Kowalski Wojciech, Kochel Mateusz, Kierys Agnieszka, Gorgol Marek, Drewniak Marek, Zaleski Radosław
Faculty of Mathematics, Physics and Computer Science, Maria Curie-Skłodowska University, 1 Maria Curie-Skłodowska Square, 20-031 Lublin, Poland.
Department of Circular Economy, Institute of Energy and Fuel Processing Technology, Zamkowa 1, 41-803 Zabrze, Poland.
Materials (Basel). 2025 Aug 19;18(16):3876. doi: 10.3390/ma18163876.
Activated alumina is widely used in industry as an adsorbent. Its strong affinity toward water allows for the profound dehydration of gas streams. To optimize such processes, a deeper insight into water interaction with activated alumina is required. This knowledge can be obtained using positron annihilation lifetime spectroscopy, a sensitive tool that unravels previously unknown aspects of adsorption processes. Activated alumina (Compalox AN/V-813) was subjected to such a study supported by detailed characterization using scanning electron microscopy, X-ray diffraction, and N adsorption-desorption. A complex porous structure of the material, consisting mainly of boehmite and η-AlO or γ-AlO, was found. It is responsible for significant differences in adsorption and desorption. The course of adsorption is close to the classical layer-by-layer description. However, there are indications of initial water capture at active sites and final water reorganization consisting of filling the smallest free volumes that remain empty. The narrow mesopore inlets that keep water in the pores even at a relative vapor pressure of 0.4 are primarily responsible for the course of the desorption process. During adsorption, water is mainly maintained in the form of small clusters up to the highest pressures, whereas during desorption, it is continuous until narrow pore openings.
活性氧化铝作为吸附剂在工业中广泛应用。它对水具有很强的亲和力，能够使气流深度脱水。为了优化此类过程，需要更深入地了解水与活性氧化铝的相互作用。利用正电子湮没寿命谱可以获得这方面的知识，这是一种能揭示吸附过程中先前未知方面的灵敏工具。对活性氧化铝（Compalox AN/V - 813）进行了这样一项研究，并通过扫描电子显微镜、X射线衍射和N吸附 - 脱附等详细表征手段予以支持。发现该材料具有复杂的多孔结构，主要由勃姆石和η - AlO或γ - AlO组成。这种结构导致吸附和解吸存在显著差异。吸附过程接近经典的逐层描述。然而，有迹象表明在活性位点存在初始水捕获，以及最终水的重新排列，包括填充剩余的最小自由体积。即使在相对蒸汽压为0.4时仍能将水保持在孔中的狭窄中孔入口是解吸过程的主要原因。在吸附过程中，直到最高压力水主要以小簇的形式存在，而在解吸过程中，水在狭窄孔口之前一直是连续的。
