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The influences of the physical features and chemical properties of activated carbon on Hg 0 adsorption were investigated. The textural characteristics of the samples were studied by Brunauer−Emmett−Teller analysis and scanning electron microscopy. The chemical properties of the samples were characterized by energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results show that the oxygen-containing functional groups on activated carbon have a great influence on Hg 0 adsorption and the functional groups increase the acidity, polarity, and hydrophobicity of the carbon surface and promote the Hg 0 adsorption. The Hg 0 adsorption of activated carbon mainly manifests as chemical adsorption. The desorbed activated carbon almost has no Hg 0 removal ability although it still has a huge surface area and a microspore structure. The oxygen-containing functional groups on the surface play a key role in Hg 0 adsorption. Among them, carbonyl, carboxyl, and ester groups promoted mercury adsorption, while the phenolic hydroxyl group induced inhibition. The process of Hg 0 adsorption on modified activated carbon could be described with the pseudo-second-order model, which indicated that the chemisorption is the dominant step in the Hg 0 removal process by modified activated carbon. Kinetic calculation results also show that under a given gas condition, modified activated carbon possessed a bigger equilibrium adsorption capacity but displayed poor adsorption kinetics.

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Due to the continued increasing levels of CO2 emissions that is contributing to climate change, CO2 mitigation technologies, particularly carbon capture and storage, are being developed to address the goal of abating CO2 levels. Carbon capture technologies can be applied at the pre-combustion, oxy-fuel combustion, and post-combustion stages, the latter being the most widely used due to its flexibility. Among the several CO2 separation processes available for carbon capture, absorption is the most widely used where amine solutions are used as absorbents. This paper highlights the use of a wetted wall column fabricated by Siy and Villanueva (2012) and simulated flue gas to determine the performance of CO2 absorption in terms of the percentage of CO2 absorbed, the steady state time, and the overall gas mass transfer coefficient. The concentrations used were 1, 5, 10, and 15% NH3(aq) at a constant temperature range of 12-17ºC, solvent flow rate of 100 mL/min, and simulated flue gas flow rate of 2 L/min. It was found that increasing the solvent concentration resulted in a proportional increase both in the percentage of CO2 absorbed and the overall gas mass transfer coefficient. The average percentage of CO2 absorbed ranged within 52.25% to 95.29% while the overall mass transfer coefficient ranged from 0.1843 to 0.7746 mmol/m2∙s∙kPa. However, erratic behavior was seen for the time required for the system to reach steady state. Using Design ExpertTM for analysis, the results showed that the effect of varying the concentration had a significant effect on the percentage of CO2 absorbed and the overall gas mass transfer coefficient. The results proved that the greater the aqueous ammonia concentration, the greater the percentage of CO2 absorbed. The range of 5-10% aqueous ammonia is recommended because the percentage of CO2 absorbed peaks at an average of 92% beyond the range of 5-10%.