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Vo1. 1, No. 2Adsorption of Surfactant Dispersed Nanometer Magnetite139Figure 8. Sodium tripolyphosphate for the depression of calcite on MR-30 adsorption. CONCLUSIONS Using the magnetic reagent methods to make fine particles magnetic is discussed in this study. A model for the adsorption of magnetic reagent is established on the basis of a doublelayer surfactant structure. The inner layer surfactant has a functional group with affinity to the magnetic nucleus. A second layer of surfactant can be built on the first layer through a hydrophobic interaction. The functional group of the second layer orient outward and can interact with particles. The adsorption of outer layer surfactants on particles will, thus, facilitate the coupling of a magnetic nucleus on the particle to make the particle magnetic. The adsorption of second layer surfactants generally follows the same principles governing the adsorption of surfactants. Ferromagnetic materials and what are commonly referred to as nonmagnetic (actually diamagnetic to weak paramagnetic) materials generally have a magnetic susceptibility difference of about 6 to 7 orders of magnitude. A very small amount of magnetic reagent adsorption will be sufficient to make the nonmagnetic fine particles processable by common magnetic means. Thus, favorable economics can be obtained for the use of magnetic reagents in many applications. ACKNOWLEDGEMENT The author is grateful to J. Liu, R. S. Kramer, and R. Lizak for their help in carrying out experiments.
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J. Y. Hwang Vo1. 1, No. 2 140 REFERENCES 1. V.K. La Mer and T. W. Healy, Rev. Pure & Appl. Chem., 13, 112-133 (1963). 2. R. J. Pugh and J. A. Kitchener, J. Colloid and Interface Science, 35, 656-664 (1971). 3. J. Y. Hwang, G. Kullerud, M. Takayasu, F. J. Friedlaender, and P. C. Wankat, IEEE Trans. On Magnetics, MAG-18, 1689-1691 (1982). 4. J. Y. Hwang, G. Kullerud, F. J. Friedlaender, and M. Takayasu, Soc. Of Mining Engineers of AIME, Transactions 280, 1961-1964 (1986). 5. J. Y. Hwang, U.S. Patent 4,834,898 (1989). 6. J. Y. Hwang, U.S. Patent 4,906,382 (1990). 7. J. Y. Hwang, Symposium of 6thCoal Contractors Conference, DOE, 290-297 (1990). 8. J. Rubio and J. A. Kitchener, J. Colloid and Interface Science, 57, 132-142 (1976).