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.
The concentration dependence of the kinetics and equilibrium characteristics for the exchange of cesium ions on cobalt hexacyanocobaltate(III) has been studied. It is found that the rate of cesium sorption increases with decreasing cesium concentration in solution. The exchange reaction proceeds via two stages, the first stage is rather fast followed by a much slower one. The equilibrium characteristics of the distribution coefficients for cesium are interpreted in terms of the Langmuir-Hückel isotherm. The heat of sorption and activation energy are determined from the temperature dependence of the exchange reaction.
Two chemical processes involving precipitation of cesium from waste solutions with iron(II)hexacyanocobaltate(III) and triphenylcyanoborate
have been conducted. Various parameters have been investigated such as pH, molar ratio of Fe2+/Co(CN)
, molar ratio of triphenylcyanoborate to cesium and the nature of the simulated wastes. High percentage of cesium removal
from different waste solutions has been achieved by using iron(II)hexacyanocobaltate(III). Precipitation of cesium with triphenylcyanoborate
depends mainly on the concentration of triphenylcyanoborate and cesium as well as the molar ratio in solution. Triphenylcyanoborate
can be used as a selective precipitant for cesium in both acidic and alkaline solution of pH not more than 10.