Studies On Synthesis And Adsorption Properties For Composite Materials Containing Phosphonate Groups

The matrix of adsorbents is mainly devided into three kinds: inorganic materials, organicpolymers and biomaterials. Materials containing phosphonate groups have the character ofchelating bonds with some metal ions. Because of their excellent adsorbing selectivity to rareand heavy metal ions, they are widely used in the fields of water treatment, metallurgy, etc. Inthis paper, a series of adsorbents containing phosphonate groups with silica gel or buckwheathull as matrix were got by different synthesis methods, and were applied to adsorption formetal ions. The structure and properties of the adsorbents were systematically characterizedby infrared spectroscopy(FT-IR), scanning electronic microscope(SEM)，X-ray diffractometry(XRD) and thermogravimetry analysis(TG). The adsorption capabilities of the adsorbentscontaining phosphonate groups with silica gel or buckwheat hull as matrix and aminomethylene phosphonic acid resin(D418) for several metal ions were investigated.1. With silica gel as matrix, two kinds of functionalized silica gel withpoly(triethylenetetramine bis(methylene phosphonic acid)), SG-T-P-1and SG-T-P-2, wereprepared by so-called heterogeneous synthesis and homogeneous synthesis methods,respectively. Adsorption properties of SG-T-P-2for Hg(II) in aqueous were investigated.Adsorption properties of SG-T-P-1and SG-T-P-2for Hg(II) in dry ethanol solution were alsoinvestigated. The experimental results showed that the adsorption capacities of SG-T-P-2forHg(II) were better than the adsorption capacities of SG-T-P-2in dry ethanol solution. And theadsorption processes of Hg(II) followed pseudo second-order model and film diffusion wasdominated in the adsorption process. The linear langmuir isotherm model is the best-fit modelto predict the experimental data.2. With silica gel as matrix, using vinyl triethoxysilane (VTES) as coupling agent, thecomposite microsphere of polystyrene containing amino bis(methylene phosphonic acidencapsulation silica gel(SG-PS-N-P) was synthesized. The experimental results showed thatthe adsorption of Au(III) prior to other metal ions for SG-PS-N-P. And the adsorptionprocesses of Au(III) followed pseudo second-order model and film diffusion was dominatedin the adsorption process. The linear langmuir isotherm model is the best-fit model to predictthe experimental data. The adsorption selectivity, desorption and regeneration capacities ofAu(III) are excellent. When2%thiourea in0.1mol/L HCl was used, the adsorbed Au(III)could be completely eluted. The optimal conditions were obtained at pH2.0using16.61mg adsorbent at initial Au(III) concentrations of7.28mmol/L by the design of Box-Behnken.Under these conditions, the adsorption capacities of SG-PS-N-P for Au(III) were3.4785±0.005mmol/g.3. The static adsorption capability of amino methylene phosphonic acid resin(D418) forseveral metal ions was investigated. The experimental results showed that the adsorptionprocesses of Au(III) followed pseudo second-order model and film diffusion was dominatedin the adsorption process. All the adsorption processes exhibited spontaneous andendothermic adsorption in nature and was carried out by chemical mechanism. The linearlangmuir isotherm model is the best-fit model to predict the experimental data. The adsorptionselectivity, desorption and regeneration capacities of Au(III) are excellent. When5%thioureain0.1mol/L HCl was used, the adsorbed Au(III) could be completely eluted.4. With buckwheat hull as matrix, pretreated buckwheat hull(BH) and1-hydroxyethylidene-1,1-diphosphonic acid(HEDP)-modified buckwheat hull (HEDP-BH)were prepared. Metal ions Au(III), Hg(II), Cu(II), Pb(II), Co(II), Zn(II), Ni(II), Cd(II) andCr(II) were chosen as representatives to investigate the adsorption capacities of the BH andHEDP-BH. The results of adsorption for metal ions showed that BH had good adsorptioncapacities for Au(III) and Hg(II), and HEDP-BH had good adsorption capacities for Au(III).Besides, the adsorption capacities of HEDP-BH for Au(III) were better than the adsorptioncapacities of BH.(1) The results of adsorption of BH and HEDP-BH for Au(III) showed thatthe linear langmuir isotherm model is the best-fit model to predict the experimental data. Thekinetics data indicated that the adsorption process of Au(III) was governed by the filmdiffusion and followed pseudo-first-order rate model for BH, pseudo-first-order rate modeland pseudo-second-order model both could be well interpret the adsorption of HEDP-BH. Allthe adsorption processes of Au(III) exhibited spontaneous and endothermic adsorption innature. The adsorption selectivity of Au(III) is excellent.(2) The results of adsorption of BHfor Hg(II) showed that the linear langmuir isotherm model is the best-fit model to predict theexperimental data. The experimental results showed that the adsorption processes of Hg(II)followed pseudo second-order model and film diffusion was dominated in the adsorptionprocess. The adsorption selectivity of Au(III) is excellent.