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Vo1. 1, No. 2Adsorption of Surfactant Dispersed Nanometer Magnetite133ADSORPTION OF MAGNETIC REAGENTThe adsorption of magnetic reagents on fine particles is similar to the adsorption ofsurfactants in many aspects. Common mechanisms for the adsorption of surfactants on particlesinclude chemical bonding, electrokinetic force, van der Waals force, and hydrogen bonding. These principles can be applied to control the adsorption of magnetic reagents, although the extent of these forces may vary from the adsorption of surfactant alone. Experiments to verify the adsorption mechanisms have been conducted. Some examples are discussed here. There are many factors affecting the adsorption of surfactants. In addition to properties inherited with the surfactants and particles themselves, other factors, such as water chemistry,can play important roles through their ability to modify the properties of surfactants and particles. Examples include pH, activators and depressants, material concentrations, etc. Thesefactors were investigated to understand the adsorption of magnetic reagents on fine particles. Minerals of research grade, including quartz, calcite, kaolinite and pyrite, were ground to -325 mesh for this study. Grinding was carried out in a ceramic mill to avoid magnetic contamination. Kaolinite was prepared with a blender to eliminate oxidation problems, pyrite samples were washed with dilute hydrochloric acid and dried before grinding. After grinding, the product was stored under a nitrogen atmosphere. The magnetic susceptibility of each mineral was measured with a Johnson & Matthey magnetic susceptibility balance at 2 kilogauss. The results were: 0.44 x 10-6cgs/g for kaolinite,3.94 x 10-6cgs/g for calcite, and 1.46 x 10-6cgs/g for pyrite. The adsorption study was carried out with standard procedures for each test. In each test,a gram of a mineral powder was slurried in 30 ml of deionized water. Sodium hydroxide and hydrochloric acid were utilized to adjust pH. The salinity of water was maintained at 2 x 10-3molar of sodium chloride. A magnetic reagent was added at a dosage equivalent to 0.002 g magnetite per gram of mineral, unless otherwise stated. After 3 minutes of mild stirring to condition the mineral particles and magnetic reagent, the mineral particles were filtered, dried, and measured for magnetic susceptibility. The degree of adsorption for the magnetic reagent on a mineral was determined by the amount of magnetic susceptibility increase.Figure 1 shows the adsorption of MR-30 on quartz and calcite. MR-30 is an anionic magnetic reagent using sodium oleate as the outer layer. In the pH range of this study, calcite, adsorbed MR-30 consistently. Magnetic susceptibility of calcite was increased from 3.94 x 10-6cgs/g to 38 x 10-6cgs/g at the standard dosage. On the other hand, quartz did not adsorb MR-30 in the pH range from 5 to 9. The magnetic susceptibility of quartz at pH 9 was 0.8 x 10-6cgs/g after conditioning with MR-30. It is well known that calcite can adsorb sodium oleate through chemical bonding. The adsorption of MR-30 on calcite showed a consistent trend. Quartz is also known for its incapability to adsorb sodium oleate. Experimental results showed that quartz cannot adsorb MR-30 as well. The isoelectric point of quartz is close to pH 3, which may explain the adsorption at low pH.