Extraction sulfate complexes

Historically, ferrous sulfamate, Fe(NH2S02)2, was added to the HNO scmbbing solution in sufficient excess to ensure the destmction of nitrite ions and the resulting reduction of the Pu to the less extractable Pu . However, the sulfate ion is undesirable because sulfate complexes with the plutonium to compHcate the subsequent plutonium purification step, adds to corrosion problems, and as SO2 is an off-gas pollutant during any subsequent high temperature waste solidification operations. The associated ferric ion contributes significantly to the solidified waste volume. 

The physical nature of the sulfate complexes formed by plutonium(III) and plutonium(IV) in 1 M acid 2 M ionic strength perchlorate media has been inferred from thermodynamic parameters for complexation reactions and acid dependence of stability constants. The stability constants of 1 1 and 1 2 complexes were determined by solvent extraction and ion-exchange techniques, and the thermodynamic parameters calculated from the temperature dependence of the stability constants. The data are consistent with the formation of complexes of the form PuSOi,(n-2)+ for the 1 1 complexes of both plutonium(III) and plutonium(IV). The second HSO4 ligand appears to be added without deprotonation in both systems to form complexes of the form PuSOifHSOit(n"3) +. ... 

Sulfate process streams are commonly used in metal recovery because they are readily derived by leaching with sulfuric acid or by oxidation of sulfidic ores. Metal recovery from such streams rarely involves the formation of metal sulfate complexes because the sulfate ion is a weak ligand for base metal cations and consequently acidic ion exchange extractants are commonly employed (see Section 9.17.5), which generate sulfuric acid which can be returned to the leaching stage,... 

Numerous determinations have been made of the stability constants of sulfate complexes of plutonium(IV), and the results vary by three orders of magnitude. The most plausible values (14) have come from careful ion exchange studies at I = 2 M and 25°, which indicate the presence of two species, Pu(S0i+) and Pu(S0i )2, with stepwise stability constants of 6.6 X 10 and 5.8 X 10, respectively. This Ki is in satisfactory agreement with the value 4.6 X 10 obtained potentiometrically at I = 1 M and 25° ( ). Spectrophotometric and electrophoretic studies indicate that plutonyl(VI) forms complexes containing as many as four sulfate groups, with anionic species predominating at sulfate concentrations above 1 M (15). The monosulfato complex has a reported stability constant of 14.4 as determined by extraction studies at I - 2 M and 25° (16). 

Similar chemistry, but with a different chelate ligand, is used to purify copper(II). The copper complex is loaded into the organic phase at a pH between 2 and 4, then back-extracted into water as the Cu2+aq ion using dilute sulfuric acid at pH 0. It is recovered as either copper sulfate or, with following electrochemical reduction, copper metal. Solvent extraction involving complex formation is also employed in the separation of cobalt-nickel mixtures. 

Amine extraction. As explained in Sec. S.4, long-chain organic amines act as liquid anion-exchange media for the uranyl sulfate complex anion throu a reversible reaction such as... 

Vdovenko et al. investigated the extraction of Pu(IV) by a rnixture of 7 to 9 carbon primary aliphatic amines dissolved in chloroform. They determined that the extracted complex involves 4 amine molecules, i. e. (RNHg) Pu(SO ), by the amine concentration dependence method, and by direct macroscopic measurements of the stoichiometry of the reaction. From comparisons of the adsorption spectra in the aqueous and organic phases, they conclude that the Pu(IV) exists primarily as a neutral sulfate complex in the aqueous phase. Therefore,... 

Extractions from mixtures of HgSO and HNOg proceeded by the formation of the same amine Pu sulfate complex above, but the distribution coefficient decreased with increasing HNOg concentration because of the formation of amine nitrate complex. This effect is illustrated by the data in Table IV-19. 

The macrocyclic Schiff base L37 contains an hexyl linker between the two amine groups. In anion transport experiments, the corresponding metal complexes of L37 are found to successfully extract sulfate anion from aqueous solution to organic solvents. In the case of the copper complex of receptor L37, it was found that more than... 

Because of the anion complexation observed in the solid state, it was proposed that cyclo[8]pyrrole could function as an anion extractant, specifically for sulfate. Sulfate receptors that can act as extractants of this ion are highly desirable because sulfate is a problematic species in the vitrification process that is proposed for the disposal of certain radioactive wastes. The original reported short-chained forms of cyclo[8]pyrrole presented solubility issues, but a newer derivative, octamethyl-octaundecylcyclo[8]pyrrole, 2b, originally developed as a precursor for liquid crystals, proved to be amenable to extraction studies. It was found that 2b was able to selectively extract sulfate in the presence of high levels of nitrate. This cyclo[8]pyrrole was thus able to overcome the so-called Hofmeister bias or the inherent propensity for nitrate to partition before sulfate. While the kinetics are slow—reducing utility in the context of near-term applications—this is the first example where this level of selectivity is seen in a sulfate versus nitrate extraction experiment. ... 

Mobile phase M, = toluene-chloroform (50 1) A/j = benzene-methyl isopropylketone (50 1) Mi = methanol-water-acetic acid (50 30 4). Conditions Ascending technique, run 15 cm. layer thickness 0.25 mm, activation at 120°C for 30 min. Detection (a) metal dithizonates were self detected, (b) 5% aqueous copper sulfate solution for metal diethyidithiocarbamates and (c) 0.25% PAN [l-(2-pyridylazo)-2-naphthol solution) in methanol followed by exposure to ammonia vapors for metal ions. Remarks (1) Best separations on RP-18 with My (2) The extracts of complexes of metals originating from biological samples require careful protection from environmental contamination and (3) The developed TLC method was applied for analysing human placentas collected from patients of the obstetrics Clinic in Tychi (Poland) for Pb. Cd, Zn, Cu, Ni, Mn. and Co content. 

The concentration of aqueous solutions of SDS were analyzed using a methylene blue colorimetric procedure (5). This method involves the measurement of the extinction of a strongly colored methylene blue-dodecyl sulfate complex extracted from the test solution with chloroform. The absorbance of the solution was determined using a Beckman DU Spectrophotometer at a wavelength of 654 my. 

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... 

Carrageenan. The term carrageenan [19000-07-1] is the generic description for a complex mixture of sulfated polysaccharides that are extracted from certain genera and species of the class Fhodophjceae red seaweed. 

The typical SEA process uses a manganese catalyst with a potassium promoter (for solubilization) in a batch reactor. A manganese catalyst increases the relative rate of attack on carbonyl intermediates. Low conversions are followed by recovery and recycle of complex intermediate streams. Acid recovery and purification involve extraction with caustic and heat treatment to further decrease small amounts of impurities (particularly carbonyls). The fatty acids are recovered by freeing with sulfuric acid and, hence, sodium sulfate is a by-product. 

After sulfuric acid work-up (accompanied by the formation of sodium sulfate), the resorcinol is extracted and isolated in a 94% yield based on y -benzenedisulfonic acid [98-48-6]. In addition to the technical complexity that goes along with the manipulation of soHds at high temperature, this process produces large amounts of salts (sulfite and sulfate salts) which economically as well as environmentally are not always desired. 

The discovery of aqua regia by the Arab alchemist Jabir Ibn Hayyan (ad 720—813) provided a new extraction technology. Amalgamation of silver in ores with mercury was extensively used during the late fifteenth century by the Spaniards in Mexico and BoLvia. In 1861 the complex ores of the Comstock Lode, Nevada, were ground together with mercury, salt, copper sulfate, and sulfuric acid, and then steam-heated to recover the silver. 

Several solvent uses have been proposed. Dimethyl sulfate has been used as a solvent for the study of Lewis acid—aromatic hydrocarbon complexes (148). It also is effective as an extraction solvent to separate phosphoms haUde—hydrocarbon mixtures and aromatic hydrocarbons from aUphatics, and it acts as an electrolyte in electroplating iron (149—152). The toxicity of dimethyl sulfate precludes its use as a general-purpose solvent. 

---