Activated charcoal silica

The adsorbent should have a high affinity and capacity for the enzyme and it should not absorb the reaction product or enzyme inhibitors. Among the materials used the more popular are cation and anion exchange resins, activated charcoal, silica gel, alumina, control pore glasses and ceramics. 

In order to increase the contact of a catalyst with hydrogen and the compounds to be hydrogenated platinum (or other metals) is (are) precipitated on materials having large surface areas such as activated charcoal, silica gel, alumina, calcium carbonate, barium sulfate and others. Such supported catalysts are prepared by hydrogenation of solutions of the metal salts, e.g. chloroplatinic acid, in aqueous suspensions of activated charcoal or other solid substrates [28. Supported catalysts which usually contain 5, 10 or 30 weight percent of platinum are very active, and frequently pyrophoric. 

An inert gas is bubbled through the sample. The volatile hydrocarbons are transferred into the vapor phase and trapped over a sorbent bed containing 2,6-diphenylene oxide polymer (Tenax GC). A methyl silicone (3% OV-1 on Chromosorb-W, 60/80 mesh) packing protects the trapping material from contamination. Other adsorbents such as Carbopack B and Carbosieve S III may also be used. If pentane and other low boiling hydrocarbons need to be detected, the sorbent trap should be filled with activated charcoal, silica gel, and Tenax, respectively, in equal amounts. 

Before the mid-1940s few systematic attempts appear to have been made to optimize the properties of such common adsorbents as activated charcoal, silica gel and activated alumina. The increase in research and development activity after the Second World War was largely due to the demand for improved catalysts and adsorbents. It was already known that the extent of the accessible surface was of fundamental importance (Rideal, 1932). In the 1940s the interest in gas adsorption was undoubtedly stimulated by the perceived success of the BET method for the determination of the surface area. 

Ishihara et al. [12-16] Batch flow reactor PE, PP, PS Active charcoal, silica-alumina, NaY zeolite... 

Commonly used stationary phases in gas-solid chromatography are activated charcoal, silica gel, Fluorosil, and molecular sieves 5A, X, or Y (synthetic zeolites). These are useful to temperatures as high as 500°C. At high temperatures the... 

The adsorption of biomolecules onto carriers that are insoluble in water is the simplest method of immobilization. An aqueous solution of the biomolecules is contacted with the active carrier material for a defined period of time. Thereafter the molecules that are not adsorbed are removed by washing. Anionic and cationic ion exchange resins, active charcoal, silica gel, clay, aluminum oxide, porous glass, and ceramics are being currently used as active material. The carrier should exhibit high affinity and capacity for the biomolecule and the latter must remain active in the adsorbed state. The carrier should adsorb neither reaction products nor inhibitors of the biocatalyst. 

The following nickel-carrier catalysts have been described nickel-kieselguhr,169 nickel-pumice,170 nickel-kieselguhr containing thorium oxide,171 nickel on magnesium oxide, barium oxide, or beryllium oxide,172 nickel on aluminum oxide,173 and nickel-zinc oxide-barium oxide-chromium oxide.174 Other carriers for nickel catalysts are active charcoal, silica, fuller s earth, and oxides such as magnesia, alumina, and bauxite. 

If one is forced to use liquid air in the presence of oxygen-sensitive compoimds, the cooling flask should be covered with a protective jacket made of copper sheeting. The same protective measure should be taken when liquid air is used for cooling vessels containing activated charcoal (silica gel should preferably be used in these cases). 

Fig. XVII-29. Nitrogen isotherms the volume adsorbed is plotted on an arbitrary scale. The upper scale shows pore radii corresponding to various relative pressures. Samples A, Oulton catalyst B, bone char number 452 C, activated charcoal F, Alumina catalyst F12 G, porous glass S, silica aerogel. (From Ref. 196).

Because of their selectivity, molecular sieves offer advantages over silica gel, alumina or activated charcoal, especially in their very high affinity for water, polar molecules and unsaturated organic compounds. Their relative efficiency is greatest when the impurity to be removed is present at low concentrations. Thus, at 25° and a relative humidity of 2%, type 5A molecular sieves adsorb 18% by weight of water, whereas for silica gel and alumina the figures are 3.5 and 2.5% respectively. Even at 100° and a relative humidity of 1.3% molecular sieves adsorb about 15% by weight of water. 

Hydroxy-1-naphthaleneacetic acid [10441-45-9] M 202.2, pK )-4.2, pKej,(2) -8.3. Treated with activated charcoal and crystd from EtOH/water (1 9, v/v). Dried under vacuum, over silica gel, in the dark. Stored in the dark at -20° [Gafni, Modlin and Brand J Phys Chem 80 898 1976. Forms a lactone (m 107°) readily. 

Hydrogen chloride [7647-01-0] M 36.5. Passed through cone H2SO4, then over activated charcoal and silica gel. Fumes in moist air. Hydrogen chloride in gas cylinder include ethylene, 1,1-dichloroethane and ethyl chloride. The latter two may be removed by fractionating the HCl through a trap cooled to -112°. Ethylene is difficult to remove. Fumes in moist air. HARMFUL VAPOURS. 

Purified by Soxhlet extraction with pet ether for 24h, followed by dissolution in acetone MeOH H20 90 5 5(v/v) and recrystn [Politi et al. J Phys Chem%9 2345 1985. Also purified by two recrystns from absolute EtOH, aqueous 95% EtOH, MeOH, isopropanol or a 1 1 mixture of EtOHrisopropanol to remove dodecanol, and dried under vacuum [Ramesh and Labes J Am Chem Soc 109 3228 1987]. Also purified by foaming [see Cockbain and McMullen Trans Faraday 5oc 47 322 1951] or by liquid-liquid extraction [see Harrold J Colloid Sci 15 280 I960]. Dried over silica gel. For DNA work it should be dissolved in excess MeOH passed through an activated charcoal column and evaporated until it crystallises out. 

Certain highly porous solid materials selectively adsorb certain molecules. Examples are silica gel for separation of aromatics from other hydrocarbons, and activated charcoal for removing liquid components from gases. Adsorption is analogous to absorption, but the principles are different. Layers of adsorbed material, only a few molecules thick, are formed on the extensive interior area of the adsorbent - possibly as large as 50,000 sq. ft./lb of material. 

Adsorptive Properties. Substances such as silica gel and activated charcoal can be used to collect (adsorb) certain solids from solution. The adsorber bed may be discarded when depleted or recycled by washing and heating. 

Sorbent tubes Small glass tubes that contain sampling media such as silica gel or activated charcoal. 

A common approach for personal dosimetry is collection of pollutant on, e.g., silica gel, organic resins or activated charcoal in small tubes worn on the operator s lapel (Table 9.2). Silica gel is useful for polar chemicals charcoal finds wide use for non-polar substances. The pollutant is then solvent-extracted or thermally desorbed for subsequent analysis by, e.g., chromatography. 

Chromatographic Characterization of TTXs. The vast majority of reports have identified TTX and anhydro-TTX in bacterial cultures using HPLC, TLC, and GC-MS. Yasumoto et al. (30) showed that TTX-like substances extracted from a Pseudomonas sp. culture could bind to activated charcoal at pH 5.5 and be eluted with 20% ethanol in 1% acetic acid. In addition, HPLC analysis demonstrated TTX and anhydro-TTX-like fluorophors following strong base treatment. These compounds migrated on silica gel comparably to TTX and anhydro-TTX. Furthermore, when analyzed by electron ionization (EI)-MS and fast atom... 

The MW-promoted cracking of organic molecules in the presence of silica-supported graphite [10 a] or activated charcoal [10 b] has also been reported. 

The concept of using colloids stabilized with chiral ligands was first applied by Bonnemann to hydrogenate ethyl pyruvate to ethyl lactate with Pt colloids. The nanoparticles were stabilized by the addition of dihydrocinchonidine salt (DHCin, HX) and were used in the liquid phase or adsorbed onto activated charcoal and silica [129, 130]. The molar ratio of platinum to dihydrocinchonidine, which ranged from 0.5 to 3.5 during the synthesis, determines the particle size from 1.5 to 4 nm and contributes to a slight decrease in activity (TOF = l s ). In an acetic acid/MeOH mixture and under a hydrogen pressure up to 100 bar, the (R)-ethyl lactate was obtained with optical yields of 75-80% (Scheme 9.11). 

Great difficulties were experienced in laboratories trying to extend Tsvett s approach. Activated charcoal, Cy alumina, and silica gels provided a range of adsorbents with different properties. Irreproduc-ibility between different batches of adsorbent were almost inevitable, and very irritating, before the theoretical complexities of adsorption analysis were understood. Operationally, there were serious difficulties in the nondestructive monitoring of the elution of colorless solutes like amino acids. 

Jansson et al. [189] used the conventional approach of blending the solid particles with solvent after which an aliquot was taken to determine the volatile compounds (e.g., phenols and chlorobenzenes). A second fraction was taken after the lipid removal for determination of compounds sensitive to concentrated sulfuric acid. The bulk lipids were removed by oxidative dehydration with Si02 /H2S04 and further cleaned-up with GPC. The chloroparaffins were isolated at this stage. Separation on silica isolated the OCPs, and the organochlorines and organobromines were finally fractionated on active charcoal. 

Faber and Rogers (165) have reported EPR spectra of Mn++, Cu++, and VO++ adsorbed on cation- and anion-exchange resins, activated charcoal, zeolite, and silica gel. Spectra similar to those shown on Figs. 26(b) and 28 were observed for VO and Cu++ adsorbed on various substrates, with the omission of the nitrogen hfs of Fig. 28. 

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