Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2000-12-20
2003-06-10
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S688000, C428S454000, C428S448000
Reexamination Certificate
active
06576335
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to materials and methods for selectively recovering metal ions, such as copper, from aqueous streams. More specifically, the invention relates to producing high yields of high purity solid metal-ion-capturing material, by covalently binding a chelating moiety to a solid-phase material. The invention is particularly beneficial for recovering copper from aqueous solutions in the copper mining and copper plating industries, because the solid-phase material is selective to copper in the presence of iron and other metals, and results in energy and material savings compared to conventional copper recovery methods.
2. Related Art
Copper chelating moieties have been used in the past for removing copper from aqueous streams in the copper mining industry. Liquid phase chelates in aqueous-immiscible organic solvents are employed in liquid-liquid phase extraction processes to remove copper from the mining product or waste streams. After the aqueous stream is separated from the solvent stream, the solvent containing the chelated copper is then back-extracted with strong acid in order to remove the copper, and the copper is typically recovered by electro-winning. This solvent extraction/electro-winning (SX/EW) process requires large amounts of flammable and toxic solvent, and large amounts of time and energy. This SX/EW process also requires periodic addition of chelating agent due to losses in the process. One chelating agent used in the conventional SX/EW process is a liquid-phase salicylaldoxime copper capturing moiety.
Other methods of metal ion recovery using salicylaldoxime has been studied and described in the literature. Sarkar et al., in “Sorption recovery of metal ions using silica gel modified with salicylaldoxime,”
Talanta,
42 (1996) pp.1857-1863, describes sorbent materials for metal ions, wherein the sorbent material consists of salicylaldoxime physically adsorbed onto solid phase materials. The Sarkar et al. sorbent synthesis is reported as: 1) refluxing silica gel with 6 M HCl for about 3 hours to remove any contaminating metals such as iron; 2) washing the silica gel with deionized water and drying it under reduced pressure at 150° C.; 3) refluxing the dried silica gel with salicylaldoxime in ethanol (10% w/w) at 70-80° C. for four hours; and 4) filtering and drying under vacuum to obtain the solid sorbent. Sarkar, et al. reports that IR spectrum of the resulting sorbent shows IR peaks coinciding with peaks of salicylaldoxime itself, suggesting that the sorbent synthesis techniques resulted in the salicylaldoxime being retained within the sorbent as such, without any structural change. Consistent with this finding was that ethanol easily removed all the salicylaldoxime from the sorbent when ethanol was passed over the sorbent. These findings were consistent with the salicylaldoxime being physically adsorbed in the Sarkar et al sorbent, rather than being chemically/covalently bonded to the solid material.
In Hammen, U.S. Pat. No. 5,240,602, chromatographic materials have been described that include a silica-based solid support, an affinity ligand, and a polymeric non-ionic, hydrophilic spacer with a coupling group connecting the affinity ligand to the support. These affinity materials use preferential dissolution to create a chromatographic effect, in which the materials of interest are preferentially, but only temporarily, attracted by the affinity materials. These affinity materials do not chelate materials of interest, and do not capture the materials of interest in any way that requires regeneration of the affinity materials. Therefore, the affinity materials do not provide a way to remove metal ions from a stream. Hammen uses polymers as a spacer between the silica-based solid support and the affinity ligand, including PEG, PVA, PPG, polyethylene dithiol, and polymers of glycine, serine, or threonine. The Hammen polymer is attached to the solid support by a substitution mechanism. Hammen discloses nitrogen-based linkages between the affinity ligand and the solid support, which linkages may be appropriate for a chromatographic use but which would be low in selectivity and prone to degradation in other uses.
What is still needed is a solid-phase metal ion capturing material that is durable, highly selective to the desired metals, and acid/base stable, so that it is appropriate for large-scale metal recovery, regeneration, and re-use. Economical copper-recovery materials and methods are still needed that do not require hazardous and toxic flammable solvents, complex and costly process plant equipment, and high-energy-consumption process steps. What are needed are such materials and methods that lower the cost per pound of recovered copper metal in copper mining and plating industries, and that do so with lowered environmental impact compared to conventional technologies.
SUMMARY OF THE INVENTION
The present invention comprises a solid-phase metal ion recovery material including a metal ion capturing agent chemically bound to a solid support, and methods for making the recovery material. The invention further comprises methods of recovering metal ions from aqueous streams, such as mining or metal plating product and waste streams, by direct contact between the aqueous stream and the solid-phase recovery material. The invented materials and methods may eliminate the use of liquid-liquid extraction processes and large volumes of organic solvents conventionally used in metal ion recovery in the mining and plating industries. Metal ion recovery materials according to the invention preferably comprise chelating heads covalently bound to ceramics or ceramic precursors via non-polymeric tethers. The chelating head may be any known chelating ligand, for capturing copper, zinc, uranium, plutonium, or other materials. The tether is an organic compound covalently attached to the chelating head and functionalized by a linker that attaches to an olefin portion of the organic compound. The linker is chosen to be appropriate for the selected solid support, for example, a silica linker for use with silica solids, a titania linker for use with titania solids, an alumina linker for use with alumina solids, etc. Several preferred recovery materials are highly selective for copper (II) in the presence of iron (III) and many other materials that are typically present in the digested earth materials of a conventional copper mining operation. Also, several preferred recovery materials are highly selective for copper in the presence of the materials that are present in a commercial metal plating stream.
The invented metal ion recovery material includes an organic metal-capturing compound, hereafter also called “capturing compound,” or “capturing agent,” that is covalently linked to a solid support. Covalent linkage may include, for example, covalent binding directly to the surface of a silica-based solid. Also, covalent linkage may include condensation of silica-based ceramic precursors into a solid, some to all of which precursors are associated with capturing agent prior to the condensation and/or some to all of which precursors become associated with capturing agent during the condensation.
The metal-capturing compound comprises a chelating moiety or chelating “head” covalently bound to a “tail” or “tether” that covalently binds the chelating head to the surface of the solid support, for example, via a silica linker if the solid support is a silica-based material. Thus, the entire linkage between the chelating head and the solid support is chemical, rather than physical, and so is very durable. In addition, the preferred synthesis routes result in the invented metal ion recovery material being acid/base stable.
The chelating head may be any of a variety of chelating heads, which captures and chelates with the material of interest, preferably a metal ion. “Capturing” herein means irreversible binding under the existing conditions (pH, temperature, etc.) of the feed stream. Release of the captured metal ions ma
Harrup Mason K.
Peterson Eric S.
Wey John E.
Bechtel BWXT Idaho LLC
Dawson Robert
Keehan Christopher M.
Pedersen & Company PLLC
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