氨基功能化SBA-15的制备及其对水中Pb^(2+)的吸附研究

STUDY ON PREPARATION OF FUNCTIONALIZED SBA-15 AND ADSORPTION OF AQUEOUS Pb(Ⅱ)

以3-氨丙基三甲氧基硅烷为改性剂,利用后嫁接方法,制备出氨基修饰SBA-15(记为N-SBA-15)。利用X射线衍射仪、傅立叶红外光谱仪、N2吸附-脱附对样品进行表征,并探讨了吸附动力学与吸附等温特性。结果表明,改性后的SBA-15吸附水中Pb2+时在120 min内可以达到吸附平衡,吸附过程符合拟2级动力学模型。Langmuir模型及Dubinin-Radushkevich模型很好地描述了Pb2+在氨基修饰SBA-15上的吸附行为,其中基于D-R模型计算得出的318 K时最大吸附量为1.172 mmol/g,平均吸附自由能在318 K时为-24.88 kJ/mol,表明吸附可能属于表面络合作用,可以归为化学过程,且该过程是自发和吸热的。

Mesoporous silica SBA-15 （denoted as N-SBA-15） functionalized by 3-aminopropyltrimethoxy-silane was studied as potential adsorbent to remove lead ions. The materials were characterized by X-ray powder diffiaction （XRD）, Fourier-transform infrared spectroscopy （FT-IR） and N2 adsorption- desorption isotherms. The adsorption kinetic data were analyzed using various kinetic models, such as pseudo-first-order and pseudo-second-order model. The pseudo-second order kinetic model was found to be well suited for the entire adsorption process. Adsorption equilibrium data could be also described well by Langmuir and Dubinin-Radushkevich （D-R） isotherm models. Based on the D-R model, the maximum adsorption quantity of Pb（lI） ions was 1.172 mmol/g at 318 K. The adsorption energy E of-24.88 kJ/mol at 318 K was calculated from the D-R model and was in the range of chemo- sorption, suggesting that the adsorption process was mainly a surface complexation. It was also proposed that the aqueous Pb（II） ions could react with the free amino groups on N-SBA-15 to form stable metal complexes and thus were removed. Thermodynamic calculation results showed that the adsorption of Pb（II） ions on amine-functionalized-SBA- 15 was spontaneous and endothermie.