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Sorption
Published in Igor Bello, Vacuum and Ultravacuum, 2017
Activated alumina is the trade name for a porous alumina prepared by dehydrating aluminum hydrate, Al2O3 · nH2O with n = 1 or 3, to obtain n = 0.5. Transitional structures, such as gamma and eta alumina, are characteristic with high porosity and an internal surface area from 200 to 400 m2/g. They are produced in the forms of powders, granules, pellets (2–4 mm), and balls (1–8 mm in dia). They have a chalky white appearance. For sorption, they are conditioned by degassing at 250 °C. In vacuum technology, activated alumina is employed to trap backstreaming oil vapors. Otherwise, activated alumina is widely used in chemistry to purify fluids, particularly to remove fluorine and chlorine from drinking water.
Engineering Aspects
Published in Bruno Langlais, David A. Reckhow, Deborah R. Brink, Ozone in Water Treatment, 2019
William D. Bellamy, François Damez, Bruno Langlais, Antoine Montiel, Kerwin L. Rakness, David A. Reckhow, C. Michael Robson
Activated alumina: Activated alumina is a porous, amorphous form of aluminum oxide matrixed with trace quantities of other materials. It can be represented by the formula A12O3 · nH20. The desiccant is typically provided in a bead form and is available in several sizes, ranging in diameter from 1/10 in. to 1/2 in. (2.5 to 12.7 mm).
General introduction
Published in Abdulai Salifu, Fluoride Removal from Groundwater by Adsorption Technology, 2017
The most acceptable and commonly used adsorbent is activated alumina (AA) which is considered the industry standard for drinking water defluoridation in developed countries. Activated alumina is, however, generally both expensive and not readily available in most developing countries, its regeneration and disposal of the exhausted adsorbent are major challenges (Maliyekkal et al., 2006).
Fluoride removal from water using alumina and aluminum-based composites: A comprehensive review of progress
Published in Critical Reviews in Environmental Science and Technology, 2021
Sikpaam Issaka Alhassan, Lei Huang, Yingjie He, Lvji Yan, Bichao Wu, Haiying Wang
This section of the paper focused on the use of activated alumina (AA) and aluminum-based composites for adsorption of fluoride. The advantages of activation as well as some defects have also been highlighted and the mechanisms of adsorption and adsorption efficiency of various materials have been reviewed and compared. Activated alumina is a kind of aluminum oxide, semi-crystalline (Rabia et al., 2018) with surface area significantly over 200 m2·g−1 and mostly used as desiccant and sorbent for elements such as fluoride, arsenic and selenium in water. It has a high surface area to weight ratio due to its high porosity with amphoteric properties (Salvador et al., 2015). Its amphoteric nature allows it to behave as an acid in basic medium and as a base in acidic medium. Because of its high affinity, it is mostly a preferable desiccant for moisture removal from air as well as a catalyst in natural gas and refining operations. There are two common methods of activating Al2O3 thus, thermal treatment otherwise called physical activation and chemical treatment with acid in the laboratory.
Moisture transport during contact sorption drying of coal fines
Published in International Journal of Coal Preparation and Utilization, 2020
M. J. van Rensburg, M. Le Roux, Q. P. Campbell, E. S. Peters
Activated alumina is an inorganic solid that is manufactured from predominantly aluminum oxide, in combination with trace elements of silicon, iron (iii), and sodium oxides (BASF 2009). The sorbent is manufactured to have interconnected cavities containing water of hydration in its molecular structure. During the final manufacturing phase, the water of hydration is removed thermally from the molecular structure to create open sites, leading to its great affinity for water (Honeywell UOP 2011). Activated alumina is hydrophilic in nature, causing a small contact angle between the water and solid surface, resulting in the adsorption of water in liquid form. The sorbent material is also hygroscopic in nature, creating an additional affinity for water vapor from the atmosphere (Almatis 2017). These sorbents are produced with a tailor-made enhanced pore distribution and surface area to increase its sorption and retention capacity. An increased available surface area leads to an increased number of active sites where water can adhere to the sorbent surface. The sorbent beads used in this study were designed to have an average pore volume of 0.5, creating sufficient space for accumulation of water (BASF 2009). Activated alumina is largely chemically inert to many liquids and gases, causing it to maintain its solid structure during moisture adsorption and therfore enabling regeneration or dehydration (Ducreux and Nedez 2011).
The regeneration of various solid desiccants using novel heated surface plate based on heat pipe vacuum tube collector: an experimental investigation
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Rahul Srivastava, Chandrashekara M., Avadhesh Yadav
Activated alumina is a type of aluminum oxide. It is having a porous solid structure. The desiccant is resistant to thermal shock and abrasion and does not shrink and swell. It has higher adsorbing capacity for water at elevated temperatures. It does not change its color when it adsorbs the humidity Activated alumina has drawn the attention of many researchers and several reports are available for that.