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.
NaOH regeneration of Pb and phenol-laden activated carbon. I. Batch study results
Abstract Granular activated carbon (GAC) has been used to remove organics and metals simultaneously from wastewaters (4). For a regeneration procedure to be effective on GAC containing both metals and organics, it must remove both the metals and organic compounds. In this study, GAC saturated with Pb and phenol was regenerated using an NaOH rinse in batch mode. Four variables were investigated: 1) regenerant concentration (0, 0.1, and 1.0 N), 2) regenerant to carbon mass ratio (5:1 and 10:1), 3) regenerant temperature (22 and 80°C), and 4) regeneration time (0.33, 1, 3, 7, and 21 days). Maximum regenerations of 47% for Pb and 48% for phenol were observed. The 1.0 N NaOH regenerated a higher percentage of both Pb and phenol when compared to the other regenerants. The 10:1 regenerant to carbon ratio resulted in increased regeneration over the 5:1 regenerations. Pb regeneration was slightly higher at 80°C than at 22°C whereas phenol regeneration was slightly lower at 80°C than at 22°C. Maximum regenerations ...
SR topography of plastically deformed Fe-Si bicrystals - observation in situ and post mortem
SR reflection topography was applied to study the interaction of slip dislocations with the grain boundaries in Fe-4at%Si bicrystals deformed by compression. Three experimental settings with either a white or monochromatic beam were used and the corresponding orientation contrast analysed. Dislocation transmission through the grain boundary was observed in bicrystals with favourable geometry of the slip systems.