- Email: [email protected]
Chelating ion-exchangers containing n-substituted hydroxylamine functional groups
Ana~~tico Chimica A.&n, 94 (1977) 317-322 OElszvier Scientific Publishing Company, Amsterdam
-Printed
in The Netherhnds
Thesepzr8tion of iron(III), copper(II uranyIfI1) ions from a seriesof salt solutions by chelating ion ex&ange on I3uolite CS-316 resin by pH control is described. Recoveries of t&se &XIS ftom ~0b3it and nickel salt soiutlons were quantitative. Iron may afso be separated from copper by selective sorption with pW control, and uranium from iron and copper by selective desorption with sodium carbonate solution 3s eiuent.
One of the few commercW chelating ion exchange resins available is Duolite XX-346 for which the chef&@ ability is attributed to amidoxime graups. Very fittIe evaluation has been performed on this exchanger. The available data f 13 give a brief description and suggestions that the resin chelates “‘very strongly” with nine elements including copper, iron and waGurn; “strongly” with three elements, and “moderately” with a further siu elements including cobalt and nickel. Stztble complex formation with iron(IIr) is indicated at gW 1.5, with copper(II j at pH 3.0, and with uranyf(fi) at pH 2.0. This exchanger should therefore be capable of separating iron, copper, and uranium from cobalt and nickel at the pH values recommended. In this respect it should behave in a manner similar to the hydroxamie acid exchanger described in Part Df of this series f 21. The possibi!ity of separating iron from copper by selective sorption of iron is also indicated. The separation of uranyt ions from copper or iron by selective sorption is examined, tugether with se&ctive dution of uranium by sodium carbonate sulutiun. Removal of the three ions from solutions of other salts, and their separztions from each other, are also investigated.
Duo&e CS-346, a micrabead chelating 2x1 ex&anger containing the amidoxime _fun&ioti group (Diamond Sfxamrock Ghemicai Co., U,S.A.) was washed with water, then with 1 M hydroc’nloric SC’%to convert it to $he hyd.rogCtnfo’&, and fimdly nith deionized water until the effluent was
318
chlordc!.frt+. The resin was stored swollen state.
in an air-tight
container
in the fully
Jfeial capacities Sodium capacity. This WRS determined by cquilibntion of the resin with 0.25 31 sodium hydrogcncarhonatc? and measurement of the sodium uptake as previously dsscribcd [ 21. Multivaknt metal capacttics. To obtain more fundamental capacity data than have Men rcportcd prc*viously for metal ion solutions containing acetate? buffers, the following proccdurr, though tedious, was adopt& for total capacity determination of a metal ion frum a backinK electrolyte which consisted only of sodium sulphatc. The fully swollen Duolite CS346 resin (0.50 : O.Oi g) was equilibrated for 24 11with I XI sodium sulphatc solution whose pli had been adjusted to the rccluircd value by the addition of sodium hydroxide or sulphuric acid solutions. The pIi of the cquilibrafing solution was adjustrui rwrlarly over the period until it rem&& constant at the sl*icctcd value. This solution was dwantcd from the resin, which was then c~ui1ibmtt-d for 4R h with 1 LI sodium sulphatc! .uAution which was 20 mh! with rcspcct to the- ion under test, and whose pli had been adjust& as de.scrihd prmiously. During the equilibration, the pii was brought back regularly to the initial value by the addition of sodium hydroxide, the ~utlibration continuing for 24 h after the plI became constant. After f&r&ion and washing of the resin with 1 hf sodium sulphatc solution of the silrno pi1 as the final equilibrating solution, the meti wns cluti from the resin by equilibration for 48 h with 2 hl sulphuric acid. For iron(lII), 4 hl sull:huric acid was used. The copper. iron, cobalt, and nickel contents of the eluatcs were dctermin& with a Corning-EEL 240 mark II atomic obsnrption spcc’Lrophotometc!r. Uranium was dctcrmincd calorimetrically by Bhydroxyquinoline in the preu’nce of EDTA (3 J ; acid elution or sodium carbonok clution techniques were employcxl. Watct rcagain and tvuilrbration rate ‘Ihzsc rc*sin properties were dekrmincd as described prc?viously (2, 41. Cabah sulphate. nickel sulphate and copper sulphate (Hopkin and \Villiams, IA.) wen? used. Chlumn scpamttins A &ss column (length 50 cm, i.d. 1 cm) was filled to a height of ca. 30 cm with 15 g of fully swollen Duolitr! CS-346. The column ~3s washed with SO b& volumes of deionized water, and then conditioned with IO hcd volumes of backing electrolyte adjusted to the required pH. The sample snlution was pa,sscd on to the column at a flow rate of 1 to 2 ml min-‘. The co!umn was then wasbc(i with 5 hcd volumes of water, adjusted for pH. The rctiincd metal ions were r~lutccl with 10 bed volumes of 2 hi sulphuric acid (or 4 h! sulphuric acid for iron), and the metal content-s were
319
determined as descri’oed under metal capacities. Iron was separated from copper at pH 1.5; iron and copper were separated from other metals at pH 3.0. For the determination of t.he iron and copper contents of cobalt sulphate and nickel sulphate, 100 g of the salt was dissolved in 500 ml of deionized water and the pH adjusted to 3.0 by the addition of sulphuric acid. solution. The solution was passed through the column at 2-3 ml min-* the column was washed with 10 bed volumes of water, and the iron and copper were eluted with acid as described. For the iron content of copper sulphate, 10 g of the salt was dissolved in 500 ml of deionized water and the pH was adjusted to 1.5 with sulphuric acid before the solution was passed through the column. For tests on the selective sorption of many1 ions over iron and copper at pH 3, resin was equilibrated with solutions containing vsrious amounts of EDTA (disodium salt), which were 5 m&I in each metal ion species. After the washing procedures described, the ions were eluted with 4 M sulphuric acid, and the concentration of each was determined. RESULTS
AND
DISCUSSION
The properties of Duolite CS-346 are given in Table 1, the vanadium capacity of 1.7 mmol g-’ representing the functional group content of the resin. In comparison with a hydroxamic acid resin described earlier [2] the metal capacities are low and the time to 50% occupation of resin sites is quite high. This slow equilibration rate (ca. 100 min) is due to the low water regain of 1.2 g g-l ; with the hydroxamic acid resin, a water regain of 1.7 g g-i results in a tlh value for copper of 22 min. These apparently poor properties of the Duolite resin arise because the polymer is in better physical form than either hydroxamic acid or amidoxime bead polymers produced by the authors. This is because Duolite (X-346 contains a second monomeric vinyl species; it is a copolymer whereby suitable physical characteristics have been incorporated at the expense of high capacity and fast equilibration. TABLE
1
Properties
of Duolite
Water regain Sodium-hydrogen
CS-346 smidoxime
exchange
Capacities:Vanadium (V), (pH 3.2) Iron(LIi). (pH 1.5) Cow&W, (PH 3.0) Urangl(If), (pH 2.0) Equilibration r&e’ (f& for copper (pH 4) for iron (pH 28)
ion-exchange
1.2 g g-‘ 1.66 mm01 g-* 1.7 0.4 0.5 0.2
mm01 mm01 mm01 mm01
98 tin 120 min
g-’ g-’ g-’ g-’
resin
320 Fqure 1 shows the capacity vs. pH contours for iron, copper. nnd uranyl ions together with cobalt and nickel capacities; it is apparent that the former three ionic spcics should be capable of removal from cobalt and nickel rulutions. The curves indicate the pssibility of a quantitative sepa_tIon of iron from copper but not of iron from uranium nor of uranium from copper by sefcctfvc sorption at a chosen pH. Elution of I mg and 10 mg of uranium. which had brun quantitatively removed from solution by the column, show& that 59 mi of 2 M wdicm carbonate removed 81% of uranium from the rnsur;with 230 nJ of 2 M sodium carbonatr.quantitative removal of unnium was achieved and a complctc separation of umniurn, copper and iron was obtained. the copper and iron remaining on the column. ‘fhblc 2 shows that the rccovwics of iron, copper. and urar?ium from solutions containing cob&t and nickel at pH 3 are quantitative. With B 254oId cxccss of cobalt and nickel present, neither of these elements could
f’% 1. C=P.~~Y (SD46 resin.
m. pfi wmtour~
for iron.
copp+t.
uranyl.
nirkrl,
and cobaft on Duofitr
of iron( coppar and wampQtX) ions a: pff 3 0 from w&Cioru uf mbrft and nickrl iora in sodium rulphntc barking tfrctroiytc .
ion
mruurrd _. F*(llI) Fcf SIX) Cu; if) CuftI) uo: (II) UO,(II) _ .
.,
_.
_
noight of Ion prcrnt (mg) Iniliat
-- - __ _ . -.-1.oo
5.00 1.00 s.co I.00 5.00 --.
._
_ .,t
*
.
__--_.-_.
Weight or ion rlutzd (ma)
(%I
0.99 5.06 0.93 4.36 0.99 4.98
99 101 99 99 99 100
.- __ - ,-
_ _
Hocovery
__,__^,_
- -._
.-
,_.
containing
331 be detected in the acid eluate con+tiling
the iron, copper, or uranium. Recoveries of I mg and 5 mg of iron from solutions containing 25 mg of copper at pH 1.5 were also studied: 99% of the iron was recovered in each case, and copper was not detected in the iron-containing acid eluate from the column, As the recoveries were quantitative, the removal and determination of iron and copper from the various laboratory grades of cobalt and nickel salts was obvious, as was the determination of iron in copper salts. Table 3 gives the results obtained with a column of Duolite CS-346 to remove the Wo metals followed by their determination by atomic absorption spectrometry after elution; the grades of salts tested lie well within specification hmits. Attempts to obtain comparative results by spraying the salt solutions directly into the flame of the atomic absorption spectrometer were not successful as the high salt concentration caused repeated blocking of the nebuhzer unit. The determination of iron and copper in many systems is therefore possible; alkali and alkaline earth salts will not be retained on the exchanger and, from the metals whose retention is given as “moderate” or %eak”, zinc, cadmium, chromium, tin, manganese, bismuth, and Iead salts should be qu~titatively stripped of iron and copper by this method. Although the separation of iron, copper, and uranium can be quantitative, the procedure is tedious, involving their sorption at pH 3 followed by selective elution of uranium with 2 M sodium carbonate_ As it is not possible to desorb copper ions selectively from a column loaded with copper and iron by control of eluent pH, it is necessary to elute both species with acid, increase the eluate pH to 1.5, and then selectively sorb iron. The copper in the effluent may then be sorbed at pH 3 as described. As an alternative approach, the selective sorption of uranium from a solution containing a competing ligand for iron and copper was examined. As EDTA is well known as a masking agent for iron and cop-per in the determination of ‘uranium [ 31, sorption characteristics of the ions in the
The iron and copper contents oi some cobalt and nickel salts, and iron content of capper sulphate Sait
Iron content Found
Specification (m=
Cobalt sulphak Cobalt sulphate Nickel sulphate Nickel sulphate Cupper suiphate Copper sulphate *Specified
(G.P.R.) (AnalaR) (G.P.R.) (Am&R)
(G.P.R.) (AnalaR)
6.5 2.9 17.2 4.1 156.0 30.0
as “heavy metals 0.04%”
(ppm)
100 20 400= 20 500 100
Copper content Found
Specification (ma)
1 19.7 2.3 14.4 0.8 -
(ppm)
50 10 400a 10 -
322 TABLE
4
.%trc:crr rorpf~on iron(ILI). copper(U). -__ ----EF)TA (dl) _0 20 50 ._ -_
Metal ___--
unnyl was as o function of EDTA and ufanyl(Il) ions ----
ion crrpatrrs
at pif
.__._---.
FC(IU) ._--.. 0.38 0.01 0.01
of
-_.
CU~lI) . . --.
UO,(II) -
0.03 0.01 o.oozi
0.01 0.06 0.03
____.._.
3 0 (mmol
.----
cantent
of a solution.
5 mhl tn
a-‘)
-
-
- _-
,-_-
prewnce of this ligand were studid by batch equilibration. Table 4 shows the effect of EDNA on sorption characteristics. In its absence. the resin s&ctivcly retains iron(II1) ions from the mixture. In the presence of a slight excess of FJ)TA. iron(III) and copper(H) chelation ti suppre. with conrqucnt incrca.u? in uranyl capacity. When the conccntrcltion of EDTA is further incr~~, the uranyl cqacity is advusely affect&. Of the other species which the manufacturers claim to be strongly retained, Duolitc CS346 resin could bc important in the recovery of gold and the platinum group metals if sAxtivc sorption is possible and efficient cluents arc found. The authors thank the Diamond chelating ion exchanger.
S~KUIXCW~Company
1 Dlrmood Shamrorh Chrmical Co. Duolitc -346 Trchmc-rl 2 P. Vernon mm! H. Ecctes. AnaI. Chlm. Acta. 82 (1976) 369. 3 A. I. Vogel. A Tcxtbcmk of QuJntaativc l~~rcaaic Analyris. London. 1962. 4 F. Vernon and ti. Ecclc~. Anal. Chim. Acta. 72 (1974) 331.
for the gift of the
.Shrrt
(1972).
3td rdn..
Iaogmmr.
-Printed
in The Netherhnds
Thesepzr8tion of iron(III), copper(II uranyIfI1) ions from a seriesof salt solutions by chelating ion ex&ange on I3uolite CS-316 resin by pH control is described. Recoveries of t&se &XIS ftom ~0b3it and nickel salt soiutlons were quantitative. Iron may afso be separated from copper by selective sorption with pW control, and uranium from iron and copper by selective desorption with sodium carbonate solution 3s eiuent.
One of the few commercW chelating ion exchange resins available is Duolite XX-346 for which the chef&@ ability is attributed to amidoxime graups. Very fittIe evaluation has been performed on this exchanger. The available data f 13 give a brief description and suggestions that the resin chelates “‘very strongly” with nine elements including copper, iron and waGurn; “strongly” with three elements, and “moderately” with a further siu elements including cobalt and nickel. Stztble complex formation with iron(IIr) is indicated at gW 1.5, with copper(II j at pH 3.0, and with uranyf(fi) at pH 2.0. This exchanger should therefore be capable of separating iron, copper, and uranium from cobalt and nickel at the pH values recommended. In this respect it should behave in a manner similar to the hydroxamie acid exchanger described in Part Df of this series f 21. The possibi!ity of separating iron from copper by selective sorption of iron is also indicated. The separation of uranyt ions from copper or iron by selective sorption is examined, tugether with se&ctive dution of uranium by sodium carbonate sulutiun. Removal of the three ions from solutions of other salts, and their separztions from each other, are also investigated.
Duo&e CS-346, a micrabead chelating 2x1 ex&anger containing the amidoxime _fun&ioti group (Diamond Sfxamrock Ghemicai Co., U,S.A.) was washed with water, then with 1 M hydroc’nloric SC’%to convert it to $he hyd.rogCtnfo’&, and fimdly nith deionized water until the effluent was
318
chlordc!.frt+. The resin was stored swollen state.
in an air-tight
container
in the fully
Jfeial capacities Sodium capacity. This WRS determined by cquilibntion of the resin with 0.25 31 sodium hydrogcncarhonatc? and measurement of the sodium uptake as previously dsscribcd [ 21. Multivaknt metal capacttics. To obtain more fundamental capacity data than have Men rcportcd prc*viously for metal ion solutions containing acetate? buffers, the following proccdurr, though tedious, was adopt& for total capacity determination of a metal ion frum a backinK electrolyte which consisted only of sodium sulphatc. The fully swollen Duolite CS346 resin (0.50 : O.Oi g) was equilibrated for 24 11with I XI sodium sulphatc solution whose pli had been adjusted to the rccluircd value by the addition of sodium hydroxide or sulphuric acid solutions. The pIi of the cquilibrafing solution was adjustrui rwrlarly over the period until it rem&& constant at the sl*icctcd value. This solution was dwantcd from the resin, which was then c~ui1ibmtt-d for 4R h with 1 LI sodium sulphatc! .uAution which was 20 mh! with rcspcct to the- ion under test, and whose pli had been adjust& as de.scrihd prmiously. During the equilibration, the pii was brought back regularly to the initial value by the addition of sodium hydroxide, the ~utlibration continuing for 24 h after the plI became constant. After f&r&ion and washing of the resin with 1 hf sodium sulphatc solution of the silrno pi1 as the final equilibrating solution, the meti wns cluti from the resin by equilibration for 48 h with 2 hl sulphuric acid. For iron(lII), 4 hl sull:huric acid was used. The copper. iron, cobalt, and nickel contents of the eluatcs were dctermin& with a Corning-EEL 240 mark II atomic obsnrption spcc’Lrophotometc!r. Uranium was dctcrmincd calorimetrically by Bhydroxyquinoline in the preu’nce of EDTA (3 J ; acid elution or sodium carbonok clution techniques were employcxl. Watct rcagain and tvuilrbration rate ‘Ihzsc rc*sin properties were dekrmincd as described prc?viously (2, 41. Cabah sulphate. nickel sulphate and copper sulphate (Hopkin and \Villiams, IA.) wen? used. Chlumn scpamttins A &ss column (length 50 cm, i.d. 1 cm) was filled to a height of ca. 30 cm with 15 g of fully swollen Duolitr! CS-346. The column ~3s washed with SO b& volumes of deionized water, and then conditioned with IO hcd volumes of backing electrolyte adjusted to the required pH. The sample snlution was pa,sscd on to the column at a flow rate of 1 to 2 ml min-‘. The co!umn was then wasbc(i with 5 hcd volumes of water, adjusted for pH. The rctiincd metal ions were r~lutccl with 10 bed volumes of 2 hi sulphuric acid (or 4 h! sulphuric acid for iron), and the metal content-s were
319
determined as descri’oed under metal capacities. Iron was separated from copper at pH 1.5; iron and copper were separated from other metals at pH 3.0. For the determination of t.he iron and copper contents of cobalt sulphate and nickel sulphate, 100 g of the salt was dissolved in 500 ml of deionized water and the pH adjusted to 3.0 by the addition of sulphuric acid. solution. The solution was passed through the column at 2-3 ml min-* the column was washed with 10 bed volumes of water, and the iron and copper were eluted with acid as described. For the iron content of copper sulphate, 10 g of the salt was dissolved in 500 ml of deionized water and the pH was adjusted to 1.5 with sulphuric acid before the solution was passed through the column. For tests on the selective sorption of many1 ions over iron and copper at pH 3, resin was equilibrated with solutions containing vsrious amounts of EDTA (disodium salt), which were 5 m&I in each metal ion species. After the washing procedures described, the ions were eluted with 4 M sulphuric acid, and the concentration of each was determined. RESULTS
AND
DISCUSSION
The properties of Duolite CS-346 are given in Table 1, the vanadium capacity of 1.7 mmol g-’ representing the functional group content of the resin. In comparison with a hydroxamic acid resin described earlier [2] the metal capacities are low and the time to 50% occupation of resin sites is quite high. This slow equilibration rate (ca. 100 min) is due to the low water regain of 1.2 g g-l ; with the hydroxamic acid resin, a water regain of 1.7 g g-i results in a tlh value for copper of 22 min. These apparently poor properties of the Duolite resin arise because the polymer is in better physical form than either hydroxamic acid or amidoxime bead polymers produced by the authors. This is because Duolite (X-346 contains a second monomeric vinyl species; it is a copolymer whereby suitable physical characteristics have been incorporated at the expense of high capacity and fast equilibration. TABLE
1
Properties
of Duolite
Water regain Sodium-hydrogen
CS-346 smidoxime
exchange
Capacities:Vanadium (V), (pH 3.2) Iron(LIi). (pH 1.5) Cow&W, (PH 3.0) Urangl(If), (pH 2.0) Equilibration r&e’ (f& for copper (pH 4) for iron (pH 28)
ion-exchange
1.2 g g-‘ 1.66 mm01 g-* 1.7 0.4 0.5 0.2
mm01 mm01 mm01 mm01
98 tin 120 min
g-’ g-’ g-’ g-’
resin
320 Fqure 1 shows the capacity vs. pH contours for iron, copper. nnd uranyl ions together with cobalt and nickel capacities; it is apparent that the former three ionic spcics should be capable of removal from cobalt and nickel rulutions. The curves indicate the pssibility of a quantitative sepa_tIon of iron from copper but not of iron from uranium nor of uranium from copper by sefcctfvc sorption at a chosen pH. Elution of I mg and 10 mg of uranium. which had brun quantitatively removed from solution by the column, show& that 59 mi of 2 M wdicm carbonate removed 81% of uranium from the rnsur;with 230 nJ of 2 M sodium carbonatr.quantitative removal of unnium was achieved and a complctc separation of umniurn, copper and iron was obtained. the copper and iron remaining on the column. ‘fhblc 2 shows that the rccovwics of iron, copper. and urar?ium from solutions containing cob&t and nickel at pH 3 are quantitative. With B 254oId cxccss of cobalt and nickel present, neither of these elements could
f’% 1. C=P.~~Y (SD46 resin.
m. pfi wmtour~
for iron.
copp+t.
uranyl.
nirkrl,
and cobaft on Duofitr
of iron( coppar and wampQtX) ions a: pff 3 0 from w&Cioru uf mbrft and nickrl iora in sodium rulphntc barking tfrctroiytc .
ion
mruurrd _. F*(llI) Fcf SIX) Cu; if) CuftI) uo: (II) UO,(II) _ .
.,
_.
_
noight of Ion prcrnt (mg) Iniliat
-- - __ _ . -.-1.oo
5.00 1.00 s.co I.00 5.00 --.
._
_ .,t
*
.
__--_.-_.
Weight or ion rlutzd (ma)
(%I
0.99 5.06 0.93 4.36 0.99 4.98
99 101 99 99 99 100
.- __ - ,-
_ _
Hocovery
__,__^,_
- -._
.-
,_.
containing
331 be detected in the acid eluate con+tiling
the iron, copper, or uranium. Recoveries of I mg and 5 mg of iron from solutions containing 25 mg of copper at pH 1.5 were also studied: 99% of the iron was recovered in each case, and copper was not detected in the iron-containing acid eluate from the column, As the recoveries were quantitative, the removal and determination of iron and copper from the various laboratory grades of cobalt and nickel salts was obvious, as was the determination of iron in copper salts. Table 3 gives the results obtained with a column of Duolite CS-346 to remove the Wo metals followed by their determination by atomic absorption spectrometry after elution; the grades of salts tested lie well within specification hmits. Attempts to obtain comparative results by spraying the salt solutions directly into the flame of the atomic absorption spectrometer were not successful as the high salt concentration caused repeated blocking of the nebuhzer unit. The determination of iron and copper in many systems is therefore possible; alkali and alkaline earth salts will not be retained on the exchanger and, from the metals whose retention is given as “moderate” or %eak”, zinc, cadmium, chromium, tin, manganese, bismuth, and Iead salts should be qu~titatively stripped of iron and copper by this method. Although the separation of iron, copper, and uranium can be quantitative, the procedure is tedious, involving their sorption at pH 3 followed by selective elution of uranium with 2 M sodium carbonate_ As it is not possible to desorb copper ions selectively from a column loaded with copper and iron by control of eluent pH, it is necessary to elute both species with acid, increase the eluate pH to 1.5, and then selectively sorb iron. The copper in the effluent may then be sorbed at pH 3 as described. As an alternative approach, the selective sorption of uranium from a solution containing a competing ligand for iron and copper was examined. As EDTA is well known as a masking agent for iron and cop-per in the determination of ‘uranium [ 31, sorption characteristics of the ions in the
The iron and copper contents oi some cobalt and nickel salts, and iron content of capper sulphate Sait
Iron content Found
Specification (m=
Cobalt sulphak Cobalt sulphate Nickel sulphate Nickel sulphate Cupper suiphate Copper sulphate *Specified
(G.P.R.) (AnalaR) (G.P.R.) (Am&R)
(G.P.R.) (AnalaR)
6.5 2.9 17.2 4.1 156.0 30.0
as “heavy metals 0.04%”
(ppm)
100 20 400= 20 500 100
Copper content Found
Specification (ma)
1 19.7 2.3 14.4 0.8 -
(ppm)
50 10 400a 10 -
322 TABLE
4
.%trc:crr rorpf~on iron(ILI). copper(U). -__ ----EF)TA (dl) _0 20 50 ._ -_
Metal ___--
unnyl was as o function of EDTA and ufanyl(Il) ions ----
ion crrpatrrs
at pif
.__._---.
FC(IU) ._--.. 0.38 0.01 0.01
of
-_.
CU~lI) . . --.
UO,(II) -
0.03 0.01 o.oozi
0.01 0.06 0.03
____.._.
3 0 (mmol
.----
cantent
of a solution.
5 mhl tn
a-‘)
-
-
- _-
,-_-
prewnce of this ligand were studid by batch equilibration. Table 4 shows the effect of EDNA on sorption characteristics. In its absence. the resin s&ctivcly retains iron(II1) ions from the mixture. In the presence of a slight excess of FJ)TA. iron(III) and copper(H) chelation ti suppre. with conrqucnt incrca.u? in uranyl capacity. When the conccntrcltion of EDTA is further incr~~, the uranyl cqacity is advusely affect&. Of the other species which the manufacturers claim to be strongly retained, Duolitc CS346 resin could bc important in the recovery of gold and the platinum group metals if sAxtivc sorption is possible and efficient cluents arc found. The authors thank the Diamond chelating ion exchanger.
S~KUIXCW~Company
1 Dlrmood Shamrorh Chrmical Co. Duolitc -346 Trchmc-rl 2 P. Vernon mm! H. Ecctes. AnaI. Chlm. Acta. 82 (1976) 369. 3 A. I. Vogel. A Tcxtbcmk of QuJntaativc l~~rcaaic Analyris. London. 1962. 4 F. Vernon and ti. Ecclc~. Anal. Chim. Acta. 72 (1974) 331.
for the gift of the
.Shrrt
(1972).
3td rdn..
Iaogmmr.