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Proceedings of an International Conference on Mitigation of Heat Exchanger Fouling and Its Economic and Environmental Implications

ISSN:
1-56700-172-6 (Print)

THE INFLUENCE OF IMPURITY ELEMENTS AND MAGNETIC FIELDS ON THE CRYSTALLISATION FORM OF CALCIUM CARBONATE

S. Kobe
"Jozef Stefan" Institute Jamova 39 1000 Ljubljana SLOVENIA

S. Novak
"Jozef Stefan" Institute Jamova 39 1001 Ljubljana SLOVENIA

M. Vedenik-Novak
Termoelektrarna-Toplarna Toplarniska 19 1000 Ljubljana SLOVENIA

Abstract

Under normal conditions calcium carbonate crystallises as calcite, exhibiting hexagonal symmetry. It accumulates on surfaces exposed to hard water. Under the influence of an applied magnetic field, the unstable orthorhombic crystal form of calcium carbonate, aragonite was observed. Aragonite and vaterite do not agglomerate and accumulate.
From the results obtained in our recent work it can be concluded that the change which occurs under the influence of an applied magnetic field is the nucleation and crystallisation of a non-stable modification of CaCo3 (aragonite), influenced by the impurity ions (Fe2+, Cu2+, Zn2+). With a new approach and the application of FT - IR spectroscopy, as used in thin film characterisation, the crucial importance of impurity elements, which influence the formation of aragonite under an applied magnetic field, has been confirmed.
Ions such as Fe2+, Cu2+ and Zn2+ inhibit the growth of certain crystal planes and promote others. Our results support the suggestion from previous results reported by Donaldson [2] and Herzog [3] that the application of a magnetic field to hard water successfully inhibits the growth and agglomeration of calcium carbonate as calcite. In our work the suggestion that impurity ions such as Fe2+ [3] or Zn2+ [14] are crucial for this behaviour has been confirmed. In addition, Cu2+ ions have been observed to be of particular importance [18].
Measuring the pH and zeta-potentials also confirmed the magnetic field's influence on the electrokinetic changes in the solution with controlled amounts of CaC03 and impurity elements.