The study of the mechanism of magnetic water treatment for the prevention of scale and corrosion.

Abstract

Scaling and corrosion cost industries all over the world millions of rands each year. Chemical treatment of water to prevent scale is expensive and can be hazardous. As a result industry is always looking for new, cheaper alternate methods of reducing scale. One such method is magnetic water treatment. Magnetic water treatment involves passing hard water (the main cause of scale) through a magnetic field. This method favors the precipitation of calcium carbonate in the form of aragonite instead of calcite. Aragonite is a softer, less tenacious material that does not adhere to the walls of pipes or heating surfaces. These particles remain in suspension and may settle out somewhere along the system where the velocity of the water has been reduced. A simple bench-top heating system was set up to determine whether magnetic treatment works and, if it does, to determine the optimum conditions under which it operates. A saturated solution of calcium carbonate was circulated through the heating system with, and without the magnets, so that comparisons could be made. The precipitate was analysed (via X-ray diffraction) to calculate the proportions of calcite and aragonite, while atomic absorption was used to test the hardness of the filtrate. This gave an indication of the effectiveness of the magnetic system. pH graphs and absorption graphs were plotted to compare the rates of precipitation. The precipitate was also observed under the electron microscope in order to view the different structures of calcite and aragonite. Experiments were carried out at different temperatures and different flow rates in order to test the effect of these parameters on the magnetic system. Results showed that the magnetic field increased the rate of precipitation and caused aragonite rather than calcite to be formed. This was in contradiction with most literature surveyed, which stated that magnetism increased the dissolution of calcium carbonate. Results indicated that the higher the temperature, the greater was the rate of precipitation and as a result, the greater the amount of aragonite formed, even without the magnets. Increased flow rate also increased the amount of aragonite formed. As a result hereof, conclusive results could not be obtained at high temperatures and high flow rates.