可回收球形高岭土分子筛的制备及其对Cd²⁺/Fe³⁺的吸附性能研究

Preparation of recyclable spherical kaolin-based molecular sieves and their adsorption performance for Cd2 /Fe3

  • 摘要: 为解决矿山废水中重金属污染问题以及传统粉末吸附剂易流失、难分离等缺陷,本研究以高岭土为原料,通过碱改性-水热晶化结合交联成型工艺制备可回收球形Na-P型分子筛,并系统研究其对矿山废水中Cd2+和Fe3+的吸附行为及作用机制。选用扫描电子显微镜(SEM)、X 射线衍射(XRD)、能谱分析(EDS)、傅里叶变换红外光谱(FT-IR)及 X 射线光电子能谱(XPS)对材料结构进行表征。结果表明,球形高岭土基分子筛表面具有稳定的三维多孔结构,交联成型后仍保持完整Na-P型分子筛晶体骨架。Cd2+和 Fe3+的最佳吸附 pH 均为 6,最大吸附容量分别为19.29和19.89 mg·g-1。吸附过程遵循拟二级动力学模型和Langmuir等温模型,证明以化学吸附和单层吸附为主。在二元竞争吸附体系中Fe3+表现出更强竞争吸附能力,可优先占据活性位点并抑制Cd2+去除。机理分析表明,Cd2+和Fe3+的去除主要来源于离子交换、静电吸引及表面配位作用。循环实验结果显示,球形高岭土基分子筛经5次吸附-脱附循环后对Cd²⁺和Fe³⁺的去除率仍保持在 80 %以上,说明球形三维骨架显著提高了材料结构稳定性和循环复用性能。相比粉末分子筛,球形高岭土基分子筛在保持吸附活性的同时,进一步提升材料可回收性与工程适用性,在矿山废水重金属治理领域应用潜力突出,发展前景良好。

     

    Abstract: To address the heavy metal pollution in mine wastewater and overcome the drawbacks of conventional powdered adsorbents such as easy loss and difficult separation, recyclable spherical Na-P molecular sieves were prepared using kaolin as raw material via alkali modification, hydrothermal crystallization combined with cross-linking forming process. The adsorption behavior and mechanism of the as-prepared adsorbent toward Cd2+ and Fe3+ in mine wastewater were systematically investigated. The structural properties of the material were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS).The results show that the spherical kaolin-based molecular sieves exhibit a stable three-dimensional porous structure and retain the complete crystal framework of Na-P molecular sieves after cross-linking forming. The optimal adsorption pH for both Cd2+ and Fe3+ is 6. The maximum adsorption capacities were 19.29 and 19.89 mg·g-1 .The adsorption process complies with the pseudo-second-order kinetic model and Langmuir isotherm model, indicating that the adsorption is dominated by chemical adsorption and monolayer adsorption. In the binary competitive adsorption system, Fe3+ shows stronger competitive adsorption capacity, preferentially occupying active sites and inhibiting the removal of Cd2+. Mechanism analysis reveals that the removal of Cd2+ and Fe3+ is mainly attributed to ion exchange, electrostatic attraction, and surface complexation.Recycling experiments demonstrate that the removal efficiencies of Cd2+ and Fe3+ by spherical kaolin-based molecular sieves remain above 80% after 5 adsorption–desorption cycles, suggesting that the spherical three-dimensional framework significantly improves the structural stability and reusability of the material. Compared with traditional powdered molecular sieves, the spherical kaolin-based molecular sieves not only maintain adsorption activity but also enhance recyclability and engineering applicability, showing promising application prospects in the treatment of heavy metal-contaminated mine wastewater.

     

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