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ammonium carbonate solutions using Acorga M5640 in Iberfluid
Hydrometallurgy 50 Ž1998. 143–151
Extraction of nickel from ammoniacalrammonium carbonate solutions using Acorga M5640 in Iberfluid F.J. Alguacil ) , A. Cobo (CSIC), AÕda. Gregorio del Amo 8, Ciudad UniÕersitaria, Centro Nacional de InÕestigaciones Metalurgicas ´ 28040 Madrid, Spain Received 26 March 1998; revised 21 July 1998; accepted 21 July 1998
Abstract Acorga M5640 diluted in Iberfluid was used to extract nickel from ammoniacalrammonium carbonate solutions. The influence of equilibration time, extractant concentration, equilibrium pH and ammonium carbonate concentration on nickel extraction has been studied. The extent of nickel extraction decreases at equilibrium pH values above 10, whereas the variation of the ammonium carbonate concentration in the range 0–100 grl only slightly influences the percentage of metal extraction. The loading capacity of a solution of 2.5% vrv Acorga M5640 was determined to be 1.3 grl Ni at pH 9.5, whereas in the case of 10% vrv extractant the loading increases to 5.2 grl metal. For a solution which contained 1 grl nickel and 50 grl ammonium carbonate ŽpH 9.5. conditions were established for nickel extraction, selective ammonia stripping and nickel stripping. The percentage of metal extraction and stripping exceeding 99%. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Nickel; Acorga M5640; Ammoniacalrammonium carbonate solutions
1. Introduction The processing of laterites by hydrometallurgical techniques involved an ammoniacal leaching step to bring nickel into solution as its ammine complexes w1–4x. The presence of other metals in the solution leads to solvent extraction as a technique to extract and separate nickel from these ammoniacal solutions. Various extractants have been studied in this role w5–11x. )
Corresponding author
0304-386Xr98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 3 8 6 X Ž 9 8 . 0 0 0 4 7 - 4
144
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
No data are available in the literature about the use of Acorga M5640 in the extraction of nickel from ammoniacal aqueous media. Thus the performance of this extractant for nickel extraction from ammoniacalrammonium carbonate media and stripping was investigated. 1.1. Experimental Acorga M5640 Žnow marketed by Zeneca. was obtained from ICI Chem.; it was used as received from the manufacturer, diluting to the desired concentration in Iberfluid organic diluent. The extractant is derived from Acorga P50, thus its active compound is the 2-hydroxy-5-nonylbenzaldehyde oxime and according to the literature a fatty ester is also added, as modifier, to the reagent w12x. Iberfluid, obtained from Calvo Sotelo ŽSpain., has the specifications: boiling range 210–2848C, flash point 968C, aromatics - 2%, density Ž208C. 785 kgrm3. All other chemicals used in this work were of AR grade. Extraction and stripping experiments were carried out in separatory funnels thermostatted at the required temperature and mechanically shaken. Nickel was analyzed by AAS, whereas the ammonia concentration was estimated by the Indophenol procedure w13x.
2. Results and discussion 2.1. Kinetics of nickel extraction The effect of equilibrium time on nickel extraction was studied using an aqueous phase ŽpH 9.5. containing 1 grl nickel and 50 grl ammonium carbonate and organic solutions of 5% and 1% vrv Acorga M5640 in Iberfluid. Temperature was 208C and experiments were carried out at a 1:1 phase ratio for various periods of time, 2.5 to 60 min. Fig. 1 shows that equilibrium was attained in near 5 min for the experimental conditions quoted. The kinetics seems to be slower with respect to those obtained using LIX 64 N Žnear 1 min. but of the same order as that of LIX 87QN. 2.2. Effect of pH The variation in nickel extraction with aqueous pH was studied at a fixed ammonium carbonate concentration of 50 grl. The initial metal concentration was 1 grl, whereas the organic phase contained 2.5% or 1% vrv Acorga M5640 in Iberfluid. Single-stage experiments were performed at a 1:1 ŽO:A. phase ratio, 208C and 10 min of contact time. The results obtained are shown in Fig. 2. As can be observed from this figure, nickel extraction remained constant up to equilibrium pH of near 10 and then decreased. This decrease can be explained by the formation at these pH values of higher . coordination number complexes ŽNiŽNH 3 . 2q n , n s 6 , which inhibit the extraction of nickel by the oxime.
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
Fig. 1. The kinetics of nickel extraction.
Fig. 2. The influence of pH on nickel extraction.
145
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
146
In an aqueous solution which contained metal and ammonium ions at a pH value where free ammonia is produced, the above metal–ammine complexes should be formed and
ž
E log D Me pH
/
NH q 4
s n y m aver
Ž 1.
where D is the corresponding metal distribution coefficient, n is the number of protons Žor oxime molecules. involved in the metal extraction equilibrium Žin the present case 2. and m aver is the average coordination number of the metal by ammonia in the aqueous solution, thus a plot of log D Me Žor percent extraction. vs. pH decreases at higher pH values due to the increase in the average number of ammonia ligands complexing the metal ion at these pH values w14,15x. The shape of the curve ŽFig. 2. is very similar to that obtained using other suitable nickel extractants from ammoniacal media w5,10,11,14x. 2.3. Effect of ammonium carbonate The influence of ammonium carbonate concentration on nickel extraction was studied by varying its concentration between 0 and 100 grl. Initial nickel concentration in the aqueous feed was 1 grl at a pH of 9.5, the organic solution contained 1% vrv Acorga M5640 and experiments were carried out at 208C, 10 min of contact time at O:A phase ratio of 1. Table 1 shows the results obtained: the increase of ammonium carbonate concentration in the initial aqueous phase only slightly decreases the percentage of nickel extraction using Acorga M5640 diluted in Iberfluid. 2.4. Loading capacity The loading capacity of Acorga M5640 was determined by two procedures. In the first procedure, 25 ml of the organic solution containing 2.5% vrv Acorga M5640 was contacted for 10 min and 208C with fresh volumes of the aqueous solution containing 1 grl Ni, 50 grl ammonium carbonate ŽpH 9.5. when the phase ratio O:A was 1. In this case, a maximum loading of 1.3 grl was reached after two extraction stages. The second procedure was carried out by contacting 10% vrv of the extractant with various organic:aqueous phase ratios of 2:1, 1.33:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6 and 1:10, other experimental conditions were the same as described above. The results show that a maximum loading of near 5.2 grl was obtained at a phase ratio of 1:6.
Table 1 The effect of ammonium carbonate concentration on nickel extraction Ammonium carbonate, grl
% Ni extraction
– 25 50 75 100
50.0 49.5 47.3 46.5 45.3
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
147
These loadings compare well and are of the same magnitude as that encountered using LIX 87QN, e.g., 10% vrv Acorga M5640: 5.2 grl Ni at pH 9.5, 10% vrv LIX 87QN: 4.3 grl Ni at pH 9.6 w10x. 2.5. Extraction isotherm Having established the possibility of extracting nickel with Acorga M5640 in Iberfluid, further studies were carried out to optimise conditions for the extraction of this metal and the stripping of nickel from loaded organic solutions. The extraction isotherm was obtained by contacting an aqueous solution of 1 grl Ni, 50 grl ammonium carbonate ŽpH 9.5. and an organic phase of 10% vrv Acorga M5640. The results, shown in Fig. 3, indicate that almost near complete nickel extraction is possible in two counter-current stages at the A:O ratio of 5, the raffinate should contain less than 0.01 grl nickel. This showed the extremely high efficiency of the present extraction system. It is well known from literature that oxime extractants pick up some ammonia when operated in ammoniacal aqueous systems w10,16,17x. The ammonia content of the loaded organic Ž10% vrv Acorga M5640. was estimated to be near 0.1 grl. The value is not high but needs to be eliminated prior to nickel stripping. 2.6. SelectiÕe ammonia stripping The loaded Acorga phase containing 4.95 grl nickel and 0.1 grl ammonia was equilibrated at an O:A phase ratio of 1 with aqueous solutions of various pH values
Fig. 3. Nickel equilibrium loading isotherm.
148
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
Table 2 Selective ammonia stripping Initial pH
Equilibrium pH
%NH 3 stripping
%Ni stripping
4 3 2.75 2.5
9.2 8.1 6.4 3.3
28.3 83.3 100 100
– 0.004 0.2 1.3
Žadjusted with H 2 SO4 . at 208C and 10 min. The results obtained are shown in Table 2, and indicated the possibility of the selective ammonia stripping in a single stage at an equilibrium pH value of around 6.5; there is almost negligible loss of nickel from the organic solution. 2.7. Nickel stripping To determine the adequate pH value for nickel stripping, experiments were carried out using a 55 grl Ni Žtypical of spent electrolyte. aqueous solution adjusted to various pH values. The loaded organic solution of 10% vrv Acorga M5640 contained around 4.9 grl Ni and experiments were carried out at 1:1 phase ratio and 208C and 20 min of contact time. Table 3 presents the results obtained from this set of experiments: near complete nickel stripping can be achieved in one stage using an aqueous solution of a pH around 0.5. At pH 1.0 using batchwise conditions three stages are needed for the stripping of nickel from the loaded organic solution. Nickel stripping kinetics have been determined using the loaded organic solution with 4.9 grl of metal and an aqueous phase of pH 1.0 and 55 grl Ni at 1:1 phase ratio and 208C. Fig. 4 indicates that nickel stripping equilibrium is achieved within 20 min of contact. Fig. 5 shows the nickel stripping isotherm obtained at 208C and 20 min of equilibration time using a loaded organic solution with 4.9 grl Ni Ž10% vrv Acorga M5640. and an aqueous phase of pH 1.0; various O:A phase ratios were used. According to the data obtained, it is possible to achieve almost quantitative nickel stripping in two counter-current stages at an O:A ratio of 1.75; in these conditions the stripped organic solution contained less than 0.01 grl Ni, whereas the pregnant electrolyte solution should contain 57.8 grl of metal Žthus it was enriched with 2.8 grl Ni..
Table 3 Nickel stripping Initial pH
%Ni stripped
1.5 1.0
26.9 59.2 Ž1st stage. 36.7 Ž2nd stage. 3.9 Ž3rd stage. 99.8
0.5
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
Fig. 4. The kinetics of nickel stripping.
Fig. 5. Nickel stripping isotherm.
149
150
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
3. Conclusions The oxime Acorga M5640 has been used to study the conditions for the extraction of nickel from ammoniacalrammonium carbonate aqueous media. The influence of pH on the percentage of nickel extraction only seems important above pH 10 Ždecreasing metal extraction. whereas in the range of pH values 8–10, there is no important variation in the percentage of nickel loading in the organic solution. The presence of ammonium carbonate Ž0–100 grl. in the aqueous solution has negligible influence on nickel extraction. The loading capacity of Acorga M5640 was found to be 5.2 grl Ni Ž10% vrv extractant. or 1.3 grl Ž2.5% vrv.. For a solution of 1 grl Ni, 50 grl ammonium carbonate at pH 9.5 it is possible to obtain almost complete nickel extraction in two stages at an A:O phase ratio of 5:1; the organic phase also picks up some ammonia which needs to be eliminated prior to nickel stripping. Selective ammonia stripping can be performed at an equilibrium pH of near 6.5 at an O:A ratio of 1. From the ammonia-free loaded organic solution, nickel stripping is carried out using a solution of pH 1.0 at an O:A ratio of 1.75.
Acknowledgements To the CSIC ŽSpain. for support to carry out this work. To Mr. Lopez and Mr. ´ Bascones for assistance in part of the experimental work.
References w1x J.E. De Graff, The treatment of lateritic nickel ores, a further study of the Caron process and other possible improvements: Part I. Effect of reduction conditions, Hydrometallurgy 5 Ž1980. 47–65. w2x J.E. De Graff, The treatment of lateritic nickel ores, a further study of the Caron process and other possible improvements: Part II. Leaching conditions, Hydrometallurgy 5 Ž1980. 255–271. w3x S. Anand, S.C. Das, R.P. Das, P.K. Jena, Leaching of manganese nodules in ammoniacal medium using glucose as reductant, Hydrometallurgy 16 Ž1986. 335–344. w4x C.K. Gupta, T.K. Mukherjee, Hydrometallurgy in Extraction Processes, Vol. I. CRC Press, Boca Raton, FL, 1990, pp. 142–149. w5x S. Przeszlakowski, H. Wydra, Extraction of nickel, cobalt and other metals wCu, Zn FeŽIII.x with a commercial b-diketone extractant, Hydrometallurgy 8 Ž1982. 49–64. w6x G.M. Ritcey, in: T.C. Lo, M.H.I. Baird, C. Hanson ŽEds.., Handbook of Solvent Extraction, Wiley, New York, 1983, pp. 673–687. w7x W.C. Cooper, Y.F. Mak, Solvent Extr. Ion Exch. 2 Ž7r8. Ž1984. 959–984. w8x M. Cox, in: J. Rydberg, C. Musikas, G.R. Choppin ŽEds.., Principles and Practices of Solvent Extraction, Marcel Dekker, New York, 1992, pp. 357–412. w9x M.J. Price, J.G. Reid, in: D.H. Logsdail, M.J. Slater ŽEds.., Solvent Extraction in the Process Industries, Vol. 1. Elsevier, London, 1993, pp. 159–166. w10x P.V.R. Bhaskara Sarma, K.C. Nathsarma, Extraction of nickel from ammoniacal solutions using LIX 87QN, Hydrometallurgy 42 Ž1996. 83–91. w11x F.J. Alguacil, A. Cobo, Solvent extraction equilibrium of nickel with LIX 54, Hydrometallurgy 48 Ž1998. 291–299. w12x J. Szymanowski, Hydroxyoximes and Copper Hydrometallurgy, CRC Press, Boca Raton, FL, 1993, p. 25.
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
151
w13x Z. Marczenko, Spectrophotometric Determination of Elements, Ellis Horwood, Chichester, 1976, pp. 392–393. w14x N.M. Rice, M. Nedved, G.M. Ritcey, The extraction of nickel from ammoniacal media and its separation from copper, cobalt and zinc using hydroxyoxime extractants: I. SME-529, Hydrometallurgy 3 Ž1978. 35–54. w15x K.S. Rao, P.V.R.B. Sarma, P.K. Jena, Erzmetall 43 Ž1990. 366–369. w16x D.S. Flett, J. Melling, Extraction of ammonia by commercial copper chelating extractants, Hydrometallurgy 4 Ž1979. 135–146. w17x F.J. Alguacil, A. Cobo, Sep. Sci. Technol., Ž1998. in press.
Extraction of nickel from ammoniacalrammonium carbonate solutions using Acorga M5640 in Iberfluid F.J. Alguacil ) , A. Cobo (CSIC), AÕda. Gregorio del Amo 8, Ciudad UniÕersitaria, Centro Nacional de InÕestigaciones Metalurgicas ´ 28040 Madrid, Spain Received 26 March 1998; revised 21 July 1998; accepted 21 July 1998
Abstract Acorga M5640 diluted in Iberfluid was used to extract nickel from ammoniacalrammonium carbonate solutions. The influence of equilibration time, extractant concentration, equilibrium pH and ammonium carbonate concentration on nickel extraction has been studied. The extent of nickel extraction decreases at equilibrium pH values above 10, whereas the variation of the ammonium carbonate concentration in the range 0–100 grl only slightly influences the percentage of metal extraction. The loading capacity of a solution of 2.5% vrv Acorga M5640 was determined to be 1.3 grl Ni at pH 9.5, whereas in the case of 10% vrv extractant the loading increases to 5.2 grl metal. For a solution which contained 1 grl nickel and 50 grl ammonium carbonate ŽpH 9.5. conditions were established for nickel extraction, selective ammonia stripping and nickel stripping. The percentage of metal extraction and stripping exceeding 99%. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Nickel; Acorga M5640; Ammoniacalrammonium carbonate solutions
1. Introduction The processing of laterites by hydrometallurgical techniques involved an ammoniacal leaching step to bring nickel into solution as its ammine complexes w1–4x. The presence of other metals in the solution leads to solvent extraction as a technique to extract and separate nickel from these ammoniacal solutions. Various extractants have been studied in this role w5–11x. )
Corresponding author
0304-386Xr98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 4 - 3 8 6 X Ž 9 8 . 0 0 0 4 7 - 4
144
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
No data are available in the literature about the use of Acorga M5640 in the extraction of nickel from ammoniacal aqueous media. Thus the performance of this extractant for nickel extraction from ammoniacalrammonium carbonate media and stripping was investigated. 1.1. Experimental Acorga M5640 Žnow marketed by Zeneca. was obtained from ICI Chem.; it was used as received from the manufacturer, diluting to the desired concentration in Iberfluid organic diluent. The extractant is derived from Acorga P50, thus its active compound is the 2-hydroxy-5-nonylbenzaldehyde oxime and according to the literature a fatty ester is also added, as modifier, to the reagent w12x. Iberfluid, obtained from Calvo Sotelo ŽSpain., has the specifications: boiling range 210–2848C, flash point 968C, aromatics - 2%, density Ž208C. 785 kgrm3. All other chemicals used in this work were of AR grade. Extraction and stripping experiments were carried out in separatory funnels thermostatted at the required temperature and mechanically shaken. Nickel was analyzed by AAS, whereas the ammonia concentration was estimated by the Indophenol procedure w13x.
2. Results and discussion 2.1. Kinetics of nickel extraction The effect of equilibrium time on nickel extraction was studied using an aqueous phase ŽpH 9.5. containing 1 grl nickel and 50 grl ammonium carbonate and organic solutions of 5% and 1% vrv Acorga M5640 in Iberfluid. Temperature was 208C and experiments were carried out at a 1:1 phase ratio for various periods of time, 2.5 to 60 min. Fig. 1 shows that equilibrium was attained in near 5 min for the experimental conditions quoted. The kinetics seems to be slower with respect to those obtained using LIX 64 N Žnear 1 min. but of the same order as that of LIX 87QN. 2.2. Effect of pH The variation in nickel extraction with aqueous pH was studied at a fixed ammonium carbonate concentration of 50 grl. The initial metal concentration was 1 grl, whereas the organic phase contained 2.5% or 1% vrv Acorga M5640 in Iberfluid. Single-stage experiments were performed at a 1:1 ŽO:A. phase ratio, 208C and 10 min of contact time. The results obtained are shown in Fig. 2. As can be observed from this figure, nickel extraction remained constant up to equilibrium pH of near 10 and then decreased. This decrease can be explained by the formation at these pH values of higher . coordination number complexes ŽNiŽNH 3 . 2q n , n s 6 , which inhibit the extraction of nickel by the oxime.
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
Fig. 1. The kinetics of nickel extraction.
Fig. 2. The influence of pH on nickel extraction.
145
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
146
In an aqueous solution which contained metal and ammonium ions at a pH value where free ammonia is produced, the above metal–ammine complexes should be formed and
ž
E log D Me pH
/
NH q 4
s n y m aver
Ž 1.
where D is the corresponding metal distribution coefficient, n is the number of protons Žor oxime molecules. involved in the metal extraction equilibrium Žin the present case 2. and m aver is the average coordination number of the metal by ammonia in the aqueous solution, thus a plot of log D Me Žor percent extraction. vs. pH decreases at higher pH values due to the increase in the average number of ammonia ligands complexing the metal ion at these pH values w14,15x. The shape of the curve ŽFig. 2. is very similar to that obtained using other suitable nickel extractants from ammoniacal media w5,10,11,14x. 2.3. Effect of ammonium carbonate The influence of ammonium carbonate concentration on nickel extraction was studied by varying its concentration between 0 and 100 grl. Initial nickel concentration in the aqueous feed was 1 grl at a pH of 9.5, the organic solution contained 1% vrv Acorga M5640 and experiments were carried out at 208C, 10 min of contact time at O:A phase ratio of 1. Table 1 shows the results obtained: the increase of ammonium carbonate concentration in the initial aqueous phase only slightly decreases the percentage of nickel extraction using Acorga M5640 diluted in Iberfluid. 2.4. Loading capacity The loading capacity of Acorga M5640 was determined by two procedures. In the first procedure, 25 ml of the organic solution containing 2.5% vrv Acorga M5640 was contacted for 10 min and 208C with fresh volumes of the aqueous solution containing 1 grl Ni, 50 grl ammonium carbonate ŽpH 9.5. when the phase ratio O:A was 1. In this case, a maximum loading of 1.3 grl was reached after two extraction stages. The second procedure was carried out by contacting 10% vrv of the extractant with various organic:aqueous phase ratios of 2:1, 1.33:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6 and 1:10, other experimental conditions were the same as described above. The results show that a maximum loading of near 5.2 grl was obtained at a phase ratio of 1:6.
Table 1 The effect of ammonium carbonate concentration on nickel extraction Ammonium carbonate, grl
% Ni extraction
– 25 50 75 100
50.0 49.5 47.3 46.5 45.3
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
147
These loadings compare well and are of the same magnitude as that encountered using LIX 87QN, e.g., 10% vrv Acorga M5640: 5.2 grl Ni at pH 9.5, 10% vrv LIX 87QN: 4.3 grl Ni at pH 9.6 w10x. 2.5. Extraction isotherm Having established the possibility of extracting nickel with Acorga M5640 in Iberfluid, further studies were carried out to optimise conditions for the extraction of this metal and the stripping of nickel from loaded organic solutions. The extraction isotherm was obtained by contacting an aqueous solution of 1 grl Ni, 50 grl ammonium carbonate ŽpH 9.5. and an organic phase of 10% vrv Acorga M5640. The results, shown in Fig. 3, indicate that almost near complete nickel extraction is possible in two counter-current stages at the A:O ratio of 5, the raffinate should contain less than 0.01 grl nickel. This showed the extremely high efficiency of the present extraction system. It is well known from literature that oxime extractants pick up some ammonia when operated in ammoniacal aqueous systems w10,16,17x. The ammonia content of the loaded organic Ž10% vrv Acorga M5640. was estimated to be near 0.1 grl. The value is not high but needs to be eliminated prior to nickel stripping. 2.6. SelectiÕe ammonia stripping The loaded Acorga phase containing 4.95 grl nickel and 0.1 grl ammonia was equilibrated at an O:A phase ratio of 1 with aqueous solutions of various pH values
Fig. 3. Nickel equilibrium loading isotherm.
148
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
Table 2 Selective ammonia stripping Initial pH
Equilibrium pH
%NH 3 stripping
%Ni stripping
4 3 2.75 2.5
9.2 8.1 6.4 3.3
28.3 83.3 100 100
– 0.004 0.2 1.3
Žadjusted with H 2 SO4 . at 208C and 10 min. The results obtained are shown in Table 2, and indicated the possibility of the selective ammonia stripping in a single stage at an equilibrium pH value of around 6.5; there is almost negligible loss of nickel from the organic solution. 2.7. Nickel stripping To determine the adequate pH value for nickel stripping, experiments were carried out using a 55 grl Ni Žtypical of spent electrolyte. aqueous solution adjusted to various pH values. The loaded organic solution of 10% vrv Acorga M5640 contained around 4.9 grl Ni and experiments were carried out at 1:1 phase ratio and 208C and 20 min of contact time. Table 3 presents the results obtained from this set of experiments: near complete nickel stripping can be achieved in one stage using an aqueous solution of a pH around 0.5. At pH 1.0 using batchwise conditions three stages are needed for the stripping of nickel from the loaded organic solution. Nickel stripping kinetics have been determined using the loaded organic solution with 4.9 grl of metal and an aqueous phase of pH 1.0 and 55 grl Ni at 1:1 phase ratio and 208C. Fig. 4 indicates that nickel stripping equilibrium is achieved within 20 min of contact. Fig. 5 shows the nickel stripping isotherm obtained at 208C and 20 min of equilibration time using a loaded organic solution with 4.9 grl Ni Ž10% vrv Acorga M5640. and an aqueous phase of pH 1.0; various O:A phase ratios were used. According to the data obtained, it is possible to achieve almost quantitative nickel stripping in two counter-current stages at an O:A ratio of 1.75; in these conditions the stripped organic solution contained less than 0.01 grl Ni, whereas the pregnant electrolyte solution should contain 57.8 grl of metal Žthus it was enriched with 2.8 grl Ni..
Table 3 Nickel stripping Initial pH
%Ni stripped
1.5 1.0
26.9 59.2 Ž1st stage. 36.7 Ž2nd stage. 3.9 Ž3rd stage. 99.8
0.5
F.J. Alguacil, A. Cobo r Hydrometallurgy 50 (1998) 143–151
Fig. 4. The kinetics of nickel stripping.
Fig. 5. Nickel stripping isotherm.
149
150
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3. Conclusions The oxime Acorga M5640 has been used to study the conditions for the extraction of nickel from ammoniacalrammonium carbonate aqueous media. The influence of pH on the percentage of nickel extraction only seems important above pH 10 Ždecreasing metal extraction. whereas in the range of pH values 8–10, there is no important variation in the percentage of nickel loading in the organic solution. The presence of ammonium carbonate Ž0–100 grl. in the aqueous solution has negligible influence on nickel extraction. The loading capacity of Acorga M5640 was found to be 5.2 grl Ni Ž10% vrv extractant. or 1.3 grl Ž2.5% vrv.. For a solution of 1 grl Ni, 50 grl ammonium carbonate at pH 9.5 it is possible to obtain almost complete nickel extraction in two stages at an A:O phase ratio of 5:1; the organic phase also picks up some ammonia which needs to be eliminated prior to nickel stripping. Selective ammonia stripping can be performed at an equilibrium pH of near 6.5 at an O:A ratio of 1. From the ammonia-free loaded organic solution, nickel stripping is carried out using a solution of pH 1.0 at an O:A ratio of 1.75.
Acknowledgements To the CSIC ŽSpain. for support to carry out this work. To Mr. Lopez and Mr. ´ Bascones for assistance in part of the experimental work.
References w1x J.E. De Graff, The treatment of lateritic nickel ores, a further study of the Caron process and other possible improvements: Part I. Effect of reduction conditions, Hydrometallurgy 5 Ž1980. 47–65. w2x J.E. De Graff, The treatment of lateritic nickel ores, a further study of the Caron process and other possible improvements: Part II. Leaching conditions, Hydrometallurgy 5 Ž1980. 255–271. w3x S. Anand, S.C. Das, R.P. Das, P.K. Jena, Leaching of manganese nodules in ammoniacal medium using glucose as reductant, Hydrometallurgy 16 Ž1986. 335–344. w4x C.K. Gupta, T.K. Mukherjee, Hydrometallurgy in Extraction Processes, Vol. I. CRC Press, Boca Raton, FL, 1990, pp. 142–149. w5x S. Przeszlakowski, H. Wydra, Extraction of nickel, cobalt and other metals wCu, Zn FeŽIII.x with a commercial b-diketone extractant, Hydrometallurgy 8 Ž1982. 49–64. w6x G.M. Ritcey, in: T.C. Lo, M.H.I. Baird, C. Hanson ŽEds.., Handbook of Solvent Extraction, Wiley, New York, 1983, pp. 673–687. w7x W.C. Cooper, Y.F. Mak, Solvent Extr. Ion Exch. 2 Ž7r8. Ž1984. 959–984. w8x M. Cox, in: J. Rydberg, C. Musikas, G.R. Choppin ŽEds.., Principles and Practices of Solvent Extraction, Marcel Dekker, New York, 1992, pp. 357–412. w9x M.J. Price, J.G. Reid, in: D.H. Logsdail, M.J. Slater ŽEds.., Solvent Extraction in the Process Industries, Vol. 1. Elsevier, London, 1993, pp. 159–166. w10x P.V.R. Bhaskara Sarma, K.C. Nathsarma, Extraction of nickel from ammoniacal solutions using LIX 87QN, Hydrometallurgy 42 Ž1996. 83–91. w11x F.J. Alguacil, A. Cobo, Solvent extraction equilibrium of nickel with LIX 54, Hydrometallurgy 48 Ž1998. 291–299. w12x J. Szymanowski, Hydroxyoximes and Copper Hydrometallurgy, CRC Press, Boca Raton, FL, 1993, p. 25.
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