Structure control and quantitative evaluation of porous materials are essential for many industrial and consumer applications of clay minerals, and nanotubular halloysite (HNT) has been used extensively for such purposes; performance enhancements are still needed, however. The objective of the present study was to improve the gas-adsorption capacity of HNT by controlling the particle size and porosity. This was accomplished through acid treatment and particle-size fractionation by centrifugation. Various particle sizes were obtained and porosities ranged from macropores to mesopores. Natural halloysite nanotubes were modified by sulfuric acid in various concentrations to selectively remove the alumina composition of the tubes. X-ray diffraction and energy dispersive X-ray spectroscopy were used to verify the mineralogical and compositional changes. Surface modification by the acid treatment increased the inner space volume of the tubes and decreased the mass of the nanotubes because of the elimination of alumina. The gas adsorption capacity of both natural and modified halloysite nanotubes was measured quantitatively using N 2 adsorption and the Brunauer-Emmett-Teller (BET) method, and the morphology was determined from transmission electron microscopy (TEM) images. The results showed that the modified halloysite nanotube was 7.47 times more efficient at gas adsorption than pristine halloysite. Moreover, the dealumination of the surface increased the inner space. Greatly increased porosity characteristics, including gas adsorption and macroporosity, were obtained through modification by acid treatment.

中文翻译：

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改良埃洛石纳米管以提高气体吸附能力

多孔材料的结构控制和定量评估对于粘土矿物的许多工业和消费应用至关重要，纳米管状埃洛石 (HNT) 已广泛用于此类目的；但是，仍然需要提高性能。本研究的目的是通过控制粒径和孔隙率来提高 HNT 的气体吸附能力。这是通过酸处理和离心的粒度分级完成的。获得了各种粒径，孔隙率从大孔到中孔不等。天然埃洛石纳米管通过不同浓度的硫酸进行改性，以选择性地去除管中的氧化铝成分。X 射线衍射和能量色散 X 射线光谱被用来验证矿物和成分的变化。由于消除了氧化铝，酸处理的表面改性增加了管的内部空间体积并减少了纳米管的质量。使用N 2 吸附和Brunauer-Emmett-Teller (BET) 方法定量测量天然和改性埃洛石纳米管的气体吸附能力，并从透射电子显微镜(TEM) 图像确定形态。结果表明，改性埃洛石纳米管的气体吸附效率是原始埃洛石的 7.47 倍。此外，表面的脱铝增加了内部空间。通过酸处理改性获得了大大增加的孔隙率特性，包括气体吸附和大孔隙率。