ISSN:
1573-2932
Keywords:
adsorption
;
BTEX
;
hexadecyltrimethylammonium
;
hydrocarbon
;
montmorillonite
;
partitioning
;
organo-clay
;
trimethylammonium adamantane
;
trimethylphenylammonium
Source:
Springer Online Journal Archives 1860-2000
Topics:
Energy, Environment Protection, Nuclear Power Engineering
Notes:
Abstract Organo-clay can be utilized for the containment of environmentalpollutants originating from waste sites or accidental spills. Abatch study was conducted using organo-clays produced from aWyoming montmorillonite (SWy) and three organic cations(trimethylphenylammonium (TMPA), trimethylammonium adamantane(Adam), and hexadecyltrimethylammonium (HDTMA)) to characterizeBTEX (benzene, toluene, ethylbenzene, o-, m-, p-xylene) sorption. Sorption data were fitted to two models,with Freundlich resulting in greater correlations of the datathan the Langmuir model (R 2 at P ≤0.001-0.05). The Freundlich conditional index (n f),which describes the experimental sorption characteristics,decreased curvilinearly with organic-cation molecular weights,thus suggesting organo-clays with smaller cations had greaterhydrocarbon retention. Sorption of BTEX followed the order ofTMPA 〉 Adam 〉 HDTMA organo-clays. A similar sequence in themagnitudes of log K d and log K omsupportedthis finding. Positive log K om/K ow valuesfor TMPA and Adam derivatives indicated there was a greaterretention of BTEX by these organo-clays than octanol. The orderof log K om for SWy-HDTMA, although concentration-dependent, was analogous to the log K ow order,indicating partitioning was the dominant sorption mechanism forthe HDTMA-clay. Isotherms for SWy-TMPA and SWy-Adam followed aconvex up pattern. In contract, a concave up curvature, notedfor SWy-HDTMA isotherms, was probably caused by a cosorptiveenhancement process resulting from an effective increase in organic matter content of the organo-clay due to furtherhydrocarbon sorption,in concurrence with a decrease inadsorbate activity coefficients. Values of binding affinityconstant, K f, for SWy-TMPA were consistently higherthan SWy-Adam. The K f values determined for totalBTEX sorption by TMPA and Adam derivatives were higher thanthose for the individual hydrocarbons. With SWy-HDTMA, the same order was observed for benzene and toluene; however, ethylbenzene and xylenes had greater K f values thanthat for the BTEX mixture, possibly due to higher partitioningaffinity of the larger alkylbenzenes. With SWy-HDTM, thesequence of K f values was: ethylbenzene 〉 m-xylene 〉 p-xylene 〉 o-xylene 〉 toluene 〉benzene. Trends for SWy-TMPA and SWy-Adam were in contrast tothat of the partitioning order, suggesting that adsorption, ratherthan partitioning, was the primary sorption mechanism for thesetwo organo-clays. With respect to the equilibriumconcentrations, the sorbed amounts for total BTEX mixture weregenerally higher than those for the individual compounds. Ascompared to benzene and toluene, the large-size alkylbenzenesshowed greater partitioning affinity due to their high hydrophobicity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1005167524630
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