by use of the above compound or mono-pyridyl derivative thereof.

Abstract: Methods for removing an oxyanion from an aqueous source containing said oxyanion, comprising contacting said aqueous source with an aqueous-insoluble hydrophobic solution containing an oxyanion extractant compound dissolved in an aqueous-insoluble hydrophobic solvent to result in formation of an oxyanion salt of said extractant compound and extraction of said oxyanion salt into said aqueous-insoluble hydrophobic solution, wherein said extraction results in an extraction affinity (D) of said oxyanion of at least 1, wherein D is the concentration ratio of said oxyanion in the organic phase divided by the concentration of said oxyanion in the aqueous phase; wherein said extractant compound has the following composition: wherein at least one of R1-R10 is or contains a hydrocarbon (R) group containing at least 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms.

Abstract: Methods for removing oxyanions from water according to the following steps: (i) dissolving an oxyanion precipitating compound into the aqueous source to result in precipitation of an oxyanion salt of the oxyanion precipitating compound; and (ii) removing the oxyanion salt from the water containing the oxyanion to result in water substantially reduced in concentration of the oxyanion; wherein the oxyanion precipitating compound has the following composition: wherein A is a ring-containing moiety and Xm? is an anionic species with a magnitude of charge m. The invention employs bis-iminoguanidinium compounds according to Formula (1a) as well as neutral precursor compounds according to Formula (1), which can be used for removing undesirable species from aqueous solutions or air, such as removal of sulfate from water and carbon dioxide from air.

Abstract: A method for removing carbon dioxide from a gaseous source, the method comprising: (i) contacting said gaseous source with an aqueous solution of a carbon dioxide sorbent that reacts with carbon dioxide to form an aqueous-soluble carbonate or bicarbonate salt of said carbon dioxide sorbent; (ii) contacting the aqueous solution from step (i) with a bis-iminoguanidine carbon dioxide complexing compound, which is different from the carbon dioxide sorbent, to result in precipitation of a carbonate or bicarbonate salt of said carbon dioxide complexing compound and regeneration of the carbon dioxide sorbent; and (iii) removing the precipitated carbonate or bicarbonate salt from the aqueous solution in step (ii) to result in a solid form of said carbonate or bicarbonate salt of the carbon dioxide complexing compound. The method may further include a step (iv) of regenerating the carbon dioxide complexing compound by subjecting the precipitated salt to sufficient heat and/or vacuum.

Abstract: Methods for removing an oxyanion from an aqueous source containing said oxyanion, comprising contacting said aqueous source with an aqueous-insoluble hydrophobic solution containing an oxyanion extractant compound dissolved in an aqueous-insoluble hydrophobic solvent to result in formation of an oxyanion salt of said extractant compound and extraction of said oxyanion salt into said aqueous-insoluble hydrophobic solution, wherein said extraction results in an extraction affinity (D) of said oxyanion of at least 1, wherein D is the concentration ratio of said oxyanion in the organic phase divided by the concentration of said oxyanion in the aqueous phase; wherein said extractant compound has the following composition: wherein at least one of R1-R10 is or contains a hydrocarbon (R) group containing at least 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms.

Abstract: Methods for removing oxyanions from water according to the following steps: (i) dissolving an oxyanion precipitating compound into the aqueous source to result in precipitation of an oxyanion salt of the oxyanion precipitating compound; and (ii) removing the oxyanion salt from the water containing the oxyanion to result in water substantially reduced in concentration of the oxyanion; wherein the oxyanion precipitating compound has the following composition: wherein A is a ring-containing moiety and Xm? is an anionic species with a magnitude of charge m. The invention employs bis-iminoguanidinium compounds according to Formula (1a) as well as neutral precursor compounds according to Formula (1), which can be used for removing undesirable species from aqueous solutions or air, such as removal of sulfate from water and carbon dioxide from air.

Abstract: A method for removing carbon dioxide from a gaseous source, the method comprising: (i) contacting said gaseous source with an aqueous solution of a carbon dioxide sorbent that reacts with carbon dioxide to form an aqueous-soluble carbonate or bicarbonate salt of said carbon dioxide sorbent; (ii) contacting the aqueous solution from step (i) with a bis-iminoguanidine carbon dioxide complexing compound, which is different from the carbon dioxide sorbent, to result in precipitation of a carbonate or bicarbonate salt of said carbon dioxide complexing compound and regeneration of the carbon dioxide sorbent; and (iii) removing the precipitated carbonate or bicarbonate salt from the aqueous solution in step (ii) to result in a solid form of said carbonate or bicarbonate salt of the carbon dioxide complexing compound. The method may further include a step (iv) of regenerating the carbon dioxide complexing compound by subjecting the precipitated salt to sufficient heat and/or vacuum.

Abstract: Methods for removing oxyanions from water according to the following steps: (i) dissolving an oxyanion precipitating compound into the aqueous source to result in precipitation of an oxyanion salt of the oxyanion precipitating compound; and (ii) removing the oxyanion salt from the water containing the oxyanion to result in water substantially reduced in concentration of the oxyanion; wherein the oxyanion precipitating compound has the following composition: wherein A is a ring-containing moiety and Xm? is an anionic species with a magnitude of charge m. The invention employs bis-iminoguanidinium compounds according to Formula (1a) as well as neutral precursor compounds according to Formula (1), which can be used for removing undesirable species from aqueous solutions or air, such as removal of sulfate from water and carbon dioxide from air.

Abstract: The present invention relates to urea-functionalized crystalline capsules self-assembled by sodium or potassium cation coordination and by hydrogen-bonding water bridges to selectively encapsulate tetrahedral divalent oxoanions from highly competitive aqueous alkaline solutions and methods using this system for selective anion separations from industrial solutions. The method involves competitive crystallizations using a tripodal tris(urea) functionalized ligand and, in particular, provides a viable approach to sulfate separation from nuclear wastes.

Abstract: The present invention relates to urea-functionalized crystalline capsules self-assembled by sodium or potassium cation coordination and by hydrogen-bonding water bridges to selectively encapsulate tetrahedral divalent oxoanions from highly competitive aqueous alkaline solutions and methods using this system for selective anion separations from industrial solutions. The method involves competitive crystallizations using a tripodal tris(urea) functionalized ligand and, in particular, provides a viable approach to sulfate separation from nuclear wastes.