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Ph-Responsive Copolymers As Silica Scale Inhibitors

Silicon is an important element of our Planet’s crust, which is transferred into water streams through dissolution.1 Hence, it is usually found as water-soluble silicate or colloidal silica in natural surface waters (sea, rivers, lakes), or underground waters. When such water is used for industrial purposes (eg. industrial cooling), silicate can enter the operating system and can pose a threat to its proper operation. The main reason is the solubility of amorphous silica, a product of the silicate polycondensation process.

Product Number: 51322-17703-SG
Author: Georgia Skordalou, Konstantinos D. Demadis
Publication Date: 2022
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In the present work two synthetic co-polymers, U-PVPyPEGMA-H and Q-PVPyPEGMA-H, with pyridine and polyethylene glycol grafts on a methacrylate backbone, were studied for their potential to influence silicic acid polycondensation in vitro in silicate-supersaturated (500 ppm, 8.3 mM) aqueous solutions. The aim of this study was to evaluate the impact of several experimental parameters on the silicic acid polycondencation process. Working pH plays a significant role on the silicification reaction either in the absence or presence of polymers. In the presence of polymers, pH affects the protonation state of the pyridine N atom, transforming U-PVPyPEGMA, for example, from a silica formation catalyst (at pH=5.0) to a silicic acid stabilizer (at pH = 7.0). Furthermore, the state of N atom on the pyridine ring (non-protonated, protonated, quaternized) strongly affects the silicic acid autocondensation process. Based on our results, a “free” (non-protonated) pyridine ring induces silica inhibition, whereas protonation or quaternization enhances silica formation. Another parameter that was studied was the concentration of the polymers. As the concentration is increased, enhances the silicic acid stabilization activity or the catalytic activity of the polymers. Polymer MW was found to have no major effect on polymer activity either as stabilizers or catalysts.

In the present work two synthetic co-polymers, U-PVPyPEGMA-H and Q-PVPyPEGMA-H, with pyridine and polyethylene glycol grafts on a methacrylate backbone, were studied for their potential to influence silicic acid polycondensation in vitro in silicate-supersaturated (500 ppm, 8.3 mM) aqueous solutions. The aim of this study was to evaluate the impact of several experimental parameters on the silicic acid polycondencation process. Working pH plays a significant role on the silicification reaction either in the absence or presence of polymers. In the presence of polymers, pH affects the protonation state of the pyridine N atom, transforming U-PVPyPEGMA, for example, from a silica formation catalyst (at pH=5.0) to a silicic acid stabilizer (at pH = 7.0). Furthermore, the state of N atom on the pyridine ring (non-protonated, protonated, quaternized) strongly affects the silicic acid autocondensation process. Based on our results, a “free” (non-protonated) pyridine ring induces silica inhibition, whereas protonation or quaternization enhances silica formation. Another parameter that was studied was the concentration of the polymers. As the concentration is increased, enhances the silicic acid stabilization activity or the catalytic activity of the polymers. Polymer MW was found to have no major effect on polymer activity either as stabilizers or catalysts.

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