Column adsorption

Adsorption HPLC is the classification in which the highly polar silica particles are exposed (no adsorbed or bonded liquid phase). Aluminum oxide particles fit this description too and are also readily available as the stationary phase. As mentioned earlier, this classification can also be thought of as normal phase 

SACHEM Inc., located in Cleburne, Texas, is a producer of high-purity bulk chemicals for companies that have high-purity requirements in their chemical processing. As stated in Workplace Scene 1.2, one of their products is tetramethylammonium hydroxide (TMAH), which is sold to semiconductor industries. The analysis of TMAH for trace anions such as chloride, nitrate, nitrite, and carbonate is critical for SACHEM s quality control laboratory. If these ions are present on the integrated circuit boards manufactured by one of their semiconductor customers, they may cause corrosion severe enough to affect the functionality and performance of the electronic devices in which the circuit boards are used. In SACHEM s quality control laboratory, ion chromatography procedures have been developed to measure the anion concentrations in TMAH. Because the concentration levels are trace levels, a clean room environment, like that described in Workplace Scene 1.2, is used. A special procedure for carbonate analysis is required so that the absorption of carbon dioxide from the atmosphere can be minimized. 

Kay Lones of SACHEM Inc. conducts analyses for trace anions in ultrapure TMAH products at the parts per billion level by using ion chromatography in a clean room like that described in Workplace Scene 1.2. 

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M. S. Tswett, the Polish botanist, in 1906 used adsorption columns in his investigations of plant pigments. It was not untU about 1930 that the method was used extensively by chemists. The most startling results have been obtained in the fields of plant pigments and natural products, but... 

The Aromax process was developed in the early 1970s by Toray Industries, Inc. in Japan (95—98). The adsorption column consists of a horizontal series of independent chambers containing fixed beds of adsorbent. Instead of a rotary valve, a sequence of specially designed on—off valves under computer control is used to move inlet and withdrawal ports around the bed. Adsorption is carried out in the Hquid phase at 140°C, 785—980 kPA, and 5—13 L/h. PX yields per pass is reported to exceed 90% with a typical purity of 99.5%. The first Aromax unit was installed at Toray s Kawasaki plant in March 1973. In 1994, IFP introduced the Eluxyl adsorption process (59,99). The proprietary adsorbent used is designated SPX 3000. Individual on-off valves controlled by a microprocessor are used. Raman spectroscopy to used to measure concentration profiles in the column. A 10,000 t/yr demonstration plant was started and successfully operated at Chevron s Pascagoula plant from 1995—96. IFP has Hcensed two hybrid units. 

Adsorption. Adsorption (qv) is an effective means of lowering the concentration of dissolved organics in effluent. Activated carbon is the most widely used and effective adsorbent for dyes (4) and, it has been extensively studied in the waste treatment of the different classes of dyes, ie, acid, direct, basic, reactive, disperse, etc (5—22). Commercial activated carbon can be prepared from lignite and bituminous coal, wood, pulp mill residue, coconut shell, and blood and have a surface area ranging from 500—1400 m /g (23). The feasibiUty of adsorption on carbon for the removal of dissolved organic pollutants has been demonstrated by adsorption isotherms (24) (see Carbon, activated carbon). Several pilot-plant and commercial-scale systems using activated carbon adsorption columns have been developed (25—27). 

A countercurrent moving-bed adsorption column is used to remove benzene from a gaseous emission. Activated carbon is employed as the adsorbent. The flowrate of the gas is 1.2 kg/s and it contains 0.027 wt/wt% of benzene. It is desired to recover 99% of this pollutant. The activated carbon entering the column has 2 X 10 wt/wt% of benzene. Over the operating range, the adsorption isotherm (Yaws et al., 1995) is linearized to... 

The annualized fixed cost of the adsorption column along with its ancillary equipment (e.g., regeneration, materials handling, etc.) is estimated to be about 90,000/yr. Therefore, the TAC for the interception system is 119,000/yr. 

In order to obtain paromomycin In free base form, the hydrochloride is dissolved in water as a 3% solution, the solution Is poured into an adsorption column containing an anion exchange resin (Amberlite IR-45 or preferably IRA-411 or IRA-400) in the hydroxyl form and the column is washed with a small amount of water. 

Purification of Antibiotic 66-40 — Dissolve 28 g of crude Antibiotic 66-40 in 100 ml of distilled water and charge to an anion exchange adsorption column (Dowex 1 X2) in the hydroxyl form. Slurry 2,000 g of the resin in water in to a column 2yj in diameter and 36 "high. Elute the column with distilled water at a rate of about 23 ml/min collecting 100 ml fractions and monitor with a conductivity meter and by disc testing against Staphylococcus aureus. 

Vz grams of the residue were dissolved in 10 ml of benzene, and the solution was passed over a chromatographic adsorption column containing 50 grams of alumina (Alcoa activated alumina. Grade F-20) which had previousiy been shaken for about 20 minutes with a mixture of 100 ml of benzene containing 1.5 ml of 10% acetic acid. 

Adsorption column chromatography has been employed to separate the constituents of pyrethrum. Florisil and aluminum oxide have been used as adsorption columns to retain much of the pigmented materials. The pyrethroids may be caused to elute with several solvents. In our experience mixtures of hexane with ethyl acetate, methanol, ethyl ether, dichloromethane, or acetone have provided different elution patterns. 

Shimoda, M., Wu, Y., and Osajima, Y. (1996). Aroma compounds from aqueous solution of haze (Rhus succedanea) honey determined by adsorptive column chromatography. /. Agric. Food Chem. 44, 3913-3918. 

Its principles include polar extraction with acetone-water (2 1, v/v), homogeneous partitioning of the target molecules into an organic solvent, GPC cleanup on Bio-Beads, fractionation by adsorption column chromatography on silica gel (Si02) deactivated with 1.5% water and finally GC with various selective detection methods (NPD, BCD, FPD). 

Johnston, W.A. Designing Fixed-Bed Adsorption Columns, Chemical Engineering, Nov. 27, 1972, p. 87. 

Hirsch, D.E. Hopkins, R.C. Coleman, H.J. Cotton, F.O. Thompson, C.J. Separation of High-Boiling Petroleum Distillates Using Gradient Elution Through Dual-Packed (Silica Gel-Alumina Gel) Adsorption Columns, Anal. Chem. 1972, 44, 915. 

Propagation problems. These problems are concerned with predicting the subsequent behavior of a system from a knowledge of the initial state. For this reason they are often called the transient (time-varying) or unsteady-state phenomena. Chemical engineering examples include the transient state of chemical reactions (kinetics), the propagation of pressure waves in a fluid, transient behavior of an adsorption column, and the rate of approach to equilibrium of a packed distillation column. 

Eluxyl A process for separating /7-xylene from its isomers, using an adsorbent-solvent technique. The process is based on simulated countercurrent adsorption where the selective adsorbent is held stationary in the adsorption column. The feed mixture to be separated is introduced at various levels in the middle of the column, as in the Sorbex process. The /r-xylene product can be more than 99.9 percent pure. Developed by IFP and Chevron Chemical. A large pilot plant was built in Chevron s site at Pascacougla, MS, in 1994 and a commercial plant on the site was announced in 1996, Since then, the process has been widely licensed. 

Let s start with two components, A and B again, and follow their path through an adsorption column. Well, if A and B are different, they are going to stick on the adsorbant to different degrees and spend more or less time flying in the carrier gas. Eventually, one will get ahead of the other. Aha Separation—Just like column and thin-layer chromatography. Only here the samples are vaporized, and it s called vapor-phase chromatography (VPC). 

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