| With the acceleration of China’s industrialization development, heavy metal wastewater pollution has become one of the serious problems of water pollution in China, which wastewater of Cr(VI) pollution problem is particularly significant. The Research priorities now is how to make the effective treatment of wastewater containing chromium at a low price, Fly ash is collected from the flue gas after the burning of coal, it is the main solid wastes emitted from coal-fired power plant. Fly ash is one of the industrial waste residue, which discharge mainly from coal industrial in our country at present.The purpose of this paper is to study with modified fly ash as adsorption material in wastewater treatment containing chromium, in order to achieve the purpose of using waste treat waste.In this paper, the fly ash was modified and used to deal with the wastewater containing chromium, Through the treatment effect evaluation for the methods of modification. The adsorptivity of initial fly ash is very poor, removal rate was only1.5%in Dealing with50ml of10mg/L wastewater.But with calcination、acid, alkali, salt modified,the adsorptivity of the fly ash is greatly increased,The best modified fly ash modified by50%mass fraction of CaO under800℃. The microscopic morphology of modified fly ash is analyzed by scanning electron microscope, the results show that800℃high temperature calcination made fly ash from smooth dense vitreous structure of particle size changed to2um-35um small amorphous granular material, and modified by alkali, fly ash corroded and generate the mesh、rough structure on the surface; fly ash particles generated minerals sulfate crystals which modified by mix acid; modified by calcium oxide is generated on the surface of spherical structure. X-ray diffraction analyses was also used to analyse the crystal composition, results showd that through the alkali modification, the fly ash generated natrolite; mixed acid modified fly ash generated gypsum crystals; modified by calcium oxide, fly ash are mainly calcite, and portlandite.Through the experiment above, CaO modified fly ash was selected for the follow-up study, The factors:dosage、the oscillating time、pH、and temperature was used to study on the properties of modified fly ash adsorption Cr (Ⅵ), and orthogonal experiment used to determine the optimum process conditions of chromium-containing waste water treatment.The results showed that the removal rate can reach96.02%in dealing with lOmg/L of50mL chromium-containing wastewater under the condition of time of30minutes, modified fly ash dosage for9g, and reaction pH value for7.Then CaO modified fly ash was carried on thermodynamic and kinetic analysis and the parameters of thermodynamic and kinetic were confirmed under the temperature of298K、308K、318K.The experimental results showd that the adsorption process of chromium-containing wastewater by modified fly ash conformed to the Freundlich isotherm model and correlation coefficient R2between0.9916to0.9956,△H0is8.809kJ/mol,△G0between3.241to3.099,△S0etween0.019to0.0175.Its adsorption behavior is conformed to the pseudo second-roder kinetic model and correlation coefficient R2is between0.9992to0.9999. Its rate constant under different temperature between8.861to4.138, its activation energy Ea obtained by Arrhenius equation is18.609kJ/mol, adsorption is physical adsorption.According to the chamber test, column adsorption process was carried out to study dynamic adsorption process of modified fly ash and maximum adsorption capacity of modified fly ash was0.4499mg/g.Finally, on the basis of static adsorption and dynamic adsorption of modified fly ash was studied by column adsorption process, through the column adsorption to determine the maximum adsorption capacity of fly ash is0.4499mg/g, closed to Thomas breakthrough curve adsorption capacity, which is0.4367mg/g. |
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