Υβριδικό σύστημα νανοσιδήρου-ιοντοανταλλακτικής ρητίνης για την απομάκρυνση Cr(VI) από ρυπασμένα νερά

Αλεξοπούλου, Μαρία; Alexopoulou, Maria

dc.contributor.author	Αλεξοπούλου, Μαρία	el
dc.contributor.author	Alexopoulou, Maria	en
dc.date.accessioned	2016-10-11T09:42:00Z
dc.date.available	2016-10-11T09:42:00Z
dc.date.issued	2016-10-11
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/43775
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.11565
dc.rights	Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/gr/	*
dc.subject	Νανοσωματίδια	el
dc.subject	Ιοντοανταλλαγή	el
dc.subject	Ιοντοανταλλακτικές ρητίνες	el
dc.subject	Εξασθενές χρώμιο	el
dc.subject	Στήλες	el
dc.title	Υβριδικό σύστημα νανοσιδήρου-ιοντοανταλλακτικής ρητίνης για την απομάκρυνση Cr(VI) από ρυπασμένα νερά	el
heal.type	bachelorThesis
heal.classification	Προστασία περιβάλλοντος	el
heal.language	el
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2016-07-20
heal.abstract	Ενσωμάτωση νανοσωματιδίων ρητίνης σε υπόστρωμα κατιονικής ρητίνης δικτυωτού τύπου, με εμπορικό όνομα Amberlyst 15Р και η αξιολόγηση των νανοσωματιδίων για την αναγωγή του εξασθενούσ χρωμίου σε δοκιμές παρτίδας και σε δοκιμές σε στήλες	el
heal.abstract	Iron nanoparticles have been extensively used since 2000 for the onsite treatment of contaminated soil and groundwater by a wide variety of contaminants both organic and inorganic. Nano ZVI is more efficient compared to micro or millimeter scale ZVI, due to the small particle size, large specific surface area and high reactivity. Nanoscale ZVI is usually produced as colloidal suspension appropriate for direct injection in the contaminated aquifers. However due to the limited mobility of nano zero valent iron (nZVI) via injection technologies and their potential toxicity in ecosystems an alternative mode of nZVI application is recently under investigation. In this category of technologies iron nanoparticles are fixed on a permeable matrix and this composite material is applied for the treatment of contaminated waters under flow conditions, such as an underground permeable reactive wall for in-situ treatment of groundwater or fixed bed reactors and filters for water treatment in above ground installations. The objective of the present study was to obtain the fixation of nano zero valent iron (nZVI) on the porous matrix of a reticular cationic resin, Amberlyst 15, and the evaluation of the nZVI particles. This composite resin-nanoiron material (R-nFe) was used for the treatment of Cr(VI) contaminated waters by conducting a series of column tests, with variable column configuration. Specifically, three reducing agents were examined for the reduction of adsorbed trivalent iron to the elemental state. Loaded R-Fe resin was treated with green tea extract, gallic acid and NaBH4 solutions as reductants. In order to confirm whether the reductants were able to reduce adsorbed Fe(III) to the elemental state, Fe(0), a number of preliminary tests were performed. Based on the results of these tests, the green tea extract was chosen for the synthesis of resin-nanoiron composite material (denoted as R-nFe-GT), because it presents similar performance to the two other tested chemical reagents and is also an environmental friendly reducing medium. The effectiveness of R-nFe-GT in reducing Cr(VI) was evaluated by conducting two categories of tests (a) batch tests under agitated conditions and (b) column tests under flow conditions. During the batch tests it was found that Cr(VI) follows a kinetic law of first order with respect to the concentration of Cr(VI). Column tests were carried out using 3 columns of variable dimensions, so as to obtain a different contact time of the flowing solution with the composite reactive material. Namely the residence time was 2.9, 12.4 and 21.0 min in the three columns. These 3 columns were filled with R-nFe-GT, while a fourth one was filled with silica sand as a typical inert material. At a first stage, a KBr solution with an initial concentration of 80 mg/L was added, in order to evaluate the transport of a chemically inert solution. Afterwards, a Cr(VI) solution of 5 mg/L was introduced to the columns. After the completion of the tests, the solid material of the 3 columns was separated in 3, 5 and 10 slices respectively, and each slice was analysed for total Fe and Cr, to check the mass balance of the two elements and evaluate the distribution of Cr along the columns. The reduction of Cr(VI) during the flow of the solution through the R-nFe-GT bed was slower compared to what was expected from the batch tests. Namely the kinetic constant describing Cr(VI) reduction under agitated conditions was equal to 1.78×10-3 min-1 per mM of nFe, while the same constant as derived from the column tests was equivalent to 3.21-4.08 ×10-5 min-1 per mM nFe. The slower kinetics during the column tests could be attributed to the interference of an additional resistance, i.e. the mass transport of Cr(VI) from the bulk aqueous solution to the surface of the R-nFe-GT beads. Another effect which may contribute to the low performance of the composite material is the Donnan exclusion effect. According to this effect a resin or membrane with fixed functional groups of a certain charge inhibits the intrusion of co-ions through the pores. This may be the case with Amberlyst 15, which contains fixed sulfonic groups of negative charge and may inhibits the intrusion of chromate anions.	en
heal.advisorName	Παπασιώπη, Νυμφοδώρα	el
heal.committeeMemberName	Παπασιώπη, Νυμφοδώρα	el
heal.committeeMemberName	Ξενίδης, Άνθιμος	el
heal.committeeMemberName	Πασπαλιάρης, Ιωάννης	el
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Μηχανικών Μεταλλείων Μεταλλουργών. Τομέας Μεταλλουργίας και Τεχνολογίας Υλικών. Εργαστήριο Μεταλλουργίας	el
heal.academicPublisherID	ntua
heal.numberOfPages	92 σ.	el
heal.fullTextAvailability	true