<p>Prirodna organska materija zemljišta/sedimenata predstavlja glavnu oblast<br />za sorpciju hidrofobnih organskih jedinjenja, a njene osobine utiču na stepen<br />retencije i konsekventnu (bio)dostupnost organskih jedinjenja. Da bi se procenio<br />ekotoksikološki rizik zagađenih zemljišta/sedimenata po okolinu, dizajnirala<br />odgovarajuća strategija remedijacije ili predvidela sudbina i transport organskih<br />polutanata u zagađenim zonama, neophodno je razumevanje mehanizma sorpcije i<br />desorpcije na nivou mehanizma uspostavljenih veza. U radu je izvršeno ispitivanje<br />sorpcije i desorpcije odabranih hidrofobnih organskih polutanata, pentahlorbenzena<br />i lindana, na sekvencijalno ekstrahovanim huminskim kiselinama i huminima iz<br />jednog uzorka sedimenta u cilju pronalaženja veze između strukturnih<br />karakteristika izolovanih huminskih kiselina i humina i sorpcionih i desorpcionih<br />parametara. Afinitet za sorpciju, nelinearnost izotermi i prividna sorpciono-desorpciona histereza korelirani su sa osobinama sorbenata dobijenim iz<br />elementarne i FTIR spektroskopske analize. Predloženo je da je mehanizam<br />sorpcije na huminskim kiselinama rezultat odigravanja raspodele i specifične<br />adsorpcije, pri čemu se pri nižim koncentracijama pentahlorbenzena i lindana prvo<br />popune sorpciona mesta u kondenzovanoj aromatičnoj oblasti, a tek potom pri<br />višim koncentracijama sorpciona mesta u amorfnim alifatičnim oblastima.<br />Sveukupno viši koeficijenti nelinearnosti dobijeni za sorpciju pentahlorbenzena na huminskim kiselinama u odnosu na nelinearnost sorpcionih izotermi lindana, ukazuju na to da u ukupnoj sorpciji pentahlorbenzena veći značaj ima mehanizam raspodele i smeštanje molekula pentahlorbenzena u hidrofobne šupljine huminskih kiselina, u odnosu na specifičnu adsorpciju. Ovi zaključci su potvrđeni rezultatima spektroskopskih istraživanja interakcija odabranih organskih jedinjenja i N-metilformamida. Predloženi mehanizam sorpcije ne može objasniti sorpciju pentahlorbenzena i lindana na uzorcima humina, većje pretpostavljeno da nelinearna sorpcija za uzorke humina može biti rezultat ostvarivanja površinskih interakcija, a visoki afinitet za sorpciju rezultat je raspodele organskih jedinjenja u amorfnim alifatičnim oblastima koje pružaju odlično okruženje za sorpciju.</p><p>U cilju daljeg proučavanja mehanizma sorpcije, izvršeno je ispitivanje kinetike<br />desorpcije tri odabrana hidrofobna organskajedinjenja, pentahlorbenzena, lindana i<br />pentahloranilina, posredstvom čvrstog adsorbenta, XAD-4 makroporozne<br />jonoizmenjivačke smole. Na osnovu rezultata dobijenih za uzorak sedimenta i<br />frakciju < 125 µm za dva ravnotežna vremena (15 i 90 dana) i za sva odabrana<br />organska jedinjenja može se zaključiti da se za procenu potencijalne (bio)dostupne<br />frakcije organskih jedinjenja može koristiti jednostavna desorpcija u prisustvu<br />XAD-4 makroporozne jonoizmenjivačke smole i to na dva načina: (1) ekstrakcijom<br />sedimenta tokom 24 časa, kada frakcija koja se desorbuje odgovara frakciji<br />jedinjenja koja se nalazi u brzo-desorbujućem domenu organske materije, ili (2)<br />ekstrakcijom tokom 6 časova, kada frakcija koja se desorbuje odgovara polovini<br />one frakcije jedinjenja koja se nalazi u brzo-desorbujućem domenu organske<br />materije.</p> / <p>Natural organic matter of soil/sediment make the main region for sorption of hydrophobic organic compounds, ant its properties influence the degree of retention and, consequently, (bio)availability of organic compounds. In order to assess the ecotoxicological risks of contaminated soils/sediments to the environment and design the appropriate remediation strategy or predict the fate and transport of organic pollutants in contaminated zones, it is necessary to understand the mechanisms of sorption/desorption at the level of the mechanism of established bonds. Study of the sorption and desorption of selected hydrophobic organic pollutants, pentachlorobenzene and lindane, on sequentially extracted humic acids and humins from a single sediment sample with the aim of finding the relationship between the structural characteristics of the isolated humic acids and humin and sorption and desorption parameters. Sorption affinity, nonlinearity of isotherms, and apparent sorption-desorption hysteresis were correlated to the sorbent characteristics obtained from elemental analysis and FTIR spectroscopic data. The proposed sorption mechanism on humic acids assumes that at low concentrations of pentachlorobenzene and lindane the sorption sites in the condensed aromatic region are occupied first, and then, at their higher concentrations, the sorption sites in the amorphous and aliphatic regions. Generally higher nonlinearity coefficient obtained for the sorption of pentachlorobenzene on umic acids compared with the nonlinearity of sorption isotherms for lindane, indicate that in the overall sorption of pentachlorobenzene of higher significance is the echanism of distribution and insertion of pentachlorobenzene molecule into hydrophobic dips of humic acids, compared to specific adsorption. These conclusions were confirmed with the results of spectroscopic investigation of intermolecular interaction of chosen organic compounds and N-methylformamide.Since suggested sorption mechanism could not explain sorption of pentachlorobenzene and lindane onto humin samples, it is supposed that the nonlinearity can be a result of surface interactions, while the high sorption affinity is result of distribution of organic compounds in the amorphous aliphatic regions that offer an excellent environment for sorption.</p><p>With the aim of further insight into the sorption mechanism, investigation of desorption kinetics of three chosen hydrophobic organic compounds, pentachlorobenzene, lindane and pentachloroaniline, in the presence of soild adsorbent XAD-4 macroporous ion-exchange resin was performed. On the basis of the results obtained for sediment sample and fraction < 125 µm at two equilibrium times (15 and 90 days) and for all selected organic compounds, it can be concluded that the assessment of the potential (bio)avialable fraction of organic compounds may be obtained by using simple method of desorption in the presence of XAD-4 macroporous ion-exchange resin, performed in two ways: (1) by sediment <br />extraction during 24 hours, when the desorbing fraction corresponds to the fraction of he compound that is found in the fast-desorbing domain of organic matter, or (2) by 6-hour extraction, when the desorbing fraction corresponds to one half of the fraction appearing in the fast-desorbing domain of the organic matter.</p>
| Identifer | oai:union.ndltd.org:uns.ac.rs/oai:CRISUNS:(BISIS)16659 |
| Date | 25 May 2009 |
| Creators | Tričković Jelena |
| Contributors | Ivančev-Tumbas Ivana, Nikolić Aleksandar, Dalmacija Božo, Bošković Goran |
| Publisher | Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, University of Novi Sad, Faculty of Sciences at Novi Sad |
| Source Sets | University of Novi Sad |
| Language | Serbian |
| Detected Language | English |
| Type | PhD thesis |
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