巯基化介孔硅酸钙的合成及其对Pb²⁺的吸附特性

Synthesis of Thiol-Functionalized Mesoporous Calcium Silicate and Its Adsorption Charateristics for Pb²⁺

摘要: 以硝酸钙和硅酸钠为原料，十六烷基三甲溴化铵为模板剂，(3-巯基丙基)三甲氧基硅烷为改性剂，采用后接枝法制备巯基化介孔硅酸钙(MCS-SH)，并对其结构进行了表征。考察了其对Pb²⁺的吸附性能，探讨了吸附热力学特征。结果表明，MCS-SH在改性后仍维持较稳定的介孔结构，为夹缝孔，比表面积和孔径范围分别为129.32 m²∙g⁻¹和5~49 nm，接入的−SH量为0.4594 mmol∙g⁻¹；MCS-SH对Pb²⁺的吸附符合Langmuir模型，更符合Redlich-Peterson模型；MCS-SH对Pb²⁺吸附是一个熵增自发进行的过程，为吸热反应，存在物理吸附和化学吸附。根据Langmuir吸附模型，在293 K下MCS-SH对Pb²⁺的最大吸附容量为618.09 mg∙g⁻¹，远大于文献报道的吸附剂。MCS-SH在pH 5.0~7.5的范围内对Pb²⁺具有优异的吸附性能。

Abstract: Thiol-functionalized mesoporous calcium silicate (MCS-SH) was synthesized by post-grafting method using calcium nitrate tetrahydrate and sodium metasilicate nonahydrate as raw materials, cetyl trimethyl ammonium bromide as template, and (3-mercaptopropyl) trimethoxysilane as modifying agent, and its structures were characterized. The adsorption performance of MCS-SH for Pb²⁺ was investigated, and the adsorptive thermodynamics were explored. The results show that MCS-SH has still maintained mesoporous slit-pore structure in the modification process, with a specific surface area of 129.32 m²∙g⁻¹ and pore size mainly distributed in 5-49 nm. The amount of substance of −SH grafted to MCS-SH is calculated to be 0.4594 mmol∙g⁻¹ according to the sulfur content determined. The equilibrium adsorption data of MCS-SH for Pb²⁺ fitted to Langmuir model, and fitted better to Redlich-Peterson model. The adsorption of MCS-SH towards Pb²⁺ is an endothermic reaction and spontaneous process driven by an increase in entropy, and there exists both physical and chemical adsorption. The maximum adsorption capacity for Pb²⁺ deduced from the Langmuir model was 618.09 mg∙g⁻¹, which is much higher than those of adsorbents in the literature. MCS-SH exhibited an excellent adsorption performance for Pb²⁺ in the pH range of 5.0-7.5.