{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T12:19:13Z","timestamp":1787660353040,"version":"build-2736575974"},"reference-count":55,"publisher":"MDPI AG","issue":"17","license":[{"start":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T00:00:00Z","timestamp":1787616000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The development of low-cost and sustainable adsorbents for carbon dioxide (CO2) capture has gained increasing attention as a strategy to mitigate greenhouse gas emissions. In this study, activated biochars produced from babassu, elephant grass, and Pinus elliottii were evaluated as CO2 adsorbents after different activation treatments. The biochars were produced by slow pyrolysis at 400 \u00b0C and subsequently modified using three activation routes: steam activation, chemical activation with KOH, and KOH activation followed by acid washing. The materials were characterized by proximate analysis, specific surface area measurements, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and CO2 adsorption tests. Steam activation produced the highest specific surface areas, reaching 1270.53, 1027.28, and 907.87 m2 g\u22121 for babassu, elephant grass and Pinus, respectively. Despite the superior textural properties achieved through steam activation, the highest CO2 adsorption capacities were obtained for the samples subjected to chemical activation followed by acid washing. These results indicate that adsorption performance is governed not only by the development of surface area but also by pore accessibility and the surface chemistry of the adsorbent. Maximum adsorption capacities of 82.78, 81.19, and 85.24 mg g\u22121 were obtained for ACKAW B, ACKAW CE, and ACKAW P, respectively. Adsorption\u2013desorption cycling experiments demonstrated regenerability and stable performance over repeated cycles. The results indicate that KOH activation followed by acid washing is an effective strategy for producing high-performance biochar-based adsorbents for CO2 capture.<\/jats:p>","DOI":"10.3390\/molecules31172971","type":"journal-article","created":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T11:27:19Z","timestamp":1787657239000},"page":"2971","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Biomass-Derived Activated Biochars to CO2 Adsorption"],"prefix":"10.3390","volume":"31","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7856-2781","authenticated-orcid":false,"given":"Oscar de Almeida","family":"Neuwald","sequence":"first","affiliation":[{"name":"Engineering of Processes and Technologies Post-Graduate Program, University of Caxias do Sul\u2014UCS, Caxias do Sul 95070-560, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ana Paula","family":"Prigol","sequence":"additional","affiliation":[{"name":"Engineering of Processes and Technologies Post-Graduate Program, University of Caxias do Sul\u2014UCS, Caxias do Sul 95070-560, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luiz Gustavo","family":"Tyska","sequence":"additional","affiliation":[{"name":"Engineering of Processes and Technologies Post-Graduate Program, University of Caxias do Sul\u2014UCS, Caxias do Sul 95070-560, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7338-2570","authenticated-orcid":false,"given":"M\u00e1rcia","family":"Borghetti","sequence":"additional","affiliation":[{"name":"Engineering of Processes and Technologies Post-Graduate Program, University of Caxias do Sul\u2014UCS, Caxias do Sul 95070-560, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daniele","family":"Perondi","sequence":"additional","affiliation":[{"name":"Engineering of Processes and Technologies Post-Graduate Program, University of Caxias do Sul\u2014UCS, Caxias do Sul 95070-560, Brazil"},{"name":"UCSGRAPHENE Research and Development Unit, University of Caxias do Sul\u2014UCS, Caxias do Sul 95070-560, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8630-1995","authenticated-orcid":false,"given":"Marcelo","family":"Godinho","sequence":"additional","affiliation":[{"name":"Engineering of Processes and Technologies Post-Graduate Program, University of Caxias do Sul\u2014UCS, Caxias do Sul 95070-560, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"101890","DOI":"10.1016\/j.jcou.2022.101890","article-title":"Biomass\/Biochar Carbon Materials for CO2 Capture and Sequestration by Cyclic Adsorption Processes: A Review and Prospects for Future Directions","volume":"57","author":"Karimi","year":"2022","journal-title":"J. CO2 Util."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"123624","DOI":"10.1016\/j.seppur.2023.123624","article-title":"CO2 Capture Using Biochar Derived from Conditioned Sludge via Pyrolysis","volume":"314","author":"Liu","year":"2023","journal-title":"Sep. Purif. Technol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"57","DOI":"10.1039\/C7EE02110K","article-title":"A Search for Selectivity to Enable CO2 Capture with Porous Adsorbents","volume":"11","author":"Oschatz","year":"2018","journal-title":"Energy Environ. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"100118","DOI":"10.1016\/j.nxsust.2025.100118","article-title":"Path of Carbon Dioxide Capture Technologies: An Overview","volume":"6","author":"Shyam","year":"2025","journal-title":"Next Sustain."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"121131","DOI":"10.1016\/j.seppur.2022.121131","article-title":"A High Adsorption Capacity Bamboo Biochar for CO2 Capture for Low Temperature Heat Utilization","volume":"293","author":"Ji","year":"2022","journal-title":"Sep. Purif. Technol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"120592","DOI":"10.1016\/j.seppur.2022.120592","article-title":"Straw and Wood Based Biochar for CO2 Capture: Adsorption Performance and Governing Mechanisms","volume":"287","author":"Cao","year":"2022","journal-title":"Sep. Purif. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1016\/j.jiec.2024.12.026","article-title":"Carbon-Based Adsorbents for CO2 Capture: A Systematic Review","volume":"147","author":"Deng","year":"2024","journal-title":"J. Ind. Eng. Chem."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"102727","DOI":"10.1016\/j.jcou.2024.102727","article-title":"Advancements in CO2 Capture by Absorption and Adsorption: A Comprehensive Review","volume":"81","author":"Soo","year":"2024","journal-title":"J. CO2 Util."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"115589","DOI":"10.1016\/j.rser.2025.115589","article-title":"Review and Analysis of Porous Adsorbents for Effective CO2 Capture","volume":"215","author":"Foorginezhad","year":"2025","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"101098","DOI":"10.1016\/j.pecs.2023.101098","article-title":"Biochar as the Effective Adsorbent to Combustion Gaseous Pollutants: Preparation, Activation, Functionalization and the Adsorption Mechanisms","volume":"99","author":"Wen","year":"2023","journal-title":"Prog. Energy Combust. Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"109582","DOI":"10.1016\/j.rser.2019.109582","article-title":"Biochar-Based Adsorbents for Carbon Dioxide Capture: A Critical Review","volume":"119","author":"Dissanayake","year":"2020","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3089","DOI":"10.1007\/s12649-018-0347-1","article-title":"Use of Biochar Produced from Elephant Grass by Pyrolysis in a Screw Reactor as a Soil Amendment","volume":"10","author":"Ferreira","year":"2019","journal-title":"Waste Biomass Valorization"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"128","DOI":"10.1016\/j.jcou.2019.04.012","article-title":"Strategic Use of Biochar for CO2 Capture and Sequestration","volume":"32","author":"Jung","year":"2019","journal-title":"J. CO2 Util."},{"key":"ref_14","unstructured":"Basu, P. (2010). Biomass Gasification and Pyrolysis, Elsevier."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"695","DOI":"10.1016\/j.renene.2017.04.035","article-title":"A Comprehensive Review on the Pyrolysis of Lignocellulosic Biomass","volume":"129","author":"Dhyani","year":"2018","journal-title":"Renew. Energy"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Nasriani, H.R., and Nasiri Ghiri, M. (2026). Biomass Pyrolysis: Recent Advances in Characterisation and Energy Utilisation. Processes, 14.","DOI":"10.3390\/pr14081321"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"625","DOI":"10.3390\/biomass4030034","article-title":"Elephant Grass (Pennisetum purpureum): A Bioenergy Resource Overview","volume":"4","author":"Johannes","year":"2024","journal-title":"Biomass"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"104109","DOI":"10.1016\/j.geoforum.2024.104109","article-title":"Care Narratives: Babassu Breakers and Mother Palm Trees","volume":"156","author":"Lima","year":"2024","journal-title":"Geoforum"},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Jang, H.A., Pyo, S.W., Choi, Y.I., Lee, H., Bae, E.K., and Ko, J.H. (2026). Expanding the Research Frontiers of Pinus Species in Wood Biology. Forests, 17.","DOI":"10.3390\/f17010048"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"120184","DOI":"10.1016\/j.envpol.2022.120184","article-title":"Recent Developments in Modification of Biochar and Its Application in Soil Pollution Control and Ecoregulation","volume":"313","author":"Bao","year":"2022","journal-title":"Environ. Pollut."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Yao, J., Wang, Z., Liu, M., Bai, B., and Zhang, C. (2023). Nitrate-Nitrogen Adsorption Characteristics and Mechanisms of Various Garden Waste Biochars. Materials, 16.","DOI":"10.3390\/ma16165726"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1330","DOI":"10.1016\/S1872-5813(25)60568-8","article-title":"Research on Biochar Prepared by Trace KOH Catalyzed CO2 Activation vs KOH Activation as Advanced Candidate for Carbon Capture","volume":"53","author":"Deng","year":"2025","journal-title":"Ranliao Huaxue Xuebao\/J. Fuel Chem. Technol."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Zhang, L., and Zuo, S. (2024). The Significance of Lignocellulosic Raw Materials on the Pore Structure of Activated Carbons Prepared by Steam Activation. Molecules, 29.","DOI":"10.3390\/molecules29133197"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"127997","DOI":"10.1016\/j.seppur.2024.127997","article-title":"Investigation of Effectiveness of KOH-Activated Olive Pomace Biochar for Efficient Direct Air Capture of CO2","volume":"352","author":"Monteagudo","year":"2025","journal-title":"Sep. Purif. Technol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1016\/j.joei.2022.10.017","article-title":"Direct Air Capture of CO2 by KOH-Activated Bamboo Biochar","volume":"105","author":"Zhang","year":"2022","journal-title":"J. Energy Inst."},{"key":"ref_26","first-page":"100438","article-title":"Sustainable Biochar Synthesis via Synergistic H2O2-KOH Modification for Enhanced CO2 Physisorption","volume":"15","author":"Wang","year":"2025","journal-title":"Carbon Capture Sci. Technol."},{"key":"ref_27","first-page":"e05250","article-title":"Enhanced CO2 Adsorption of Alkali-Modified Sludge Biochar via Hydrothermal Activation: Mechanisms and Kinetics","volume":"23","author":"Liu","year":"2025","journal-title":"Case Stud. Constr. Mater."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"123034","DOI":"10.1016\/j.jenvman.2024.123034","article-title":"Enhancing Biochar Production: A Technical Analysis of the Combined Influence of Chemical Activation (KOH and NaOH) and Pyrolysis Atmospheres (N2\/CO2) on Yields and Properties of Rice Husk-Derived Biochar","volume":"370","author":"Premchand","year":"2024","journal-title":"J. Environ. Manag."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"149296","DOI":"10.1016\/j.scitotenv.2021.149296","article-title":"CO2 Capture by Adsorption on Biomass-Derived Activated Char: A Review","volume":"798","author":"Goel","year":"2021","journal-title":"Sci. Total Environ."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"7401","DOI":"10.1007\/s13399-022-02905-3","article-title":"Modification of Biomass-Derived Biochar: A Practical Approach towards Development of Sustainable CO2 Adsorbent","volume":"14","author":"Amer","year":"2024","journal-title":"Biomass Convers. Biorefin."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"103217","DOI":"10.1016\/j.jcou.2025.103217","article-title":"Activated Biochars from Heavy Metal-Contaminated Biomass for CO2 Capture: Adsorption Performance and Dominant Mechanisms","volume":"101","author":"Abbaspour","year":"2025","journal-title":"J. CO2 Util."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"526","DOI":"10.1016\/j.apenergy.2013.02.028","article-title":"Activated Carbons Prepared from Hydrothermally Carbonized Waste Biomass Used as Adsorbents for CO2","volume":"112","author":"Hao","year":"2013","journal-title":"Appl. Energy"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"267","DOI":"10.1007\/s13399-026-07199-3","article-title":"CO2 Adsorption Evaluation of Different Biochars Produced from Peanut Shell Pyrolysis","volume":"16","author":"Bonato","year":"2026","journal-title":"Biomass Convers. Biorefinery"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"718","DOI":"10.1016\/j.proeng.2016.06.591","article-title":"Carbon Dioxide Adsorption on Sawdust Biochar","volume":"Volume 148","author":"Madzaki","year":"2016","journal-title":"Procedia Engineering"},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Kwon, C.W., Tae, S., and Mandal, S. (2025). Comparative Analysis of CO2 Adsorption Performance of Bamboo and Orange Peel Biochars. Molecules, 30.","DOI":"10.3390\/molecules30071607"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"105136","DOI":"10.1016\/j.rineng.2025.105136","article-title":"Effect of Pyrolysis Temperature of Domestic Sewage Sludge Biochar on CO2 Adsorption","volume":"26","author":"Oktaviana","year":"2025","journal-title":"Results Eng."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"113352","DOI":"10.1016\/j.jece.2024.113352","article-title":"Enhancing Carbon Dioxide Uptake in Biochar Derived from Husk Biomasses: Optimizing Biomass Particle Size and Steam Activation Conditions","volume":"12","author":"Villardon","year":"2024","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_38","doi-asserted-by":"crossref","unstructured":"Straka, P., Cihl\u00e1\u0159, J., and Bi\u010d\u00e1kov\u00e1, O. (2025). Production of Syngas and Hydrogen-Rich Gas from Lignocellulosic Biomass via Ru\/Al2O3 Catalyst-Assisted Slow Pyrolysis. Catalysts, 15.","DOI":"10.3390\/catal15111033"},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1016\/j.biortech.2016.06.082","article-title":"Performance of Rotary Kiln Reactor for the Elephant Grass Pyrolysis","volume":"218","author":"Silvestre","year":"2016","journal-title":"Bioresour. Technol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"1781","DOI":"10.1016\/j.fuel.2006.12.013","article-title":"Characteristics of Hemicellulose, Cellulose and Lignin Pyrolysis","volume":"86","author":"Yang","year":"2007","journal-title":"Fuel"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"163","DOI":"10.1016\/j.enconman.2017.10.006","article-title":"Steam Gasification of Biochar Derived from Elephant Grass Pyrolysis in a Screw Reactor","volume":"153","author":"Ferreira","year":"2017","journal-title":"Energy Convers. Manag."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"614","DOI":"10.1016\/j.cej.2017.04.004","article-title":"Preparation and Characterization of a Metal-Rich Activated Carbon from CCA-Treated Wood for CO2 Capture","volume":"321","author":"Poletto","year":"2017","journal-title":"Chem. Eng. J."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Chang, S., Wang, L., and Yao, L. (2025). Properties of Sunflower Straw Biochar Activated Using Potassium Hydroxide. Molecules, 30.","DOI":"10.3390\/molecules30061332"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"154133","DOI":"10.1016\/j.scitotenv.2022.154133","article-title":"Insights into CO2 Adsorption on KOH-Activated Biochars Derived from the Mixed Sewage Sludge and Pine Sawdust","volume":"826","author":"Li","year":"2022","journal-title":"Sci. Total Environ."},{"key":"ref_45","first-page":"100309","article-title":"Prediction of CO2 Adsorption of Biochar under KOH Activation via Machine Learning","volume":"13","author":"Zhang","year":"2024","journal-title":"Carbon Capture Sci. Technol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"126875","DOI":"10.1016\/j.molliq.2025.126875","article-title":"Synthesis and Application of Biochar and KOH-Activated Carbon from Olive Mill Solid Waste for Polyphenol Removal","volume":"421","author":"Rabichi","year":"2025","journal-title":"J. Mol. Liq."},{"key":"ref_47","doi-asserted-by":"crossref","unstructured":"Zhao, Y., Huang, L., and Sun, G. (2025). Preparation of High-Performance KOH-Activated Biochar from Agricultural Waste (Sapindus mukorossi) and Its Application in Organic Dye Removal. Sustainability, 17.","DOI":"10.3390\/su17198674"},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Nazbakhsh, M., Nabavi, S.R., and Jafarian, S. (2025). Optimized Production of High-Performance Activated Biochar from Sugarcane Bagasse via Systematic Pyrolysis and Chemical Activation. Sustainability, 17.","DOI":"10.3390\/su17041554"},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Nunes, I.d.S., Schnorr, C., Perondi, D., Godinho, M., Diel, J.C., Machado, L.M.M., Dalla Nora, F.B., Silva, L.F.O., and Dotto, G.L. (2022). Valorization of Different Fractions from Buti\u00e1 Pomace by Pyrolysis: H2 Generation and Use of the Biochars for CO2 Capture. Molecules, 27.","DOI":"10.3390\/molecules27217515"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"106608","DOI":"10.1016\/j.biombioe.2022.106608","article-title":"CO2 Capture over Steam and KOH Activated Biochar: Effect of Relative Humidity","volume":"166","author":"Zhang","year":"2022","journal-title":"Biomass Bioenergy"},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"115223","DOI":"10.1016\/j.wasman.2025.115223","article-title":"Turning Plastic and Biomass Waste into Adsorbents: CO2\/CH4 Separation and Comparison with Commercial Carbons","volume":"210","author":"Pereira","year":"2026","journal-title":"Waste Manag."},{"key":"ref_52","doi-asserted-by":"crossref","first-page":"17168","DOI":"10.1021\/acs.iecr.3c00445","article-title":"The Application of Biochar for CO2 Capture: Influence of Biochar Preparation and CO2 Capture Reactors","volume":"62","author":"Zhang","year":"2023","journal-title":"Ind. Eng. Chem. Res."},{"key":"ref_53","doi-asserted-by":"crossref","first-page":"842","DOI":"10.1016\/j.carbon.2020.11.059","article-title":"Pore Size Characterization of Micro-Mesoporous Carbons Using CO2 Adsorption","volume":"173","author":"Dantas","year":"2021","journal-title":"Carbon"},{"key":"ref_54","doi-asserted-by":"crossref","first-page":"27","DOI":"10.18226\/23185279.v6iss3p27","article-title":"CO2 Gasification of Elephant Grass in a Fixed Bed Reactor","volume":"6","author":"Manera","year":"2018","journal-title":"Sci. Cum Ind."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"106874","DOI":"10.1016\/j.catcom.2024.106874","article-title":"DoE-Driven Thermodynamic Assessment of COX-Free Hydrogen Production from Methane Decomposition","volume":"187","author":"Biondo","year":"2024","journal-title":"Catal. Commun."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/17\/2971\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,25]],"date-time":"2026-08-25T11:27:49Z","timestamp":1787657269000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/17\/2971"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,25]]},"references-count":55,"journal-issue":{"issue":"17","published-online":{"date-parts":[[2026,9]]}},"alternative-id":["molecules31172971"],"URL":"https:\/\/doi.org\/10.3390\/molecules31172971","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,25]]}}}