Preparation And Adsorption Properties Of And Imprinted Cross-linked Chitosan Adsorbent Under Microwave Irradiation

In this paper, with heavy metal ions(Cu(II), Au(III)) as imprinted ion, the chitosan as raw material,and different cross-linking agents,the novel imprinted cross-linked chitosan adsorbent were prepared under microwave irradiation.the optimal preparation conditions, adsorption conditions,and further the thermodynamics and kinetics were studied. Research contents and results specifically are as follows:1.Preparation of Cu(II) imprinted cross-linked chitosan adsorbent under microwave irradiationUsing Cu(II) as imprinted ions, chitosan as the raw material, formaldehyde as pre crosslinking agent, epichlorohydrin as crosslinking agent, adopting the ball forming process by dropping to alkali,a novel chitosan adsorbent was prepared by microwave method. The effect of operation conditions on the performance of synthetic adsorbent was investigated. The results show that, effects of chitosan concentration, amount of crosslinking agent, the microwave reaction time and acid treatment conditions on adsorbent are very significant. When the synthetic conditions are as follows: chitosan concentration chitosan 6%,formaldehyde 17.4ml,epichlorohydrin 8.76 ml, microwave reaction time 6min, acidification time 10 h, acidification temperature 70 ℃, the adsorption capacity of the resulting crosslinked chitosan microspheres for Cu(II) could reach 0.945mmol/g.2.The adsorption characteristics of Cu(II) ions imprinted cross-linked chitosan microsphere adsorbentCu(II) ions imprinted cross-linked chitosan adsorbent were used to study the adsorption properties of Cu(II) ions. The results show that,the best p H value of adsorption was 6 at low concentration of Cu(II) ions in the solution; It took 9h to reach adsorption equilibrium; The higher the temperature,and the greater the initial concentration of Cu(II) ions was, the greater the adsorption capacity of adsorbents was; the more the adsorption agent added was, the less adsorption capacity per unit mass of the adsorbent was. The thermodynamic results showed that, the higher the temperature was, the greater the adsorption amount was, indicating that the adsorption process of Cu(II) ions imprinted cross-linked chitosan adsorbent for Cu(II) ion was endothermic process. In the four model analysis, the fitting degree of Freundlich adsorption model is highest, and ΔH>0,ΔG<0, indicating that the adsorption process was spontaneous adsorption reaction process. The adsorption process of Cu(II) ions imprinted cross-linked chitosan adsorbent for Cu(II) ions conforms to the two stage adsorption kinetic equation, the activation energy of adsorption of Cu(II) ions was 14.77 k J/mol.Regeneration experiments showed that while Cu(II) ions imprinted cross-linked chitosan adsorbent was used for 5 times, the decline of adsorption rate is very small, showing that the adsorbent has a very good regeneration effect, and can be used repeatedly.3.Kinetic and thermodynamic studies on the adsorption of Au(III) onto Au(III) imprinted crosslinked chitosan modified by β- cyclodextrinThe hydrophobic cavity structure of β- cyclodextrin was introduced in the chitosan.Using Au(III) as the imprinted ion, L- cystine as crosslinking agent, the Au(III) imprinted crosslinked chitosan modified by β- cyclodextrin was prepared(Au(III)-ICCTS-CD). The Au(III)-ICCTS-CD was characterized by scanning electron microscopy and infrared spectroscopy. Effect of p H on adsorption of Au(III)-ICCTS-CD of Au(III), and Au(III)-ICCTS-CD adsorption kinetic and thermodynamic properties of Au(III) were studyed. the best p H of adsorption of Au(III)-ICCTS-CD for Au(III) is 4.0 at 298 K. The adsorption process can be described by two order adsorption kinetic equation. The activation energy Ea = 18.12 k J/mol.The adsorption process accords with Langmuir isothermal adsorption model, and should be single molecule layer adsorption.