Chitosan Modified Bentonite And The Adsorption Effect On Heavy Metal Ions

In this paper, a type of adsorbent with environmental safety character through bentonitemodified by chitosan was developed, and use it to remove heavy metal ions from water.First, the Na-base bentonite was purified. With the purified Na-base bentonite as rawmaterial and chitosan as modifier, a new type of adsorbent which was mad from bentonitemodified by chitosan was prepared. With scanning electron microscopy （SEM）, infraredspectrum（IR） and XRD analysis, the results show that both the positive and negative attracttogether, form a kind of complex adsorbent.Second, through static adsorption experiments, the adsorption of three metal ions Pb²⁺,Cu²⁺and Zn²⁺in water by Na-base bentonite modified by chitosan was studied. In a singlesystem, the influence of reaction time, absorbent dosage, pH value, temperature, initialconcentration of metal ions, and anionic on the the adsorption was investigated, and the bestadsorption conditions was obtained. The adsorption mechanism and thermodynamics wereresearched. Pb²⁺, Cu²⁺and Zn²⁺adsorption process which conform to the Langmiur andFreundlich model, rising temperature is good for reaction. In the composite system, thecompetitive relationship is researched between the two metal ions. The order of adsorptioncapacity is Pb²⁺> Cu²⁺> Zn²⁺.Finally, the Na-base bentonite was modified by18alkyl three methyl brominatedammonium and a kind of organic bentonite was gotten. By orthogonal experiments, the bestpreparation conditions of organic bentonite modified by chitosan were determined.The orderof the influence factors is: the adding amount of18alkyl three methyl brominatedammonium> reaction temperature> reaction time. With scanning electron microscope（SEM）and infrared spectrum（IR） analysis, the results show that the surface area of bentoniteincreased after being modified, the three combine with each other. The mechanism of theadsorption of Pb²⁺on organic bentonite modified by chitosan and thermodynamics wereresearched. Pb²⁺adsorption process conforms to the Langmiur model, and reducing thereaction temperature is good for adsorption.