Asian Journal of Applied Science and Technology (AJAST) Volume 8, Issue 4, Pages 155-165, Oct-Dec 2024 ISSN: 2456-883X 155 Removal of carbon dioxide by adsorption using various adsorbents: A Review Achugbu O.E. 1* , Nwabanne J.T. 1 , Okey-Onyesolu C.F. 1 & Modozie B.U. 2 1 Department of Chemical Engineering, Nnamdi Azikiwe University, Awka, 420110, Nigeria. 2 Department of Pharmaceutical and Medicinal Chemistry, Nnamdi Azikiwe University, Awka, 420110, Nigeria. Corresponding Author Email: oe.achugbu@unizik.edu.ng * DOI: https://doi.org/10.38177/ajast.2024.8414 Copyright © 2024 Achugbu O.E. et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Article Received: 08 October 2024 Article Accepted: 12 December 2024 Article Published: 18 December 2024 ░ 1. Introduction Carbon dioxide (CO 2 ) is the major greenhouse gas which causes global warming. Large amount of carbon dioxide emanate from burning fossil fuels such as petroleum, mineral coal, and natural gas by the power, manufacturing, and transport sectors [1]. The IPCC’s 2018 report on warming of our planet states that CO 2 removal of 100-1000 gigatons (GT) will be needed in the next 100 years to prevent our planet’s mean temperatures from rising beyond 1.5°C (2.7°F) its levels before the period of industrial revolution [2]. The primary source of energy used worldwide is fossil fuels, and this situation is probably going to persist for some decades to come. To allow for the continuous burning of fossil fuels while lowering CO 2 emissions into the atmosphere and so preventing climate change worldwide, carbon dioxide capture is crucial. Solvents or solid adsorbents are capable of capturing carbon dioxide (CO 2 ), with solid adsorbents appearing to have several advantages over solvents. The different limitations of using absorbents include the following: low CO 2 absorption capacity, high equipment deterioration rate, amine breakdown in the flue gases triggered by SO 2 , NO 2 and O 2 leading to absorbent makeup rate, large equipment size, and excessive energy consumption during extremely high temperatures absorption [3]. Sequel to the above listed limitations, solid adsorption processes are preferred to absorption and equally studied to solve those characteristic setbacks in chemical absorption. According to [4], in addition to this, adsorption is also a preferred method because desorption can be carried out under supportive conditions and the desorbed carbon dioxide stored in a container. Also, it has been suggested that amines can be impregnated or grafted on these adsorbents which have porous surfaces in order to increase the rate of mass transfer of CO 2 into them and improve their initial limited adsorption capacity. ABSTRACT The purpose of this work is to put together a concise review of previous open access works on the removal of CO2 using various adsorbents. Previous works on this focused on comparing the adsorption capacity of activated amine-modified and non-modified adsorbents. Most of the adsorbents used by previous researchers were thermally and chemically activated. Thermal and chemical activation play vital roles in the modification of the adsorbents by clearing their active sites of impurities and increasing the porosity of the adsorbents. For comparative analyses, some researchers enhanced part of their activated adsorbents using amine groups which have great affinity for CO2. The following amine groups were used by previous researchers to enhance the adsorbents for higher CO2 uptake: monoethanolamine (MEA), diethanolamine (DEA), Triethanolamine (TEA), Tetraethylenepentamine (TEPA), polyethylenimine (PEI), methyl-diethanolamine, pentaethylenehexamine or the combination, PEI/MEA or even NaOH. On wet impregnation, these amine groups subsequently occupy the active sites released during activation. During the adsorption experiment, the carbon dioxide gas is chemisorbed by these amine groups as it comes in contact with the adsorbents surfaces. Results obtained by previous researchers on the adsorption capacity of the plain and amine-enhanced adsorbents were not all in agreement. While majority claimed that the adsorbents modified with amine groups adsorbed better than the unmodified ones, few claimed the reverse was their results. Most of the adsorbents used showed good adsorption-desorption regenerability of 7-16 cycles. The review further showed that the Freundlich isotherm model was found to be the best for fitting the CO2 adsorption isotherm. Keywords: Carbon dioxide; Adsorbents; Amines; Removal; Adsorption; Desorption; Carbon capture; Global warming; Greenhouse gases.