K.C. Nathsarma

Separation and recovery of cobalt(II) and nickel(II) from sulphate solutions using sodium salts of D2EHPA, PC 88A and Cyanex 272

Abstract Separation and recovery of divalent cobalt and nickel ions from sulphate solutions containing 0.01 M metal ions each and 0.1 M Na 2 SO 4 have been carried out using 0.03, 0.05 and 0.06 M sodium salts of D2EHPA, PC 88A and Cyanex 272 in kerosene. The percentage extraction of metal ions increased with increasing equilibrium pH. Cobalt was preferentially extracted over nickel with the extractants; however, 0.05 M NaPC 88A and NaCyanex 272 were found to be suitable for the separation study. The highest separation factor was achieved with 0.05 M NaCyanex 272 at equilibrium pH 6.85. Recovery of cobalt from cobalt–nickel bearing solution was achieved with 0.05 M Cyanex 272 and PC 88A at equal phase ratio followed by their stripping with 0.02 M H 2 SO 4 at O:A ratio of 2:1. Nickel was extracted from the cobalt-free raffinate in two stages at equal phase ratio with PC 88A and Cyanex 272 followed by their stripping with 0.02 M H 2 SO 4 at O:A ratio of 4:3 and 2:1, respectively.

Separation of divalent manganese and cobalt ions from sulphate solutions using sodium salts of D2EHPA, PC 88A and Cyanex 272

Abstract The extraction and separation of Mn(II) and Co(II) from sulphate solutions have been carried out using sodium salts of di-(2-ethylhexyl) phosphoric acid (D2EHPA), 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC 88A) and bis-(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) in kerosene. The percentage extraction for the metal ions was increased with increasing equilibrium pH in the case of all the extractants. Manganese was preferentially extracted over cobalt with the extractants and NaD2EHPA was found to be the most suitable extractant for separation, the separation factor being maximum with 0.05 M NaD2EHPA at equilibrium pH 4.45. Manganese and cobalt extractions were carried out at O:A ratio of 9:8 and 1:1, respectively, followed by their strippings at O:A ratio of 2:1 and 4:3 using 0.02 M H 2 SO 4 .

Extraction and separation of Mn(II) and Zn(II) from sulphate solutions by sodium salt of Cyanex 272

Abstract Solvent extraction of divalent zinc and manganese from sulphate solutions was carried out using the sodium salt of Cyanex 272. Extraction of metal ions increased with increasing equilibrium pH and extractant concentration. The extracted species were ZnA 2 · 3HA for zinc and MnA 2 · 3HA for manganese. One mole of hydrogen ion was released for one mole of metal extracted under the experimental conditions used in this work. The zinc and manganese loading capacity of 0.1 M Na-Cyanex 272 was determined. The influence of NaCl, NaNO 3 , Na 2 SO 4 and NaSCN on the extraction of metal ions was studied. The presence of Na 2 SO 4 in solution had a remarkable depressing effect on extraction systems. The separation factor was pH dependent.

Sodium salts of D2EHPA, PC-88A and Cyanex-272 and their mixtures as extractants for cobalt(II)

Abstract Extraction of cobalt(II) from an acidic sulphate solution has been studied using sodium salts of D2EHPA, PC-88A and Cyanex-272 in benzene; the corresponding pH0.5 values are 6.0, 6.25 and 6.6, respectively. The extracted species appear to be CoA2(HA)2. The electronic spectra of the extracted organic phase support the nature of the species extracted. The loading capacity of 0.1 M extractants in benzene has been determined. The influence of NaCl, NaNO3, Na2SO4 and NaSCN on the extraction systems has been investigated. Synergism has been observed with the binary mixture of all the three extractants used. Of the three extractants, sodium salt of Cyanex-272 has been found to be the best synergist and sodium salt of D2EHPA the least.

Processing of nickel- and cobalt-containing leach liquors obtained from different raw materials

Abstract Acidic as well as ammoniacal leach liquors obtained from three different raw materials, namely, lateritic nickel ores, copper converter slag and Indian Ocean manganese nodules, were treated for removal of impurities and separation of copper, nickel and cobalt. Precipitation and solvent extraction techniques were used for these purposes. Iron and silica impurities from acidic solutions were removed by lime precipitation. In ammoniacal medium, iron was coprecipitated with manganese. Manganese was removed as manganese dioxide by oxidative precipitation from both media; this removal also results in some loss of cobalt due to its adsorption on the manganese dioxide matrix. From sulphate solutions, copper was extracted using LIX 64N ® ∗ followed by nickel-cobalt coextraction using di-2-ethylhexylphosphoric acid (D2EHPA). From the loaded solvent, nickel and cobalt were separated by the crowding technique. From ammoniacal solution, both copper and nickel were coextracted with LIX 64N and separated by selective stripping from the loaded organic phase. Cobalt was recovered either by sulphide precipitation or by adsorption on lignite followed by desorption with sulphuric acid/spent electrolyte.

Extraction of nickel from ammoniacal solutions using LIX 87QN

Abstract Extraction of nickel from ammoniacal-ammonium carbonate solutions using LIX 87QN as the extractant has been studied in detail. The effects of pH (ammonia concentration) and ammonium carbonate concentration on nickel extraction were studied using an aqueous solution containing 5.577 kg/m 3 of nickel and 10 vol% LIX 87QN diluted with kerosene (distilling between 170 and 240°C). The concentration of nickel in the organic phase decreased from 4.43 to 1.82 kg/m 3 when the equilibrium pH was increased from 8.6 to 10.0. When the ammonium carbonate concentration of the aqueous phase was increased from 45 to 150 kg/m 3 , the concentration of nickel in the organic phase decreased from 4.43 to 3.55 kg/m 3 . The loading capacity of a 10 vol% solvent in kerosene, obtained from an aqueous solution containing 60 kg/m 3 of ammonium carbonate and at an equilibrium pH of 9.95 was found to be 4.24 kg/m 3 . For a solution containing 5.21 kg/m 3 of nickel and 60 kg/m 3 of ammonium carbonate it was found that complete nickel extraction is possible in two counter-current stages at an A:O phase ratio of 2:3. The loaded organic was found to contain 0.15 kg/m 3 of ammonia, which has been selectively stripped by a single-stage scrubbing with dilute sulphuric acid at an equilibrium pH of > 7. There was no loss of nickel during this operation. From the ammonia-free loaded organic, nickel stripping was carried out in two counter-current stages at an A:O ratio of 5:4 with a spent electrolyte of pH 1.55 containing 57 kg/m 3 of nickel, 12 kg/m 3 each of sodium sulphate and boric acid. The stripping efficiency was found to be about 98%.

Separation of iron and manganese from sulphate solutions obtained from indian ocean nodules

Abstract Leach liquors obtained by sulphuric acid pressure leaching of Indian Ocean manganese nodules were treated for iron and manganese separation. This separation was carried out by sequential precipitation. Iron was precipitated by pH adjustment using lime slurry. The separation is 99.5%, with about 6.7% loss of copper and 2% loss of cobalt. From the iron-free solution manganese was precipitated as manganese dioxide in the presence of an oxidising agent, potassium perdisulphate. Under optimum conditions manganese precipitation is quantitative. There is a loss of about 27% of the cobalt due to adsorption on the manganese dioxide matrix. Kinetics of precipitation and specific reaction rates have been determined. The loss of cobalt by adsorption has been shown by fitting the data to the classical adsorption equation due to Freundlich.

Solvent extraction of zinc, manganese, cobalt and nickel from nickel laterite bacterial leach liquor using sodium salts of TOPS-99 and Cyanex 272

Abstract The extraction and separation of zinc, manganese, cobalt and nickel from nickel laterite bacteria leach liquor were carried out using sodium salts of TOPS-99 and Cyanex 272 in kerosene. The unwanted metal ions were removed by precipitation method and solvent extraction was used to extract/separate Zn, Mn, Co and Ni. The nickel laterite leach liquor which was obtained from bioleaching of chromite overburden samples contained 3.72 g/L Fe, 2.08 g/L Al, 0.44 g/L Ni, 0.02 g/L Co, 0.13 g/L Mn, 0.14 g/L Zn and 0.22 g/L Cr. From this leach liquor, 100% Fe, 96.98% Al and 70.42% Cr were removed by precipitation with CaCO3 at pH 4.4 followed by precipitation of remaining Al and Cr with 50% ammonia at pH 5.4. After precipitation, the extraction of Zn from the Fe, Al and Cr free leach liquor was carried out with 0.1 mol/L TOPS-99 followed by Mn extraction with 0.04 mol/L NaTOPS-99. The yields of Zn and Mn were 97.77% and 95.63%, respectively. After Mn extraction, cobalt was removed from the leach liquor using 0.0125 mol/L NaCyanex 272 and finally nickel extraction was carried out using 0.12 mol/L NaTOPS-99 with 99.84% yield. The stripping of loaded organic (LO) phases were achieved with dilute H2SO4.