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研究报告

Composite modification of diatomite and its adsorption characteristic of Cd²⁺ in aqueous solutions

摘要：鉴于单一常规方法对硅藻土吸附性能的改善空间有限,为了显著改善硅藻土的吸附性能,应用酸活化-钠化-柱撑-焙烧复合改性工艺对硅藻土实施了改性,并通过扫描电镜(SEM)、X射线衍射(XRD)和红外光谱(IR)对硅藻土改性前后微观形貌、物相组成和官能团的变化进行了分析,探究了硅藻土改性前后对Cd²⁺的吸附能力与机制.结果表明,最佳复合改性工艺条件为:硫酸体积分数10%,NaCl质量分数6%,OH/Al摩尔比2.2,焙烧温度150℃;改性后,硅藻土对Cd²⁺的吸附容量由原来的5.44 mg·g^-1提升至9.60 mg·g^-1,提升了76.5%;改性前后硅藻土对Cd²⁺的吸附均符合Langmuir等温吸附模型和二级动力学模型,吸附以物理过程为主.SEM、XRD和IR分析结果均表明,经复合改性,硅藻土壳体杂质得到清除,聚合羟基铝离子(Al₁₃)成功引入硅藻土孔道并发挥柱撑作用,硅藻土壳体孔隙结构得到了充分改善.

Abstract：As an alternative solution to overcome the limitation in conventional single-methods for material modification, a composite modification technology (acid activating-Na modifying-pillaring-baking) was applied to improve diatomite adsorption capacity. The changes in micro-morphology, phase composition and functional groups of the modified diatomite were analyzed by using Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and Infrared Spectrum (IR). The behavior and the mechanism of Cd²⁺ ion adsorption onto diatomite were analyzed before and after the modification. The obtained results shown that the optimal conditions for diatomite composite modification were 10% of sulfuric acid, 6% of sodium chloride, 2.2 of the OH/Al molar ratio, and 150℃ of the baking temperature. After modification, the adsorption of Cd²⁺ onto diatomite was raised from 5.44 mg·g^-1 to 9.60 mg·g^-1, with an increasing percentage of 76.5%. The Cd²⁺ ion adsorption data obtained both before and after the modification fit well with the Langmuir isotherm model and the pseudo-second-order kinetics model, suggesting that the adsorption was mainly a physical process. The analysis results of SEM, XRD and IR indicate that the impurity substances in diatomite shells were effectively removed, polymeric hydroxyl aluminium ions (Al₁₃) were successfully introduced into diatomite pillar channels, and the pore structure of modified diatomite was significantly improved.