Nitrogen-doped porous carbons obtained from coconut shell by urea modification and KOH activation are found to exhibit very high CO2 uptake at 1 bar, almost 5 mmol g–1 at 25 °C and over 7 mmol g–1 at 0 °C, respectively. The high CO2 uptake of the sorbent can be ascribed to its high microporosity and nitrogen content. In addition, these sorbents possess high CO2/N2 selectivity, stable cyclic ability, high initial heat of CO2 adsorption, fast adsorption kinetics, and high dynamic CO2 capture capacity under simulated flue gas conditions. When combined with the low cost of the coconut-shell precursor, these properties make them exceptionally attractive sorbent candidates for CO2 capture.

Porous carbons synthesized by KOH activation of petroleum coke can have high surface areas, over 3000 m(2)/g, and high CO(2) sorption capacity, over 15 wt % at 1 bar. This makes them attractive sorbents for carbon capture from combustion flue gas. Quenched solid density functional theory (QSDFT) analysis of high-resolution nitrogen-sorption data for such materials leads to the conclusion that it is the pores smaller than 1 nm in diameter that fill with high-density CO(2) at atmospheric pressure. Upon increasing pressure, larger and larger pores are filled, up to about 4 nm at 10 bar. An ideal CO(2)/N(2) selectivity of such carbon materials tends to decrease substantially upon increasing pressure, for example, from about 8-10 at 1 bar to about 4-5 at 10 bar. All in all, this work confirms the robust CO(2)-filling properties of porous carbon sorbents, their low-pressure selectivity advantages, and points to the critical role of <1 nm pores that can be controlled with activation conditions.

Activated carbon derived from finger citron residue (FAC) was tested as a new type of adsorbents to remove the harmful dyes (anionic dye methyl orange (MO) and cationic dye methylene blue (MB)) from contaminated water. Liquid phase adsorption experiments were conducted and the maximum adsorptive capacity was determined. Various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and isotherm constant calculation. It was found that the adsorption capacity of FAC is much higher than those of the other types of activated carbons. Maximum equilibrium adsorption capacities of 934.58 mg/g and 581.40 mg/g for MO and MB were achieved.Three simplified kinetic models including pseudo-first-order, pseudo-second-order and intra-particle diffusion equations were used to investigate the adsorption process.The pseudo-second-order equation was followed for adsorption of MO and MB on FAC. Temperature-dependent adsorption behaviors of MO and MB show that the adsorption is a spontaneous and endothermic process accompanying an entropy increases (the driving force of the adsorption). This work indicates that FAC could be employed as a low cost alternative to commercially available activated carbon in the removal of dyes from wastewater.

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