Topic
Activated alumina
About: Activated alumina is a research topic. Over the lifetime, 1430 publications have been published within this topic receiving 31090 citations.
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TL;DR: A lanthanum-impregnated activated alumina was synthesized as a representative REMA, and its As uptake mechanisms were explored using multiple complementary characterization techniques, and the surface reaction and structural configuration were incorporated in a CD-MUSIC model to satisfactorily predict macroscopic As adsorption behaviors.
Abstract: Rare earth-modified adsorbents (REMAs) have been widely used to remove oxyanion pollutants from water, including arsenic (As). However, the molecular-level structural information and reactions at the liquid/solid interface are still murky, which limits the design of applicable REMAs. Herein, a lanthanum-impregnated activated alumina (LAA) was synthesized as a representative REMA, and its As uptake mechanisms were explored using multiple complementary characterization techniques. Our adsorption experiments showed that LAA exhibited 2–3 times higher As adsorption capacity than AA. In contrast to the bidentate configuration formed on most metal oxide surfaces, our EXAFS and DFT results suggest that As(III) and As(V) form monodentate surface complexes on LAA through As-O-La coordinative bonding. In situ flow cell ATR-FTIR observed a strong dependence of As-O peak positions on pH, which could be interpreted as the change in the fractions of As(V) surface complexes with zero- to double-protonation on LAA, AA, a...
62 citations
TL;DR: The spectral and chemical properties of potassium fluoride on activated alumina, an extensively used basic catalyst in organic synthesis, show that its unusually high reactivity relative to other fluoride-containing basic systems is due to the reaction of the fluoride ion with alumina to produce potassium hexafluoroaluminiate, potassium hydroxide and potassium aluminate as discussed by the authors.
62 citations
TL;DR: Pilot-plant tests of two treatment methods, activated alumina and ion exchange, for removing arsenic from drinking water were evaluated at the Fallon, Nevada, Naval Air Station (NAS) as discussed by the authors.
Abstract: Pilot-plant tests of two treatment methods, activated alumina and ion exchange, for removing arsenic from drinking water were evaluated at the Fallon, Nevada, Naval Air Station (NAS). The arsenic concentration was 0.080-0.116 mg/liter, exceeding the 0.05 mg/liter maximum contaminant level. Although the valence of arsenic was not determined, in prechlorination process and test results suggest it was probably arsenic V. Chlorinated drinking water from the NAS was used for evaluating the efficacy of treatment under several different conditions. The activated alumina and ion exchange systems were operated through three different loading and regeneration cycles each. The major water quality factors affecting the removal of arsenic by these methods were pH of feedwater, arsenic concentration, sulfate concentration, and alkalinity. The major operational factors affecting removal were flow rate, down time, and media clogging. Capital and operating costs for arsenic removal are estimated for the activated alumina method at optimum pH (5.5) for each of the three small community systems drawing water from the same aquifer. In addition, several containers of the regeneration waste were used for a special study to characterize, dewater, and render the waste non-toxic for disposal in a sanitary landfill.
62 citations
TL;DR: In this paper, activated alumina balls (3-5 mm diameter) were used for amide synthesis from carboxylic acids and amines under neat reaction conditions that produce no toxic by-products and has the advantages of being low-cost, easily available, heterogeneous, reusable and environmentally benign with no troublesome/hazardous disposal of the catalyst.
61 citations
TL;DR: In this paper, two 13X-type zeolites, activated alumina and highly pure silica, were compared in terms of capacity for water vapor and carbon dioxide removal from air.
Abstract: Pretreatment stage is usually a requirement for any adsorption based air separation process. Carbon dioxide and water vapor present in the atmosphere act as contaminants, deactivating adsorbents, particularly zeolites used in oxygen pressure swing adsorption processes. Such systems usually present one or more prelayers to ensure full removal of these two contaminants, protecting the oxygen/nitrogen selective layer. In the present study, two 13X-type zeolites—one activated alumina and one highly pure silica—are compared in terms of capacity for water vapor and carbon dioxide removal from air. Water and carbon dioxide adsorb irreversibly on these adsorbents up to a certain extension and then effective adsorption isotherms and breakthroughs curves were obtained. The effective properties were attained after three cycles under close to vacuum pressure swing adsorption conditions. A combination of two layers for the precolumns is suggested: the first, composed by either silica or alumina to remove most of the w...
60 citations