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Identifier 000376709
Title Συστηματική μελέτη παρεμποδιστικής ικανότητας ουδέτερων πολυμερών με βάση το πολυαιθυλενοξείδιο στον πολυμερισμό του πυριτικού οξέος.
Alternative Title Systematic study of the inhibitory activity of polyethylene oxide-based neutral polymers in the polymerization of silicic acid.
Author Πρεάρη, Μελίνα Γεώργιος
Thesis advisor Δημάδης, Κωνσταντίνος
Reviewer Μήλιος, Κωνσταντίνος
Σπύρος, Απόστολος
Abstract Silicic acid stabilization plays an important role in both biological and industrial systems. For example, in marine life certain unicellular organisms (diatoms) manage to retain high levels of silicic acid in supersaturated solutions, before its condensation to yield amorphous silica (SiO2). The latter is used to construct their skeleton. On the other hand, the retardation of silicic acid condensation represents an extremely difficult task in industrial systems, as silica scale deposition poses severe problems to industrial water systems (like evaporative cooling towers and power plants). The present research is part of an on-going effort to discover environmentally friendly chemical additives with high inhibitory efficiency for the control of colloidal silica formation. Specifically, we tested linear polyethylene oxides (PEGs), in order to investigate their inhibitory role. Shortterm (8-hours) and long-term (3-days) experiments were carried out at neutral pH and supersaturated silicic acid solutions. Two important parameters, which were closely examined, were the length of PEGs polymeric chains and their dosage. A variety of molecular weights were tested (1.550 amu, 2.000 amu, 6.000 amu, 10.000 amu, 12.000 amu και 20.000 amu), as well as a wide range of concentrations (20 ppm, 40 ppm, 60 ppm, 80 ppm, 100 ppm και 185 ppm). Moreover, during the experimental process, an additional factor monitored was solution turbidity. Finally, a number of significant conclusions were reached from this research. Specifically, the results provided a strong proof that the inhibitory efficiency is highly dependent on the PEG chain length. Also, beyond a certain chain length (E.O. > 136) silicic acid stabilization levels off. Moreover, the smaller dosages lead to less effectiveness of PEGs as inhibitors. On the other hand, further increase above a specific dosage (60 ppm) does not improve inhibitory efficiency. As far as the monitoring of turbidity is concerned, a correlation exists between the percentage of PEGs effectiveness and the percentage of turbidity. Finally, the SEM results confirmed the amorphous nature of colloidal silica while the FT-IR revealed no superficial detachment of PEGs to the silica colloidal particles.
Language Greek
Subject Inhibitory efficiency
Linear polythylene oxides
Polymerization of silicic acid
Stabilization of silicic acid
Γραμμικά πολυμερή αιθυλενοξειδίου
Παρεμποδιστική ικανότητα
Πολυμερισμός πυριτικού οξέος
Σταθεροποίηση πυριτικού οξέος
Issue date 2012-11-16
Collection   School/Department--School of Sciences and Engineering--Department of Chemistry--Post-graduate theses
  Type of Work--Post-graduate theses
Permanent Link https://elocus.lib.uoc.gr//dlib/d/d/5/metadata-dlib-1353568169-990056-17879.tkl Bookmark and Share
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