Adsorption Characteristics Of Organic Compounds Research Articles

Adsorption of phenol and reactive dye from aqueous solution on activated carbons derived from solid wastes

Activated carbons were produced from several solid wastes, namely, waste PET, waste tires, refuse derived fuel and wastes generated during lactic acid fermentation from garbage. Activated carbons having various pore size distributions were obtained by the conventional steam-activation method and via the pre-treatment method (i.e., mixture of raw materials with a metal salt, carbonization and acid treatment prior to steam-activation) that was proposed by the authors. The liquid-phase adsorption characteristics of organic compounds from aqueous solution on the activated carbons were determined to confirm the applicability of these carbons, where phenol and a reactive dye, Black5, were employed as representative adsorbates. The hydrophobic surface of the carbons prepared was also confirmed by water vapor adsorption. The characteristics of a typical commercial activated carbon were also measured and compared. It was found that the activated carbons with plentiful mesopores prepared from PET and waste tires had quite high adsorption capacity for large molecules. Therefore they are useful for wastewater treatment, especially, for removal of bulky adsorbates.

Adsorption on Carbon and Zeolite of Pollutants from Flue Gas during Incineration

The volatile organic compound, polycyclic aromatic hydrocarbon, dioxin, and metallic components released from incineration threaten human health. These pollutants, appearing in a molecular state, cannot be effectively removed by baghouse and electrostatic precipitators through capture and filtration mechanisms. Previous studies indicate that activated carbon is conventionally used to remove organic compounds from gas at low temperatures (less than 30°C). However, the adsorption characteristics of organic compounds from a gas phase at high temperatures (over 120°C) are seldom mentioned. Moreover, the complex compositions of flue gas cause the adsorption characteristics of organic compounds and heavy metals on adsorbent tubes to be more complicated. This research examines the adsorption characteristics of organic compounds and heavy metals at various incineration conditions. The evaluated parameters include: (1) the operating temperatures; (2) the characteristics of adsorbents (activated carbon and zeolite); and (3) waste compositions and the presence of heavy metals. The results indicate that activated carbon has a high adsorption capacity compared with zeolite.

Influence of surface pretreatment of bismuth and cadmium electrodes to the electric double layer and adsorption characteristics of organic compounds

Influence of the surface structure of electrodes on the electric double layer properties, as well as on the adsorption characteristics of various organic compounds has been investigated by cyclic voltammetry, impedance and electron microscopic methods at variously prepared Bi, Sb and Cd electrodes. The systematic trends of the influence of surface roughness and energetic inhomogeneity on the electric double layer characteristics (value of differential capacity, potential of diffuse minimum, Parsons-Zobel factor, inner layer capacity, roughness function) have been established. The dependencies of the shape of adsorption-desorption maxima of organic compounds and other adsorption parameters (values of attraction interaction, adsorption equilibrium constant, shape of adsorption isotherm) on the electrode surface structure have been investigated. The Debye-length dependent roughness function has been calculated. The approximate values of the linear parameter of homogeneous regions, which prevail at the surface of polycrystalline electrodes have been calculated using various theoretical models. The established values of linear parameters of homogeneous regions have been compared with the characteristics obtained from the electron microscopic studies.

Adsorption characteristics in reversed-phase liquid chromatography using methanol/water and acetonitrile/water mobile phases.

Adsorption characteristics of organic compounds on an octadecylsilyl (ODS)-silica gel for two mobile phases, i.e, methanol/water (70/30, v/v) and acetonitrile/water (70/30, v/v) are compared. It is confirmed that the values of adsorption equilibrium constant, isosteric heat of adsorption, and activation energy of surface diffusion are smaller in 70 vol % acetonitrile than in 70 vol % methanol. On the contrary, the values of surface diffusion coefficient, Ds, are larger in 70 vol % acetonitrile than in 70 vol % methanol. These results indicated that the interaction between ODS ligands and solute molecules was weaker in 70 vol % acetonitrile than in 70 vol % methanol. The ratio of Ds to molecular diffusivity, Dm, is about 0.3 irrespective of chromatographic conditions, i.e., the type of organic modifiers and sample compounds, and temperature. It is possible to calculate Ds from Dm, which can be estimated by various correlations previously proposed in the literature. The almost constant ratio of Ds to Dm suggests the presence of a kind of correlation between surface and molecular diffusions.

Adsorption characteristics of organic compounds dissolved in water on surface-improved activated carbon fibres

The adsorption characteristics of low-molecular-weight organic compounds dissolved in water on hydrogenated activated carbon fibre (ACF) have been measured in terms of the amount adsorbed, the heat of immersion, and the heat of adsorption. The adsorption isotherms of the organics were found to conform to the Freundlich equation. The amounts of adsorbed polar compounds were increased by using ACF treated with hydrogen gas, which suggests that ACF has a relatively high hydrophobicity. The average electrostatic field strength increased as the number of functional groups on the ACF surface increased. The heats of adsorption decreased with increasing average electrostatic field strength. It was found that removing the polar functional groups attracting water molecules on the ACF surface resulted in an increase in the degree of adsorption of the low-molecular-weight organics from aqueous solution.