Column packing methods Subject

The Waters system uses a plastic cartridge which is inserted into a device (the Z-module) that subjects the column to radial compression, ie pressure is applied along the radial axis of the column tube. The flexible wall of the column then moulds itself into the voids that are present in the wall regions of the column. This method is claimed to produce an improvement in the packed bed structure, better column performance and longer useful column life. 

In accordance to U.S. 40 Code Federal Regulation part 136, standard method 6410B of the APHA, the American Water Works Association (AWWA), and the Water Environment Federation (WEE), as well as EPA methods 606,625, and 1625, can be employed for the analysis of phthalates in municipal and industrial discharges. As equivalent to EPA 625, method 6410 procedure employs LEE with methylene chloride for the isolation of phthalates and other base or neutral analytes at pH >11. Alternatively, water samples may be subjected to continuous LEE for 24 h. Phthalates, together with other extracted analytes are separated on a chromatographic column packed with 3% SP-2250 or equivalent, and quantified on a MS analyzer. 

Gas chromatography has found some applications in the determination of simple aromatics in water. Mel kanovitskaya [31] has described a method for determining C6-C8 aromatics in subterranean waters. In this method the sample (25-50mL) is adjusted to pH8-9 and extracted for 3min with 0.5 or l.OmL of nitrobenzene the extract is washed with 0.3mL of 5% hydrochloric acid or 5% sodium hydroxide solution and with 0.3mL of water adjusted to pH7. The purified extract is subjected to gas chromatography at 85°C on a column (lm><4mm) packed with 15% of polyoxyethylene glycol 2000 on Celite 545 (60-80 mesh) and operated with nitrogen (lOmL min ) as carrier gas, decane as internal standard and flame ionisation detection. 

Forced-flow leaching is an extraction technique that can provide a nearly quantitative recovery of many organic compounds. In this technique, the sample of interest is packed into a 20 cm x 4 mm stainless steel column. An extraction solvent is pumped under a gas pressure of 2.5 kg/cm through the column, which is heated close to the solvent s boding point. The results are comparable to Soxhlet extraction, but the extraction time is reduced from 24 to 0.5 hr using the forced-flow technique. An advantage of this method is that the sample is subjected continuously to fresh, hot solvent, and the effluent from the column can be collected easUy for further treatment. 

Chapter 16 presents an introduction to the subject of mass transfer as it applies to separation operations with particular emphasis on the design and operation of packed columns. The concluding chapter deals with the important topic of energy conservation in distillation and includes a method for computing thermodynamic eflSciency so that alternative separation processes can be compared. 

This chapter introduces how continuous distillation columns work and serves as the lead to a series of nine chapters on distillation. The basic calculation procedures for binary distillation are developed in Chapter 4. Multicomponent distillation is introduced in Chapter 5. detailed conputer calculation procedures for these systems are developed in Chapter 6. and sinplified shortcut methods are covered in Chapter 7. More complex distillation operations such as extractive and azeotropic distillation are the subject of Chapter 8. Chapter 9 switches to batch distillation, which is commonly used for smaller systems. Detailed design procedures for both staged and packed columns are discussed in Chapter 10. Finally, Chapter 11 looks at the economics of distillation and methods to save energy (and money) in distillation systems. 

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