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EP-4737598-A1 - METHOD FOR RECOVERING PRECIOUS METALS FROM AQUEOUS WASTE STREAMS

EP4737598A1EP 4737598 A1EP4737598 A1EP 4737598A1EP-4737598-A1

Abstract

The present invention relates to a method for recovering one or more precious metals from an aqueous waste stream, wherein the aqueous waste stream is mixed with one or more thiosulfates whereby the one or more precious metals are precipitated into a precipitate, and wherein the precipitate is separated.

Inventors

  • MERTENS, Martijn
  • PLUCKERS, Geert

Assignees

  • Indaver nv

Dates

Publication Date
20260506
Application Date
20251103

Claims (15)

  1. A method for recovering one or more precious metals from an aqueous waste stream, wherein the aqueous waste stream comprises water in an amount of more than 20 wt.%, wherein one or more precious metals are present as homogeneous catalysts in the aqueous waste stream, wherein the one or more precious metals are selected from: gold, silver, iridium, platinum, palladium, rhodium and/or ruthenium, wherein the aqueous waste stream is mixed with one or more thiosulfates whereby the one or more precious metals are precipitated into a precipitate, and wherein the precipitate is separated.
  2. The method according to any one of the preceding claims, wherein the mixing is carried out at a pH between 1 and 3.5.
  3. The method according to any one of the preceding claims, wherein the thiosulfates are added in a concentration between 0.1 and 10 wt.%.
  4. The method according to any one of the preceding claims, wherein the thiosulfates are added in a molar ratio between 10: 1 and 100: 1.
  5. The method according to any one of the preceding claims, wherein the waste stream comprises water in an amount of more than 60 wt.%.
  6. The method according to any one of the preceding claims, wherein the mixing is carried out at a temperature between 20 and 70°C.
  7. The method according to any one of the preceding claims, wherein one precious metal constitutes at least 80 wt.% of the one or more precious metals.
  8. The method according to claim 7, wherein the precious metal is palladium.
  9. The method according to any one of the preceding claims, wherein the precious metals are present in the waste stream in a total concentration from 1 to 2000 ppm, preferably between 10 and 1500 ppm.
  10. The method according to any one of the preceding claims, wherein the aqueous waste stream is mixed with the one or more thiosulfates for at least 5 minutes.
  11. The method according to any one of the preceding claims, wherein the one or more thiosulfates are selected from the list of: sodium thiosulfate, ammonium thiosulfate, potassium thiosulfate, calcium thiosulfate, magnesium thiosulfate, barium thiosulfate, or combinations thereof.
  12. The method according to any one of the previous claims, wherein the one or more thiosulfates comprise at least potassium thiosulfate and/or sodium thiosulfate.
  13. The method according to any one of the preceding claims, wherein the mixing is performed at a pH between 1 and 3.5, wherein the waste stream comprises water in an amount of more than 30 wt.%, preferably more than 60 wt.%, and wherein the one or more thiosulfates comprise sodium thiosulfate.
  14. The method according to any one of the preceding claims, wherein the separating of the precipitate is carried out by means of a horizontal plate filter, wherein the precipitate is retained as a filter cake.
  15. The method according to claim 14, wherein the filter cake is incinerated in a furnace.

Description

TECHNICAL FIELD The invention relates to a method for recovering one or more precious metals from an aqueous waste stream, as well as a use. PRIOR ART Homogeneous catalysts are catalysts that are in the same phase as the reactants. In the pharmaceutical and chemical industries, these catalysts often consist of organometallic complexes that are dissolved in the reaction mixture. After the reaction, the catalysts enter the liquid phase of the waste materials, whether or not partially. Certain homogeneous catalysts contain valuable metals, such as precious metals. Precious metals are rare elements of high economic value. They are the most stable metals, making them very useful catalysts. Moreover, recently under the Critical Raw Materials Act, more emphasis has been placed on the necessity of a secure supply and promoting the recycling of critical materials, which is directly related to the need for improved recovering techniques for valuable metal catalysts from liquid waste streams. There is a need for an improved purification/recovering these precious metal catalysts from aqueous waste streams. SUMMARY OF THE INVENTION The invention concerns a method for recovering one or more precious metals from an aqueous waste stream according to claim 1. It has been determined that thiosulfates can be used for precipitating precious metals from aqueous waste streams. It has been found that this also occurs without the formation of substances such as for example SO2. Thiosulfates can precipitate precious metals from solutions, even at low concentrations. This makes it possible to recover valuable metals from dilute waste streams where other methods might not be economical or effective. This improved method for recovering precious metals from aqueous waste streams makes it possible to recover precious metals efficiently and effectively, which contributes to the sustainable use of these valuable resources. In a second aspect, the invention concerns a use according to claim 16. DETAILED DESCRIPTION Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning as commonly understood by a person skilled in the art to which the invention pertains. For a better understanding of the description of the invention, the following terms are explained explicitly. The terms "waste stream", "waste materials" and "liquid waste materials" as used in the text all refer to liquid industrial waste materials, such as from the pharmaceutical and/or fine-chemical industry. The term "precious metals" as used in the text is intended to mean elements that in the general prior art are considered precious metals, namely ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), gold (Au) and silver (Ag). The term "platinum-group metals" or "PGM" as used in the text is intended to mean precious metals that belong to the platinum-group metals, namely ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt). The term "recover" refers to the process of extracting or recovering certain materials or substances from a mixture, waste stream or used products in order to reuse or recycle them. In the context of precious metals, recovering means that these valuable metals are separated and purified from a liquid, preferably aqueous, waste stream, whereby the metals are converted from a non-usable form back to a usable, optionally pure, form. The purpose of recovering is to increase the availability of materials, reduce waste, and improve the sustainability of resources. The term "thiosulfates" refers to salts of thiosulfuric acid and form a class of ionic sulfur compounds with the overall formula S2O32-. The term "TMT" is synonymous with "trimercapto-s-triazine trisodium salt" and "1,3,5-Triazine-2,4,6-trithiol trisodium salt" and refers to the component with CAS number 17766-26-6 and chemical formula C3N3S3Na3. As used in this document, the articles "a", "an" and "the" refer to both the singular and the plural, unless the context clearly indicates otherwise. For example, "a segment" means one or more segments. The terms "comprise", "comprising", "consist of", "consisting of", "provided with", "contain", "containing", "encompass", "encompassing", "include" and "including" are used herein as synonyms and are intended as inclusive or open terms indicating the presence of what follows, without excluding or preventing the presence of other components, characteristics, elements, members or steps known from or disclosed in the prior art. Quoting numerical intervals by endpoints comprises all integers, fractions and/or real numbers between the endpoints, these endpoints included. In a first aspect, the invention concerns a method for recovering o one or more precious metals from a liquid waste stream, preferably an aqueous waste stream. In an embodiment, the liquid waste stream is a solvent-borne waste stream or an aqueous waste strea