Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Ion-exchange polymer or process of preparing
Reexamination Certificate
1998-12-28
2001-05-15
Barry, Chester T. (Department: 1724)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Ion-exchange polymer or process of preparing
C521S038000, C210S673000, C210S681000, C423S139000, C526S222000, C526S225000
Reexamination Certificate
active
06232353
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates generally to the recovery of metal ions from aqueous media. More particularly, the present invention relates in one embodiment to an ion exchange resin, in another embodiment to a process for removing iron(III) cations from an aqueous medium containing sulfuric acid and other polyvalent metal cations using that ion exchange resin, and in a still further embodiment to a generalized process for removing polyvalent metal ions from aqueous acid solution.
2. Background of the Invention
Removal of radionuclides and other heavy metal ions from aqueous solutions has been the subject of extensive research. One of the areas in which this research is primarily focused is removing heavy metal ions from aqueous solutions through selective complexation.
Selective complexation is typically performed using ligands polymerized on polymer supports. Chang et al.
Talanta
42:1127 (1995) describe using immobilized imidazolines for trace metal recovery. Tomita et al.
J. Poly. Sci., Poly. Chem. Ed
. 34:271 (1996) discuss using immobilized kojic acid for trace metal recovery. Lan et al.
Anal Chim. Acta
287:101 (1994) teach using immobilized quinolinol for trace metal recovery. Buchanan et al.
Can. J. Chem
. 69:702 (1991) describe using immobilized crown ethers for trace metal recovery. Kawamura et al.
Ind. Eng. Chem. Res
. 32:386 (1993) disclose using immobilized polyethylenimines for trace metal recovery. Van Berkel et al.
Europ. Poly. J
. 28:747 (1992) discuss using immobilized pyrazoles for trace metal recovery. Kamble et al.
J. Appl. Poly. Sci
. 56:1519 (1995) teach using immobilized oximes for trace metal recovery. Lezzi et al.
J. Appl. Poly. Sci
. 54:889 (1994) discuss using immobilized dithiocarbamates for trace metal recovery.
Ion exchange resins with phosphorous-containing ligands are an important group of metal ion chelating agents. The selectivity of these types of ligands can be varied by changing the structure of the phosphorous ligand. The ability of these ligands to strongly coordinate different metal ions leads to significant levels of ionic complexation under highly acidic conditions.
Horwitz et al.
Solv. Extr. Ion Exch
. 11:943 (1993) have shown that immobilized diphosphonic acid groups have very high affinities for a series of metal ions because of the coordinating ability of the phosphoryl oxygen and a ligand structure that permits chelation of the metal ions. High loadings at equilibrium are attained under contact times on the order of days unless the phenyl rings within the polymer are sulfonated, which reduces the equilibration time to on the order of ten minutes. Chiarizia et al.
Solv. Extr. Ion Exch
. 12:211 (1994).
The introduction of bifunctionality into ion exchange resins has been discussed as a coupling of an access mechanism (permitting all ions into the matrix rapidly) with a recognition mechanism (a second ligand selectively complexes a targeted metal ion). Alexandratos et al.
Macromolecules
21:2905 (1988). Studies with diphosphonate-immobilized polymer have shown that both ligands on the resin complex far greater levels of metal ions than either one could alone. Alexandratos et al.
Macromolecules
29:1021 (1996).
The access mechanism introduced by the sulfonic acid ligand is due to the ligand's hydrophilicity that permits rapid entry of metal ions into the matrix. It has been found that monofunctional phosphonic acid microporous resin cross-linked with 2 percent divinylbenzene (hereinafter “DVB”) lost most of its ability to complex Eu(III) from 1 N HNO
3
compared to the performance of this material in 0.04 N acid. Trochimczuk et al.
J. Appl. Poly. Sci
. 52:1273 (1994). These results were attributed to a collapse of the microporous structure in high ionic strength solutions that restricts access.
Trochimczuk et al., above, describe that linking sulfonic acid groups and phosphonic acid groups to different phenyl rings increases the amount of Eu(III) complexed from high ionic strength solutions. The results suggested an increased access of the metal ions into the polymer matrix coupled with increased complexation by the phosphonate ligands. However, the advantage of increased complexation was offset by the decreased resin capacity from the lower level of substitution necessitated by the copolymerization with styrene. In addition, when a cross-linked phosphonate polymer that was not copolymerized with styrene was sulfonated, a relatively small metal binding capacity was again observed in 1 N nitric acid.
Copper metal is obtained from copper ores by several well-known processes. One of the most frequently used processes is referred to as a solvent extraction-electrowinning (SX-EW) process in which copper(II) ions are first leached from the ore using sulfuric acid followed by extraction with a kerosenebased copper-specific solvent mixture. The copper ions are then stripped from the solvent mixture using a copper sulfate-sulfuric acid electrolyte solution (CuSO
4
—H
2
SO
4
electrolyte solution). The copper recovery process is then completed by electrowinning of copper from the copper-enriched strip solution.
Small amounts of iron(II) and iron(III) cations are commonly transferred with the copper cations to the electrowinning solution. Iron transfer occurs by chemical co-extraction (binding to the oxime molecule) and by entrainment of iron-containing aqueous solution in the copper-loaded organic solution. As copper is depleted from the CuSO
4
—H
2
SO
4
electrolyte solution during copper electrowinning (EW), the concentration of iron in solution increases. This build up of iron in solution results in a loss of current efficiency in the electrowinning process due to a continuous oxidation/reduction of Fe
2+
/Fe
3+
. That loss of current efficiency can amount to about 2-3 percent per gram of iron in solution. The conventional treatment technique for iron control has been to periodically bleed or purge a portion of the iron-rich, copper-depleted electrolyte and replace it with a sulfuric acid electrolyte solution.
In a copper electrowinning process, lead-based alloys are used as oxygen-evolving anodes. Soluble cobalt(II) (50-200 ppm) ions are added to the aqueous sulfuric acid copper-containing electrolyte to control corrosion of the lead anode, and to prevent “spalling” and possible lead contamination of the copper cathode. During bleed of the spent (copper-depleted) electrolyte to control iron concentration, cobalt is lost from the system. Cobalt must be continually added to the electrowinning electrolyte to make up cobalt lost through the bleed stream. Cobalt replacement to control lead anode corrosion is a major operating expense in copper SX-EW plants. Removal of the iron from the electrowinning electrolyte solution while retaining the cobalt is desired.
Sulfonic acid functional group cation exchange resins are widely used in the water treatment industry and other industrial processes for the removal of cations, such as iron, from aqueous process streams. Such resins also bind and accumulate other cations, such as calcium, magnesium, and sodium, that are undesirable in an iron removal process, necessitating frequent regeneration of the resin.
Gula et al., U.S. Pat. No. 5,582,737, the disclosure of which are incorporated herein by reference, describe a process that separates and removes iron(III) from aqueous sulfuric acid solution containing additional metal ions such as copper and cobalt ions as are found in depleted copper electrowinning electrolyte solutions. That process utilizes gem-diphosphonic acid ion exchange particles that are preferably also sulfonated to remove the iron(III) ions, while permitting (1) copper, cobalt and other mono- and divalent metal ions to be recycled into the copper electroplating recovery process, thereby saving on the costs of cobalt that would otherwise be discarded, and (2) regeneration of the ion exchange particles for further use and recycle to the separation and removal steps.
The process for regenerating the gem-diphosphonic acid ion exchang
Alexandratos Spiro
Chiarizia Renato
Horwitz E. Philip
Shelley Christopher A.
ARCH Development Corporation
Barry Chester T.
Welsh & Katz Ltd.
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