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.
Removal of chlorophenols from aqueous solution by anion-exchange resins
Abstract The effects of pH value and chloride ion concentration on the removal of chlorophenols from aqueous solutions by Purolite A-510 resin [macroreticular polystyrene-divinylbenzene resin with R(CH3)2(C2H4OH)N+ group] are discussed by the species distributions of chlorophenols. Those chlorophenols include phenol, 2-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol. The investigations showed that the chlorophenols could be removed effectively at alkaline conditions where the ion-exchange reaction was dominant. Also, the removal of chlorophenols increased with the number of chlorine atoms on the chlorophenols. The removal of chlorophenols via the ion-exchange reaction was hindered by the presence of chloride ions. The effect of chloride ions, however, was diminished in acidic solutions where the adsorption reaction was dominant. The proposed equilibrium model, which considers both adsorption and ion-exchange reactions, adequately describes the sorption behavior of chlorophenols. The partition ...
Adsorption and desorption of phenol on anion-exchange resin and activated carbon.
Adsorption and desorption of phenol on activated carbon and strong base anion-exchange resin were investigated in a fixed-bed column. Phenol was effectively adsorbed on both adsorbents. Experimental breakthrough curves were compared with values calculated on the assumption of surface diffusion controlling. Two methods of regeneration of adsorbents were carried out, that is, caustic desorption and acid desorption. Regeneration by sodium hydroxide or hydrochloric acid was effectively performed for the resin. On the other hand, regeneration of the activated carbon by sodium hydroxide was not performed completely. The adsorption capacity for activated carbon decreased gradually during the repetition process of adsorption and desorption, while the capacity for anion-exchange resin remained constant. 14 references, 9 figures, 1 table.