| Abstract |
Deposition of amorphous silica is an significant problem in cooling water recirculating
systems. In supersaturated waters with respect to silicate ions, condensation polymerization
occurs leading to formation colloidal silica SiO2 deposits on critical surfaces. This impedes
heat transfer and leads to inefficient cooling.
There has been a lot of attention drawn to the prevention of silicate polymerization and
deposition of silica by use of chemical additives, called scale inhibitors. Organic biopolymers
responsible for silica morphogenesis in biological systems (especially in diatoms) have been
used as “guides” to devise synthetic polymers that might be silica inhibitors in vitro. Candidate
inhibitors that we studied in this thesis include: the cationic sequence of three cationic
biopolymers known as CATINs, which are based on inulin, the cationic-anionic (Zwitterionic)
phosphonomethylated chitosan, PCH) that is a phosphonomethylation derivative of chitosan,
and finally a sequence of five synthetic cationic-anionic (zwitter-ionic) polymers (terpolymers)
which are composed of negative, positive and neutral monomers respectively:
MAA, PEG and MAD. We found that the degree of inhibition of these polymers depends on
the following parameters: (1) additive dosage (2) charge density (3) polymerization time (4)
any presence of anionic polymers (5) initial levels of soluble silicates and other factors.
Additionally, because industrial waters are rich in silicate and magnesium ions (Mg2+),
we studied the catalytic action of Mg2+ on silicate condensation and found that it accelerates
silicate polymerization when pH > 9, without itself being deposited. However, the addition of
EDTA restricted its catalytic action.
The present thesis constitutes a natural continuation or our research to inhibit deposition
of sparingly soluble inorganic salts using environmentally acceptable chemical additives.
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Πολυμερισμός πυριτικών σε υδατικά συστήματα : σχηματισμός και παρεμπόδιση σχηματισμού διοξειδίου του πυριτίου (SiO2, silica) με φυσικά και συνθετικά πολυμερή
