Application Of Modified Chitosan On Speciation Of Environmental Trace Element

The problem of environment has already become a global focus. The analysis of environmental pollution has attracted large attention in current analytical chemistry region. The environmental trace elements are very important pollutants for their effect of nutrition and toxicity on life. The effect of nutrition and toxicity of the environmental trace elements is decided not only by their amounts but also by their speciation. It is very important to know the effect of nutrition and toxicity of the environmental trace elements by speciation of the environmental trace elements. Speciation analysis of element has become an advanced region.Enrichment and separation are necessary prior to determination of trace elements because their content is low. The methods of enrichment and separation include extraction, precipitation, ion-exchange and adsorption. The bio-adsorbents have attracted more attention for their advantages of large source, low cost and easy operation. Chitosan is one of these bio-adsorbents, there are many reports about chitosan, however, the reports about application of modified chitosan to speciation of trace elements are few. This thesis concentrates research on chitosan modification and their application to speciation of trace elements. The major contents and novelty of this thesis are given in the following.(1) The cross-linked chitosan was synthesized with Diethylene Triamine (DCCTS), and applied to speciation of inorganic selenium and arsenic. The characterization of DCCTS was performed by FTIR and SEM. The adsorption behavior of Se(â…¥) and Se(â…£), As(â…¤) and As(â…¢) on DCCTS was studied. The results indicated that the adsorption efficiency of Se(â…¥) was94%at pH3.6, whereas5%of Se(â…£). Thus DCCTS can concentrate and separate Se (â…¥) from Se (â…£) solution at pH3.6. The results also showed that the adsorption efficiency of As(â…¤) was96%at pH3.0, whereas which of As(â…¢) was lower than10%. DCCTS can concentrate and separate As(â…¤) from As(â…¢) solution at pH3.0. Speciation of Se(â…¥) and Se(â…£), As(â…¤) and As(â…¢) in environmental water samples was performed using DCCTS as adsorbent and ICP-OES, GFAAS as determination means, respectively. The result was approving.(2) The grafting chitosan was prepared with2-Hydroxyethyl trimethyl ammonium chloride(HGCTS), and applied to speciation of inorganic chromium. The adsorption behavior of Cr(â…¥) and Cr(â…¢) on HGCTS was studied. The results indicated that the adsorption efficiency of Cr(â…¥) was97%at pH4.0, whereas5%of Cr(â…¢). Thus HGCTS can concentrate and separate Cr(â…¥) from Cr(â…¢) solution at pH4.0. The adsorption mechanism of Cr(VI) on HGCTS was electrostatic attraction and ion exchange. The adsorption agreed very well with the Langmuir model and the Pseudo second-order kinetic model. A novel method for speciation of Cr(â…¥) and Cr(â…¢) in environmental water samples has been developed using HGCTS as adsorbent and FAAS as determination means.(3) The grafting chitosan was prepared with aminothiourea (AGCTS), and applied to speciation of Mn(â…¦) and Mn(â…¡). The adsorption behavior of Mn(â…¦) and Mn(â…¡) on AGCTS was studied. The results indicated that the adsorption efficiency of Mn(â…¦) was96%at pH3.3, whereas4%of Mn(â…¡). Thus AGCTS can concentrate and separate Mn(â…¦) from Mn(â…¡) solution at pH3.3. The effect of pH, temperature and contact time was investigated. A novel method for speciation of Mn(â…¦) and Mn(â…¡) in environmental water samples has been developed using AGCTS as adsorbent and GFAAS as determination means.(4) The cross-linked chitosan was synthesized with aminoacetic (ACCTS), and applied to speciation of Sb(â…¢) and Sb(â…¤). The results showed that the adsorption efficiency of Sb(â…¢) and Sb(â…¤) was low on ACCTS before chelated with ammonium pyrrolidine dithiocarbamate (APDC) and after chelated with APDC, the adsorption efficiency of Sb(â…¢)-APDC was98%at pH5.0, whereas which of Sb(â…¤)-APDC was lower than10%. Thus, ACCTS can concentrate and separate Sb(â…¢) at pH5.0after chelated with APDC. A novel method for speciation of Sb(â…¢) and Sb(â…¤) in environmental water samples has been developed using ACCTS as adsorbent and GFAAS as determination means.(5) The thiourea cross-linked chitosan with Fe(â…¢) as template (Fe(â…¢)-TCCTS) was synthesized. The adsorption behavior of Fe(III) and Fe(â…¡) on Fe(â…¢)-TCCTS was studied. The results indicated that the adsorption behavior of Fe(â…¢) and Fe(â…¡) on Fe(â…¢)-TCCTS was similar, but the adsorption content of Fe(â…¢) was higher than which of Fe(â…¡). The adsorption agreed very well with the Langmuir model and the Pseudo second-order kinetic model. Fe(â…¢)-TCCTS can adsorb Fe(â…¢) selectively. It can be applied to remove iron ion from waste water.