Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.
Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China.
J Colloid Interface Sci. 2014 Mar 1;417:369-78. doi: 10.1016/j.jcis.2013.11.071. Epub 2013 Dec 12.
Hierarchical porous γ-Al2O3 hollow microspheres were synthesized by a modified spray drying method. Ageing the precipitated precursor and spray-drying assisted by NH4Cl salts are considered as two key steps for the synthesis of γ-Al2O3 hollow microspheres. The mechanism of the formation of hierarchical porous γ-Al2O3 hollow microsphere was proposed involving phase transformation from aluminum hydroxide to laminar boehmite during ageing and a following self-assembling process with NH4Cl as the template during spray drying. The meso-/macro-pores in γ-Al2O3 mainly arise from the stacking of the laminar boehmites which are obtained by ageing the precipitated precursors at 90°C. NH4Cl, which was the byproduct from the reaction between AlCl3·6H2O and NH3·H2O, was demonstrated to be an excellent template to act as the core and the barrier for separation of laminar boehmites. No extra NH4Cl was added. The as-synthesized hierarchical porous γ-Al2O3 hollow microsphere presented remarkably higher adsorption capacity, which is thirty times higher adsorption rate for Congo Red than the solid microsphere containing only small mesopores.
采用改进的喷雾干燥法合成了具有分级多孔结构的γ-Al2O3 中空微球。将沉淀前驱体老化和 NH4Cl 盐辅助喷雾干燥视为合成γ-Al2O3 中空微球的两个关键步骤。提出了形成分级多孔γ-Al2O3 中空微球的机制，涉及在老化过程中氢氧化铝向层状薄水铝石的相变，以及在喷雾干燥过程中以 NH4Cl 为模板的自组装过程。γ-Al2O3 中的中孔/大孔主要源于通过在 90°C 下老化沉淀前驱体制备的层状薄水铝石的堆叠。NH4Cl 是 AlCl3·6H2O 和 NH3·H2O 反应的副产物，被证明是一种极好的模板，可以作为层状薄水铝石的核和分离的屏障。没有添加额外的 NH4Cl。合成的具有分级多孔结构的γ-Al2O3 中空微球表现出更高的吸附能力，其对刚果红的吸附速率比仅含有小中孔的固体微球高 30 倍。
