Work on this subject began as an investigation of magnetic water treatment. Experiments were conducted to test the hypothesis that magnetic fields promote the nucleation of a particular crystal form of ferric hydroxide, a form which would very effectively induce the heterogeneous nucleation of CaCO3, thus providing competitive sites for CaCO3 precipitation and significantly reducing the amount of scale being deposited. We found that this mechanism is unlikely since none of the seven different synthetic ferric hydroxides tested was an effective heterogeneous nucleator of CaCO3. However, we found that trace concentrations of Fe2+ strongly inhibit calcite growth. Further research showed that ferric ions are much better growth inhibitors then ferrous ions. A systematic study of how solution conditions such as iron concentration, CaCO3 supersaturation, pH, alkalinity, surface area, and ionic strength influence the effectiveness of Fe(II) and Fe(III) as calcite growth inhibitors was carried out. In this paper we present a review of results focussing on the effects that pH and supersaturation have on calcite growth inhibition by ferric ions, and on effects that oxygen has on growth inhibition by ferrous ions.

Subject
Water, Inhibitor performance, Hydroxides, Iron, Calcium, Calcite, Acidity, Supersaturation, Constants, Ion concentrations, Scale formation, Corrosion inhibitors, Water treatment facilities
Keywords:
calcite, crystal growth inhibition, growth poison, ferrous, ferric, magnetic water treatment, scale inhibition, carbonate
© 1994 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
1994
Association for Materials Protection and Performance (AMPP)
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