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Coal-based granular activated carbon (GAC) is saturated with trichloroethylene (TCE) by passing air through a fix bed adsorber. In surfactant-enhanced carbon regeneration, an aqueous solution of anionic surfactant, sodium dodecyl sulfate (SDS), is passed through the bed to induce desorption of TCE. More than 95% of the sorbed TCE was removed in the desorption operation with a 0.1 M SDS solution at a superficial flow rate of 1 cm/min. The desorption rate of TCE from pores of GAC is limited by pore diffusion and not significantly affected by either the concentration of SDS in the regenerant (when well above the critical micelle concentration) or its flow rate. From the breakthrough curve of a subsequent adsorption cycle without a flushing step following the desorption, only 7% of the virgin carbon effective adsorption capacity is observed for the regenerated carbon. With a water flushing step following the regeneration step, the effective adsorption capacity is significantly improved to about 15% of that of virgin carbon. Increased temperature of the flushing water also enhances the effective adsorption capacity of the regenerated GAC. Separate batch adsorption-desorption isotherms of SDS on GAC support the enhanced desorption of SDS at elevated temperatures. The drastic reduction in the effective adsorption capacity of regenerated GAC results from the residual SDS remaining in the pores of GAC as confirmed by thermal gravimetric analysis. Both the regeneration and water flush steps are rate limited under conditionsused here. [ABSTRACT FROM AUTHOR]

Surfactant enhanced carbon regeneration (SECR) was employed to regenerate a polymeric resin saturated with trichloroethylene (TCE), using an aqueous solution of the anionic surfactant sodium dodecyl sulfate (SDS). More than 95% of the sorbed TCE was removed in the desorption operation with a 0.1 M SDS solution at a superficial flow rate of 1 cm/min. The desorption rate of TCE from pores of the resin is limited by the concentration of SDS in the regenerant and its flow rate. From the breakthrough curve of the subsequent adsorption cycle without a flushing step following the desorption, only 40% of the effective adsorption capacity of the virgin resin is observed for the regenerated resin. With a water flushing step following the surfactant regeneration step, the effective adsorption capacity is significantly improved to about 60% of that of the virgin resin. Thermal gravimetric analysis indicates that the reduction in the effective adsorption capacity of regenerated resin resulted from the residual SDS remaining in the pores of the resin. The regeneration step is equilibrium limited whereas the water flushing step is rate limited under the studied conditions. Despite the loss of subsequent cycle adsorption capacity, SECR may still be economical as an in-situ, low temperature regeneration method. [ABSTRACT FROM AUTHOR]

Abstract: In this study, an alternative non-energy intensive system for the production of 2,6-DMN (catalytic isomerization in a solvent media and adsorptive purification) was investigated using the pulse test technique. The integrations of the isomerization to the adsorption were accomplished in two different approaches; subsequent adsorption after the isomerization and the reactive adsorption based technique. By subsequently connecting the adsorption unit after the isomerization with the selected adsorbent, catalyst and desorbent, the system shows a potential for producing high purity 2,6-DMN. Moreover, the results also suggest a possibility to enhance the overall productivity of 2,6-DMN by separating the chemical from the product stream during the isomerization. However, the results from the reactive adsorption study indicate only a narrow possible operating window for the high purity 2,6-DMN production. Carrying out the system at the temperatures that the isomerization can reach its equilibrium entails the reduction in either the 2,6-DMN separation due to the very fast in the reaction kinetics or the 2,6-DMN yield by the backward isomerization from 2,6- to 1,6- and 1,5-DMN. On the other hand, operating the system below the equilibrium of the isomerization at appropriate temperatures is only a possible approach to produce high purity 2,6-DMN using the reactive adsorption technique. [Copyright &y& Elsevier]

Phenol hydroxylation with TS-1 was studied in a chromatographic reactor. TS-1 not only acts as the catalyst for the reaction but also the adsorbent for the separation. The reaction/separation was carried out at 60°C with water and 0.2 wt% of aqueous H2O2 as the desorbent. Separation of hydroquinone(HQ) can be achieved in all cases. With water as the desorbent, separation of catechol(CT) depends on the phenol feed concentration, which has been confirmed from both reaction/separation in the chromatographic reactor and equilibrium competitive adsorption experiment. Some unknown by-products not commonly reported in batch experiments have been observed here. TS-1 can also be regenerated using just water. With the aqueous mixture of H2O2 as the desorbent, separation of HQ and CT is possible. Reactive separation schemes based on the simulated counter-current technology have been proposed according to the experimental results. [ABSTRACT FROM AUTHOR]