Global warming resulting from the emission of greenhouse gases, especially CO 2 , has become a widespread concern in the recent years. Though various CO 2 capture technologies have been proposed, chemical absorption and adsorption are currently believed to be the most suitable ones for post-combustion power plants. The operation of the chemical absorption process is reviewed in this work, together with the use of absorbents, such as the ionic liquid, alkanolamines and their blended aqueous solutions. The major concerns for this technology, including CO 2 capture efficiency, absorption rate, energy required in regeneration, and volume of absorber, are addressed. For adsorption, in addition to physical adsorbents, various mesoporous solid adsorbents impregnated with polyamines and grafted with aminosilanes are reviewed in this work. The major concerns for selection of adsorbent, including cost, adsorption rate, CO 2 adsorption capacity, and thermal stability, are compared and discussed. More effective and less energy-consuming regeneration techniques for CO 2 -loaded adsorbents are also proposed. Future works for both absorption and adsorption are suggested.

Adsorption of carbon dioxide near its critical point on DeGussa IV activated carbon is investigated in this study. A volumetric method was used to measure the adsorption/desorption isotherms at 284, 300, 305, 310, and 314 K over a large pressure range. At subcritical temperatures, adsorption isotherms display a discontinuity at the vapor pressure of carbon dioxide, and desorption hysteresis is observed. However, there is no desorption hysteresis if adsorption is terminated before vapor−liquid transition occurs. At supercritical temperatures, adsorption isotherms display a plateau, and the excess decreases beyond the critical pressure. No hysteresis occurs during the desorption process. The adsorption isotherms can be represented very well by the simplified local density model.

The absorption of carbon dioxide from gases containing 1-10 mol % CO 2 in a rotating packed bed was investigated in this study. The aqueous solutions of NaOH, monoethanolamine, and 2-amino-2-methyl-1-propanol were used as the absorbents. The overall volumetric mass-transfer coefficient (K G a) was observed as a function of the rotating speed, gas flow rate, liquid flow rate, absorbent concentration, and CO 2 concentration. The obtained results indicated that K G a of a rotating packed bed was comparable to a tower packed with the EX packing, implying a great potential of a rotating packed bed applied to the reduction of the greenhouse gas CO 2 from the exhausted gases.

Global warming due to the accumulation of atmospheric CO 2 has received widespread attention in recent years. Although various CO 2 capture technologies have been proposed, using the captured CO 2 from power plants is increasingly popular because of concerns with regard to the safety of underground and ocean CO 2 storage. Various techniques related to utilization of CO 2 from the exhausted gas of power plants are discussed in this article. The existing and under-development technologies for CO 2 utilization in the world are briefly reviewed. Two categories, direct utilization of CO 2 and conversion of CO 2 to chemicals and energy products, are used to classify different forms of CO 2 utilization. Regarding the direct utilization of CO 2 , in addition to its use in soft drinks, welding, foaming, and propellants, as well as the use of supercritical CO 2 as a solvent, CO 2 capture via photosynthesis to directly fix carbon into microalgae has also attracted the attention of researchers. The conversion of CO 2 into chemicals and energy products via this approach is a promising way to not only reduce the CO 2 emissions, but also generate more economic value. Since CO 2 is just a source of carbon without hydrogen, a clean, sustainable and cheap source of hydrogen should be developed. This article reviews the literature on the production of biofuel from microalgae cultivated using captured CO 2 , the conversion of CO 2 with hydrogen to chemicals and energy products, and sustainable and clean sources of hydrogen, in order to demonstrate the potential of CO 2 utilization.