Activation Of Coal-bearing Kaolinite And Their Adsorptive Properties

Coal-bearing kaolinite is not widely used in our daily life, due to its inactive nature and low specific surface area. But activated kaolinite possesses a high surface area and high reactivity, and thus can be used as a promising low cost adsorbent. In this study, the coal-bearing kaolinite was activated with direct acid activation, microwave-assisted acid activation and mechanochemical activation. The morphological and structural properties of the obtained samples were characterized by X-ray diffraction analysis, thermogravimetric analysis, N2 adsorption-desorption analysis, elemental analyses, high-resolution transmission electron microscopy, and Fourier transformed infrared spectroscopy. The adsorption abilities of original coal-bearing kaolinite and the activated coal-bearing kaolinites for methylene blue (MB) have been investigated. For this, the effect of time, pH, MB concentration and temperature on adsorption have been studied in details. The result is summarized as follows:(1) Coal-bearing kaolinite was directly treated with concentrated sulfuric acid to improve its surface properties and adsorption ability. The obtained samples were characterized by several kinds of charaterizition method. The adsorption abilities of original coal-bearing kaolinite and the activated coal-bearing kaolinite for MB have been investigated. After activation, the specific surface area and maximum adsorption capacity for MB increased from 13.6 to 257.8 m~2/g and from 78.1 to 101 mg/g, respectively.(2) Coal-bearing kaolinite was treated with concentrated sulfuric acid under microwave exposure to improve its surface properties. The obtained sample was characterized by X-ray diffraction analysis, N2 adsorption-desorption analysis, Elemental analyses, Fourier transformed infrared spectroscopy, and Transmission electron microscopy. The obtained sample possessed a mesoporous and microporous structure with a high surface area of 299.5 m~2/g, and showed higher removal efficiency for MB than for original kaolinite, with a maximum adsorption capacity of 104.2 mg/g.(3) Coal-bearing kaolinite was treated with high-energy ball milling, and then, it was treated with hydrochloric acid. The obtained sample was characterized by several kinds of charaterizition method, and its adsorption ability for MB was investigated. The maximum specific surface area and the maximum MB adsorption capacity of treated samples reached as high as 373.5 m~2/g and 161.3 mg/g, respectively.