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Bioinorganic Chemistry and Applications
Volume 3, Issue 3-4, Pages 135-149
http://dx.doi.org/10.1155/BCA.2005.135

Chemistry of Organophosphonate Scale Growth lnhibitors: 3. Physicochemical Aspects of 2-Phosphonobutane-1,2,4-Tricarboxylate (PBTC) And Its Effect on CaCO3 Crystal Growth

Department of Chemistry, University of Crete, 300 Leoforos Knossos, Crete, Heraklion GR-71409, Greece

Copyright © 2005 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Industrial water systems often suffer from undesirable inorganic deposits, such as calcium carbonate, calcium phosphates, calcium sulfate, magnesium silicate, and others. Synthetic water additives, such as phosphonates and phosphonocarboxylates, are the most important and widely utilized scale inhibitors in a plethora of industrial applications including cooling water, geothermal drilling, desalination, etc. The design of efficient and cost-effective inhibitors, as well as the study of their structure and function at the molecular level are important areas of research. This study reports various physicochemical aspects of the chemistry of PBTC (PBTC = 2-phosphonobutane-1,2,4-tricarboxylic acid), one of the most widely used scale inhibitors in the cooling water treatment industry. These aspects include its CaCO3 crystal growth inhibition and modification properties under severe conditions of high CaCO3 supersaturation, stability towards oxidizing microbiocides and tolerance towards precipitation with Ca2+. Results show that 15 ppm of PBTC can inhibit the formation of by ∼35 %, 30 ppm by ∼40 %, and 60 ppm by ∼44 %. PBTC is virtually stable to the effects of a variety of oxidizing microbiocides, including chlorine, bromine and others. PBTC shows excellent tolerance towards precipitation as its Ca salt. Precipitation in a 1000 ppm Ca2+ (as CaCO3) occurs after 185 ppm PBTC are present.