Reclaiming Gold from Legacy Leach Pads: RZOLV’s Environmental Reprocessing Opportunity

Across the gold industry, legacy heap-leach pads and cyanide-impacted tailings represent one of mining’s most familiar unresolved challenges. Many of these materials are no longer active ore, but they are not necessarily waste either. They may contain residual gold and silver, trapped process solution, soluble metals, residual free cyanide, weak-acid-dissociable cyanide, metal-cyanide complexes, and long-term closure liabilities. In many cases, the value is still there — but the question is how to recover it without extending the same cyanide-management burden that created the liability in the first place.

That is the opportunity RZOLV Technologies is now framing: a two-stage environmental reprocessing pathway designed to first reduce cyanide risk, then recover residual precious metals using a non-cyanide chemistry.

The concept is straightforward but strategically important. Rather than re-cyaniding historical material, the proposed RZOLV flowsheet begins with an alkaline electrochemical prewash stage intended to destroy or substantially reduce residual free and WAD cyanide. Only after cyanide reduction is confirmed would the material be acidified into the RZOLV operating window of approximately pH 1.5 to 2.5, where the company’s non-cyanide redox-complexation chemistry may recover residual gold and silver.

“RZOLV’s environmental reprocessing concept is designed to reduce cyanide risk first, recover stranded value second, and move spent pads closer to a cleaner closure profile.”

In simple terms, the process separates two jobs that should not be confused. Cyanide destruction is addressed first, under alkaline conditions where hydrogen cyanide risk can be controlled. Gold recovery comes second, under controlled low-pH RZOLV conditions.

A new angle on an old mining problem

Heap leaching changed the economics of gold mining by allowing lower-grade ore to be processed at scale. But the legacy of historical cyanide leaching is complex. Spent pads and tailings often remain chemically active long after mining has stopped. Operators may still need to manage residual cyanide, ponded or entrained solution, dissolved metals, pad draindown, liner integrity, water balance, and closure obligations.

At the same time, many spent pads and tailings still contain gold. Some of that gold may remain because of poor historical solution contact, coarse crush size, permeability issues, incomplete leaching, copper interference, preg-robbing behavior, or operating constraints. In other words, a material can be both an environmental liability and a recoverable resource.

The difficulty is that conventional retreatment often implies renewed cyanide use. That can mean additional reagent handling, detoxification, permitting, water treatment, monitoring, and public scrutiny. For institutional investors, mine owners, and retreatment specialists, this creates a familiar trade-off: the ounces may be attractive, but the environmental and regulatory overlay can complicate the investment thesis.

The two-stage RZOLV environmental flowsheet

The proposed flowsheet begins with characterization. Before any treatment, the material would be tested for residual gold, silver, copper, iron, arsenic, zinc, lead, mercury, free cyanide, WAD cyanide, total cyanide, pH, alkalinity, acidity, entrained solution, mineralogy, leachability, acid-base behavior, permeability, and particle size.

From there, the material would enter an alkaline electrochemical cyanide-destruction prewash. The report contemplates operation above approximately pH 10 to 10.5, with ORP controlled high enough for cyanide oxidation. The treatment target would be reduction of free and WAD cyanide, with ventilation and HCN monitoring included as part of the safety framework.

The intended chemistry is to oxidize cyanide toward cyanate and downstream nitrogen species, depending on conditions. Importantly, the report cautions that cyanide disappearance alone is not enough. Cyanate, ammonia, nitrate, nitrite, thiocyanate, total nitrogen, metals, and toxicity would all need to be tracked.

After electrochemical treatment, the material would be rinsed or drained to remove treated cyanide-bearing solution and reaction products. Verification would include free cyanide, WAD cyanide, total cyanide, pH, ORP, HCN gas, metals in wash solution, and cyanate/ammonia/nitrate monitoring.

Only then would the material be acidified into the RZOLV leach window of approximately pH 1.5 to 2.5. This is a critical design feature. RZOLV’s low-pH chemistry may provide a non-cyanide recovery route, but acidifying cyanide-bearing material without prior detoxification and verification would be unsafe. The report therefore describes the electrochemical prewash as the safety and permitting bridge before low-pH RZOLV leaching.

Recovering the value without adding new cyanide

Once residual cyanide risk has been controlled and the material has been conditioned to the RZOLV operating window, the company’s chemistry is introduced to recover residual gold and potentially silver. The operating variables include pH, ORP control, RZOLV reagent dose, oxidant moderation, copper and iron monitoring, residual cyanide monitoring, time-series gold assays, and final residue assays.

The predicted recovery ranges are intentionally feed-specific. The report estimates that previously cyanided oxide heap residues may yield 40% to 75% of remaining recoverable gold, while spent pads with accessible residual gold may yield 50% to 85%. Tailings with fine liberated gold may offer 60% to 90%, while partially refractory residues may be lower and strongly refractory sulfide residues may require liberation or oxidation pretreatment.

The key point is not that RZOLV will recover all residual gold from all tailings. The point is that it may create a non-cyanide pathway for the portion of residual gold that remains solution-accessible.

For legacy assets, that distinction matters. A spent pad with marginal residual grade may not justify a complex cyanide retreatment campaign if the result is additional detox burden and extended closure liability. But a process that reduces residual cyanide first, recovers value without new cyanide, and then supports residue washing, neutralization, and environmental validation may create a more compelling remediation-and-recovery model.

Why carbon recovery matters

One of the most commercially important parts of the report is its emphasis on activated carbon as the projected base-case downstream recovery route.

RZOLV’s primary function is to dissolve residual gold under controlled low-pH, non-cyanide conditions. But dissolving gold is only half the job. The gold must be recovered from solution in a form that miners understand and can operate. The report states that internal RZOLV testwork has demonstrated that gold dissolved by RZOLV can be recovered onto activated carbon, supporting carbon as the preferred downstream recovery route for the proposed tailings and spent-pad reprocessing flowsheet.

That matters because activated carbon is familiar across the gold industry. Carbon columns, carbon-in-column, carbon-in-leach, carbon-in-pulp, and carbon-in-solution infrastructure are well understood by operators, engineers, and regulators. If RZOLV-dissolved gold can be recovered through carbon adsorption, the technology may face a lower adoption barrier than a process requiring entirely unfamiliar downstream recovery infrastructure.

The report frames this as a practical bridge between RZOLV’s non-cyanide leach chemistry and conventional gold-plant operating practice. It also strengthens the environmental argument because dissolved gold is not merely mobilized; it is captured into a recoverable product stream.

Closure, not just recovery

The environmental reprocessing thesis is broader than gold recovery. The report predicts potential environmental benefits including reduced free and WAD cyanide, reduced residual precious-metal inventory, reduced long-term liability, improved closure economics, and a stronger remediation profile. It also highlights that solution recycle may reduce discharge volume and that residue washing and neutralization would be part of the closure-oriented treatment sequence.

That is the larger story. RZOLV is not being positioned simply as another lixiviant. In this concept, it is part of a staged environmental reprocessing platform: reduce cyanide risk, recover stranded value, recycle or recondition solution, wash and neutralize residue, validate leachability and toxicity, and move the material toward a better closure profile.

For mine owners, that could mean a different way to think about legacy pads and tailings. For institutional investors focused on retreatment stories, it could mean a different value proposition: not just ounces recovered, but remediation funded by recovered ounces.

The investment relevance

Institutional interest in tailings retreatment has grown because these assets can offer several advantages: known locations, historical infrastructure, established disturbance footprints, existing metallurgical data, and the possibility of residual metal value without greenfield mining risk. But environmental complexity often sits at the centre of the investment case.

A cyanide-impacted retreatment asset can look attractive on contained metal but more difficult on permitting, water treatment, community optics, detox cost, and closure bonding. RZOLV’s proposed process is directly aimed at that tension.

The company’s conceptual pathway does not eliminate the need for rigorous technical validation. It requires bench and pilot testing, including cyanide-destruction kinetics, HCN monitoring, pH-transition testing, RZOLV leach performance, reagent consumption, carbon loading, elution, electrowinning, residue leachability, toxicity testing, and full mass-balance assessment.

But if validated, the model could be compelling: recover residual gold from legacy material, avoid adding new cyanide, reduce cyanide risk before low-pH treatment, use carbon recovery to capture dissolved gold, and improve the final closure condition.

A disciplined but potentially powerful concept

The report is careful not to overstate the opportunity. It does not claim that RZOLV is a universal cyanide destroyer. It does not suggest that all spent pads or tailings can be treated the same way. It explicitly notes that the process is conceptual, feed-specific, and subject to site-specific metallurgical, environmental, engineering, regulatory, and economic validation.

That discipline is important. Cyanide-impacted materials must be treated with caution. Acidification before cyanide destruction and verification would create HCN risk. Strong metal-cyanide complexes may persist. Cyanate, ammonia, nitrate, thiocyanate, and other byproducts must be tracked. Copper, iron, arsenic, sulfur species, and other constituents may affect recovery or closure outcomes.

But the strategic thesis remains strong: legacy cyanide pads and tailings are a large and persistent industry problem; many still contain residual precious-metal value; re-cyanidation can extend environmental burdens; and a staged process that first reduces cyanide risk, then recovers value without new cyanide, could open a new category of environmental gold recovery.

The bottom line

RZOLV’s environmental reprocessing concept is not simply about leaching residual gold. It is about rethinking how legacy cyanide materials can be treated.

The proposed process offers a pathway in which alkaline electrochemical cyanide destruction reduces risk, low-pH RZOLV chemistry recovers residual gold, activated carbon captures dissolved metal into a familiar recovery circuit, and downstream washing, neutralization, recycle, and environmental validation support improved closure outcomes.

For an industry increasingly focused on tailings stewardship, brownfield recovery, water management, and ESG credibility, that could be a meaningful proposition.

If validated through representative testwork, RZOLV may help convert cyanide-impacted tailings and spent leach pads from long-term closure liabilities into controlled, non-cyanide recovery opportunities — recovering stranded value while moving legacy sites closer to a cleaner closure condition.

Disclaimer

This article is for general information and discussion purposes only and is not intended to constitute a technical report, feasibility study, preliminary economic assessment, engineering design, environmental impact assessment, permit application, closure plan, legal opinion, investment advice, or a recommendation to buy or sell any securities.

The RZOLV environmental reprocessing concept described herein is preliminary and conceptual. Any statements regarding potential cyanide reduction, residual gold recovery, environmental improvement, closure benefits, solution recycle, carbon recovery, or commercial applicability are forward-looking in nature and remain subject to site-specific metallurgical, environmental, engineering, regulatory, and economic validation.

RZOLV should not be characterized as a stand-alone cyanide-destruction reagent unless supported by specific analytical testwork. Where cyanide-bearing materials are present, residual free cyanide, weak-acid-dissociable cyanide, total cyanide, metal-cyanide complexes, pH, ORP, cyanate, ammonia, nitrate, thiocyanate, dissolved metals, and potential hydrogen cyanide gas risk must be characterized before any acidification or low-pH leaching stage is considered.

The proposed electrochemical prewash stage is intended to reduce cyanide risk under alkaline conditions before transition to the RZOLV low-pH leach environment. Any acidification of cyanide-bearing material must be managed with appropriate engineering controls, analytical verification, gas monitoring, containment, worker-safety procedures, environmental review, and regulatory oversight.

Predicted performance ranges and potential benefits are illustrative only. Actual results may vary materially depending on feed mineralogy, residual cyanide speciation, permeability, gold liberation, residual metal inventory, reagent consumption, carbon loading performance, elution efficiency, solution recycle behavior, residue leachability, toxicity, water balance, permitting requirements, and site-specific operating conditions.

No assurance can be given that the proposed process will achieve commercial recovery, cyanide reduction, environmental improvement, regulatory approval, or economic viability at any specific site. Any deployment would require representative bench-scale and, where appropriate, pilot-scale testwork, independent technical review, qualified-person oversight, environmental permitting, and compliance with all applicable laws, regulations, standards, and industry codes.