Thermoresponsive CO2 absorbent for various CO2 concentrations: tuning the pKa of ammonium ions for effective carbon capture

Honda, Ryutaro; Hamasaki, Akira; Miura, Yoshiko; Hoshino, Yu

doi:10.1038/s41428-020-00407-5

Cited by 10 publications

(13 citation statements)

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“…Although helium sweep has to be replaced by vacuum and/or steam sweep to actually purify CO 2 , , this CO 2 permeance and selectivity are high enough to realize a single-stage, low-cost, and post-combustion CO 2 capture process at point sources such as thermal power plants. The concentration of absorbed CO 2 (HCO 3 – and CO 3 2– ) in the top side of the membrane (feed gas side) is calculated to be about 2 M, assuming that the reaction between amines and CO 2 is equilibrated with the 10% CO 2 feed gas (10 kPa) and p K a of AEE is 9 . This is much higher than the one without AEE (concentrations in MG Am and MG non layers are 0.2 and 0.002 M, respectively).…”

Section: Resultsmentioning

confidence: 99%

“…The difference of CO 2 permeance between two layers is due to different concentrations of absorbed CO 2 in each layer. The concentration of absorbed CO 2 (HCO 3 – ) in the top side of the MG Am membrane (feed gas side) is calculated to be about 0.2 M, assuming that the reaction between amines and CO 2 is equilibrated with the 10% (10 kPa) CO 2 feed gas and p K a of ammonium ions in MG Am is 7.5. , This is much higher than the one without amines (the concentration in MG non layers is 0.002 M). The high CO 2 concentration accelerated CO 2 permeation by driving CO 2 diffusion in the membranes.…”

Section: Resultsmentioning

confidence: 99%

“…These materials show exceptionally high solute diffusivity, comparable to that of liquids, − and are thus attractive materials for gas separation . Moreover, the physicochemical properties of hydrogels can be tailored by introducing a variety of functional groups and modifying the cross-linking structure. − Furthermore, hydrogel-based materials can be used to capture CO 2 directly from humid gases such as post-combustion gases without a drying process …”

Section: Introductionmentioning

confidence: 99%

“…In this study, we took advantage of the adaptability of colloidal hydrogel microparticles (microgels) to prepare defect-free hydrogel nanomembranes. , It has been reported that the deformability of ionized microgels enables the autonomous assembly of defect-free colloidal crystals, despite the broad size distribution of microgels. , Composite microgel membranes − and porous membranes coated with microgels − have been prepared as temperature-responsive functional membranes for water purification and enzymatic reactions. Furthermore, the affinity between microgels and CO 2 can be tuned by incorporating amine groups and/or by modulating the microenvironment around the amine groups in the microgels. ,, Thus, defect-free hydrogel nanomembranes for CO 2 separation could be obtained if the amine-containing microgels could be assembled on the surface of a porous support.…”

Section: Introductionmentioning

confidence: 99%

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Assembly of Defect-Free Microgel Nanomembranes for CO₂ Separation

Hoshino

Gyobu

Imamura

et al. 2021

ACS Appl. Mater. Interfaces

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The development of robust and thin CO 2 separation membranes that allow fast and selective permeation of CO 2 will be crucial for rebalancing the global carbon cycle. Hydrogels are attractive membrane materials because of their tunable chemical properties and exceptionally high diffusion coefficients for solutes. However, their fragility prevents the fabrication of thin defect-free membranes suitable for gas separation. Here, we report the assembly of defect-free hydrogel nanomembranes for CO 2 separation. Such membranes can be prepared by coating an aqueous suspension of colloidal hydrogel microparticles (microgels) onto a flat, rough, or micropatterned porous support as long as the pores are hydrophilic and the pore size is smaller than the diameter of the microgels. The deformability of the microgel particles enables the autonomous assembly of defect-free 30−50 nm-thick membrane layers from deformed ∼15 nm-thick discoidal particles. Microscopic analysis established that the penetration of water into the pores driven by capillary force assists the assembly of a defect-free dense hydrogel layer on the pores. Although the dried films did not show significant CO 2 permeance even in the presence of amine groups, the permeance dramatically increased when the membranes are adequately hydrated to form a hydrogel. This result indicated the importance of free water in the membranes to achieve fast diffusion of bicarbonate ions. The hydrogel nanomembranes consisting of amine-containing microgel particles show selective CO 2 permeation (850 GPU, α CO2/N2 = 25) against post-combustion gases. Acid-containing microgel membranes doped with amines show highly selective CO 2 permeation against post-combustion gases (1010 GPU, α CO2/N2 = 216) and direct air capture (1270 GPU, α CO2/N2 = 2380). The membrane formation mechanism reported in this paper will provide insights into the self-assembly of soft matters. Furthermore, the versatile strategy of fabricating hydrogel nanomembranes by the autonomous assembly of deformable microgels will enable the large-scale manufacturing of high-performance separation membranes, allowing low-cost carbon capture from postcombustion gases and atmospheric air.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Assembly of Defect-Free Microgel Nanomembranes for CO₂ Separation

Hoshino

Gyobu

Imamura

et al. 2021

ACS Appl. Mater. Interfaces

Self Cite

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“…Carbon recycling, reusing carbon in greenhouse gases, as for example carbon dioxide (CO 2 ) as raw materials, 1 has attracted attention because of the global climate change recently observable across every region of the country. The Ministry of Economy, Trade and Industry of Japan released the roadmap for carbon recycling technologies in 2019, clarifying that the potential applications of CO 2 are categorized into chemicals, fuels, minerals, and others.…”

Section: Introductionmentioning

confidence: 99%

Instantaneous Ex Situ Mineral Carbonation Relevant to Alkali Metals in Clay Nanoparticles

et al. 2021

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Carbon recycling reusing emitted carbon dioxide (CO 2 ) as raw materials is nowadays recognized as a concept ahead of CO 2 capture and storage for controlling its emission to the air. Here, recently discovered alkali-metal-based instantaneous ex situ mineral carbonation under ambient conditions is studied for saponite clay nanoparticles. The cationic concentration of Cs + is varied for seeking the possibility of reusing Cs-contaminated soil in view of carbon recycling. The ex situ mineral carbonation dominantly occurring at the interior surfaces of 10 Å open spaces formed by overlapped nanosheets increases with increasing the Cs concentration up to 0.580 mmol g −1 due to the enlargement of the surface area. The ability of the ex situ mineral carbonation, however, deteriorates with further increasing to 0.585 mmol g −1 since the 10 Å open spaces are effectively occupied by Cs compounds as Cs 2 O reducing their fraction. The present findings of the ex situ mineral carbonation relevant to the cationic concentration imply that the practical soil associated with a Fukushima nuclear accident can stabilize CO 2 without energy consumption as well as chemical solution.

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