Investigating the Effects of Magnetic Fields on Ion Exchange Processes

In 2001, I began working with Profs. Arthur Kney and Javad Tavakoli to study the behavior of an ion-exchange water purification system in the presence of an applied magnetic field.

A back-of-the-envelope calculation demonstrates that the thermal energy is much larger than energy of a magnetic moment in any reasonable applied magnetic field. However, susceptibility measurements confirm that, even in solution, there is still a small tendency of the magnetic moments to align, completely consistent with what one would expect from Curie's law.

Whether this residual alignment could slightly enhance ion-exchange selectivity or precipitation is an open question. The published literature on this subject is confusing, sometimes contradictory, and often unreliable. There is much anecdotal evidence about changes in the crystallization and precipitation of calcium carbonate in the presence of a magnetic field, but it is more difficult to find well-controlled and well-documented repeatable studies.

If the magnetic field has any effect at all, it would likely be quite small. However, the ion exchange system used by Prof. Kney is quite sensitive and offers an opportunity to make a high-quality contribution to this field, whatever the outcome.

With support from the National Science Foundation, we were able to show that there is little or no effect, at least to within the sensitivity of our measurements. The results were published in

A. K. Kney, J. Tavakoli, A. Dougherty, ``Unique Approach to Understanding the Mechanisms involved in Magnetic Water Conditioning using Ion Exchangers,'' Proceedings for the 1st IWA Conference on Scaling and Corrosion in Water and Wastewater Systems, Cranfield, Bedfordshire, UK, (March 2003)

A. K. Kney, J. Molek, J. Tavakoli, A. Dougherty, ``The Effect of Magnetic Susceptibility on Ion Exchange Treatment of a Solution in the Presence of a Magnetic Field,'' Proceeding for Industrial Water Conference, Orlando, FL, CD Format (2002).

Three ion exchange columns were set up to remove cadmium from the incoming fluid. The columns had either a strong magnetic field, a weak magnetic field, or no magnetic field at all. For each column, as fluid was pumped through, the concentration of cadmium in the outgoing fluid was measured and normalized by the initial concentration C₀. The fluid volume was normalized by the "bed volume" of the ion exchange resin. We found that after about 2000 bed volumes, the resin no longer was effective in removing the cadmium. Although there were variations from run to run, they were uncorrelated to the strength of the magnetic field. In this run, the small magnetic field appeared to be the least effective, no magnetic field the most effective, and a large magnetic field fell in between. These variations were all within the statistical noise of the experiment.

To more directly evaluate claims related to precipitation of calcium carbonate in a magnetic field, we looked directly at the process of precipitation in a magnetic field. Prof. Keny was able to show that extraordinarily careful experimental protocols are required to ensure reproducibility. Among the important factors to consider are pH, cleaning techniques (nucleation processes are significantly affected by trace particles left on the sample cell walls), and temperature.

Once those variables are accounted for, we found no measurable affect on precipitation due to the magnetic field.

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