Desorption by ultrasound: Phenol on activated carbon and polymeric resin
An experimental feasibility study of using ultrasound to accomplish the dificult desorption of phenol from activated carbon and polymeric resin adsorbents is discussed. The desorption rates of activated carbon were found to significantly increase by ultrasound at 40 kHz and 1.44 MHz. Attrition of the activated carbon due to cavitation could be prevented by operating at a higher frequency and with an intensity below the threshold of the pulverization of carbon. According to the structural stability study of Amberlite XAD-4 and Dowex Optipore L-493 resins to withstand the abrasive cavitational effects of ultrasound at 40 kHz, the Dowex Optipore resin was stable under experimental conditions and phenol desorption rates were enhanced significantly with sonication. The ultrasonic desorption rates were favored by decreased temperature, aerated liquid medium, and increased ultrasound intensity. The desorption rates obtained without ultrasound appeared to be limited by pore diffusion, whereas those obtained in the presence of ultrasound were limited by surface reaction. The rate enhancement was due to an increase in diffusive transport within the pores caused by acoustic vortex microstreaming. The activation energy for desorption decreased with an increase in ultrasonic power density, thus making the ultrasound weaken the adsorption bond.
Regenerate activated carbon using organic solvents
Adsorption by activated carbon is widely used to remove chemical species from waters and wastewater and volatile organic compounds from vapor streams. In normal applications, the activated carbon gradually accumulates the chemical species removed from the liquid or vapor stream. This causes a progressive reduction in the carbon`s ability to remove additional chemicals from the stream, and eventually the adsorption capacity is consumed and the carbon is spent. At this point, the carbon must either be replaced or be regenerated to restore its adsorptive capacity. Solvent regeneration is one such technology. It uses solvents to dissolve adsorbed material out of the pores of the activated carbon. Then the solvent is removed by steam. This article discusses where solvent regeneration fits into the overall scheme of activated carbon applications and regeneration options. Cost-wise, solvent regeneration of activated carbon is only a few cents per pound more expensive than steam regeneration, and less than one-tenth as expensive as thermal regeneration. Because steam regeneration is appropriate for only certain industrial applications (discussed later), the choice is usually between solvent and thermal regeneration.
Adsorption from aqueous and nonaqueous solutions on hydrophobic and hydrophilic high surface-area copolymers
The adsorption of fatty acids and phenols on high surface polymeric sorbents with polar surfaces has been examined. The results obtained from equilibrium experiments with acetic and butyric acids, phenol, and substituted phenols in aqueous, toluene, and hexane solutions show that the new polar polymeric sorbents have a considerable adsorption capacity in non-aqueous solvents. 
 
The shapes of the binding isotherms of substitued phenols from aqueous solution on a new high surface area (860 m2/gm) hydrophobic adsorbent suggest that a next-neighbor interaction exists between molecules bound on adjacent sites. The equation described by A. Fowler and E. A. Guggenheim, who considered such interactions, fits the experimental data.