Aqueous raffinate

The bottoms from the solvent recovery (or a2eotropic dehydration column) are fed to the foremns column where acetic acid, some acryflc acid, and final traces of water are removed overhead. The overhead mixture is sent to an acetic acid purification column where a technical grade of acetic acid suitable for ester manufacture is recovered as a by-product. The bottoms from the acetic acid recovery column are recycled to the reflux to the foremns column. The bottoms from the foremns column are fed to the product column where the glacial acryflc acid of commerce is taken overhead. Bottoms from the product column are stripped to recover acryflc acid values and the high boilers are burned. The principal losses of acryflc acid in this process are to the aqueous raffinate and to the aqueous layer from the dehydration column and to dimeri2ation of acryflc acid to 3-acryloxypropionic acid. If necessary, the product column bottoms stripper may include provision for a short-contact-time cracker to crack this dimer back to acryflc acid (60). 

Example 2 Stage and Composition Calculation A 100-kg/h feed stream containing 20 weight percent acetic acid in water is to he extracted with 200 kg/h of recycle MIBK that contains 0.1 percent acetic acid and 0.01 percent water. The aqueous raffinate is to he extracted down to 1 percent acetic acid. How many theoretical stages wiU he required and what will the extract composition he ... 

In screening tests, it is common practice to use approximately 0.1 mol dm or 5 vol% solutions of extractant, and extraction tests are conducted at a phase ratio of 1, with a 5 min contact time. These conditions, of course, may be varied, but the object is to stay with as simple an approach as possible. Analysis of only the aqueous raffinate need be carried out, and distribution data calculated from this. 

For most exploratory work, analysis of the organic phase is not necessary. If no volume change of the phases occurs and no third phase or crud is formed, the analysis of the aqueous raffinates is sufficient, since the metal concentration in the solvent can be readily calculated from the initial metal concentration of the feed solution and the phase ratio used. 

Some consideration should be given at this point to the need to prevent loss of the organic phase in the aqueous raffinate. This loss can arise by either solubility in the aqueous phase or by entrainment of droplets not fully settled. The solvent lost in this way can offer a finite environmental hazard and be an economic cost on the process. 

The potassium penicillin is recovered by filtration and the solvent recirculated. Recovery of the organic phase from the aqueous raffinate is also very important to minimize costs and environmental impact. Butyl acetate, being a low-boiling solvent, can be recovered easily by distillation. 

In this process developed by Lurgi [17], the phenolic effluent is contacted with the solvent in a multistage mixer-settler countercurrent extractor (Fig. 10.8). The extract, containing phenol, is separated into phenol and solvent by distillation and solvent is recycled to the extractor. The aqueous raffinate phase is stripped from solvent with gas, and the solvent is recovered from the stripping gas by washing with crude phenol and passed to the extract distillation column. 

In this flow sheet, the aqueous raffinate from extraction is acidified to 5-6 mol dm with hydrochloric acid to optimize platinum extraction by the solvating extractant TBP. The coextraction of iridium is prevented by reduction with sulfur dioxide, which converts the iridium(IV) to the (III) species, which is not extractable. Once again, kinetics are a factor in this reduction step because, although the redox potentials are quite similar, [Ir(IV)/(III) —0.87 V Pt(IV)/(II) —0.77 V], iridium(IV) has a relatively labile configuration, whereas platinum(IV) has the inert arrangement. The species H2PtCl6 is extracted by TBP, from which platinum can be stripped by water and recovered by precipitation as (NH3)2PtCl2. 

In the commercial flow sheets, these elements are left in the aqueous raffinate after platinum and palladium extraction. Indium can be extracted in the -l-IV oxidation state by amines (see Fig. 11.11), or TBP (see Figs. 11.10 and 11.12). However, although the separation from rhodium is easy, the recovery of iridium may not be quantitative because of the presence of nonextractable iridium halocomplexes in the feed solution. Dhara [37] has proposed coextraction of iridium, platinum, and palladium by a tertiary amine and the selective recovery of the iridium by reduction to Ir(III). Iridium can also be separated from rhodium by substituted amides [S(Ir/ Rh) 5 X 10 ). 

Large-scale winning of copper by acidic leaching of copper ores sometimes results in waste solutions containing appreciable amounts of uranium. The uranium bearing aqueous raffinate from copper extraction is usually a dilute sulfuric acid solution. Uranium can be recovered using the same technique as described in section 12.3.1. A typical example is uranium production at the Olympic Dam mine in Australia, where the copper ore bodies are estimated to contain a total of over a million metric tons of uranium. 

Coextraction of 99.9% of Pu and U and some 90% of from 3-4 mol dm HNO3 solution into 30 vol% TBP, diluted with a mixture of aliphatic hydrocarbons or, occasionally, with pure dodecane. Fission products and trivalent actinides (Am, Cm) remain in the aqueous raffinate. 

The anolyte, containing about 75gdm CD at pFI 2, is fed to a solvent extraction circuit for the separation of Fe—Co and Fe—Ni with a tertiary alkyl amine, dissolved in kerosene. The separation is based on the tendency of the metals to form metal-chloride-amine complexes (Fig. 11.2). At low chloride ion concentration (about 75gdm ), Fe(III) is extracted to the organic solvent, while Co(II) and Ni(II) remain in the aqueous raffinate. If the chloride ion concentration is then increased to about 250 gdm, cobalt is extracted, leaving nickel behind in the raffinate. 

In the acid deficient flowsheet the acid released from A1(N03)3 hydrolysis was neutralized to give an organic product containing 0.5 M U02(N03)2 but only 0.05 M HN03. The A1(N03)3, Na2Cr207 and FPs were retained in the aqueous raffinate from the extraction section, while the organic product was passed to the U/Pu partition contacter. 

The aqueous raffinate was evaporated slightly under reduced pressure to remove ether, and then it was centrifuged. The centrifuged solids were washed with water, filtered, and dried. This insoluble material amounted to 60.8% of the starting lignin, and the methoxyl represented 51.1% of the starting methoxyl. 

It generally proceeds through the extraction of the Ln(III) at a pH ranging from 2 to 3, leaving the An(III) in the aqueous raffinate as polyaminopolycarboxylate complexes. Therefore, it requires a buffered feed, which could be the stripping solution of a front-end process (such as the TRUEX process). 

An increase of product loss, namely, uranium and plutonium, in aqueous raffinates (84, 101). 

Pereira, C., H. A. Arafat, J. R. Falkenberg, et al. 2002. Recovery of Entrained CSSX Solvent from Caustic Aqueous Raffinate Using Coalescers. Argonne National Laboratory Report ANL-02/34, Argonne, IL. 

The flowsheet has three aqueous effluents. The first is the decontaminated aqueous raffinate stream. For economic reasons, entrained solvent in the raffinate must be recovered test results show that coalescers are practical and effective [89], In the baseline SWPF, the raffinate stream will be transferred to the Saltstone Facility, where it will be disposed of in a cementitious low-activity waste form called saltstone. The... 

Partitioning of components between two immiscible or partially miscible phases is the basis of classical solvent extraction widely used in numerous separations of industrial interest. Extraction is mostly realized in systems with dispergation of one phase into the second phase. Dispergation could be one origin of problems in many systems of interest, like entrainment of organic solvent into aqueous raffinate, formation of stable, difficult-to-separate emulsions, and so on. To solve these problems new ways of contacting of liquids have been developed. An idea to perform separations in three-phase systems with a liquid membrane is relatively new. The first papers on supported liquid membranes (SLM) appeared in 1967 [1, 2] and the first patent on emulsion liquid membrane was issued in 1968 [3], If two miscible fluids are separated by a liquid, which is immiscible with them, but enables a mass transport between the fluids, a liquid membrane (LM) is formed. A liquid membrane enables transport of components between two fluids at different rates and in this way to perform separation. When all three phases are liquid this process is called pertraction (PT). In most processes with liquids membrane contact of phases is realized without dispergation of phases. 

Solvent extraction [tributyl phosphate (TBP)] operations to recover plutonium from unirradiated scrap have been performed at the Hanford Site since 1955. The aqueous raffinate (CAW stream) from the TBP plutonium extraction process contains, typically, <10 mg/L plutonium and 2-10 mg/L 2 1Am. This latter isotope is present in the plutonium scrap as the result of beta decay of Pu (t]/2 = 14.4 y) tri valent americium does not accompany plutonium from the HNO3-HF feed solution into the TBP solvent. 

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