Activated alumina

About: Activated alumina is a research topic. Over the lifetime, 1430 publications have been published within this topic receiving 31090 citations.

Optimization studies for water defluoridation by adsorption: application of a design of experiments

Abstract: Fluoride in groundwater is a worldwide problem. In Tunisia, it is one of the most abundant constituents occurring in groundwater, creating a major problem in safe drinking water supply. This paper aims to examine the fluoride removal from aqueous solutions by adsorption on activated alumina (AA) using a two-level full factorial design. For this sake, four operating parameters supposed to affect the removal efficiency were chosen: initial fluoride concentration, pH of the solution, adsorbent dose, and temperature. Factors that influence the fluoride removal efficiency were evaluated statistically by using factorial plots: the Pareto chart, main effect, interaction effect, normal probability plots, and the cube plot. Analysis of variance and P-value significant levels were used to check the significance of the effect on percentage removal. The statistical analysis allowed verifying that the four studied parameters have an influence on the fluoride elimination (P-values ≤0.05 and F-values >4.49). It ...

Modelling the uptake of natural organic matter (NOM) by different granular sorbent media

Abstract: The removal of natural organic matter (NOM) by four different granular sorbent media, activated carbon, an anion exchange resin, activated alumina and granular ferric hydroxide, respectively, was investigated. Isotherm data, kinetic parameters and column breakthrough curves were determined. Adsorption analysis was applied to describe sorption equilibria, and the film-homogeneous surface diffusion model was used to predict NOM uptake in fixed-bed columns. The results show that NOM adsorption by activated carbon and activated alumina could be modelled quite well by the approach used. NOM uptake by the anion exchange resin could be predicted with respect to capacity while two kinetic parameters were obviously not sufficient to describe the rate of uptake correctly. NOM adsorption by granular ferric hydroxide proved to be a very slow process that could not be predicted using parameters derived from batch data.

Gas-solid chromatographic separation of hydrocarbons of high molecular weight.

Abstract: THE deactivation of highly active polar sites on activated alumina with water to give a satisfactory column packing for the gas chromatographic separation of C1–C5 hydrocarbons at room temperature has been reported1. An extension of this work has shown that alumina can be similarly deactivated with inorganic bases and salts added in aqueous solution, the water being removed by subsequent heat treatment. At low degrees of deactivation, retention volumes for aromatic hydrocarbons can be varied relative to aliphatic hydrocarbons according to the extent of deactivation. However, the amount of sample required (∼100 µgm.) to obtain a response from a flame-ionization detector suggests that considerable irreversible adsorption takes place. The most promising application appears to be at the highest degrees of deactivation (lowest activity-levels, when irreversible adsorption is much reduced) for the separation of high-molecular weight hydrocarbons.

Fixed-Bed Adsorption Comparisons of Bone Char and Activated Alumina for the Removal of Fluoride from Drinking Water

Abstract: Fluoride is commonly found at elevated concentrations in groundwaters worldwide and is difficult to remove even with activated alumina (AA) adsorption, the best available technology. Conseq...

Electron transfer at alumina surfaces. Part 7.—Nature of the radical species formed from perylene on the surface of an activated alumina—cation or anion?

Abstract: The preadsorption of Lewis acids or Lewis bases on the surface of an activated alumina leads to deactivation of the reducing or the oxidizing function of the catalyst with respect to the 1,3,5-trinitrobenzene (TNB) or the perylene couple. The incorporation of small amounts of fluoride ion into alumina decreases the electron-donor properties of the oxide, as shown by radical formation with TNB or tetracyanoethylene. With perylene, 9,10-dimethylanthracene or triphenylamine as the adsorbate, small additions of fluoride ion to the oxide have exactly the opposite effect, a dramatic increase in the radical-forming power of the catalyst being observed. The effect of adsorbed TNB or benzoic acid is to decrease the reducing power of alumina for iodine, but adsorbed perylene or triphenylamine produces a marked enhancement of this activity.These results prove the existence of two different electron-transfer sites on the surface of an activated alumina: a site that can generate TNB ion radicals and a site that can produce a free-radical form of perylene. Since the radical derived from TNB is negatively charged, present findings demonstrate beyond reasonable doubt that the species formed when perylene is adsorbed on an active alumina surface is the cation radical.