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Proučavanje sorpcije hroma(VI) iz vodenih rastvora na funkcionalizovanim sepiolitima

Study of chromium(VI) sorptionon the functionalized sepiolite

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2013
marjanovic_vesna.pdf (6.967Mb)
Author
Marjanović, Vesna
Mentor
Petrović, Rada
Committee members
Janaćković, Đorđe
Onjia, Antonie
Miladinović, Jelena
Rogan, Jelena
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Abstract
Predmet ove disertacije je proučavanje sorpcije anjonskih vrsta hroma(VI) na funkcionalizovanim sepiolitima iz vodenih rastvora, na 298 K. Prirodni, kiselinski aktivirani i termokiselinski aktivirani sepioliti su funkcionalizovani kovalentnim vezivanjem (3-merkaptopropil)trimetoksi-silana i [3-(2-aminoetilamino)propil]trimetoksi- silana za silanolne grupe na površini sepiolita. Funkcionalizacija je dokazana pomoću skenirajuće elektronske mikroskopije, rendgenske difrakcione analize, infracrvene spektroskopske analize, diferencijalno-termijske analize, adsorpcionodesorpcionih izotermi azota i određivanja tačke nultog naelektrisanja, pHtnn. Utvrđeno je da je struktura polaznog materijala sačuvana tokom funkcionalizacije. Adsorpcione izoterme su ukazale da je kapacitet adsorpcije funkcionalizovanog kiselinski aktiviranog sepiolita veći nego kapaciteti adsorpcije funkcionalizovanih prirodnog i termokiselinski aktiviranog sepiolita, za sve ispitivane početne pH-vrednosti rastvora. Efikasnos...t adsorpcije na funkcionalizovanim sepiolitima je poboljšana sniženjem pH-vrednosti rastvora. Aminosilanima funkcionalizovani sepioliti imaju veći sorpcioni kapacitet nego merkaptosilanima funkcionalizovani sepioliti na svim ispitivanim početnim pHvrednostima i naročito pri početnoj pH = 2,0. Maksimalni sorpcioni kapaciteti hroma(VI) su ~ 60 mg/g aminosilaniziranog kiselinski aktiviranog sepiolita, ~ 55 mg/g aminosilaniziranog termokiselinski aktiviranog sepiolita i ~ 37 mg/g aminosilaniziranog prirodnog sepiolita, pri početnoj pH-vrednosti 2,0; dok su maksimalni sorpcioni kapaciteti ~ 8,0 mg Cr(VI) po g merkaptosilaniziranog kiselinski aktiviranog sepiolita i ~ 2,8 mg Cr(VI) po g merkaptosilaniziranog termokiselinski aktiviranog sepiolita, pri početnoj pH-vrednosti 3,0 i ~ 2,7 mg Cr(VI) po g merkaptosilaniziranog prirodnog sepiolita, pri početnoj pH-vrednosti 2,0. Proces adsorpcije na aminosilaniziranim sepiolitima, pri početnoj pH-vrednost 2,0, se može opisati kinetičkim modelom pseudodrugog reda. Pri svim ispitivanim početnim pH-vrednostima rastvora, rezultati sorpcionih eksperimenata za sve aminosilanizirane sepiolite su dobro opisani Freundlich-ovim modelom, a Dubinin-Radushkevich-ev model uspešno može opisati rezultate sorpcionih eksperimenata za sve merkaptosilanizirane sepiolite. Vrednosti termodinamičkih parametara ukazuju da je proces adsorpcije spontan i pretežno fizičke prirode.

The subject of this dissertation is the study of sorption of anionic species of chromium(VI) on the functionalized sepiolites from aqueous solution at 298 K. Natural, acid activated and thermo-acid activated sepiolites were functionalized by covalent grafting (3-mercaptopropyl)trimethoxy-silane and [3-(2-aminoethylamino)propyl]- trimethoxy-silane to the silanol groups onto the sepiolite surface. Functionalization was proved by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, differential thermal analysis, nitrogen adsorption-desorption, and the point of zero charge, pHpzc, determinations. It has been established that the structure of parent material was preserved during the functionalization. The adsorption isotherms suggested that the adsorption capacity of the functionalized acid activated sepiolite was higher than that of the functionalized natural and thermo-acid activated sepiolites, for all investigated initial solution pH values. Adsorpti...on efficiency of the functionalized sepiolites was improved by decreasing solution pH value. The amine-silane functionalized sepiolites showed a higher adsorption capacity than the mercapto-silane functionalized sepiolites at all studied initial pH values, especially at the initial pH = 2.0. The maximum chromium(VI) removal was: ca. 60 mg/g of amine-silane functionalized acid activated sepiolite, ca. 55 mg/g of amine-silane functionalized thermo-acid activated sepiolite and ca. 37 mg/g of amine-silane functionalized natural sepiolite, at an initial pH of 2.0; while, the maximum Cr(VI) removal was ca. 8.0 mg Cr(VI) per g of mercapto-silane functionalized acid activated sepiolite and ca. 2.8 mg Cr(VI) per g of mercapto-silane functionalized thermo-acid activated sepiolite, at initial pH 3.0, and ca. 2.7 mg Cr(VI) per g of mercapto-silane functionalized natural sepiolite, at initial pH 2.0. The adsorption process onto amine-silane functionalized sepiolites, at initial pH value of 2.0, followed pseudo-second-order kinetics. At all investigated initial solution pH values, equilibrium data for all amine-silane functionalized sepiolites fitted well to the Freundlich model, and Dubinin-Radushkevich model can successfully describe the equilibrium data for all mercapto-silane functionalized sepiolites. The values of the thermodynamic parameters indicate a spontaneous adsorption process of a prevalently physical nature.

Faculty:
University of Belgrade, Faculty of Technology and Metallurgy
Date:
15-03-2013
Keywords:
Hrom(VI) / Chromium(VI) / Adsorption / Sepiolite / Acid activated sepiolite / Thermo-acid activated sepiolite / Functionalization / [3-(2-Aminoethylamino)propyl]trimethoxysilane / (3-Mercaptopropyl)trimethoxy-silane / Adsorpcija / Sepiolit / Kiselinski aktiviran sepiolit / Termokiselinski aktiviran sepiolit / Funkcionalizacija / [3-(2-Aminoetilamino)propil]trimetoksi-silan / (3- Merkaptopropil)trimetoksi-silan
[ Google Scholar ]
URI
http://eteze.bg.ac.rs/application/showtheses?thesesId=843
http://nardus.mpn.gov.rs/handle/123456789/2879
https://fedorakg.kg.ac.rs/fedora/get/o:7207/bdef:Content/download
http://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=44833295

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