Study On The Preparation And Adsorption Performance Of Silica Hybrid Material

The thiourea/silica hybrid material(TU/Si O2) was prepared by choosing thiourea(TU) as the organic modifier, inorganic silica gel as inorganic carrier through chemical grafting reaction in this thesis. Firstly, the surface of silica gel was grafted the chloropropyl group by coupling reaction with chloropropyltrimethoxysilane(CPTMS) to prepare the CP-Si O2. Secondly, TU was grafted to the surface of silica gel by the chlorine substitution reaction of CP-Si O2 with TU. The effects of different promoter, reaction time, temperature, and TU content on the adsorption capacity of TU/Si O2 were investigated. It was obtained that the optical condition was reaction temperature 348 K, reaction time 24 h, mCP-Si O2/g=5, mTU/g=2, mKI/g=0.6, VCH3CH2OH/m L=50. The end-product has the great adsorption selectivity for Hg(Ⅱ).The static adsorptive behavior of TU/Si O2 for Hg(Ⅱ) was studied, and the static adsorption experimental results showed that p H for adsorption had the great effect on the adsorption capacity. The adsorption capacity of TU/Si O2 for Hg(Ⅱ) increased with the rising temperature and increasing initial concentration of Hg(Ⅱ). The fitted result of thermodynamic model showed that adsorption equilibrium data of TU/Si O2 for Hg(Ⅱ) could be well fitted by the Langmuir isotherm model, which could illustrate that the adsorption behavior was of monomolecular-layer adsorption. The value of 1/n of the Freundlich fitted parameters was between 0.1 and 0.5, which could indicate that the adsorption of TU/Si O2 for Hg(Ⅱ) was easily. The value of ΔH0 and ΔS0 were positive, which showed that adsorption for Hg(Ⅱ) on the surface of TU/Si O2 was a endothermic process tending to be disordering. The value of ΔG0 was negative, which could suggest that this adsorption was spontaneous. The result of |ΔH0|<|TΔS0| could showed that this adsorption process was mainly controlled by entropy. Kinetic experiments indicated the adsorption behavior of TU/Si O2 for Hg(Ⅱ) could be well displayed by the proposed Second-order Kinetics model, and the adsorption capacity of TU/Si O2 increased to a certain value with increasing time.The dynamic adsorptive behavior of TU/Si O2 for Hg( Ⅱ) in the single component solution and binary-component solution of Hg(Ⅱ)--Zn(Ⅱ) was studied. The flow rate, initial concentration of metal ions and amount of adsorbent have the obvious effect on the breakthrough and exhaust time, and the time would be minimizing with the high flow rate and high-concentration of mental ions. And the adsorption capacity of adsorbent could be increased with the low flow rate and high-concentration of mental ions. The dynamic adsorption study for binary-component solution of Hg(Ⅱ)--Zn(Ⅱ) showed that this hybrid material had the great adsorptive selectivity for Hg(Ⅱ), the breakthrough and exhaust time for Hg(Ⅱ) were much longer than for Zn(Ⅱ). And there were competing adsorption and substituting adsorption in the binary-component solution. Compared with the result of the single component solution of Hg(Ⅱ), the exist of Zn(Ⅱ) has the little impact on the adsorptive behavior of Hg(Ⅱ). The experimental results of dynamic adsorption could be well fitted with Thomas model and Yan model, and the operating time predicted by the models was close to the experimental results.