Precious Metal Electrowinning Patents: Leaders & Trends 2026
- 77 records, one clear leader. The ranked leader sits at 16 records against a fifth-place assignee at 8 and a tenth-place assignee at 2 — a steep drop-off rather than an even spread.
- Filing has cooled, not stopped. From a 2021 peak of 7 filings the count moved to 6 by 2024, a -14% shift over that span; 2025-2026 figures are still filling in as publications catch up with filing.
- Claim space is heavily metallurgical. 96.1% of the 77 records sit in C22B (metal extraction and refining), with far smaller footprints in compounds chemistry and powder metallurgy — the electrochemical subclasses barely register.
Filing growth compares 2021 (7 records) with 2024 (6) — a three-year span. 2024 is the most recent year we treat as complete: publication lags filing by roughly 18 months, so 2025 onwards are still filling in and any growth rate that ends there would understate the field.
What this landscape covers
This landscape tracks patent activity naming precious metal refining, gold electrowinning and silver refining alongside process-specific terms such as the Miller process, the Wohlwill process, anode slime treatment, cathode stripping, electrolyte purification and fire assay. The scope spans 2015 through the 2026 data cut-off, covering 77 published records assigned to 19 ranked companies.
The routes at stake are the ones refiners actually run in production: chlorination-based purification (Miller), electrolytic purification (Wohlwill), and the wet-chemical and hydrometallurgical steps that recover value from anode slimes and spent electrolyte. Filing offices skew toward jurisdictions with active refining capacity — Australia, the United States, WIPO's PCT route, South Africa, Canada and the EPO all carry meaningful volume, which tracks with where mined and secondary precious metal actually gets processed.
Filing trend and technology composition
Two views of the same 77-record corpus: activity over time, and where records sit across the IPC scheme. Because a single record can carry more than one classification, the composition shares add up to well over 100%.
A peak in 2021, a modest pullback since
Filings ran at 6 in 2017 and reached a peak of 7 in 2021. By 2024 — the most recent year that can be treated as complete, given the roughly 18-month lag between filing and publication — the count had eased to 6, a -14% move over that three-year span. Years after 2024 will keep rising as more publications land; they should not be read as a slowdown yet.
Metallurgy dominates; electrochemistry barely appears
C22B (metal extraction and refining) covers 96.1% of the 77 records, making it close to a universal tag across this corpus. C01G (compounds of other metals) and B22F (powder metallurgy) follow at 28.6% and 19.5% respectively, reflecting the chemistry and post-processing steps that surround the core refining step. C25B and C25C — the subclasses that cover electrolytic production directly — each appear in only one record, a striking gap given how central electrowinning and Wohlwill-style electrolysis are to the field's own vocabulary.
Shares are the percentage of the 77 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Precious Metal Electrowinning and Refining with Eureka
This page is one run against one query. Ask Eureka your own question about precious metal electrowinning and refining and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited records in this corpus
Method of refining precious metals (WO2025123148A1)
A method of refining a precious metal, involving contacting the precious metal with a refining solution under conditions to solubilize the precious metal, the refining solution having an acid, an oxidant, an optional ligand source, and a water-miscible solvent; and forming a leached solution comprising leached precious metal.Filed by EXCIR WORKS CORP, published 2025-06-19 — one of the few filings from this assignee active in the most recent year of the trend.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4892631A | Recovery of precious metals from complex ores | 26 |
| 2 | WO2015102865A1 | Process for dissolving or extracting at least one precious metal from a source material containing the same | 19 |
| 3 | WO2011154607A1 | Method of gold leaching | 14 |
| 4 | US20120067169A1 | Method for processing precious metal source materials | 10 |
| 5 | WO2017199254A1 | A process for recovering gold from ores | 4 |
| 6 | US4722831A | Process for purifying silver refinery slimes | 4 |
| 7 | US20190292628A1 | A process for recovering gold from ores | 3 |
| 8 | WO2011000051A1 | Smelting method | 3 |
| 9 | US20120144959A1 | Smelting method | 3 |
| 10 | WO1987001366A1 | Process for purifying silver refinery slimes | 3 |
Citation counts are pulled from within this searched corpus and skew toward older records simply because they have had longer to accumulate citations — treat them as a signal of influence on later filings, not as a ranking of current commercial relevance.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three read-outs from the trend, the classification split and the citation table, translated into what they mean if you are deciding where to file or what to design around.
The peak has passed, but the field hasn't gone quiet
Filings dropped from 7 in 2021 to 6 in 2024. That is a real pullback, not a collapse — and because 2025-2026 records are still being published, the true current rate is higher than the chart shows today.
Almost everything is filed as metal extraction and refining
With C22B present in nearly every record, differentiation happens inside the subclass rather than across it. The much smaller C01G and B22F footprints mark where compounds chemistry and powder handling intersect the core refining claims.
Direct electrolytic claims are almost absent
Despite gold electrowinning and the Wohlwill process being central to the search terms, the subclasses that cover electrolytic metal and compound production carry only one record apiece. Claims that sit squarely in electrowinning process control look comparatively open.
Older complex-ore recovery art still anchors the field
The most-cited record in this corpus dates back well before the 2015 filing window and covers recovery from complex ores — a reminder that foundational hydrometallurgical claims from outside the search window still shape freedom-to-operate analysis today.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to precious metal electrowinning and refining, with the prior art for and against each one.
A steep leader, then a long tail
The ranking covers all 19 companies the data endpoint returns for this search — not a top-50 or top-100 cut. The leader holds 16 records; by fifth place that has fallen to 8, and by tenth place to just 2, marking a long tail of single- and few-filing entrants rather than a broad, even field.
One assignee holds a clear lead
The top-ranked company's 16 records sit well ahead of the rest of the ranking, giving it the deepest claim coverage across the Miller-, Wohlwill- and slime-treatment-adjacent filings in this corpus.
A second tier forms quickly after the leader
By fifth place the count has already halved to 8 records, showing that meaningful filing activity is not spread evenly — it clusters among a handful of names before dropping off sharply.
Some of the strongest activity is collaborative
Nine co-assignee pairs appear across the corpus, with the strongest pairings linking a bromine-chemicals specialist to an advanced-technology refiner, and a services engineering firm to a commercial refinery — signs of process licensing or joint development rather than pure in-house R&D.
Only a handful of names are active in the most recent year
Most of the assignees with historical volume — including several among the ranked leaders — show zero filings in the latest year, while EXCIR WORKS CORP registers one. Given publication lag, this says more about who has publications already through the pipeline than who has stopped filing.
| Assignee | Recent year | YoY |
|---|---|---|
| EXCIR WORKS CORP | 1 | — |
| Precious Metals Recovery Pte Ltd | 0 | — |
| ASARCO LLC | 0 | — |
| Prior Engineering Services AG | 0 | — |
| ENVIRO METALS LLC | 0 | -100% |
| Bromine Compounds Ltd | 0 | — |
| TENOVA ADVANCED TECH LTD | 0 | — |
| RAND REFINERY | 0 | — |
Where to take this analysis
The trend and ranking above answer who is active and where the claim density sits. The next step is usually narrower: checking a specific claim against this art, or scoping a filing into the gaps identified here.
Map a specific process route against this art
Take a candidate process — a leaching chemistry, a stripping method, an electrolyte purification step — and check it against the most-cited records and the leader's filings before drafting claims.
Explore with EurekaTrack the leader's and co-filers' pipelines
Recent-year momentum shows most historical filers quiet in the latest year. Watching publication feeds for the ranked leader and its co-assignees will surface the next wave before it is fully indexed.
Set up monitoring in EurekaScope filings into the electrochemical gap
With C25B and C25C each covering just one record, a claim written squarely around electrowinning process control has comparatively little art to design around today.
Draft with EurekaCommon questions on this landscape
This dataset ranks 19 companies by record count, with the top-ranked assignee holding 16 records against a fifth-place company at 8 and a tenth-place company at 2. That drop-off means the field has one clearly dominant filer rather than several evenly matched competitors. Names include process-equipment and refinery operators alongside specialty chemical suppliers, reflecting that refining patents come from both equipment builders and the refineries that run the equipment.
Filings peaked at 7 in 2021 and eased to 6 by 2024, a -14% change over that three-year span — a modest pullback rather than a collapse. Because publication typically lags filing by around 18 months, the 2025 and 2026 figures in any chart are still incomplete and will rise as more records publish. Read the trend as cooling slightly from a 2021 high point, not as a field in decline.
Both terms sit inside the search scope for this landscape, and the vast majority of records classify under C22B, the general metal extraction and refining subclass, rather than under the electrolytic-production subclasses C25B or C25C. That imbalance suggests most patent activity addresses the chemical and mechanical steps around these processes — feed preparation, slime treatment, purification chemistry — rather than the electrolytic step itself, which appears comparatively under-claimed in this corpus.
The clearest gap sits in the electrochemical subclasses: C25B and C25C, covering electrolytic compound and metal production respectively, each contain only one of the 77 records in scope, despite gold electrowinning and the Wohlwill process being core search terms for this landscape. Anode slime hydrometallurgy and electrolyte purification for electrolytic refining cells also look thinner than the dominant C22B claim mass. A first claim in these areas would need to tie directly to electrode, cell or electrolyte-control specifics rather than general extraction chemistry to stand apart from the existing art.
Citation counts inside this corpus favour older records simply because they have had more time to accumulate citations from later filings — the top-cited record here, at 26 citations, predates the 2015 start of the main filing window. Use citation rank as a signal of which foundational techniques later filers built on, not as a measure of which patents are commercially important today. For current relevance, pair citation data with the recent-year filing momentum figures for individual assignees.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.