Synthesis Of Fe₃O₄/Kaolin Nanocomposites And Their Adsorptive Properties

Composite materials have been widely used in aerospace, automotive, chemical industry, textile, machinery manufacture and medical fields, i.e., composite materials are necessary for human’s life. In recent years, the composite materials exhibit a broad potential uses in the water treatment field in which they are used as adsorbents. The main advantage of composite materials is that they could effectively combine more than two kinds of materials with different function; hence, they usually possess multi-function. For example, activated kaolin with high specific surface area can be used as a low cost adsorbent. On the other hand, the main disavantage of the activated kaolin is that it can not be readily separated from treated water, due to its small particle size and high dispersity. But in this case, if the kaolin is combined with a magnetic material, it will possess high adsorption ability and magnetic properties, and would be separable from the treated system via magnetic separation technology.Ferroferric oxide (Fe3O4) is a non-toxic and ferromagnetic material with a saturation magnetization of92emu/g, which makes it to be widely used in biomedical field. Therefore, we think that Fe3O4can also be used as a magnetic carrier in environmental applications. In this paper, magnetic Fe3O4/kaolin nanocomposite material was prepared by ultrasonic dispersing method and thermal decomposition method using Erdos activated coal-bearing kaolin, Fe(NO3)3·9H2O, urea and Fe3O4magnetic fluid as raw materials, and its adsorption abilities for Cr (VI) and methyl blue were investigated. The results are summarized as follows: 1. Erdos activated coal-bearing kaolin with a high specific surface area of465m2/g was obtained via calcination and acid treatment processes; Fe3O4magnetic fluid with an average particle size of7nm was synthesized by thermal decomposition method using Fe-urea complex as precursor.2. Magnetic Fe3O4/kaolin nanocomposite material was prepared by ultrasonic dispersing method using Erdos activated kaolin and Fe3O4magnetic fluid as raw materials, and it was characterized by X-ray powder diffraction (XRD), magnetic measurements (VSM), infrared spectroscopy (IR), N2adsorption-desorption (BET method), transmission electron micrograph (TEM) and differential thermogravimetric analysis (DTA-TG). The result shows that both magnetization and the specific surface area of the composite are increased with the increase of Fe3O4content. When the Fe3O4content is39wt%, the composite material exhibits the best performance with the maximum saturation magnetization of22emu/g and the maximum specific surface area of344m2/g. The maximum adsorption capacities of the composite for Cr (VI) and methyl blue reach at20.8mg/g and26.8mg/g, respectively.3. Fe3O4/kaolin nanocomposite material (40wt%Fe3O4) was prepared by thermal decomposition method using Erdos activated kaolin, urea and Fe(NO3)3·9H2O as raw materials, and it was characterized by XRD, IR, BET method, VSM, and DTA-TG. The specific surface area of the synthesized composite is measured to be19.8m2/g, which is much smaller that of the composite prepared by ultrasonic dispersion method.