| At present, the study of appliance of modified bentonite in wastewater treatment is mostly about the adsorption of organic pollutants on organobentonite, but little sdudy is done about the adsorption of inorganic pollutants and especially hazardous anion. The study of adsorption of Cr(Ⅵ) in wastewater on modified bentonite was investigated in this thesis.Organobentonite and Na-bentonite were prepared with Ningming's bentonite through microwave dry process and its adsorption behavior and mechanism of Cr(Ⅵ) in wastewater were investigated. The results showed that the adsorption rate was affected by pH, adsorption time, dosage of adsorbents and adsorption temperature. Organobentonite was a good adsorbent for Cr(Ⅵ) hazardous anion. The adsorption rate reached 95% in treating 50mg/L Cr( Ⅵ ) wastewater under the conditions of 2g/L organobentonite, adsorption temperature at 28°C, adsorption time in 30 min and pH at 5.6. The adsorption mechanism of organobentonite was mainly the ion exchange adsorption and the adsorption through the formation of precipitation of HDTMA-complex salt. The adsorption of Cr(Ⅵ) on organobentonite represented by Langmuir adsorption isotherm.Al-modified bentonite was prepared with Ningming's bentonite through microwave dry process. The optimum processing condition of Al-modified bentonite was obtained by optimizing experiment results using orthogonalmethod. Al-modified bentonite's adsorption behavior and mechanism of Cr(Ⅵ) in wastewater were investigated. The results showed that the adsorption ability of Cr(Ⅵ) on Al-modified bentonite was not so good on organobentonite, but it was better than that on Na-bentonite. The adsorption rate reached 92% in treating 50mg/L Cr(Ⅵ) wastewater under the conditions of 30g/L Al-modified bentonite, adsorption temperature at 28℃, adsorption time in 25 min and pH at 5.6. The adsorption mechanism included three aspects. Firstly, the negative charge of bentonite was reduced after modified and thus the electrostatic repulsion between Cr(Ⅵ) and bentonite was reduced, so the adsorption of Cr(Ⅵ) on Al-modified bentonite was more easier. Secondly, AlCl3 is an inorganic flocculant, and aluminium cations in water solution can improve ion's charge characteristic in water solution efficiently, so the adsorption of Cr(Ⅵ) on Al-modified bentonite was more easier. Thirdly, Al-modified bentonite's magnified surface area and bridge-linking of cation made adsorption of Cr(Ⅵ) on Al-modified bentonite more effective, so adsorption rate was enhanced. |
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