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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: The results of the present study indicate that for optimum removal of fluoride ion the system pH should be maintained at pH5.1 as discussed by the authors, and that at the optimum pH condition, the rate of fluoride adsorption onto activated alumina increases as the ratio of the fluoride ion concentration to activated aluminina dosage decreases.
Abstract: Adsorption of fluoride ion from aqueous solution by activated alumina was carried out in six 2-l reactors under different pH values and ratios of initial fluoride ion to activated alumina. The results of the present study indicate that for optimum removal of fluoride ion the system pH should be maintained at pH5. Also, at the optimum pH condition, the rate of fluoride adsorption onto activated alumina increases as the ratio of fluoride ion concentration to activated alumina dosage decreases. However, no remarkable change in adsorption rate constant was found when the ratio indicated previously exceeded 10\u-² mg/mg of fluoride ion of activated alumina. Fluoride ion adsorption could be modeled by the Langmuir Isotherm.
38 citations
TL;DR: The reaction mechanism of amino acid activation on alumina surface and its significance for mineral-catalyzed prebiotic peptide bond formation are discussed.
Abstract: The catalytic properties of various forms of alumina were tested for alanine dimerization reaction. The catalytic efficiency of alumina depends on the structure, as well as on acid/base properties of the catalyst. The highest yields of Ala2 were achieved on activated alumina with surface of neutral pH (about 3% conversion after 2 weeks). Thermal analysis of Ala + alumina reaction systems shows that the thermal behavior of amino acid changes substantially in contact with the activated surface of the alumina catalyst. The reaction of Ala is detected as being strongly endothermic by differential thermal analysis of pure amino acid (above 250°C). The alanine endothermic reaction is shifted substantially to lower values (below 200°C) and hardly detectable if activated alumina is present. The reaction mechanism of amino acid activation on alumina surface and its significance for mineral-catalyzed prebiotic peptide bond formation are discussed.
38 citations
TL;DR: In this article, the Gibbs energies were calculated as (−14.01, −13.23, and −9.07) kJ·mol−1 at (323, 298, and 273) K, respectively, for adsorption loadings between (1.3 and 2.3) mmol·g−1.
Abstract: Adsorption of ammonia was measured volumetrically on activated alumina at temperatures of (273, 298, and 323) K and gas pressures up to 108 kPa. It was found that the final adsorption amounts at the terminal pressure point were (3.13, 2.53, and 1.89) mmol·g−1 at (273, 298, and 323) K, respectively. The Langmuir, Freundlich, Sips, and Toth isotherm models were employed to correlate the adsorption isotherms. Ammonia diffusivities in these adsorbents at (298 and 323) K and at five different pressure points were calculated from the adsorption kinetic uptake curves by using a classical diffusion model. It was found that the average diffusivity values were (4.02·10−14 and 4.71·10−14) m2·s−1, respectively, at (298 and 323) K. The heat of adsorption values are between (−35.6 and −15) kJ·mol−1 for adsorption loadings between (1.3 and 2.3) mmol·g−1. The Gibbs energies were calculated as (−14.01, −13.23, and −9.07) kJ·mol−1 at (323, 298, and 273) K, respectively. The value of the entropy lies within (−65 to −3) J·mo...
38 citations
TL;DR: Evaluating the potential of an anaerobic microbial consortium to biologically mobilize arsenate (As(V)) adsorbed onto activated alumina (AA), a common adsorbent used for treating arsenic in drinking water found it confirmed that VFA, present in landfill leachates, served as an electron donating substrate supporting enhanced rates of As(V) reduction to As(III).
38 citations
TL;DR: Bone char, goethite coated sand (G-IOCS) and hematite-coated sand (H-ICS) were evaluated for treating water with elevated levels of arsenic and fluoride present individually or together as mentioned in this paper.
Abstract: Since many at risk to arsenic and fluoride contamination cannot afford or do not have access to modern, centralized water treatment facilities, simple and low-cost solutions must be found. Bone char, goethite coated sand (G-IOCS) and hematite coated sand (H-IOCS) were evaluated for treating water with elevated levels of arsenic and fluoride present individually or together. Results obtained were compared to conventional media used in developed countries; activated alumina and granular ferric oxide. Fluoride adsorption capacity was higher in bone char than in G-IOCS and H-IOCS. Fluoride removal was not affected by the presence of environmentally significant arsenic (III) and arsenic (V) concentrations. On a mass basis, bone char’s fluoride adsorption capacity was comparable to that of activated alumina both in the presence and absence of 0.25 mg/L of arsenic (III) and arsenic (V) in solution. Bone char also showed higher capacity to remove arsenic (III) and arsenic (V) from solution than both G-IOCS and H-...
37 citations