Preparation Of Inorganic Flocculant And Adsorbent Using Active Components Extracted From Coal-Bearing Kaolinite By Direct Acid Leaching Method

Coal-bearing kaolinite is an important non-metallic mineral resource in China,with a high utilization value;and the many attention from government and business have been focused on its utilization.However,the utilization rate of the coal-bearing kaolinite is still very low at present.Further increasing in the uses of this mineral strongly depend on the innovation of processing technology and the lowering of processing cost.Although high temperature calcination is an indispensable step in the process of modifing coal-bearing kaolinite and can effectively activate the coal-bearing kaolinite,but it has a disadvantage of high-cost.Therefore,the development of a simple and low-cost activation method is very crucial to the extended application of coal-bearing kaolinite.In this study,the polymerized aluminum sulfate,γ-Al₂O₃,and Fe₃O₄/activated coal-bearing kaolinite nanocomposite were prepared using the active ingredient extracted from Inner Mongolian coal-bearing kaolinite by a direct acid leaching method.Meanwhile,the flocculation performance and the adsorption ability of the synthesized materials for organic dyes were studied.The result is summarized as follows:Al extraction from an Inner Mongolian coal-bearing kaolinite by direct concentrated sulfuric acid leaching was carried out under different conditions.A maximum extraction efficiency of 83.8 % was obtained after 2-h leaching at 250 ℃.Al2（SO4）3×18H2O was prepared from leached aluminum using ethanol as a precipitant;and,then the polymerized aluminum sulfate and γ-Al₂O₃ were prepared using the aluminum sulfate as raw materials.The obtained samples were characterized by X-ray diffraction（XRD）,thermogravimetric analysis（TGA）,Fourier transform infrared spectroscopy（FT-IT）and high-resolution transmission electron microscopy.When the Ca（OH）₂ was used as an alkalizer,the obtained polymerized aluminum sulfate（S-PAS）showed a higher flocculation efficiency and better stability,and the flocculation performance of S-PAS was found to be better than commercially available polymerized aluminum sulfate（O-PAS）.When the concentration of S-PAS was 10 mL/L,the S-PAS exhibited the best flocculation performance for the domestic sewage with the highest turbidity removal rate of 90 %.The synthesized γ-Al₂O₃ has a mesoporous structure with a specific surface area of 183.5 m²/g.The adsorption of the γ-Al₂O₃ on Congo red（CR）,weak acid dark blue 5R（5R）and Direct Fast Scarlet 4BS（4BS）fit well with the pseudo-second order rate equation,Langmuir adsorption model,and Freundlich adsorption model.The maximum adsorption capacity of CR,5R,and 4BS have been measured to be 2014.0,400.0,and 2480.0 mg/g,respectively.Fe₃O₄/activated coal-bearing kaolinite nanocomposite was synthesized by thermal decomposition method using iron nitrate as an iron source and activated coal-bearing kaolinite as a base material.The synthesized composite was characterized using X-ray diffraction,N₂ adsorption-desorption,vibrating sample magnetometer,and high-resolution transmission electron microscopy.In addition,the adsorption abilities of the magnetic nanocomposite for methylene blue（MB）were investigated.The results showed that the nanocomposite is a ferromagnetic material with a specific surface area of 26.0 m²/g.The adsorption of MB fit well with the pseudo-second-order model,Langmuir adsorption model,and Freundlich adsorption model,with a maximum adsorption capacity of 30.8 mg/g.