A correlation was developed to estimate the adsorption equilibrium capacity of various adsorbents and organic compounds using a combination of Polanyi potential theory and linear solvation energy relationships (LSERs). Polanyi theory provided the basic mathematical form for the correlation. LSERs were used to normalize the Polanyi theory based on the fundamental interaction forces between the solvent, adsorbate, and adsorbent expected in aqueous-phase adsorption. The correlation was developed using 56 organic compounds and eight adsorbents. The following classes of organic compounds were used: (i) halogenated aliphatics, (ii) aromatics and halogenated aromatics, (iii) polyfunctional organic compounds and (iv) sulfonated aromatics. The adsorbents were (i) three coal-based activated carbons (F-300, F-400, and APA), (ii) one coconut shell based activated carbon (580-26), (iii) one unspecified activated carbon, and (iv) three synthetic polymeric adsorbents (XAD-4, XAD-7, and XEN-563). The proposed correlation, which considers the fundamental solvent−adsorbate−adsorbent interaction forces, showed a significant improvement in predicting the adsorption capacity over a correlation that considered only van der Waals forces. However, the correlations did not predict the adsorption capacities of highly soluble organic compounds such as polysulfonated aromatics and polyfunctional organic compounds.
A thermodynamic model is developed to predict adsorption equilibrium in the International Space Station water processor's multifiltration beds. The model predicts multicomponent adsorption equilibrium behavior using single-component isotherm parameters and fictitious components representing the background matrix. The fictitious components are determined by fitting total organic carbon and tracer isotherms with the ideal adsorbed solution theory. Multicomponent isotherms using a wastewater with high surfactant and organic compound concentrations are used to validate the equilibrium description on a coconut-shell-based granular activated carbon (GAC), coal-based GAe, and a polymeric adsorbent. Water Environ. Res., 70, 14 (]998).A substantial amount of potable water is required for life support of the crew aboard the International Space Station (ISS). Water for drinking, food preparation, and personal hygiene accounts for more than 90% by weight of the basic consumables (water, oxygen, and food) required for survival aboard the ISS. Life support of a four-person crew would require transport of approximately 20 900 kg (46 100 Ib) of water per year to the ISS without onboard water recycling. The economic limitations of transporting water to the ISS necessitate onboard recovery and reuse of the aqueous waste streams (Carter et ai., 1991).The aqueous waste streams processed by the ISS water processor include urine distillate, waste shower and hand wash water, humidity condensate, ora] hygiene and wet shave waste, and a mixture of humidity condensate and evaporated urine from the Research Animal Holding Facility. These waste streams are complex mixtures of unknown composition. Wastewater is recycled aboard the ISS using a series of four treatment processes. In one stage of the treatment process, adsorption media and ionexchange resins are combined in multi filtration beds (MFBs) for removal of ionic and non ionic contaminants from the wastewater. A schematic of an MFB is shown in Figure I. The empty bed contact time is also reported for each layer of the MFB.A technique termed the fictive component analysis (FCA) was developed to model adsorption equilibrium for wastewaters of unknown composition on the MFB adsorbents. The FCA uses imaginary compounds (fictive components [FCs]) to represent the background compounds making up the overall total organic carbon (TOC) in unknown mixtures (Sontheimer et at., 14 1988). The FC parameters are determined such that the FCs give the same competitive adsorption effect as the unknown mixture. Hubele andFrick and used the FCA to predict adsorption isotherms of TOC, where each FC represented a portion of the total TOC, and the sum of the FC TOC concentrations equaled the overall TOC concentration. Crittenden et at. (1985) used the FCA to predict the adsorption isothenns of tracer compounds in the presence of a multicomponent background matrix made up of similar-sized organic compounds. Crittenden et at. (1993) also used the FCA to predict removal of dissolved organic carbon in fixe...
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