Adsorption of organic molecules from aqueous solutions on carbon materials

Abstract

Adsorption of organic molecules from dilute aqueous solutions on carbon materials is a complex interplay between non-electrostatic and electrostatic interactions. Non-electrostatic interactions are essentially due to dispersion and hydrophobic interactions, whereas the electrostatic or coulombic interactions appear with electrolytes when they are ionized at the experimental conditions used. Both interactions depend on the characteristics of the adsorbent and the adsorptive and the solution chemistry. Among them the carbon surface chemistry has a great influence on both electrostatic and non-electrostatic interactions, and can be considered one of the main factors in the adsorption mechanism from dilute aqueous solutions. In this paper the current knowledge about the fundamental factors that control the adsorption process from aqueous phase will be presented.

Capacity and mechanism of phenol adsorption on lignite

“…Such adsorption implies that oxidation of the carbon surface should promote adsorption capacity. However, several works report a decrease in phenol adsorption from water with surface oxidation Mahajan et al, 1980;Leng, 1996;Franz et al, 2000;Terzyk, 2003Terzyk, , 2004Moreno-Castilla, 2004). Since lignites are rich in oxygen surface groups Küçükbayrak et al, 2000), they have a high affinity for water (Allardice and Evans, 1971;Schafer, 1972;Kaji et al, 1986;Müller and Gubbins, 1998;Lee and Reucroft, 1999).…”

Fe (ii) adsorption on Ucides Cordatus crab shells

“…It is also likely the adsorption of cations by the biomaterials due to charge difference between the metal ion and the surface. 23,24 The isotherm of adsorption of N 2 (g), at 77K, is a combination of type II and type III according to the classification of Brunauer, with a greater contribution of the last one, which indicates a nonporous biosorbent. 25 Additionally, it was observed that 51.7% of the S BET can be attributed to external surface.…”

Adsorption and desorption kinetics of benzene derivatives on mesoporous carbons

“…Hence, we may easily observe (see Online Resource) that adsorption of SA was always the strongest (the same adsorption as for BA was obtained at 2-3 times lower equilibrium concentrations) and adsorption of phenol of 50 % of SA and 65 % of BA adsorption for the same solute concentration. Explanation of this behavior is mainly the Traube's rule-the main factor affecting adsorption for similar adsorbates in the same molecular state (all adsorbates are mostly in molecular form at pH = 2) are their relative concentrations c/c s , where c s is saturation concentration (see Table 3) (DeryloMarczewska and Jaroniec 1987;Derylo-Marczewska and Marczewski 1999;Moreno-Castilla 2004). Salicylic acid has the lowest solubility (half of BA solubility), whereas solubility of phenol has solubility larger by more than 1 order of magnitude and their adsorption properties may be ordered as follows: SA [ BA [ Ph.…”

“…Salicylic acid has the lowest solubility (half of BA solubility), whereas solubility of phenol has solubility larger by more than 1 order of magnitude and their adsorption properties may be ordered as follows: SA [ BA [ Ph. Moreover, intramolecular hydrogen bond formation in SA (hydroxyl and carboxyl groups in ortho position) resulting in weaker solvation effects may also be responsible for its lower solubility in water and stronger affinity to graphene-like structures in carbons (Moreno-Castilla 2004). Partial evidence of this effect may also be seen in molar volumes (as calculated from solid density data) showing that the SA molecule occupies even less space than BA, despite having an additional hydroxyl group (Table 3).…”

“…The comparison of adsorption and desorption halftimes shows, that the desorption is much faster process than adsorption (best seen by comparing corresponding halftimes). During adsorption adsorbates are neutral molecules (pH ( pK a ) interacting strongly with weekly positive carbon surface, while during desorption adsorbates in solution are in anionic form and are very weakly adsorbed (carbon surface is also negatively charged) (Derylo-Marczewska and Jaroniec 1987;Marczewski 1997, 1999;Moreno-Castilla 2004). However, when desorption is initiated by alkalization, H ?…”