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Magnetic Particle Technology A Simple Preparation of Magnetic Composites for the Adsorption of Water Contaminants
Luiz C. A. Oliveira, Rachel V. R. A. Rios, José D. Fabris, and Rochel M. Lago* Departamento Química, ICEx, UFMG, 31270-901 Belo Horizonte, MG, Brazil; *rochel@dedalus.lcc.ufmg.br Karim Sapag Laboratorio de Ciencias de Superficies y Medios Porosos, UniversidadNacional de San Luis, Chacabuco 917, 5700 San Luis, Argentina

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Recovering contaminated sites, treating industrial effluents, and managing hazardous wastes are challenging topics in environmental science that demand a great deal of attention from chemists, biologists, and engineers. Because of the great variety of factors related to the chemical and physical features of the contaminant and thecontaminated site, remediation processes are complex and often require specific solutions where creativity and innovation are key elements. Therefore, laboratory experiments introducing innovative aspects in environmental technology that are capable of stimulating the student’s imagination are of great interest in an environmental chemistry curriculum. An innovative technology that has gainedattention is the use of magnetic materials to solve environmental problems, such as accelerating the coagulation of sewage (1), removing radionuclides from milk (2), adsorption of organic dyes (3), and oil spill remediation (4). In this article an undergraduate laboratory experiment to produce magnetic adsorbents is described. These magnetic composites show the following features: (i) they combinethe adsorption properties of adsorbents, such as activated carbon or clays, with the magnetic properties of iron oxides, (ii) they can be used to remove different types of contaminants, for example, metals or organics, from water, and (iii) they can be removed from the medium by a simple magnetic separation process. One of the pedagogical benefits of this simple experiment is that the students areexposed to stimulating environmental problems that illustrate several important aspects of basic chemistry, such as the properties, characterization, and application of different materials and composites. Preparation of the Magnetic Composites The preparation of the magnetic composites is simple and can be carried out in a 2-h laboratory by college or even high school students. The chemicalsrequired are readily available and not expensive. The composites can be prepared using the adsorbents, for example, activated carbon or clay, suspended in a 400-mL solution of FeCl3 (7.8 g, 28 mmol) and FeSO4 (3.9 g, 14 mmol) at 70 C. To this suspension a solution of NaOH (100 mL, 5 mol L 1) is added dropwise to precipitate the iron oxides. The quantity of the adsorbent can be varied between 3.3, 6.6,or 9.9 g to obtain adsorbent:iron oxide weight ratios of 1:1, 1.5:1, and 2:1. The composites are washed and dried in an oven at 100 C for 2 h. A simple test with a magnet (0.3 T) can be carried out to show that the composite material is magnetic.
248 Journal of Chemical Education •

The characterization of the prepared materials can be of important educational value, especially for more advancedstudents to get familiar with different techniques, such as: (i) X-ray diffraction—one of the most important techniques in material characterization, it gives the students information on the crystalline structure of the clays and the identification of the iron oxide phases; (ii) Mössbauer spectroscopy—an important tool for the identification of iron compounds; (iii) magnetization measurements—canbe the basis for a discussion with the students on the magnetic properties of the different materials and their modern technological applications; (iv) scanning and transmission electron microscopies (SEM and TEM)—can afford textural and structural information of the prepared materials; and (v) surface-area measurement—a fundamental technique in material science, specially in catalysis and...