Purification, recovery efficiency

A process for depolymerizing nylon-6 and polyester-nylon-6 mixed scrap was patented by Allied Chemical Corporation in 19656 and 1967.7 Ground scrap was dissolved with high-pressure steam at 125-130 psig (963-997 kPa) pressure and 175-180°C for 0.5 h in a batch process and then continuously hydrolyzed with superheated steam at 350°C and 100 psig (790 kPa) to form -caprolactam at an overall recovery efficiency of 98%. The recovered monomer could be repolymerized without additional purification. 

Use of internal standards. Mann and Jaworski (31) reported that when the recovery of 1-TI C IAA is monitored during a sample purification procedure, considerable loss of IAA can be detected. Bandurski and Schulze (32) suggested the use of reverse isotope dilution to help quantify the actual loss of IAA during sample analysis. In this procedure, one adds a trace amount of radio-labeled compound which ideally is identical to the compound being monitored. High specific activity is required so that statistically significant amounts of isotope can be detected without having to add an excessive quantity (mass) of internal standard. The amount of internal standard must be less than the amount of PGS. One may then accurately determine the recovery efficiency of the internal standard and thus of the PGS (32). 

Table II. Net recovery efficiency of internal standards of plant growth substances after extraction and purification.

The reusability of the catalyst is one of the major advantages of using RE(OTf)3 as a Friedel-Crafts catalyst. RE(OTf)3 can be easily recovered from the reaction mixture by simple extraction. The catalyst is soluble in the aqueous layer rather than in organic layer, and is recovered by removing water to give a crystalline residue, which can be re-used without further purification. The efficiency of recovery and the catalytic activity of the reused RE(OTf)3 were examined in the reaction of 1 with acetic anhydride using Yb(OTf)3 and Sc(OTf)3. As shown in Table 7, more than 90% of Yb(OTf)3 and Sc(OTf)3 were easily recovered, and the yields of acylation product 2 in the second and the third uses were almost the same as in the first. 

After purification, quality control of solvent purity is necessary. For this purpose, many different analytical methods are utilized. Generally, chromatographic methods such as GC, GC-MS, and HPLC are used. Moreover, UV, infrared, and nuclear magnetic resonance spectroscopy can also be applied but they tend to be less sensitive toward trace impurities. Water in organic solvents is usually determined by Karl-Fisher titration. On the basis of experimental data obtained before and after purification, the efficiency of the clean-up procedure is determined. In general, the efficiency of purification, e.g., the recovery, is expressed by the coefficient R. This parameter is defined as the ratio of the amount of impurities removed to the amount of solvent before purification ... 

Sulfur reduction at Cool Water is quite impressive, considering that the SO2 emissions include both the sulfur from the coal-derived fuel gas combustion and from sulfur recovery. Most currently operated pipeline natural gas purification plants remove slightly more sulfur from the natural gas but are less efficient in sulfur recovery. Combined sulfur removal and recovery efficiencies of 98% to 99.9% from natural gas and coal-derived fuel gas are common. 

After several runs of the electrolysis process, the active metal fission products such as alkali, alkaline earth and rare earth metals are accumulated in the molten salt. The accumulated fission products must be removed from the molten salt because they will affect the recovery efficiency of U and TRU. Periodically, the molten salt is removed from the electrolysis cell, purified using the salt purification process and recycled to the electrolysis cell. However, the molten salt always contains U and TRU with the fission products because the electrolysis is used to recover pure U and TRU without fission products. Therefore, fission products removed from the molten salt are always accompanied by some amount of U and TRU. It is necessary to optimize between the loss of U and TRU and the quantity of fission products removed because an increased removal of the fission products results in an increased contamination by the TRU in the waste stream. 

Recovery and Purification. AH processes for the recovery and refining of maleic anhydride must deal with the efficient separation of maleic anhydride from the large amount of water produced in the reaction process. Recovery systems can be separated into two general categories aqueous- and nonaqueous-based absorption systems. Solvent-based systems have a higher recovery of maleic anhydride and are more energy efficient than water-based systems. 

The submitters reported a melting point of 114-116°. The checkers obtained analytically pure material with a recovery of 80% after decolorization with activated carbon and recrystallization from 2-3 ml. of hexane at 0°. The product was also purified with comparable efficiency by sublimation at 85-90° (10 mm.). A small amount of a yellow, volatile impurity was removed from the cold finger before the product began to sublime. The melting point of the product after purification by the checkers was 110-112°. The reported melting point is 114-116°. 

Additional separation and recycling. Once the possibilities for recycling streams directly have been exhausted, feed purification and extraneous materials for separation eliminated that cannot be recycled efficiently, attention is turned to the fourth option in Figure 28.2, the degree of material recovery from the waste streams that are left. It should be emphasized that once the waste stream is rejected, any valuable material turns into a liability as an effluent material. The level of recovery for such situations needs careful consideration. It may be economic to carry out additional separation of valuable material with a view to recycling that additional recovered material, particularly when the cost of downstream effluent treatment is taken into consideration. 

As with most described methods for the purification of PHA from crops, no actual experimental data are available that would allow one to evaluate the efficiency of recovery of PHA based on air classification or centrifugal fractionation and the extra costs associated with the purification of PHA particles from the PHA-rich fractions. 

In this review, we focus on the use of plant tissue culture to produce foreign proteins that have direct commercial or medical applications. The development of large-scale plant tissue culture systems for the production of biopharmaceutical proteins requires efficient, high-level expression of stable, biologically active products. To minimize the cost of protein recovery and purification, it is preferable that the expression system releases the product in a form that can be harvested from the culture medium. In addition, the relevant bioprocessing issues associated with bioreactor culture of plant cells and tissues must be addressed. 

The entire wastewater treatment system focuses on removing the various types of pollutants with the highest possible efficiency from wastewaters, synchronizing this effort with the production of compatible process waters. Efficiency is not only considered in technical respect, but also deals with the costs of the purification process and with aspects of sustainability such as the use of chemicals, additives, and energy, the recovery of valuable compounds for reuse, the emission of volatile pollutants and the production of final wastes. 

This paper will focus on the use of statistically designed experiments to develop effective purification processes in the most time and cost efficient fashion. Downstream processing and the recovery of proteins by severd different techniques have been discussed in other articles (1-3) and will not be discussed here. 

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