| Adsorption method has now been treated as an effective way in sewage disposal process, while, a newsorptivematerial is essential to obtaining favorable removal efficiency. Bentonite, if handled in appropriatemethod, is surely to become an ideal adsorbing agent for its natural advantage.Three kind of modified bentonite-HACC-bentonite(1:5). HACC-bentonite(0.2:5) as well asHACC-CTMAB-bentonite, which were used to adsorb Cr(Ⅵ), Cd(Ⅱ), Cr(Ⅵ)+phenol andCr(Ⅵ)+aniline in simulation wastewater, were prepared in this research.Firstly, the effect of different preparation conditions such as preparation temperature, preparation timeand HACC dosage were investigated. Secondly, the impact of modified bentonite dosage, pH value insolution, adsorption temperature, adsorption time to adsorption capacity and adsorption rate were studiedby single factor test and the optimal conditions to adsorb Cr(Ⅵ)and Cd(Ⅱ) were obtained respectively, foradsorption Cr(Ⅵ)in simulation wastewater: the best ratio of HACC dosage to bentonite was1:5,preparation time and temperature were2h and80℃respectively. In adsorption experiment, the optimalreaction time was40min, best reaction temperature20℃, the pH value was1. Under the optimal conditionsthe adsorption rate can be no less than88%with better reproduction capacity.To adsorb Cd(Ⅱ), the best ratio of HACC dosage to bentonite was0.2:5, the preparation time andtemperature were2h and80℃respectively. In adsorption experiment, the optimal reaction time was40min,the best reaction temperature was20℃, the pH value was7. Under the optimal conditions the adsorptionrate can be no less than99.6%.Thirdly, the Langmuir and Freundlich adsorption isotherms of Cd(Ⅱ) and Cr(Ⅵ) on modifiedbentonite were examed respectively and a conclusion can be drawed that the law of adsorption of Cr(Ⅵ)and Cd(Ⅱ) on modified bentonite fit better to the Langmuir equation instead of Freundlich equation. Also,the adsorption process of Cr(Ⅵ) on HACC-bentonite can be expressed by the pseudo first-order model withR2=0.999, which means that the adsorption mechanism of Cr(Ⅵ)/Cd(Ⅱ) onto HACC-bentonite includeboth physical adsorption and chemical adsorption. For one thing, the Cr(Ⅵ) and Cd(Ⅱ) ion were replacedto the layer of bentonite through ion exchange reaction. For another, Cr(Ⅵ)/Cd(Ⅱ) combined with groupson alkyl chains of HACC through chelating.Fourthly, the modified bentonite was characterized by FTIR, XRD and SEM to observe changes in physical structure. The results showed that the HACC did not insert to the layer of bentonite partly withalkyl chains remaining in the surface.At last, CTMAB-HACC-bentonite was prepared to exam its adsorption capacity in heavy metal andorganic pollutant composite system. The results of this study appeared that there was weak competitiveadsorption between heavy metal and organic pollutant. |
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