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PREDICTING THE ADSORPTION CAPACITY OF ACTIVATED CARBON FOR ORGANIC CONTAMINANTS FROM ADSORBENT AND ADSORBATE PROPERTIES
MEZZARI, I. A., T. F. SPETH, AND D. R. KNAPPE. PREDICTING THE ADSORPTION CAPACITY OF ACTIVATED CARBON FOR ORGANIC CONTAMINANTS FROM ADSORBENT AND ADSORBATE PROPERTIES. In Proceedings, AWWA Annual Conference and Exposition, San Antonio, TX, June 11 - 15, 2006. American Water Works Association, Denver, CO, ,, (2006).
A quantitative structure-property relationship (QSPR) was developed and combined with the Polanyi-Dubinin-Manes model to predict adsorption isotherms of emerging contaminants on activated carbons with a wide range of physico-chemical properties. Affinity coefficients (βl) for 62 neutral organic contaminants, calculated from adsorption isotherm data collected by the U.S. EPA, served as a training set for QSPR development. The resulting poly-parameter QSPR βl = 6.146x10-1 * (Vs/100) – 3.123x10-1 * Ed + 1.160 * (εHOMO10) + 1.869x10-1 * q- + 1.616, which includes the molecular descriptors molecular surface volume (Vs), dielectric energy (Ed), highest occupied molecular orbital (HOMO) energy (εHOMO), and electrostatic hydrogen-bond basicity (q-), provides a new tool for predicting the affinity of aqueous contaminants for the activated carbon surface. Coefficients describing the affinity of water (βw) for the activated carbon surface were estimated from the adsorbent oxygen and ash contents using a previously developed correlation. External validation results showed that trichloroethene (TCE) isotherm predictions were in close agreement with TCE isotherm data for four activated carbons with a wide range of physicochemical properties. Model predictions also showed good agreement with experimental isotherm data obtained for the pesticides methomyl and acifluorfen as well as for the neutral form of the antimicrobial compounds sulfamethoxazole and trimethoprim. To illustrate the applicability of the developed model, single-solute adsorption isotherms were predicted for representative emerging contaminants including pharmaceutically active compounds (PhACs), endocrine disrupting compounds (EDCs), chemical warfare agents (CWAs), fluorotelomer alcohols (FTOHs), and brominated flame retardants (BFRs). Isotherm predictions showed that the adsorbability of emerging contaminants spanned approximately 6 orders of magnitude. Predicted adsorption capacities were largest for 10:2 FTOH and the BFRs and smallest for 4:2 FTOH.
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Record Details:Record Type: DOCUMENT (PAPER IN NON-EPA PROCEEDINGS)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
WATER SUPPLY AND WATER RESOURCES DIVISION
TREATMENT TECHNOLOGY EVALUATION BRANCH