Solvent loading

Ethylene Stripping. The acetylene absorber bottom product is routed to the ethylene stripper, which operates at low pressure. In the bottom part of this tower the loaded solvent is stripped by heat input according to the purity specifications of the acetylene product. A lean DMF fraction is routed to the top of the upper part for selective absorption of acetylene. This feature reduces the acetylene content in the recycle gas to its minimum (typically 1%). The overhead gas fraction is recycled to the cracked gas compression of the olefin plant for the recovery of the ethylene. 

Uranium is subsequendy stripped reductively from the loaded solvent using a bleed stream of the raffinate acid to which ferrous iron has been added to reduce uranium to its nonextractable, quadravalent state. Raffinate is acid from which uranium has already been extracted. By controlling the organic-to-aqueous volume phase ratios in the extraction and stripping circuits, uranium is concentrated by a factor of approximately 70. 

Raffinate acid from the first cycle, containing approximately 7 to 14 g/L U Og is then reoxidized and re-extracted in the second, purification cycle using a solvent containing 0.3 Af D2EHPA and 0.075 AfTOPO. The loaded solvent is washed with iron-free acid to remove iron and then with water to remove extracted and entrained acid. The solvent is stripped with ammonium carbonate [506-87-6] to yield ammonium uranyl tricarbonate [18077-77-5] which is subsequendy calcined to U Og (yellow cake). The stripped solvent is regenerated with mineral acid before recycling (39). 

Figure 1. GPC chromatograms of A erosol OT at varying sample loads (solvent benzene columns 500 A + 100 A gStyragel flow rate 0.58 mL/min injection...

After extraction, the loaded solvent contains 6 g T1 zirconium as zirconium oxide with 0.2% hafnium oxide. The raffinate is left with 0.2 to 0.3 g l l of the oxides of zirconium and hafnium of this, 70-90% is hafnium oxide. This raffinate can act as a feed solution for the recovery of pure hafnium oxide. The loaded extractant, on the other hand, is subjected to a scrubbing operation with pure zirconium sulfate solution to eliminate any co-extracted hafnium. This scrubbing operation is essentially a displacement reaction ... 

Flash chromatography is performed on E. Merck silica gel 230-400 mesh 250 g of silica gel is loaded on a 16- x 2-in size column using a minimum amount of hexanes as loading solvent. 

Irradiated UO2 is dissolved in nitric acid, resulting in a dissolver solution with the approximate composition listed in Table 12.7. This is treated by the Purex process. The main steps in the conventional Purex process are shown schematically in Fig. 12.5. All existing plants listed in Table 12.8 use some variation of the Purex process. Typically, the extractant composition (percentage TBP, diluent) and the extraction equipment (i.e., pulse columns, mixer-settlers, etc.), vary from plant to plant. However, the upper concentration limit is 30% TBP to prevent a phase reversal due to the increased density of the fully loaded solvent phase. 

The stripping of the organic loaded solvent is accomplished by neutralization of the organic solvent with an alkali solution (e.g., NaOH) to reconstitute a strong cyanide solution for recycling. 

The cross-coupling of 3-iodopyridine and 4-dimethylamino-phenylacetylene was reported to work efficiently in the presence of a nickel based catalyst system too (7.42.),60 The described conditions (e.g. catalyst loading, solvent, temperature, additive) are more or less the same as in the conventional palladium catalyzed variant, although the nickel based system gave only poor results with bromoazines. 

Adsorbent Loading solvent Relative intensity (°/o) Chemical shift (ppm from TMS) Linewidth (Hz)... 

Alternative stripping procedures using concentrated solutions containing chloride or nitrate ions to displace the vanadate from the loaded solvent, or sulfur dioxide to reduce the vanadium(V) to the oxovanadium(IV) cation have been proposed.210... 

Minor experimental modifications, such as the use of hydrophilic complex-ants to ease the scrubbing and stripping of the loaded solvents and simplify the flowsheets. 

All partitioning processes described in today s literature that claim to separate the minor An(III) from the fission products by selective extraction of the An(III) actually perform the An(III)/Ln(III) partition from a feed arising from a front-end partitioning step, which has already separated the An(III) + Ln(III) fraction from a PUREX raffinate. There are, however, other processes that perform the An(III)/ Ln(III) partition by using a selective hydrophilic complexant, introduced either in the feed to selectively complex the An(III) and prevent their extraction, or in the stripping solution to selectively back-extract the An(III) from the loaded solvent. The development and achievements of these two families of processes ( selective extraction of An(III) and selective complexation of An(III) ) will be described hereafter. 

The results indicate that the process is robust and can tolerate and recover from disruptions in operation. In addition, hydraulic stage efficiencies in the extraction and strip sections were greater than the 80% design requirement. Test results showed that the loaded solvent could be stripped of cesium and recycled to the process with... 

Z. Kolarik and E. P. Horwitz. Extraction of metal nitrates with octyl(phenyl)-n,n-diisobutyl-carbamoylmethyl phosphine oxides in alkane diluents at high solvent loading. Solvent Extr. Ion Exch., 6(1) 61—91, 1988. 

Typical sample loading solvent Hexane, toluene Water, buffers Water, buffers... 

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