This video details an experimental, closed-loop hydrometallurgical electromining system designed to leach and electrowin metals directly from ore feedstocks (specifically galena ore containing lead, silver, gold, and platinum group metals). The system utilizes an aqueous electrolyte composed of 10–15% hydrochloric acid ($\text{HCl}$) and $<5\text{ g/L}$ sodium chloride ($\text{NaCl}$). The electrochemical cell incorporates custom linseed-oil-treated graphite gouging rod anodes, titanium plate cathodes, and an open-sourced Cation Exchange Membrane (CEM).
The operational process uses anodic oxidation to regenerate the acid leach solution and elevate the Oxidation-Reduction Potential (ORP) above $1000\text{ mV}$, enabling the dissolution of precious metals and precious-metal-group species (Au, Pt, Pd, Rh, Ir). At the cathode, metals are electrowon as a fine powder/sponge off the titanium plates, settling into a lower cone tank protected against re-dissolution via a negatively polarized titanium bolt. Bench-scale performance produced $85\text{ g}$ of metal concentrate in 30–40 minutes running at $45\text{ A}$ and $6\text{ V}$ ($\sim 135\text{ W}$), consuming approximately $$0.02$ of electricity. Safety protocols require strict secondary containment (PVC vinyl liner), forced active ventilation, and gas scrubbing to manage hazardous anodic chlorine gas ($\text{Cl}_2$), hydrogen sulfide ($\text{H}_2\text{S}$), hydrofluoric gas ($\text{HF}$), and explosive cathodic hydrogen ($\text{H}_2$). Future scaling plans center on replacing batch dewatering bags with a continuous vacuum drum filter to scale capacity to industrial tonnage per day.
Key Highlights & Timestamps
0:17 Process Overview & Product Yield: Demonstrates a end-to-end extraction process yielding a 2 oz metal concentrate bar from ore using an unoptimized electromining loop operating at minimal electrical cost.
2:19 Electrochemical Cell Architecture: Explains the continuous fluid loop where leach solution enters the cathodic chamber, plates out metals, and recirculates through a bypass port to the anodic chamber for acid regeneration.
3:00 Membrane & Anode Construction: Details the open-source Cation Exchange Membrane (CEM) and the use of linseed-oil-boiled graphite gouging rods as low-cost anodes.
4:01 Electrolyte Formulation & Chemistry: Outlines the leaching solution preparation using 32% hardware-grade $\text{HCl}$ diluted with water to 10–15% $\text{HCl}$, combined with $<5\text{ g/L}$ $\text{NaCl}$ to optimize ORP without forming gold-blocking complexes.
6:37 Hazardous Gas Mitigation & Containment: Emphasizes mandatory safety measures including forced ventilation, wet scrubbing for $\text{Cl}_2$/$\text{H}_2\text{S}$/$\text{HF}$ gases, and secondary containment using a PVC vinyl shower pan liner sized to double the liquid volume.
8:47 Dewatering & Leach Tank Filtration: Shows the batch solids-handling setup using layered window screens, aquarium filter media, and an IBC-tote dewatering filter bag inside the leaching tank.
12:29 Integrated Recirculation & Cathodic Bias: Reviews the fluid path through a chemical-resistant magnetic drive pump to titanium cathode plates, highlighting a negatively biased bottom titanium bolt that prevents deposited metal powder from re-dissolving.
15:23 ORP Monitoring & Gas Explosion Risks: Demonstrates bleach-white oxidation test paper responses and ORP metrics exceeding $1000\text{ mV}$; warns against mixing anodic $\text{Cl}_2$ gas and cathodic $\text{H}_2$ gas due to explosion risks.
18:33 Lead Sponge Harvesting & Cell Discharge: Displays lead sponge deposition on the cathode, proposing ultrasonic/vibrational stripping, and harvests heavy metal precipitate through the bottom cone valve.
22:13 Filtration & Alkaline Washing: Demonstrates solid-liquid separation of the harvested metal powder using vacuum filtration and subsequent washing with sodium bicarbonate to neutralize residual acid.
23:52 Electrical Efficiency & Analytical Validation: Calculates energy consumption ($135\text{ W}$ at $45\text{ A}$ / $6\text{ V}$ for 30 min = $\sim $0.02$ electricity cost for $85\text{ g}$ concentrate) and references third-party ICP-MS analysis confirming Au, Pt, Pd, Rh, and Ir extraction.
28:22 Industrial Scale-Up Roadmap: Outlines the transition from 5-gallon batch testing to a trailer-mounted, ton-per-day continuous system incorporating an automated vacuum filtration drum.
Analyst Notes
Thermodynamic Impossibility in Aqueous Electrowinning (29:34): The presenter states an objective to electroplate elemental aluminum ($\text{Al}$) and sodium ($\text{Na}$) directly from an aqueous solution through an ion exchange membrane at room temperature. Electrowinning sodium ($E^\circ = -2.71\text{ V}$) or aluminum ($E^\circ = -1.66\text{ V}$) from aqueous solutions is thermodynamically impossible due to the standard reduction potential of water. In aqueous media, hydrogen evolution ($2\text{H}^+ + 2e^- \rightarrow \text{H}_2$, $E^\circ = 0.00\text{ V}$) occurs far preferential to sodium or aluminum reduction, resulting purely in water electrolysis (hydrogen gas generation) and hydroxide accumulation. Industrial production of reactive metals like $\text{Al}$ (Hall-Héroult process) and $\text{Na}$ (Downs cell) strictly requires anhydrous molten salt electrolytes at elevated temperatures ($>800^\circ\text{C}$).