Charcoal adsorbate concentration

The adsorbate concentration in the Nth stage along the charcoal bed can be found by solving the series of N differential equations. These solutions represent the concentration profile in the Nth stage. For a unit pulse of adsorbate at time t = 0, the solution reduces to... 

Activated charcoal adsorbs salicylate effectively, and has been given in repeated oral doses (50 g 4 hourly) to enhance clearance, although its effect on outcome is unknown. Fluid and electrolyte replacement are important and special care should be taken to maintain normal potassium concentrations. Patients with signs of poisoning, especially when plasma salicylate concentration exceeds 500 mg/1, should receive specitic elimination therapy. 

A total volume of 300 L air was sampled for toluene using activated charcoal adsorbent. The analyte was desorbed with 2 mL carbon disulfide. An aliquot of the eluant was analyzed by GC. The concentration of toluene in the eluant was found to be 13.7 mg/L. Determine its concentration in the air as mg toluene/m3 air. 

It was stated at the outset that each beaker contains an identical but unknown volume of water. Why do we get a different volume of water in each beaker The presence of a small amount of charcoal (adsorbing agent) is reducing the potassium iodide concentration in the available identical volume of water in beaker B. 

The adsorber above is a well-mixed slurry of water and charcoal. The concentration of benzene in the water and the concentration of benzene adsorbed on the charcoal are uniform throughout the adsorber. 

DPG. In order to elucidate whether the hyperbolic response of the mutant PRPP synthetase to increasing phosphate concentration in hemolysate reflects an abnormal response to inhibitors, a system devoid of inhibitors was employed. Using stroma-free charcoal-adsorbed hemolysate treated with DEAE-cellulose, the difference in reaction to increasing inorganic phosphate concentration between the mutant enzyme and the normal enzyme disappeared both exhibiting a hyperbolic response (Fig. 2). It was furthermore found that the mutant enzyme had a decreased sensitivity to inhibition by GDP, ADP,... 

The xylenes are mildly toxic. They ate mild skin irritants, and skin protection and the cannister-type masks are recommended. The oral LD q value for rats is 4300 ppm. The STEL for humans is 150 ppm. Xylenes show only mild toxicity to fish, and the threshold limit for crop damage is 800—2400 ppm. Biodegradation with activated seed is slow, and sewage digestion is impaired by 0.1% concentrations. In the event of a spih, oil-skimming equipment, adsorbent foam, and charcoal maybe used for cleanup. 

Various types of detector tubes have been devised. The NIOSH standard number S-311 employs a tube filled with 420—840 p.m (20/40 mesh) activated charcoal. A known volume of air is passed through the tube by either a handheld or vacuum pump. Carbon disulfide is used as the desorbing solvent and the solution is then analyzed by gc using a flame-ionization detector (88). Other adsorbents such as siUca gel and desorbents such as acetone have been employed. Passive (diffuse samplers) have also been developed. Passive samplers are useful for determining the time-weighted average (TWA) concentration of benzene vapor (89). Passive dosimeters allow permeation or diffusion-controlled mass transport across a membrane or adsorbent bed, ie, activated charcoal. The activated charcoal is removed, extracted with solvent, and analyzed by gc. Passive dosimeters with instant readout capabiUty have also been devised (85). 

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. 

For the charcoal, XAD, and PUF adsorbents discussed above, solvent extraction techniques have been developed for the removal and concentration of trapped analytes. Although thermal desorption has been used with Tenax-GC in some specialized air sampling situations [primarily with sampling volatile organic compounds (EPA, Method TO-17 )], this approach is not a viable alternative to solvent extraction for the charcoal, XAD, and PUF adsorbents. The polystyrene and PUF adsorbents are thermally unstable and the charcoal chemisorption bonding is more easily broken by... 

A 10 g sample is roasted at 650°C and decomposed with hydrochloric acid/hydrogen peroxide. The Pt and Pd in the solution is pre-concentrated using adsorbent materials which are composed of active charcoal and anion resin. The adsorbent materials are washed sequentially with 2% ammonium bifluoride, 5% hydrochloric acid and distilled water, and subsequently ashed in a muffle furnace at 650°C. The total residue of ca. 0.25 mg is dissolved with 2 ml fresh aqua regia, then diluted to 5ml using 10% hydrochloric solution, and determined using ICP-MS, which has a detection limit of 0.2 ppb for Pt and Pd. The residue can also be mixed with a spectral buffer, and determined by DC-arc ES, which has detection limits of 0.3 ppb for Pt and 0.2 ppb for Pd. 

Some separation techniques rely on the physical removal of one of the fractions charcoal will strongly adsorb the free fraction allowing its ready removal by centrifugation the addition of dextran reduces the tendency of charcoal to strip bound antigen from the complex alternatively, the bound fraction may be precipitated by the addition of suitable concentrations of various protein precipitants such as alcohol, ammonium sulphate and polyethylene glycol (PEG). 

Various sample enrichment techniques are used to isolate volatile organic compounds from mammalian secretions and excretions. The dynamic headspace stripping of volatiles from collected material with purified inert gas and trapping of the volatile compounds on a porous polymer as described by Novotny [3], have been adapted by other workers to concentrate volatiles from various mammalian secretions [4-6]. It is risky to use activated charcoal as an adsorbent in the traps that are used in these methods because of the selective adsorption of compounds with different polarities and molecular sizes on different types of activated charcoal. Due to the high catalytic activity of activated charcoal, thermal conversion can occur if thermal desorption is used to recover the trapped material from such a trap. 

Ovaries (100 g) of the pufferfish Fugu vermicularis porphgreus are extracted with 1% acetic acid in methanol. The extract is concentrated in vacuo and defatted by shaking with chloroform. The defatted extract is treated with activated charcoal. The toxin adsorbed is eluted with 1% acetic acid in 20% ethanol. The eluate is evaporated in vacuo to dryness. The residue is dissolved in a small a-mount of water and adjusted to pH 6 with 1 N NaOH. The toxic solution is applied to an Amberlite IRC-50 column (NH, 2.5 x 45 cm) and developed with 2 L of water, and then 1 L each of 1 and 10% acetic acid. The toxic fractions are freeze-dried, dissolved in 1 mL of water and analyzed by HPLC. 

Adsorption experiments are carried out as follows. The solid sample (for example, activated charcoal) is shaken in contact with a solution with a known concentration of acetic acid. After equilibrium is reached (after 24 h), the amount of acetic acid adsorbed is determined. 

The adsorption of a particular solute from a solution is however dependent upon the nature of the solvent, a point not envisaged by the Freundlich isotherm. The influence of the solvent on the amount of adsorption of a particular solute has been investigated in the case of iodine and charcoal by Davis (J.C.8. xci. 1666,1911) who found that the amount of iodine adsorbed by charcoal from solutions of equimolecular concentrations decreased with the nature of the solvent in the following order ... 

In some cases it has been found that the maximum on saturation adsorption of a solute from a solution corresponds to the formation of an adsorption layer one molecule thick. Thus Euler Zeit. Elehtrochem. xxviii. 446,1922) found that a maximum adsorption of silver ions by silver and gold leaf was attained in a 0 03 A solution. It was found that 5 5 and 8 5 to 9 mgm. of silver ions were adsorbed by a square metre of metallic silver and gold respectively, such a surface concentration is practically unimolecular. The adsorption of silver ions by silver bromide (K. Fajans, Zeit Phys. Ohem. cv. 256, 1928) was found on the other hand to be not complete, for only every fourth bromide ion in a silver bromide surface was found to adsorb a silver ion. Similar conclusions as to the unimolecular character of the adsorbed film in the case of chemical charcoal as an adsorbing agent for fatty and amino acids may be drawn from the data of Foder and Schonfeld Koll. Zeit xxxi. 76, 1922). 

On the addition of a neutral chloride to the solution the chlorine ion concentration is increased, and provided that the cation of the added chloride does not affect the adsorption of the hydrogen ion, i.e. on addition of a weakly adsorbed cation, such as potassium, the adsorption of the hydrogen ion can now proceed to its normal equilibrium value without having to retain any adsorbed chlorine ions by electrostatic attraction. The addition of potassium chloride to a hydrochloric acid solution will thus augment the adsorption of the acid by the charcoal, a result confirmed by Michaelis and Rona. 

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