Ion, precipitate and adsorbing colloid flotation of cobalt(II) have been investigated at different pH values, using N-dodecylpyridinium chloride (DPCl), A strong cationic surfactant, and sodium lauryl sulfate (NaLS), a strong anionic surfactant, as collectors. In case of adsorbing colloid flotation, hydrous manganese dioxide was used as an adsorbent. The precipitate flotation curves experimentally obtained with the two tested collectors were compared with the corresponding theoretical one calculated from the data published for Co(II) hydrolysis. The effects of the collector concentration, ageing of the water-MnO2–Co(II) system, bubbling time period, cobalt(II) concentration and foreign salts on the percent removal of Co(II) by adsorbing colloid flotation using DPCl as collector were determined. Removals approaching 100% could be achieved under the optimum conditions.
As a part of a research program on the treatment of radioactive process waste waters, sorbent macroflotation was tested to remove Co(II) from dilute aqueous solutions. Activated charcoal was used as the sorbent, and gelatin, cetylpyridinium chloride, dodecylamine or N-dodecylpyridinium chloride (NDPC) as the collector. In addition to the effect of the collector type on the percent removal, the effects of the pH, the charcoal and collector doses, the metal ion concentration, the ionic strength and the use of combinations of NDPC with other reagents have been investigated. At the optimum conditions removals better then 97% could be achieved in the pH range of 7.5–10.0 with NDPC plus a low concentration of a low-molecular-weight polyacrylamide. The results obtained are discussed in terms of hydrolysis of the metal ion and the electric state of both the charcoal and collector.
The effect of pH on the removal of Co(II) by kaolinite both in the absence and presence of phosphate, citrate, oxalate and EDTA anions, and cationic and anionic surfactants have been investigated and the results obtained are compared with the precipitate formation curve of Co(II) calculated theoretically from published hydrolysis data of the metal ion. In general, the results indicate that the percent adsoprtion of Co(II) increases with the pH and that kaolinite has little affinity for anionic metal complexes. Both strong cationic and anionic surfactants decrease the percent removal of Co(II) by kaolinite but the reasons are different. On the other hand, the weakly ionized anionic surfactant, potassium stearate, enhances the adsorption of Co(II) by kaolinite. The results are discussed in terms of the hydrolysis of Co(II), the properties of kaolinite, and the possible interaction between the ligands tested and both Co(II) and the clay mineral.
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 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 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 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.
Studies have shown that plots of the log of the distribution ratio versus pH for the distribution of uranium(VI) between non-plasticized and TBP-plasticized dibenzoylmethane-loaded polyurethane foams and dilute aqueous uranium(VI) solutions have a limiting slope of 0.6 at equilibrium pH values 4 and reach a maximum distribution constant at about pH 6.0. The results indicate that the extracted complex is a simple chelate, UO2Me2, where HMe denotes dibenzoylmethane. Plasticization of the foam with TBP has been found to significantly enhance the rate of extraction.
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.