E-Locus - Institutional Repository of the University of Crete - Σταθεροποίηση πυριτικού οξέος και παρεμπόδιση πολυσυμπύκνωσής του με χρήση ουδέτερων (πολυβινυλοπυρρολιδόνη PVP, πολυβινυλοαλκοόλη PVA) και κατιοντικών (πολυαιθυλενιμίνη PEI) πολυμερών

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Identifier

000416062

Title

Σταθεροποίηση πυριτικού οξέος και παρεμπόδιση πολυσυμπύκνωσής του με χρήση ουδέτερων (πολυβινυλοπυρρολιδόνη PVP, πολυβινυλοαλκοόλη PVA) και κατιοντικών (πολυαιθυλενιμίνη PEI) πολυμερών

Alternative Title

Stabilization and inhibition of silicic acid polycondensation with use of neutral (polyvinylpyrpolidone PVP, polyvinylalcohol PVA) and cationic (polyethylenimine PEI) polymers

Author

Αριστοδήμου, Ιωάννης Α.

Thesis advisor

Δημάδης, Κωνσταντίνος

Reviewer

Μήλιος, Κωνσταντίνος
Σπύρος, Απόστολος

Abstract

Silicon is the second most abundant element in Earth’s crust, mainly in the form of silicate rocks. The contact of surface water with these rocks dissolves silicate ions and transports them to the aquifer and to ground reservoirs. Diatoms are single-celled, eukaryotic organisms, take part in the world’s “Si” cycle because they are capable of processing and metabolizing “Si” from natural waters in the form of silica (SiO₂). When diatoms need to build up a new silica cell wall, the required “Si” for the silica formation is taken up from monosilicic acid [Si(OH)₄], in neutral pH environment. The purpose of this work is to attempt to inhibit silica formation (polycondensation) by stabilizing silicic acid, using neutral and cationic macromolecules. We examine a family of polyvinylpyrrolidone polymers (PVPs, with seven different molecular weights), for the stabilization of silicic acid. Through evaluation of various factors (such as molecular weight, PVP concentration, pH, and polyconcentration time) conclusions are drawn about the interactions that are responsible for the stabilization process. Also, with the addition (blend) of neutral polymers such as polyvinyl alcohol (PVA) and cationic polymers such as linear polyethylenimine (LPEI), the interaction of the polymers with each other and the effect on the silica stabilization are evaluated. Amorphous silica precipitates were collected and studied by various techniques (such as SEM/EDS, FT-IR) to evaluate the effect of polymers and their mixtures on the size, morphology and particle aggregation of SiO₂, as well as the trapping tendency of the polymers in the silica precipitates.

Language

Greek

Subject

Diatoms

Linear polyethylenimine

Polymerization

Polyvinyl alcohol

Polyvinylpyrrolidone

Silicon

Stabilization

Γραμμική πολυαιθυλενιμίνη

Διάτομα