Ion, precipitate and adsorbing colloid flotations of zinc(II) from dilute aqueous solutions have been investigated over a wide pH range using the anionic surfactant Aerosol OT or the cationic collector cetyl pyridinium chloride. In case of adsorbing colloid flotation (ACF) iron oxyhydroxide and aluminium hydroxide were used, either separately or together, as coprecipitants. The precipitate flotation curves were compared with the corresponding theoretical one calculated from the data published for Zn(II) hydrolysis. In addition to the effect of pH on the percent removal the effects of collector concentration, ionic strength, bubbling time and metal ion concentration were investigated and the optimum conditions were established. High removals could be achieved especially with ACF. The results obtained are discussed with respect to the chemical state of zinc, the ionization behaviour of the collectors and properties of the coprecipitants. The developed ACF process was applied to the removal of65Zn from radioactive process wastewater.
The removal of134Cs and60Co from radioactive process waste water using cetyl pyridinium chloride (CPC) as a collector and cobalt(II) hexacyanoferrate(II) as a precipitant for60Co and sorbent (ion exchanger) for134Cs was intensively investigated and the best removal conditions could be established. The results indicate that under the optimum conditions removals higher than 96% and 97% could be achieved for Co(II) and Cs(I), respectively. Cobalt(II) hexacyanoferrate(II) was found to have high affinity for cesium and can preferentially remove it in presence of relatively high amounts of other alkali or alkaline earth cations. A two-stage flotation process was successfully tested for the removal of both Cs(I) and Co(II) from waters containing both cations.
The liquid-liquid extraction and precipitate flotation of the second kind (i.e., without the use of surfactant collectors) have been investigated for Co(II) using 8-hydroxy quinoline (Hq) and the results are compared. Organic solvents used were chloroform in the case of liquid-liquid extraction and ethanol (used as a solvent for the collector and as a frother) in the case of flotation. From the results it appears that liquid-liquid extraction occurs through the formation of the adduct Coq2(Hq) but flotation takes place through the formation of the precipitate Coq2. Unlike precipitate flotation of the first kind, precipitate flotation of the second kind has the advantage that the recovery is not affected by the ionic strength of the medium. An induction time of about 5 minutes is required to attain the maximum flotation results. The effects of pH and Hq concentration on both of the extraction processes were also investigated and the results are discussed.
Synergistic extraction of Co(II) with 8-hydroxyquinoline (Hq)/decanoic acid [(HR)2] solution mixtures in benzene and chloroform was carried out at 25°C. The aqueous ionic strength and the total concentration of cobalt(II) were 0.1 (NaCl) and 1·10–5–1·10–3M, respectively. The synergistic effect is interpreted by the formation of the mixed ligand ion-pair complexes: [(Coq(Hq)2(HR))+, R–] and [(Coq(Hq)2(HR)3)+, R–] in benzene and chloroform, respectively.
A method is presented for the spectrophotometric determination of uranium in natural waters after a preconcentration step involving percolation of a suitable aliquot of the water sample whose pH is adjusted to 6.0–6.5 through a TBP-plasticized dibenzoylmethane-loaded polyurethane foam bed. Uranium on the foam is eluted with 0.6M HCl solution and then determined spectrophotometrically using arsenazo III as a chromogenic reagent.
The extraction of uranium(VI) from an aqueous HNO3 phase into an organic phase consisting of a polyurethane foam immobilizing a solution of di(2-ethylhexyl)phosphoric acid (HDEHP) in o-dichlorobenzene has been investigated at varying concentrations of nitric acid and HDEHP. The mechanism of the extraction is discussed on the basis of the results obtained. The aggregation number of HDEHP immobilized on the foam was obtained from the analysis of data obtained for the extraction of cerium(III) from acidic perchlorate solutions of constant ionic strength.
The partition of cerium(III) between aqueous acid perchlorate solutions and polyurethane foams loaded with solutions of di-(2-ethylhexyl)phosphoric acid (HDEHP) in nitrobenzene has been investigated and the apparent polymerization number of HDEHP on the foam has been determined. The mechanism of extraction is discussed in the light of the results. It has been found that Ce(III) is generally extracted on the foam by a cation exchange mechanism.
The extraction of cerium(III) from weakly acidic chloride solutions by HDEHP-nitrobenzene-loaded polyurethane foams could be analyzed quantitatively in terms of the equation: log(9.056 Dc)=log Kc+2.14 log (Cd–6Cc)+3 pH+log fc where Dc is the distribution ratio of cerium(III) between the foam and aqueous phases, Cd and Cc are the total HDEHP and Ce(III) concentrations on the foam, respectively, log fc=[Ce3+](sq)/[Ce(III)](aq), and Kc is the equilibrium constant of the equation: Ce
. Values of Kc under the different extraction conditions tested are given.
The effect of added TBP on the extraction of uranium(VI) with a solution of di-(2-ethylhexyl)-phosphoric acid (HDEHP) in o-dichlorobenzene from nitric acid solutions has been investigated at varying concentrations of nitric acid, HDEHP, TBP and uranium(VI). The mechanism of the synergistic effect of TBP is discussed on the basis of the results and can be summarized in the following equation: UO
where HX denotes HDEHP and the HDEHP loaded on the foam is trimerized.
The liquid-liquid extraction, ion and precipitate flotation of Co(II) from chloride media of 1·10–4M initial Co(II) concentration and =0.1 have been investigated using decanoic acid and the results are compared. Organic solvents used were chloroform in the case of liquid-liquid extraction and ethanol (used as a solvent for the collector and a frother) in the case of flotation. From the results it appears that liquid-liquid extraction takes place through the formation of the complex: (CoR2)2(HR)2 but flotation occurs through the formation of a surface active product which has the empirical formula CoR2. The effects of pH and of decanoic acid concentration on the three separation processes were also investigated and the results discussed. Good agreement was observed between the experimental precipitate flotation curves and the theoretical curve calculated from the data published for Co(II) hydrolysis.