{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,3]],"date-time":"2026-10-03T03:43:55Z","timestamp":1790999035613,"version":"4.1.0"},"reference-count":40,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2025,2,24]],"date-time":"2025-02-24T00:00:00Z","timestamp":1740355200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"European Union\u2014NextGenerationEU","award":["National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3"],"award-info":[{"award-number":["National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>The growing amount of carbon dioxide (CO2) in the atmosphere significantly contributes to global warming and climate change. This study focuses on the use of aqueous potassium carbonate (K2CO3) solutions as a solvent for CO2 absorption, emphasizing the role of titanium dioxide (TiO2) nanoparticles in enhancing performance. A detailed understanding of reaction kinetics and the dynamic behavior of the absorber is crucial for optimizing the process. However, critical parameters such as the rate constant kOH of the reaction between CO2 and OH- in K2CO3 solutions are rarely found in existing studies. This work investigates the kinetics of CO2 absorption in 25 wt% K2CO3 solutions at three temperatures (40, 55, and 70 \u00b0C), varying concentrations of TiO2 nanoparticles to identify optimal conditions. Reaction rates were measured in a stirred cell reactor, and the data were interpreted using Danckwerts theory. The results revealed a notable improvement in absorption efficiency with the addition of nanoparticles, and the study also pinpointed optimal operational parameters to prevent sedimentation issues. The presence of TiO2 nanoparticles was found to enhance the solution\u2019s physical properties, such as diffusivity and surface tension, which facilitated an improved mass transfer. The best performance was achieved with a TiO2 concentration of 0.06 wt% at 70 \u00b0C, leading to an increase of diffusivity value equal to 1.5 times and, as a consequence, the same increase has been observed for the overall reaction rate. In contrast, higher or lower concentrations negatively impacted efficiency due to poor dispersion or nanoparticle agglomeration. These results provide practical insights for developing more efficient and sustainable CO2 capture methods, contributing to solutions for the climate crisis.<\/jats:p>","DOI":"10.3390\/nano15050352","type":"journal-article","created":{"date-parts":[[2025,2,24]],"date-time":"2025-02-24T10:52:47Z","timestamp":1740394367000},"page":"352","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["Enhanced CO2 Capture Using TiO2 Nanoparticle-Functionalized Solvent: A Study on Absorption Experiments"],"prefix":"10.3390","volume":"15","author":[{"given":"Alice","family":"Chill\u00e8","sequence":"first","affiliation":[{"name":"Department of Chemical Engineering Materials Environment, Sapienza University of Rome, via Eudossiana 18, 00184 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicola","family":"Verdone","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering Materials Environment, Sapienza University of Rome, via Eudossiana 18, 00184 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mattia","family":"Micciancio","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering Materials Environment, Sapienza University of Rome, via Eudossiana 18, 00184 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giorgio","family":"Vilardi","sequence":"additional","affiliation":[{"name":"Department of Chemical Engineering Materials Environment, Sapienza University of Rome, via Eudossiana 18, 00184 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,2,24]]},"reference":[{"key":"ref_1","unstructured":"Lindsey, R. (2024, March 14). NOAA, Science & Information for a Climate-Smart Nation. Climate Change: Atmospheric Carbon Dioxide, Available online: https:\/\/content-drupal.climate.gov\/news-features\/understanding-climate\/climate-change-atmospheric-carbon-dioxide."},{"key":"ref_2","unstructured":"UNFCCC (2024, June 14). Conference of the Parties, Twenty-First Session: Adoption of the Paris Agreement. United Nations Framework Convention on Climate Change 2015. Available online: https:\/\/unfccc.int\/resource\/docs\/2015\/cop21\/eng\/l09.pdf."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"53","DOI":"10.1016\/j.applthermaleng.2009.05.005","article-title":"Pre-combustion, post-combustion and oxy-combustion in thermal power plant for CO2 capture","volume":"30","author":"Kanniche","year":"2010","journal-title":"Appl. Therm. Eng."},{"key":"ref_4","unstructured":"IEAGHG (2024, June 14). Deployment of CCS in the Cement Industry 2013. Available online: https:\/\/publications.ieaghg.org\/technicalreports\/2013-19%20Deployment%20of%20CCS%20in%20the%20Cement%20Industry.pdf."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"138","DOI":"10.1021\/ef201192n","article-title":"Post-combustion capture of CO2: Results from the solvent absorption capture plant at hazelwood power station using potassium carbonate solvent","volume":"26","author":"Mumford","year":"2012","journal-title":"Energy Fuels"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/j.gee.2019.11.004","article-title":"Kinetics study of CO2 absorption in potassium carbonate solution promoted by diethylenetriamine","volume":"6","author":"Ramezani","year":"2021","journal-title":"Green Energy Environ."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/j.ijggc.2015.02.007","article-title":"A study of the vapour-liquid equilibrium of CO2 in mixed solutions of potassium carbonate and potassium glycinate","volume":"36","author":"Lee","year":"2015","journal-title":"Int. J. Greenh. Gas Control"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"142","DOI":"10.1016\/j.ijggc.2015.06.026","article-title":"CO2 capture with potassium carbonate solutions: A state-of-the-art review","volume":"41","author":"Borhani","year":"2015","journal-title":"Int. J. Greenh. Gas Control"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3619","DOI":"10.1016\/j.ces.2004.03.029","article-title":"Carbon dioxide absorption with aqueous potassium carbonate promoted by piperazine","volume":"59","author":"Cullinane","year":"2004","journal-title":"Chem. Eng. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"922","DOI":"10.1002\/aic.690340604","article-title":"Carbon dioxide absorption into promoted carbonate solutions","volume":"34","author":"Tseng","year":"1988","journal-title":"AIChE J."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"581","DOI":"10.1016\/0009-2509(81)80146-7","article-title":"Promotion of CO2 mass transfer in carbonate solutions","volume":"36","author":"Astarita","year":"1981","journal-title":"Chem. Eng. Sci."},{"key":"ref_12","unstructured":"Choi, U.S., and Eastman, J.A. (1995, January 12\u201317). Enhancing Thermal Conductivity of Fluids with Nanoparticles. Proceedings of the ASME International Mechanical Engineering Congress & Exposition, San Francisco, CA, USA."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"22","DOI":"10.1016\/j.ijrefrig.2005.08.006","article-title":"The effect of nano-particles on the bubble absorption performance in a binary nanofluid","volume":"29","author":"Kim","year":"2006","journal-title":"Int. J. Refrig."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Salih, H.A., Pokhrel, J., Reinalda, D., AlNashf, I., Khaleel, M., Vega, L.F., Karanikolos, G.N., and Zahra, M.A. (2021). Hybrid\u2014Slurry\/Nanofluid systems as alternative to conventional chemical absorption for carbon dioxide capture: A review. Int. J. Greenh. Gas Control, 110.","DOI":"10.1016\/j.ijggc.2021.103415"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Tavakoli, A., Rahimi, K., Saghandali, F., Scott, J., and Lovell, E. (2022). Nanofluid preparation, stability and performance for CO2 absorption and desorption enhancement: A review. J. Environ. Manag., 313.","DOI":"10.1016\/j.jenvman.2022.114955"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1016\/0300-9467(79)80104-5","article-title":"The sorption of propane in slurries of active carbon in water","volume":"17","author":"Kars","year":"1979","journal-title":"Chem. Eng. J."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Zhang, H., Wang, B., Xiong, M., Gao, C., Ren, H., and Ma, L. (2022). Process intensification in gas-liquid mass transfer by nanofluids: Mechanism and current status. J. Mol. Liq., 346.","DOI":"10.1016\/j.molliq.2021.118268"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Lee, J.W., Kim, S., Torres Pineda, I., and Kang, Y.T. (2021). Review of nanoabsorbents for capture enhancement of CO2 and its industrial applications with design criteria. Renew. Sustain. Energy Rev., 138.","DOI":"10.1016\/j.rser.2020.110524"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Deka, D.J., Jang, G.G., Kasturi, A., Stamberga, D., Keum, J.K., Custelcean, R., and Tsouris, C. (2025). Pronounced reduction in the regeneration energy of potassium sarcosinate CO2 capture solvent using TiO2. Sep. Purif. Technol., 354.","DOI":"10.1016\/j.seppur.2024.128850"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Danckwerts, P.V. (1970). Gas-Liquid Reactions, McGraw-Hill Book Company.","DOI":"10.1149\/1.2407312"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"482","DOI":"10.1002\/cjce.5450700310","article-title":"Absorption of CO2 into aqueous tertiary amine\/mea solutions","volume":"70","author":"Rangwala","year":"1992","journal-title":"Can. J. Chem. Eng."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"279","DOI":"10.1002\/ghg.1738","article-title":"Characterization of technical grade carbonic anhydrase as biocatalyst for CO2 capture in potassium carbonate solutions","volume":"8","author":"Peirce","year":"2018","journal-title":"Greenh. Gases Sci. Technol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"2177","DOI":"10.1016\/j.ces.2009.12.015","article-title":"Density and N2O solubility of sodium and potassium carbonate solutions in the temperature range 25 to 80 \u00b0C","volume":"65","author":"Knuutila","year":"2010","journal-title":"Chem. Eng. Sci."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"239","DOI":"10.1021\/i160011a012","article-title":"Kinetics of Absorption of carbon dioxide in monoethanolamine solutions at short contact times","volume":"3","author":"Clarke","year":"1964","journal-title":"Ind. Eng. Chem. Fundam."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1021\/je00051a011","article-title":"Solubility and diffusivity of acid gases (carbon dioxide nitrous oxide) in aqueous alkanolamine solutions","volume":"33","author":"Versteeg","year":"1988","journal-title":"J. Chem. Eng. Data"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"452","DOI":"10.1021\/je60055a016","article-title":"Solubility and Diffusivity of Nitrous Oxide in Equimolar Potassium Carbonate-Potassium Bicarbonate Solutions at 25 \u00b0C and 1 Atm","volume":"17","author":"Joosten","year":"1972","journal-title":"J. Chem. Eng. Data"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"34","DOI":"10.1021\/j100721a006","article-title":"Viscosity of water at various temperatures","volume":"73","author":"Korson","year":"1969","journal-title":"J. Phys. Chem."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"657","DOI":"10.1016\/j.ces.2014.05.050","article-title":"Kinetics of CO2 absorption into uncatalyzed potassium carbonate\u2013bicarbonate solutions: Effects of CO2 loading and ionic strength in the solutions","volume":"116","author":"Ye","year":"2014","journal-title":"Chem. Eng. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1080\/01457630600904593","article-title":"Heat Transfer in Nanofluids\u2014A Review","volume":"27","author":"Das","year":"2006","journal-title":"Heat Transf. Eng."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"7391","DOI":"10.1016\/j.ces.2007.08.064","article-title":"Enhancement of oxygen mass transfer rate in the presence of nanosized particles","volume":"62","author":"Nagy","year":"2007","journal-title":"Chem. Eng. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1529","DOI":"10.1021\/nl060992s","article-title":"Effect of Aggregation Kinetics on the Thermal Conductivity of Nanoscale Colloidal Solutions (Nanofluid)","volume":"6","author":"Prasher","year":"2006","journal-title":"Nano Lett."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"588","DOI":"10.1115\/1.2188509","article-title":"Brownian-Motion-Based Convective-Conductive Model for the Effective Thermal Conductivity of Nanofluids","volume":"128","author":"Prasher","year":"2006","journal-title":"J. Heat Transf."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1636","DOI":"10.1007\/s42452-020-03427-1","article-title":"A review on nanofluid: Preparation, stability, thermophysical properties, heat transfer characteristics and application","volume":"2","author":"Ali","year":"2020","journal-title":"SN Appl. Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"7830","DOI":"10.1021\/acs.iecr.6b00358","article-title":"Enhanced CO2 Absorption and Desorption by Monoethanolamine (MEA)-Based Nanoparticle Suspensions","volume":"55","author":"Wang","year":"2016","journal-title":"Ind. Eng. Chem. Res."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"738","DOI":"10.1002\/ghg.2183","article-title":"Enhancement of mass transfer performance by nanoparticles during the CO2 absorption with MDEA solution in a randomly packed tower","volume":"12","author":"Liu","year":"2022","journal-title":"Greenh. Gases Sci. Technol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1378","DOI":"10.1021\/acs.jced.5b00442","article-title":"Study of Absorption Enhancement of CO2 by SiO2, Al2O3, CNT, and Fe3O4 Nanoparticles in Water and Amine Solutions","volume":"61","author":"Rahmatmand","year":"2016","journal-title":"J. Chem. Eng. Data"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"33","DOI":"10.1016\/j.fluid.2015.02.012","article-title":"Absorption and solubility measurement of CO2 in water-based ZnO and SiO2 nanofluids","volume":"392","author":"Haghtalab","year":"2015","journal-title":"Fluid Phase Equilibria"},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Karamian, S., Mowla, D., and Esmaeilzadeh, F. (2019). The Effect of Various Nanofluids on Absorption Intensification of CO2\/SO2 in a Single-Bubble Column. Processes, 7.","DOI":"10.3390\/pr7070393"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1016\/j.ijggc.2014.02.008","article-title":"CO2 gas absorption by CH3OH based nanofluids in an annular contactor at low rotational speeds","volume":"23","author":"Pineda","year":"2014","journal-title":"Int. J. Greenh. Gas Control"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1016\/j.ijheatmasstransfer.2016.04.086","article-title":"CO2 absorption enhancement by nanoabsorbents in Taylor\u2013Couette absorber","volume":"100","author":"Kang","year":"2016","journal-title":"Int. J. Heat Mass Transf."}],"container-title":["Nanomaterials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-4991\/15\/5\/352\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T16:41:40Z","timestamp":1760028100000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-4991\/15\/5\/352"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,2,24]]},"references-count":40,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2025,3]]}},"alternative-id":["nano15050352"],"URL":"https:\/\/doi.org\/10.3390\/nano15050352","relation":{},"ISSN":["2079-4991"],"issn-type":[{"value":"2079-4991","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,2,24]]}}}