4种脂肪多胺修饰硅胶对铅离子的吸附

为了合成高效铅离子吸附剂,了解其对铅离子的吸附规律。采用(3-氯丙基)三甲氧基硅烷(CPTS)架桥法,以硅胶(SG)为载体,乙二胺(EDA)、二乙烯三胺(DETA)、三乙烯四胺(TETA)和四乙烯五胺(TEPA)为表面修饰剂,合成了4种胺化硅胶,测定了它们的红外光谱、热重等性质以及对Cu2+、Zn2+和Pb2+的吸附能力。结果表明,4种胺化硅胶对Pb2+的吸附量均大于Cu2+和Zn2+的吸附量,其中DETA修饰硅胶对Pb2+的吸附量较高。4种胺化硅胶对Pb2+的吸附过程较好地符合拟二级动力学模型以及Langmuir和Scatchart等温吸附热力学模型,其对Pb2+吸附的速率常数、饱和吸附量以及吸附位点数由大到小的顺序一致,均为SG-DETASG-TEPASG-EDASG-TETA。4种胺化硅胶对Pb2+的吸附速率和吸附量呈现"奇数胺"增强效应,亲和常数则依次减小。阐明了脂肪多胺修饰硅胶对Pb2+的吸附规律,并进一步讨论了Scatchart和Langmuir热力学模型的统一性。

Four aliphatic amines modified silica gels for adsorption of Pb2+

In order to synthesize high efficient adsorbents and study their rules for Pb²⁺ adsorption, a series of polyamines, NH₂(CH₂CH₂NH)_n-1H(where n =2~5, i.e. EDA-, DETA-, TETA-and TEPA-), were attached to 3-chloropropyltrimethoxysilane(CPTS) grafted silica gel. FTIR spectra and TG analysis were used to characterize the adsorbents. The adsorption capabilities for Cu²⁺, Zn²⁺ and Pb²⁺ were also determined. The results showed that the adsorbents exhibited better adsorption capabilities for Pb²⁺ than for Cu²⁺ or Zn²⁺, and the adsorption capabilities of adsorbent modified with DETA for Pb²⁺ were higher than that of modified with EDA, TETA and TEPA. Adsorption kinetic data for Pb²⁺ could be well fitted by the pseudo-second-order kinetic equation and the adsorption equilibrium processes could well fit the Langmuir and Scatchart models. The sequence of kinetic constants, adsorption capacities, adsorption sites of adsorbents were SG-DETA > SG-TEPA > SG-EDA > SG-TETA. A clear uneven number effects (by which the amount of adsorption is enhanced in the cases of DETA and TEPA) was observed in both adsorption kinetic constants and saturated adsorption capacities for Pb²⁺. The uniformity of Scatchart and Langmuir model were discussed.