Alumina adsorptivity

Adsorption processes use a solid material (adsorbent) possessing a large surface area and the ability to selectively adsorb a gas or a liquid on its surface. Examples of adsorbents are silica (Si02), anhydrous alumina (AI2O3), and molecular sieves (crystalline silica/alumina). Adsorption processes may be used to remove acid gases from natural gas and gas streams. For example, molecular sieves are used to dehydrate natural gas and to reduce its acid gases. 

Alumina, adsorption, ca. 150 mesh, was purchased from Aldrich Chemical Co. and used as received. 

There are several potential treatment technologies that may be applicable, but are more expensive than the methods currently used. These potential treatments include sulfide precipitation, ultrafiltration, reverse osmosis, deep-well disposal, activated carbon adsorption or activated alumina adsorption, solidification, or ion exchange.19-21... 

Aluminum oxide (alumina), AI2O3, has lugh technological value. Sol-gel processing of alumina has created novel applications and improved some of its properties. Products such as catalyst earners, abrasives, fibers, films for electronic applications, aerogels, and membranes for molecular filtration have been developed based on sol-gel processing. See also Alumina Adsorption (Process) and Bauxite Aluminum and Aluminum Alloys and Engineered Materials. 

Alumina Adsorption of aliphatic amines by means of pulse chromatography and temperature-programmed desorption. 74... 

The use of adsorbents in conjunction with appropriate conditions for supercritical CO2 extraction enhances the efficiency of cholesterol extraction. Selective removal of 97% of cholesterol has been achieved with the use of silica gel as an in-line adsorbent (Huber et ah, 1996). Removal of 96% of cholesterol in milk fat fractions can be achieved by a combined supercritical C02 extraction and an alumina adsorption process (Mohamed et al., 1998). 

Studies of organoactinide surface chemistry and catalysis have been carried out by the Marks group under rigorously anhydrous/anaerobic conditions on either partially dehy-droxylated alumina (PDA) or DA at surface coverages of 0.25 0.50 molecules nm. The PDA and DA surfaces are represented schematically in equation (68). Product yields, isotopic labeling, and surface reactivity indicate that the irreversible y-alumina adsorption chemistry of Cp 2AnMe2 can be described by three methane-evolving pathways (equations 69-71). Equation (69) dominates on PDA. On DA,... 

Figure 12.21 Typical adsorption spectrum for pyridine on an alumina. Adsorption at 25 C and thermodesorption by steps up to 350°C.

HPLC measurements of plasma catechols are usually limited to dopamine, norepinephrine, and epinephrine. However, with an alumina adsorption extraction procedure it is also possible to simultaneously measure several other catechols by HPLC or microchip electrophoresis. These catechols include DHPG, the deaminated metabolite of norepinephrine and epinephrine DOPAC, the deaminated metaboHte of dopamine and 3,4-dihydroxyphenylalanine (r-dopa), the immediate precursor of dopamine. All are present in plasma at concentrations many fold higher than the catecholamines, making their detection relatively simple once appropriate chromatographic separation is achieved. 

SO2 onto activated charcoal or alkalized alumina Adsorption, plus chemical reaction heat cone. SO2... 

Isolation Alumina adsorption, final desorbing volume 800 pL. 0.2 rnolL HCIO4 ... 

Much more work on the experimental verification and quantification of this physical adsorption process has been conducted in our own laboratory for the chloroplatinic acid (HzPtCL, or CPA)/alumina system [3,4]. The Revised Physical Adsorption (RPA) model [4], with which all known sets of Pt/alumina adsorption data can be satisfactorily simulated with no adjustable parameters, is a result of these efforts. The basis of the RPA model is the a priori calculation of adsorption equilibrium constants, seen as the center regime of Fig. 1. 

Alumina Adsorption Amino acids BuOH/EtOH/HjO Ninhydrin ... 

Wetting Liquids. The wetting liquids were all reagent grade chemicals, further purified either by distillation or by percolation through silica-alumina adsorption columns until their surface tensions checked reliable literature values [1]. 

Numerous attempts were made to fractionate the oleoresin Capsicum volatiles in such a manner that a peppery aroma would be concentrated in one fraction. Vacuum fractional distillation yielded four fractions plus a residue, none of which exhibited a peppery aroma. The first fraction eluted with pentane from a deactivated (15% water by weight) alumina adsorption column had a peppery aroma, but on rechromatographing the fraction on more active alumina, the pepper aroma was lost. The aroma was also mostly lost when preparative gas chromatography was applied in an attempt to separate the peppery alumina column fraction. 

Scheme 2.5 Enzymatic synthesis of salidroside catalyzed by cross-linked apple seed meal integrated with alumina adsorption.

The synthesis of DPE was described by Nohta et al. [411]. After the usual clean-up by alumina adsorption, cation exchange column chromatography or other suitable procedure [412], 150 fil of the sample solution (adjusted to pH 6.0-6.5) are mixed with 10 fil of a 20 mM solution of potassium ferricyanide and 150 1 of acetonitrile. Subsequently, 50 fA of the DPE solution (21.2 mg ml in 0.1 M HCl) are added and the reaction mixture is allowed to stand at 37 °C for 40 min. After cooling to room temperature, 100 /A aliquots are injected onto the column. Fluorescence intensity is recorded at 485 nm after excitation at 345 nm. Procedures for the determination of norepinephrine, epinephrine and dopamine in plasma [412] and urine [413] were reported. 

In the case of the alumina adsorption system, one may investigate the oxide/ acid-base system separately. This is necessary because aluminas are amphoteric oxides of remarkable solubility with a number of different species in solution, and the possible adsorption of protons and hydroj ls at the surface leads to the development of surface charges. 

Fig. 10. Measurement of norepinephrine and epinephrine in human plasma. Explanation of traces from left to right. A (1) Norepinephrine standard (10 pmol injected) (2) epinephrine standard (10 pmol injected) (3) dopamine standard (10 pmol injected). B (1) Plasma (1.1 ml) collected during a normoglycemic baseline period. Dopamine (10 pmol) added as internal standard prior to aluminum oxide adsorption. Sensitivity changes from 100 nA to 1 nA full scale deflection immediately after elution of the solvent front. Note the small norepinephrine (0.57 nmol/liter) and epinephrine (0.74 nmol/liter) peaks (2) plasma (1.1 ml) from the same subject, insulin-induced hypoglycemia. Note the marked increase in the epinephrine (5.16 nmol/liter) peak and the small rise in norepinephrine (0.75 nmol/liter). Dopamine (10 pmol) added as internal standard. Chromatographic conditions column, Nucleosil (10 [x), 30 cm X 2.1 mm mobile phase, acetate/citrate, 0.1 M, pH 5.2 flow rate, 1.2 ml/min electrode potential, +0.65 V (carbon paste) volume injected, 100 xl plasma extraction, alumina adsorption (Fig. 8).

There were several observations made concerning the effect pH had on the adsorption on alumina. Adsorption of the DADS component onto alumina was very sensitive to variations in the feed pH. This was exhibited by the several points that did not fit smoothly on the isotherm (see Figure 11). It was also noted that for any of the surfactants if the feed pH was at or below 2.5 or 2.6 the final pH was usually below 3.0, but if the feed pH approached 3.0 the final pH would approach 4.0. 

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