HAuCl4
Well-known member
I'm teaching myself to Sx metals to high purity in as few steps as possible.
This will be a "developing tutorial thread" for those interested to contribute knowledge, specific processes or documents.
I'll probably end up posting to myself most of the time, since these processes are still regarded as "secrets" or protected by patents or both.
The initial material to "process" are chloride solutions of Au, Pt, Pd, Ag, with maybe traces of Rh, Ir and base metals Cu, Ni, Pb, Zn, other as they are encountered in the processing of jewellery and/or platinum scrap.
1-The initial broad stroke process proposed includes the digestion in aqua regia of the above mix, and separation of AgCl and other insolubles by filtration.
2-The liquid is then extracted with BDG according to the process described by Ferro to isolate gold in high purity form. (see attached .pdf)
2-b Optional. To treat the aqueous solution after BDG extraction with an ammonium oxalate solution, to effect complete removal of gold after filtration, before going to the next step.
3-The remaining aqueous solution is then extracted with n-octyl sulfide or other suitable alkyle sulfide diluted in kerosene or other, with the purpose of extracting palladium from the remaining aqueous solution of other PGMs and base metals. An sketch of the process is available free online, with some references to other patents.
http://www.patentgenius.com/patent/5266727.html
*****
BACKGROUND OF THE INVENTION
The present invention lies in the art of refining platinum group metals (PGM's) through solvent extraction. More specifically, the invention relates to a process for purifying alkyl sulfide extractant for use in extracting palladium from amixture of palladium and other PGM's. In particular, the process is directed to the removal of organosulfur compounds from alkyl sulfide extractant, as they interfere with the recovery of palladium.
Solvent extraction of aqueous solutions containing precious metals derived from ores and their subsequent products is gaining in use due to its advantages over the classical precipitation and redissolution methods. Advantages of solventextraction include a reduced cycle time, higher purity, and often higher yields. With proper selection of solvents and process conditions, extraction can be highly specific for a particular metal species, resulting in recovery of a high purity product. Typically, the required purity of PGM's is up to about 99.995%. To achieve this level of purification using precipitation and redissolution procedures requires multiple repeat processing and thus considerable time. Solvent extraction shortens the timefor purification many fold, while yielding a higher purity product.
Solvent extraction is carried out by contacting an aqueous phase solution of one or more extractable metals with an organic phase containing the extractant. The extractable metal or metals form complex compounds, with the extractant acting asthe complexing agent or ligand. Each of the extractable metals can form one or more complexes with different atomic or molecular entities occupying ligand positions in the coordination spheres of the complexes. These ligands can be anions (chloride andother halides, sulfate, nitrite), cations (nitrosyl, NO.sup.+), neutral species (H.sub.2 O, NH.sub.3) or organic compounds (ethers and other oxygenated compounds, amines, sulfides). For those metals exhibiting more than one valence state, some of whichcan be easily reduced (e.g. Au(III), Pd(IV) and Ir(IV)), care must be taken in achieving the desired chemistry for extraction and stripping. Large differences in rates of reduction and ligand substitution reactions result in separation between metalspecies. Sequential extractions using different extractant enables separation of a plurality of metal species from a single solution.
For recovery of palladium (Pd) from ores containing Pd and other PGM's, various alkyl sulfides have been used as extractant. For such an example, see U.S. Pat. No. 3,985,552 issued Oct. 12, 1972 to Edwards. In a typical extraction, a diluentsuch as a paraffinic or aromatic liquid is combined With the alkyl sulfide to form an organic phase. An aqueous phase, usually an aqueous acidic chloride solution containing Pd and other metals extracted from the ore, is contacted with the organicphase. The Pd in the aqueous phase forms a complex with the extractant and, due to its high solubility in the organic phase, the Pd complex is almost completely partitioned into the organic phase. Using n-octylsulfide (NOS) as the extractant, forexample, the equation for extraction is:
In typical commercial practice, the organic phase is first washed with a dilute HCL solution to remove entrained raffinate comprising other PGM's and small amounts of other metals, such as iron and copper, which are extracted to a low level. Thewashed, loaded organic phase, containing less contaminant metals, is then stripped using aqueous ammonia The Pd complexes with the ammonia to form Pd(NH.sub.3).sub.4.sup.2+ ion in aqueous solution. The extractant is then recycled for reuse. The aqueousPd solution, which also contains excess NH.sub.3 and Cl, is then carefully acidified to precipitate the sparingly soluble salt Cl.sub.2 Pd(NH.sub.3).sub.2. Conversion to the metal results by its ignition at high temperature (e.q., about 900.degree. C.)to form "Pd sponge."
The extraction and stripping of PGM's using alkyl sulfides is affected by organosulfur impurities such as mercaptans and disulfides present in the alkyl sulfides. During stripping the organosulfur impurities readily react with palladium andother PGM's to form a solid emulsion-like "crud" phase which disrupts the complete recovery of Pd. For example, sulfur compounds, such as mercaptans, are undesirable in the alkyl sulfide as they can tie up metals as the mercaptides and can subsequentlycause problems in the stripping step. These problems can be overcome by using highly purified alkyl sulfides, but at considerable added materials cost.
There is a need for a process for conveniently and efficiently purifying the alkyl sulfides which are used for purifying palladium and other PGM's, of the unwanted impurities. This need is met by the present invention.
*****
3-b Optional. To treat the aqueous solution after Pd extraction with a small amount of DMG, to effect complete removal of Pd after filtration, before going to the next step.
4-The remaining aqueous solution is then extracted with Tri-n-butyl phosphate or other suitable solvent, with the purpose of extracting platinum and Iridium from the remaining aqueous solution of Rh and remaining PGMs and base metals.
[Insert relevant patents or processes here]
An sketch of the above Sx process was obtained initially from:
http://www.halwachs.de/solvent-extraction.htm
I believe Halwachs was one of the first pioneers of Solvent Extraction.
Feel free to further these process with specifics and details!. 8)
After we nail this down completely, we can explore Sx to produce pure forms of other interesting metals like U and Pu!. Save the flames and contribute if you can! :shock:
This will be a "developing tutorial thread" for those interested to contribute knowledge, specific processes or documents.
I'll probably end up posting to myself most of the time, since these processes are still regarded as "secrets" or protected by patents or both.
The initial material to "process" are chloride solutions of Au, Pt, Pd, Ag, with maybe traces of Rh, Ir and base metals Cu, Ni, Pb, Zn, other as they are encountered in the processing of jewellery and/or platinum scrap.
1-The initial broad stroke process proposed includes the digestion in aqua regia of the above mix, and separation of AgCl and other insolubles by filtration.
2-The liquid is then extracted with BDG according to the process described by Ferro to isolate gold in high purity form. (see attached .pdf)
2-b Optional. To treat the aqueous solution after BDG extraction with an ammonium oxalate solution, to effect complete removal of gold after filtration, before going to the next step.
3-The remaining aqueous solution is then extracted with n-octyl sulfide or other suitable alkyle sulfide diluted in kerosene or other, with the purpose of extracting palladium from the remaining aqueous solution of other PGMs and base metals. An sketch of the process is available free online, with some references to other patents.
http://www.patentgenius.com/patent/5266727.html
*****
BACKGROUND OF THE INVENTION
The present invention lies in the art of refining platinum group metals (PGM's) through solvent extraction. More specifically, the invention relates to a process for purifying alkyl sulfide extractant for use in extracting palladium from amixture of palladium and other PGM's. In particular, the process is directed to the removal of organosulfur compounds from alkyl sulfide extractant, as they interfere with the recovery of palladium.
Solvent extraction of aqueous solutions containing precious metals derived from ores and their subsequent products is gaining in use due to its advantages over the classical precipitation and redissolution methods. Advantages of solventextraction include a reduced cycle time, higher purity, and often higher yields. With proper selection of solvents and process conditions, extraction can be highly specific for a particular metal species, resulting in recovery of a high purity product. Typically, the required purity of PGM's is up to about 99.995%. To achieve this level of purification using precipitation and redissolution procedures requires multiple repeat processing and thus considerable time. Solvent extraction shortens the timefor purification many fold, while yielding a higher purity product.
Solvent extraction is carried out by contacting an aqueous phase solution of one or more extractable metals with an organic phase containing the extractant. The extractable metal or metals form complex compounds, with the extractant acting asthe complexing agent or ligand. Each of the extractable metals can form one or more complexes with different atomic or molecular entities occupying ligand positions in the coordination spheres of the complexes. These ligands can be anions (chloride andother halides, sulfate, nitrite), cations (nitrosyl, NO.sup.+), neutral species (H.sub.2 O, NH.sub.3) or organic compounds (ethers and other oxygenated compounds, amines, sulfides). For those metals exhibiting more than one valence state, some of whichcan be easily reduced (e.g. Au(III), Pd(IV) and Ir(IV)), care must be taken in achieving the desired chemistry for extraction and stripping. Large differences in rates of reduction and ligand substitution reactions result in separation between metalspecies. Sequential extractions using different extractant enables separation of a plurality of metal species from a single solution.
For recovery of palladium (Pd) from ores containing Pd and other PGM's, various alkyl sulfides have been used as extractant. For such an example, see U.S. Pat. No. 3,985,552 issued Oct. 12, 1972 to Edwards. In a typical extraction, a diluentsuch as a paraffinic or aromatic liquid is combined With the alkyl sulfide to form an organic phase. An aqueous phase, usually an aqueous acidic chloride solution containing Pd and other metals extracted from the ore, is contacted with the organicphase. The Pd in the aqueous phase forms a complex with the extractant and, due to its high solubility in the organic phase, the Pd complex is almost completely partitioned into the organic phase. Using n-octylsulfide (NOS) as the extractant, forexample, the equation for extraction is:
In typical commercial practice, the organic phase is first washed with a dilute HCL solution to remove entrained raffinate comprising other PGM's and small amounts of other metals, such as iron and copper, which are extracted to a low level. Thewashed, loaded organic phase, containing less contaminant metals, is then stripped using aqueous ammonia The Pd complexes with the ammonia to form Pd(NH.sub.3).sub.4.sup.2+ ion in aqueous solution. The extractant is then recycled for reuse. The aqueousPd solution, which also contains excess NH.sub.3 and Cl, is then carefully acidified to precipitate the sparingly soluble salt Cl.sub.2 Pd(NH.sub.3).sub.2. Conversion to the metal results by its ignition at high temperature (e.q., about 900.degree. C.)to form "Pd sponge."
The extraction and stripping of PGM's using alkyl sulfides is affected by organosulfur impurities such as mercaptans and disulfides present in the alkyl sulfides. During stripping the organosulfur impurities readily react with palladium andother PGM's to form a solid emulsion-like "crud" phase which disrupts the complete recovery of Pd. For example, sulfur compounds, such as mercaptans, are undesirable in the alkyl sulfide as they can tie up metals as the mercaptides and can subsequentlycause problems in the stripping step. These problems can be overcome by using highly purified alkyl sulfides, but at considerable added materials cost.
There is a need for a process for conveniently and efficiently purifying the alkyl sulfides which are used for purifying palladium and other PGM's, of the unwanted impurities. This need is met by the present invention.
*****
3-b Optional. To treat the aqueous solution after Pd extraction with a small amount of DMG, to effect complete removal of Pd after filtration, before going to the next step.
4-The remaining aqueous solution is then extracted with Tri-n-butyl phosphate or other suitable solvent, with the purpose of extracting platinum and Iridium from the remaining aqueous solution of Rh and remaining PGMs and base metals.
[Insert relevant patents or processes here]
An sketch of the above Sx process was obtained initially from:
http://www.halwachs.de/solvent-extraction.htm
I believe Halwachs was one of the first pioneers of Solvent Extraction.
Feel free to further these process with specifics and details!. 8)
After we nail this down completely, we can explore Sx to produce pure forms of other interesting metals like U and Pu!. Save the flames and contribute if you can! :shock:
