Precious Metal Electrolysis Equipment

— Precious Metal Electrolysis Equipment: Gold & Silver Cells

Precious metal electrolysis equipment is an engineered cell system that dissolves a cast crude-metal anode in a controlled aqueous electrolyte under direct current and deposits the purified metal on the cathode, upgrading an anode plate of 75–97% metal into product of 99.99% (4N) purity in a single pass and 99.999% (5N) on a second pass. YuSai Machinery builds the complete electrolysis family — high-current-density gold, silver and copper cells, tellurium cells, cyclone electrowinning units, loaded-carbon desorption electrowinning sets and turnkey silver electrorefining workshops — together with the rectifier, electrolyte circuit, temperature control, fume extraction and cathode harvesting equipment that make each cell work.Cells in the family: high-current-density gold, silver and copper electrolytic cells, tellurium cells, cyclone electrowinning units, loaded-carbon desorption electrowinning sets and turnkey silver electrorefining workshops.

Product Overview

Electrolysis is the one refining step that separates metal from impurity by electrode potential rather than by a reagent that has to be invented for each feed. A cast anode plate is hung in an electrolyte that dissolves it, a current is passed, and purified metal deposits on the cathode while the impurities either stay in solution or fall to the bottom of the cell as anode slime. The selectivity comes from the voltage window: at a correctly held cell potential only the target metal is reduced at the cathode, so the refining duty is not set by what the electrolyte can dissolve but by how tightly current density, electrolyte composition and temperature are controlled.

That is why one word — electrolysis — describes four different engineering problems. Gold runs in a chloroauric acid electrolyte, HAuCl₄ with free hydrochloric acid, holding 120–150 g/L Au at 60–70 °C, on a titanium or fine-gold cathode, from an anode that must carry less than about 6% silver: above that limit the silver chloride that forms on the anode face passivates it and the anode stops dissolving cleanly. Silver runs in silver nitrate with 10–18 g/L free nitric acid and 60–150 g/L Ag at a 40 °C set point, because above that temperature the electrolyte volatilises and acid consumption climbs, while below it deposition slows and the cell gives up capacity. Copper runs in a copper sulphate–sulphuric acid electrolyte at 300 A/m² from cement or heavy plate anodes. Tellurium, indium and the other rare metals each bring their own medium and their own cell geometry. A specification sheet that offers a single machine for all of them is describing a power supply, not a refining system.

The parameter that decides how much metal a cell can deliver for a given floor area, electrolyte volume and working inventory is cathode current density. Conventional silver cells run at 250–350 A/m². The high-current-density silver cell in this equipment family runs at 750 A/m², two to three times conventional practice, which cuts by roughly 60% the time needed to dissolve the same mass of anode plate and, at equal production, reduces both the floor area and the quantity of silver immobilised in the electrolyte. The gold cell reaches 1,000 A/m². Raising current density is not free. It steepens concentration polarisation at the cathode, encourages dendritic growth that can bridge the gap to the anode and short the cell, increases the resistive voltage drop through the electrolyte, and magnifies the effect of any impurity that is capable of co-depositing. Every one of those consequences is answered here by a structural feature rather than by an operating instruction: parallel-flow circulation across the electrode array, automatic cathode scraping, sealed side extraction, titanium-clad copper busbars and screwed electrode connections that remove the contact heating a conventional cell develops at high current.

The cell is the visible part of the purchase and the smallest part of the risk. A working electrolysis line also needs a rectifier sized to the cell current, an electrolyte circuit that holds composition, level and temperature in band, a chiller that keeps the silver cell at 40 °C, filtration, a transparent enclosed cover with side extraction and a condenser that returns volatilised electrolyte to the cell instead of to the stack, a harvesting system — manual plate stripping for gold, automatic scraping and a discharge conveyor for silver powder — a washing and drying stage, melting and ingot casting, and an effluent route for bleed liquor and rinse water. This equipment family covers all of it and is delivered as one scope with one commissioning.

Electrolysis also decides what the plant does with the metals that are not the target. Silver in a gold anode leaves the circuit as silver chloride retained in the anode bag; gold in a silver anode reports to the anode bag as well. Silver-cell anode slime runs at roughly 8% of the anode mass and carries 50–70% gold and 30–40% silver, which is far too rich in silver to melt directly into a gold anode plate: it is desilvered with nitric acid until the contained gold rises above 90%, and only then cast into the anodes the gold cell consumes. Gold and silver therefore become each other’s feed rather than each other’s contamination, and the residue that neither of them claims — the platinum group metals and the refractory phases — leaves the circuit as a concentrate for hydrometallurgical separation.

Because achievable purity, cell count and operating window all follow from the feed, the line is configured against an assay rather than a catalogue. Capacity, installed power, footprint, cooling duty, extraction volume and rectifier rating are engineered from the anode analysis, the daily metal target and the site conditions; electrolyte make-up, current density, temperature and the slime route are fixed in the flowsheet and then held by instrumented control. Purity leaving the plant is released against a certificate of analysis, and melting, casting and marking sit inside the same scope, so the ingot the buyer receives is traceable to the anode lot it came from.

Key Facts

Cells in the family: high-current-density gold, silver and copper electrolytic cells, tellurium cells, cyclone electrowinning units, loaded-carbon desorption electrowinning sets and turnkey silver electrorefining workshops.
Cathode current density: up to 1,000 A/m² in the gold cell, 750 A/m² in the silver cell against 250–350 A/m² conventional silver practice, and 300 A/m² in the copper cell.
Product purity: 99.99% (4N) from a single electrolysis pass, including Au99.99 to the Shanghai Gold Exchange Grade I standard and silver to national-standard No. 1 grade; 99.999% (5N) from a second pass on the same equipment.
Feed gates: gold anode ≥ 90% Au by process requirement and 92–95% in practice, with Ag below 6% and Cu below 2%; silver anode ≥ 75% Ag, in practice ≥ 97% crude silver; copper anode approximately 98% Cu.
Electrolyte temperature: 60–70 °C for gold in a chloroauric acid electrolyte, and a 40 °C set point for silver nitrate electrolyte held on chiller control.
Configuration: cell count, capacity, footprint, rectifier rating, cooling duty and extraction volume are engineered to your feed assay and target throughput rather than to fixed catalogue numbers.

Product Core Selling Points

One equipment family across five metals. Gold, silver, copper, tellurium and dilute-solution electrowinning are engineered on a common cell architecture, so a plant that starts with one metal can add another without a second supplier, a second spares list or a second control philosophy.
High current density as a designed feature, not a datasheet claim. The silver cell runs at 750 A/m² against 250–350 A/m² conventional practice and the gold cell reaches 1,000 A/m² — two to three times conventional density, which cuts the time needed to dissolve the same anode mass by about 60% and shrinks the electrolyte inventory and floor area held per kilogram of daily output. The cost of that density — concentration polarisation, dendritic bridging, resistive drop and impurity co-deposition — is answered structurally, by parallel-flow circulation, automatic cathode scraping, oversized busbars and screwed electrode connections.
A purity ladder that is reached by repetition rather than by promise. One pass delivers 99.99% (4N), dense enough to meet the Au99.99 Shanghai Gold Exchange Grade I standard for gold and national-standard No. 1 grade for silver; a second electrolysis pass on the same cells reaches 99.999% (5N). The pass count is set in the flowsheet from your anode assay, not left to the operator.
Anode bags and slime management designed in. Silver in a gold anode leaves the circuit as silver chloride held inside the anode bag; gold in a silver anode leaves the same way. Slime is captured rather than dispersed, the cell is never opened to the shop floor to clean it, and the slime route back to a saleable product is specified with the cell.
Fume control that pays for itself. Cells are closed under a transparent cover with side extraction, and a condenser returns volatilised electrolyte to the cell. Silver loss and gold loss through evaporation stop being an operating cost, extraction volume falls because the cell is sealed, and the acid mist that reaches the scrubber is a fraction of what an open cell produces.
Electrolyte kept in specification rather than replaced. Parallel-flow circulation, chiller control, filtration and bleed management hold composition, level and temperature in band; where impurity ions reach the limit, the electrolyte is purified and returned to the cell instead of being made up from scratch.
Harvesting that matches the metal. Gold is stripped from titanium or fine-gold cathodes as a coherent deposit; silver is scraped from the cathode automatically and carried out of the cell on a discharge conveyor, so the cell runs for months between clean-outs instead of weeks.
Turnkey scope with a single interface. Anode casting and moulds, cells, rectifier, electrolyte circuit, cooling, extraction, scrubbing, washing and drying, melting and ingot casting, and the assay support are delivered as one contract, which is why there is no argument about which supplier’s equipment caused a purity excursion.

Application Scenarios

Precious metal refineries. Stand-alone refineries that buy mixed crude gold, silver and doré and need a repeatable route from assay to certified ingot in one building.
Gold refineries and doré upgrading. Operations casting doré on site that want to stop selling an unrefined alloy and start selling Au99.99 bar to the Shanghai Gold Exchange Grade I standard.
Silver refineries serving smelters. Copper and lead smelters whose anode slime is currently exported as a slime and that want the contained gold and silver refined in-house.
Copper electrorefining plants. Producers of copper cement, copper granule or fire-refined plate who need cathode copper at 99.99% and whose anode slime carries the precious metal values.
Secondary precious metal refineries. Plants processing jewellery sweeps, dental alloys, electrical contacts, spent catalysts and photographic residues into anode plates for the cells.
Electronics and PCB recyclers. Recovery of gold, silver and copper from leach liquors, stripping solutions and process residues, where the final step is electrolysis rather than precipitation.
Plating and surface finishing plants. Electrolytic recovery of gold, silver and palladium from spent plating baths, drag-out and rinse water, returning metal to the plating line instead of to a waste contractor.
Mining and CIL/CIP operations. Loaded-carbon desorption and electrowinning of gold from eluate, where the cell is part of an integrated leach–adsorb–desorb–electrowin–smelt circuit.
Printed circuit board and metal finishing waste water. Treatment of copper-bearing acidic etching and micro-etch liquor, and of complexed chemical copper waste, by electrowinning, with the metal sold back as cathode copper.
Rare metal producers. Tellurium and indium cells for producers separating these metals from copper anode slime and residue streams.
Assay, pilot and research laboratories. Small single-cell installations used to validate a flowsheet on a few kilograms before the refinery is scaled.
Refineries replacing open cells. Plants with existing cells whose fume extraction, acid consumption, silver inventory or labour cost has become the constraint, and that need a sealed, high-current-density replacement.

Applicable Raw Materials

Each feed below enters the line at the point its composition requires. Feeds that arrive as bullion, cement, slime or powder are first melted and cast into anode plates; feeds that arrive as liquor go directly to an electrowinning cell. Output is stated for each feed.

Doré bullion and gold–silver alloy plates. The classic refinery feed from a mine or a smelter, typically 60–90% gold with silver and base metals, cast into anodes after assaying and, where silver is high, after a desilverising step. Output: Au99.99 ingots; silver nitrate solution to the silver circuit.
Crude gold above 90% Au. Anodes cast from crude gold and reduced gold powder, meeting the electrolysis gate of Au ≥ 90% with Ag below 6% and Cu below 2%. Output: cathode gold at 99.99%; AgCl to the anode bag.
Crude silver above 97% Ag. Silver recovered as cement, from silver chloride reduction or from smelter bullion, melted and cast into anode plates. Output: silver powder at 99.99%; gold-bearing slime to the anode bag.
Copper and lead anode slime derivatives. Gold–silver alloy plates produced from anode slime treatment, where the precious metal content justifies a dedicated cell circuit. Output: silver powder; gold cathode; PGM-bearing residue.
Silver chloride from hydrometallurgical refining. Precipitated AgCl reduced to metallic silver and cast into anodes, closing the loop between the wet-chemical and electrolytic sections of a refinery. Output: anode-grade silver; silver powder at 99.99%.
Copper cement, copper granule and fire-refined copper plate. Copper at approximately 98% from cementation, granulation or fire refining, cast as heavy plate anodes. Output: cathode copper at 99.99%.
Copper-bearing acidic etching and micro-etch liquor. PCB etchant at 110–180 g/L Cu, and dilute micro-etch streams at 6–8 g/L Cu, treated directly by cyclone electrowinning. Output: cathode copper plate or copper powder; spent liquor to neutralisation.
Complexed chemical copper waste water. Plating and electroless copper rinses whose metal is bound in a complex and cannot be precipitated economically, broken by electrolysis on titanium composite electrodes. Output: cathode copper; effluent below 0.1 mg/L Cu²⁺.
Loaded-carbon desorption eluate. Pregnant eluate from a CIL/CIP desorption column, at gold concentrations from a few milligrams per litre upward, fed to a desorption electrowinning cell. Output: gold cathode sludge; barren eluate returned to the circuit.
Spent plating baths and drag-out. Gold, silver, palladium and copper electrolytes and rinse waters from plating lines, where the metal is recovered electrolytically and the depleted bath is returned to service or discharged. Output: metal cathode product; de-metallised bath for treatment.
Tellurium-bearing residue. Tellurium recovered from copper anode slime processing and cast or dissolved for the tellurium cell. Output: tellurium cathode product; purified electrolyte for recycle.
Spent electrolyte, bleed liquor and rinse water. Metal-bearing liquors generated inside the refinery itself, returned to a cell for recovery rather than sold or written off. Output: recovered metal; polished effluent to the treatment plant.

Finished Products

The line is configured to deliver the product form the buyer or the downstream fabricator requires, from a saleable intermediate to certified metal in the shape the market grades accept.

Gold ingots to Au99.99. The primary gold product, cast from cathode gold after washing and drying, released to the Shanghai Gold Exchange Grade I standard and marked and weighed per bar. Output: Au99.99 ingots with certificate of analysis.
High-purity gold at 99.999%. Reached on a second electrolysis pass through the same cells, for buyers who need five-nines material rather than four. Output: 99.999% gold ingots or granules.
Silver powder and silver ingots at 99.99%. Cathode silver is harvested as powder, washed with deionised hot water, dried and cast, meeting national-standard No. 1 grade with the silver content stable at 99.99% or above. Output: silver powder or 99.99% silver ingots.
High-purity silver at 99.999%. Produced by re-running the harvested silver as a fresh anode, where the impurity profile and the buyer’s specification justify it. Output: 99.999% silver.
Cathode copper at 99.99%. Copper deposited as coherent cathode plate, stripped, bundled and sold as cathode copper; copper recovered from waste water leaves the cyclone cell as plate or as powder. Output: cathode copper plate or copper powder.
Tellurium cathode product. Tellurium deposited on the cathode of the tellurium cell, harvested and finished to the purity the downstream application requires. Output: tellurium cathode plate.
Electrowon gold cathode sludge. Gold deposited from desorption eluate or dilute solution as a cathode sludge, filtered, dried and melted with the rest of the refinery’s gold. Output: gold sludge to calcination and melting.
Anode slime and silver chloride concentrates. The by-product streams that carry the metals the cell is not purifying, captured in the anode bag and delivered to the appropriate downstream circuit. Output: slime and AgCl to hydrometallurgical recovery.
Platinum group metal residue. The refractory residue that reports to the anode bag or cell bottom, containing platinum, palladium and rhodium that electrolysis does not take into solution. Output: PGM-bearing residue to refining.
Electrolyte make-up solutions. Silver nitrate produced by dissolving silver in nitric acid, and chloroauric acid produced by chloride or aqua regia dissolution of gold, both generated on site as part of the same scope. Output: cell-ready electrolyte, with NO₂ routed to the gas plant.

Precious Metal Electrolysis Equipment Process Flow

The ten stages below form the standard electrolysis flowsheet for anode-plate refining, with the electrowinning branch entering at the cell stage for feeds that arrive as liquor. Engineering setpoints — current density, electrolyte composition, temperature, circulation and extraction volume — are fixed during process design against your own anode assay.

Precious metal electrolysis process flow — anode plate to certified 99.99% and 99.999% metal.

Steps 1 — Feed Assay and Anode Preparation. Incoming material is weighed, sampled and analysed before anything is melted, because the anode composition decides which cell it can be run in and whether it needs a desilverising step first. Gold-bearing feed is checked for silver and copper against the electrolysis gates of Ag below 6% and Cu below 2%, silver-bearing feed for gold and base metals against the gate of Ag ≥ 75% and in practice ≥ 97%, and copper feed for its copper and precious metal split. Feeds that fail the gate are routed to a pretreatment — desilverising with nitric acid until the gold grade rises above 90%, or a refining pass on the silver side — rather than being pushed through a cell that cannot hold them. Reagent and utility input: sampling and splitting equipment, XRF and ICP-OES analysis. Output: cell assignment, anode specification and batch record.

Steps 2 — Anode Plate Casting and Electrode Assembly. The assayed feed is melted in an induction furnace, fluxed and deoxidised, and cast into preheated moulds of the size and thickness the cell was designed for. Anode moulds are supplied for both gold and silver plates as part of the equipment scope. Cast plates are cropped, lugs formed and the plate weighed, because the anode weight is what the cell current is set against. Cathodes are prepared at the same time: titanium sheet or rolled fine-gold sheet in the gold cell, titanium plate in the silver cell, and pure copper starter sheet in the copper cell. Both electrode sets are fitted with titanium-clad copper connections and assembled so that spacing is uniform across the array. Reagent and utility input: induction melting furnace, anode moulds, plate cropping and forming. Output: weighed anode plates and prepared cathodes.

Steps 3 — Electrolyte Make-Up and Cell Charging. Electrolyte is prepared to the analysis the flowsheet specifies: chloroauric acid solution with free hydrochloric acid at 120–150 g/L Au for gold, silver nitrate with 10–18 g/L free nitric acid at 60–150 g/L Ag for silver, and copper sulphate with sulphuric acid for copper. Gold electrolyte is made by chloride dissolution or by aqua regia dissolution followed by dilution with hydrochloric acid; silver electrolyte is made by dissolving silver in nitric acid, a reaction that evolves nitrogen dioxide and is therefore carried out with the gas routed straight to the absorption plant. The cell is charged to its working level, electrodes are lowered into position, and the anode bag is fitted so that slime and silver chloride are retained at the anode from the first minute of the run. Reagent and utility input: nitric acid or hydrochloric acid and chloride oxidant, deionised water, dosing and level control. Output: cell charged to specification; NO₂ routed to the gas plant.

Steps 4 — Electrolysis at Controlled Current Density. The rectifier is energised and the cell current is set against the cathode area to hold the flowsheet current density: up to 1,000 A/m² in the gold cell, 750 A/m² in the silver cell, and 300 A/m² in the copper cell. The crude metal dissolves at the anode, the purified metal deposits on the cathode, and the impurities either remain in solution or report to the anode bag. A superimposed alternating component can be applied to the rectifier output where a high silver content in the anode would otherwise passivate the anode face with silver chloride. Anode plate changes, cathode changes and slime build-up are managed on the schedule the current density implies, so the cell is never run past the point at which deposit quality begins to fall away. Reagent and utility input: DC rectification with optional superimposed alternating component, per-cell current monitoring. Output: cathode deposit; anode slime and AgCl retained in the anode bag.

Steps 5 — Temperature, Circulation and Concentration Control. Electrolyte is circulated across the electrode array in parallel flow, entering at the bottom of the cell and leaving at the top, which keeps the boundary layer at the cathode thin and holds concentration polarisation in check — the mechanism that makes high current density possible at all. Temperature is held to its window: 60–70 °C in the gold cell, automatically controlled, and a 40 °C set point in the silver cell, where a chiller starts and stops on the electrolyte temperature so that the cell neither volatilises its electrolyte nor loses deposition rate. Level is maintained by metered make-up, and free acid is titrated and corrected on a schedule rather than after a quality excursion. Reagent and utility input: magnetic circulation pump, plate heat exchanger or chiller, dosing and titration control. Output: electrolyte held in specification; stable deposit quality.

Steps 6 — Fume Extraction and Electrolyte Recovery. The electrodes operate under a transparent, sealed cell cover with extraction taken from the side of the cell body rather than from a hood above it. Sealing the cell is what makes the extraction economic: a small, well-directed volume of air removes the mist that collects under the cover, and the shop floor stays clear instead of being blanketed by a large open hood. Vapour leaving the cell passes a condenser that returns volatilised electrolyte — carrying silver or gold with it — to the cell, so evaporation stops being a metal loss. The residual stream goes to the acid-mist and nitrogen-oxide scrubbing train. Reagent and utility input: sealed cover, side extraction fan, condenser, ducting to the scrubber. Output: recovered electrolyte returned to the cell; off-gas to absorption.

Steps 7 — Cathode Harvest, Washing and Drying. At the end of the run the cell is de-energised and the cathodes are lifted. Gold is stripped from the plate as a coherent deposit and washed. Silver is handled by the automatic system: a scraper on both faces of the cathode removes the deposit as it forms, and a mechanical conveyor lifts the powder out of the cell across the sloped front section and discharges it directly into the washing and drying unit. Washing uses deionised hot water, and the wash water is cascaded — first wash returns to the electrolyte circuit as make-up, second wash becomes the first wash of the next batch — so that water and dissolved metal are both recovered rather than sent to effluent. Dried product is weighed and sampled for release. Reagent and utility input: cathode lifting, automatic scraper and discharge conveyor, deionised hot water, washing and drying unit. Output: washed, dried and weighed cathode product; cascade wash water to electrolyte make-up.

Steps 8 — Melting and Ingot Casting to Standard. Dried cathode gold or silver is melted under a protective atmosphere or under flux in an induction furnace, sampled, and cast into ingots of the weight the market requires. Gold is cast to Au99.99 and released against the Shanghai Gold Exchange Grade I standard; silver is cast to 99.99% with the silver content stable at or above that figure. Each ingot is marked with its weight and its batch number, which ties it back to the anode lot and to the assay records of the whole run. Where the product is sold as powder rather than as bar, the powder is packed directly from the drying stage. Reagent and utility input: induction melting furnace, ingot moulds, marking and weighing. Output: certified Au99.99 or 99.99% silver ingots, or packed powder.

Steps 9 — Anode Slime and Anode Bag Recovery. Residual anodes are lifted and the anode bag is emptied. Silver-cell slime runs at roughly 8% of the anode mass and carries 50–70% gold with 30–40% silver, so it cannot be melted straight into a gold anode and is desilvered with nitric acid until the gold grade rises above 90%, after which it is cast into anode plates for the gold cell. The silver that the nitric acid took up is recovered for the silver circuit. Gold-cell bags yield silver chloride, which is reduced and returned as anode silver. Residual anode stubs are either returned to the melting furnace or, where the cells are fitted for the duty, reloaded into a titanium anode basket and left in the cell to finish dissolving without being recast. Nothing in this stage leaves the plant as scrap. Reagent and utility input: anode lifting, bag emptying, nitric acid desilverising, titanium residual-anode baskets. Output: gold-rich slime to the gold cell; recovered silver to the silver circuit.

Steps 10 — Electrolyte Purification, Effluent and Off-Gas Control. Electrolyte that has accumulated impurity ions is purified and returned to the cell rather than replaced, which cuts both the cost of making up new electrolyte and the volume of spent liquor leaving the plant. Bleed liquor, final rinse water and cell washings that cannot be recycled are treated for residual metal before neutralisation, and the metals recovered are returned to the process. Off-gas from the cells, the electrolyte make-up stage and the melting furnace passes the acid-mist and nitrogen-oxide absorption train before the stack. Every batch closes on a weighed metal balance supported by the anode, electrolyte and product assays, and that balance is what the purity and recovery figures on this page are measured against. Reagent and utility input: electrolyte purification circuit, effluent treatment and neutralisation, NOx and acid-mist absorption. Output: closed batch metal balance; certificate of analysis; compliant effluent and stack emission.

Product Structure (Main Equipment)

The line is assembled from the equipment groups below. Materials of construction are selected per stream: high-performance polypropylene for cell bodies in atmospheric acid service, PPH for frames and structural parts, titanium for cathodes and anode baskets, titanium-clad copper for every current-carrying connection, and glass or acid-resistant polymer where the reaction has to be watched.

Cell bodies, electrodes and current distribution

One-piece moulded cell body. High-performance polypropylene with an anti-aging additive, moulded in one piece so that there is no joint line for electrolyte to creep through — the leak path that open-fabricated cells develop at the corners and that eventually contaminates the floor and the foundation.
Cell support frame. PPH structure carrying the cell, the electrode array and the cover, sized for the electrode weight and for the lifting equipment used at anode and cathode changes.
Anode plates and anode baskets. Cast crude-metal plates on lugged hangers, with titanium anode baskets available for residual-anode operation so that a partially dissolved stub can finish its run without being recast.
Anode bags. Filter bags fitted to each anode, retaining silver chloride and slime at the anode face and keeping them out of the cathode deposit — the single fitting that decides whether the powder the cell produces is saleable or has to be re-refined.
Cathode sheets. Titanium or rolled fine-gold sheet in the gold cell, titanium plate in the silver cell, and pure copper starter sheet in the copper cell.
Current distribution set. Titanium-clad copper busbars, screwed and reinforced electrode connections, and insulating board between the busbar and the cell body, which together hold the contact resistance down at high cell current instead of letting the connection points heat up.

Power supply, rectification and control

Rectifier unit. DC rectification sized to the cell current and the number of cells in the circuit, with output current and voltage displayed and adjustable, and with a superimposed alternating component available for anodes whose silver content would otherwise passivate the anode face.
Control panel and HMI. PLC with touchscreen operator interface for current, voltage, temperature, electrolyte level and reagent dosing, with recipe storage for more than one product specification.
Instrumentation set. Cell current and voltage monitoring, electrolyte temperature transmitters, level measurement, and titration support for free acid and metal concentration.
Batch logging. Per-run logging of current, temperature and dose so that any purity result can be traced back to the conditions that produced it.

Electrolyte circuit and temperature control

Circulation pump set. Magnetic-drive pumps that circulate electrolyte in parallel flow across the electrode array, bottom-in and top-out, with no mechanical seal in contact with hot acid.
Cooling unit. Plate heat exchanger or chiller with automatic start and stop on electrolyte temperature, holding the silver cell at its 40 °C set point and pulling the heat generated by the cell current out of the loop.
Electrolyte storage and circulation tanks. Hold working volume, receive make-up, and provide a point at which the circuit can be sampled, filtered and bled without stopping the cell.
Filtration unit. Removes suspended slime and particulate from circulating electrolyte; filter elements are rated for the duty rather than for a nominal micron figure alone.
Make-up and dosing system. Metered addition of electrolyte, acid and water to hold concentration and level in band, with the metering recorded against the batch

Cathode harvesting, washing and drying

Manual stripping station. For gold cathodes, where the deposit is coherent and is lifted off the plate as a sheet, washed and transferred to drying.
Automatic scraper and discharge conveyor. For silver, where scrapers on both faces of the cathode remove the deposit as it forms and a mechanical conveyor carries it out of the cell across the sloped front section and discharges it into the washing unit. This is what removes the manual scraping that causes short circuits and the powder pile-up that degrades product quality.
Solid–liquid separation port. A valve and bypass arrangement on the cell drain that lets the electrolyte be taken off before the solids, so that the first wash is not diluted by the whole cell volume.
Washing and drying unit. Deionised hot-water washing followed by drying, with cascade water management: first wash returns to the electrolyte circuit, second wash becomes the next batch’s first wash.

Anode preparation and product finishing

Induction melting furnace. Melts crude feed, anode stubs and dried cathode product, with fluxing and deoxidation as the metal requires.
Anode moulds. Cast-iron moulds for gold anode plates and for silver anode plates, in the sizes matching the cell, with non-standard sizes made to order.
Ingot moulds and casting set. Moulds for the ingot weights the market accepts, with marking and weighing equipment.
Granulation and sampling equipment. Converts metal to shot or granule where the downstream step needs a free-flowing feed, and prepares representative samples for the in-house assay.

Fume, acid-mist and effluent control

Sealed cell cover. Transparent cover closing the cell body, which allows the operator to see the deposit forming while keeping the mist inside.
Side extraction and fume condenser. Extraction taken from the side of the cell body rather than from a hood above it; vapour passes a condenser that returns volatilised electrolyte to the cell.
Nitrogen-oxide and acid-mist absorption train. Multi-stage absorption for the gas produced by electrolyte make-up, cell operation and melting, with the recovered acid returned to the process where the concentration allows.
Effluent treatment and neutralisation. Bleed liquor, spent rinse water and cell washings treated for residual metal before neutralisation, with the recovered metal returned to the circuit.
Assay laboratory equipment. XRF and ICP-OES with sample preparation so that anode, electrolyte and product assays are generated in-house on the same day as production.

Product Features

Five metals on one platform. Gold, silver, copper, tellurium and dilute-solution electrowinning share cell architecture, control platform and spares base, so adding a second metal later is an extension rather than a second plant.
Current density disclosed and designed for. The gold cell is rated up to 1,000 A/m², the silver cell at 750 A/m² and the copper cell at 300 A/m², each with the conventional figure stated alongside it so the comparison is checkable rather than implied.
Sealed, side-extracted cells. The transparent cover closes the cell and extraction is taken from the side wall, which reduces the air volume the fan has to move, the acid mist reaching the scrubber and the visible emission in the workshop.
Electrolyte recovery by condensation. Volatile electrolyte is condensed and returned to the cell, so metal that would otherwise leave through the stack stays in the circuit and the acid make-up rate falls.
One-piece cell bodies. Moulded rather than fabricated, which removes the seam failure mode that dominates cell maintenance on older designs.
Parallel-flow circulation. Electrolyte is driven across the electrode array bottom-in and top-out by magnetic pumps, keeping the cathode boundary layer thin and holding the deposition quality that high current density otherwise costs.
Automatic silver harvesting. Scrapers on both cathode faces and a discharge conveyor replace manual scraping, which removes the main cause of cathode-to-anode short circuits and the reason silver powder used to be left sitting in the cell to degrade.
Cascade wash water. First wash returns to the electrolyte, second wash serves the next batch as first wash, cutting both water consumption and the metal load reaching effluent.
Anode bags standard. Slime and silver chloride are captured at the anode, protecting cathode purity without sacrificing recovery, because the bag contents are a product stream rather than a waste stream.
Residual-anode option. Titanium anode baskets allow a partly dissolved anode to finish dissolving in the cell instead of being recast, saving a melting cycle and the metal loss that goes with it.
Instrumented and logged. Current, voltage, temperature, level and dosing are supervised and recorded per batch, so a purity certificate is supported by a data record rather than by assertion.
Configuration to the feed. Cell count, current density, rectifier rating, cooling duty, extraction volume, capacity and footprint are engineered from the anode assay and the target daily output rather than selected from a standard size list.

Technical Parameters And Specifications

The values below are the design basis of the equipment family. Cell count, capacity, installed power, footprint, cooling duty and extraction volume are engineered to your anode assay, target daily output and site conditions, and the operating window is confirmed during process design.

Precious metal electrolysis equipment — technical parameters and specifications.

Parameter	Specification
Equipment family	High-current-density gold, silver and copper electrolytic cells; tellurium cells; cyclone electrowinning units; loaded-carbon desorption electrowinning sets; turnkey silver electrorefining workshops
Operating principle	Anodic dissolution of a cast crude-metal anode and cathodic deposition of purified metal under controlled direct current
Metals recovered	Gold, silver, copper and tellurium; indium and other rare metals on the same platform. Platinum group metals are recovered by hydrometallurgical separation rather than by electrolysis
Feed form	Cast anode plates for gold, silver and copper duty; concentrated or dilute metal-bearing solution for electrowinning duty
Gold feed gate	Au ≥ 90% by process requirement, 92–95% in practice; Ag below 6%; Cu below 2%
Silver feed gate	Ag ≥ 75% by process requirement, ≥ 97% crude silver in practice; Au 0–25%
Copper feed gate	Cu approximately 98% in copper cement, granule or heavy plate
Cathode current density — gold	Up to 1,000 A/m²
Cathode current density — silver	750 A/m² standard, against 250–350 A/m² conventional silver practice; 300–500 A/m² and 600–800 A/m² in horizontal belt-discharge variants
Cathode current density — copper	300 A/m²
Cell current	Monitored per cell; 1,500 A demonstrated on the high-current-density silver cell
Anode preparation	Assay and classification, induction melting, fluxing and deoxidation, casting into preheated anode moulds, cropping and lug forming, plate weighing
Rectifier	DC rectification sized to cell current and cell count, with a superimposed alternating component available for high-silver anodes
Electrolyte — gold	Chloroauric acid (HAuCl₄) solution with free hydrochloric acid; 120–150 g/L Au
Electrolyte — silver	Silver nitrate with 10–18 g/L free nitric acid; 60–150 g/L Ag, with potassium nitrate where conductivity and pH require it
Electrolyte — copper	Copper sulphate with sulphuric acid
Electrolyte temperature — gold	60–70 °C, automatically controlled
Electrolyte temperature — silver	40 °C set point, held by a chiller with automatic start and stop
Anode	Cast crude-metal plate; titanium basket for residual-anode operation; anode bag fitted to retain slime
Cathode — gold	Titanium sheet or rolled fine-gold sheet
Cathode — silver	Titanium plate
Cathode — copper	Pure copper starter sheet
Current-carrying parts	Titanium-clad copper busbars and screwed electrode connections, insulated from the cell body
Cell body material	High-performance polypropylene with anti-aging additive, moulded in one piece to avoid electrolyte leakage; PPH support frame
Cathode harvesting	Manual plate stripping after the run for gold; automatic scraper with mechanical discharge conveyor for silver powder
Electrolyte circulation	Parallel flow across the electrode array, bottom-in and top-out, by magnetic-drive pump
Cooling and volatilisation control	Electrolyte cooling circuit with automatic start and stop; fume condenser returning volatilised electrolyte to the cell
Fume control	Transparent sealed cell cover with side extraction; 7,000 m³/h reference extraction volume on the silver cell
Anode slime	Retained in the anode bag; approximately 8% of anode mass on the silver cell, carrying 50–70% Au and 30–40% Ag
Product purity — first pass	99.99% (4N); gold to the Shanghai Gold Exchange Grade I standard; silver to national-standard No. 1 grade
Product purity — second pass	99.999% (5N) from a second electrolysis pass on the same equipment
Gold recovery	≥ 99.9%, with refining loss below 0.02%
Electrolyte management	Circulation, filtration, titration and correction in band; purification and return to the cell where impurity ions reach the limit
Waste-water duty	Copper-bearing waste water reduced from 450 mg/L to 0.062 mg/L Cu²⁺ and from 50 mg/L to 0.093 mg/L Ni²⁺
Instrumentation and control	PLC with touchscreen HMI for current, voltage, temperature, level and dosing; per-batch logging
Quality verification	Anode, electrolyte and product assay by XRF and ICP-OES; certificate of analysis released per batch
Capacity, footprint, power, utilities	Engineered to anode assay, target daily output and site conditions

Technical Advantages

Current density raised without giving up deposit quality. The silver cell runs at 750 A/m² against 250–350 A/m² conventional practice and the gold cell reaches 1,000 A/m², cutting the time needed to dissolve the same anode mass by roughly 60%. The mechanism that makes it work is parallel-flow circulation across the electrode array, which thins the cathode boundary layer and suppresses the concentration polarisation that would otherwise degrade the deposit. Result: two to three times the throughput per unit of floor area and of electrolyte inventory.
The structural consequences of high current are answered structurally. A conventional cell’s busbar arrangement and bolted electrode joints are not sized for high current, and the connection points overheat and damage the equipment. Titanium-clad copper busbars, screwed and reinforced joints, insulating board between busbar and cell body and heavier conductor sections remove the heat instead of managing it. Result: high current density with a stable, cool current path.
Short-circuit risk engineered out rather than watched for. Dendritic or powdery growth that bridges cathode to anode is the classic failure mode of a dense cell. Automatic scrapers on both faces of the silver cathode remove the deposit as it forms, the anode bag keeps slime at the anode, and the discharge conveyor prevents powder from accumulating anywhere in the cell. Result: a cell that runs for months between clean-outs instead of weeks.
Metal loss through the stack stopped at the condenser. Gold and silver electrolyte volatilises at operating temperature and would otherwise leave the cell as vapour and be lost or scrubbed to effluent. The fume condenser returns it to the cell. Result: lower metal loss, lower acid make-up and a lighter load on the scrubber.
Extraction volume cut by sealing the cell. Side extraction from a closed cell moves a far smaller air volume than an open hood above a cell, for the same or better capture. Result: lower fan power, less acid mist reaching the absorber and a cleaner workshop floor.
Anode slime treated as a product stream. Silver-cell slime at about 8% of anode mass carrying 50–70% gold is not waste: it is desilvered with nitric acid until the gold grade passes 90% and then cast into gold-cell anodes, while the silver taken up by the acid goes to the silver circuit. Result: the gold and silver circuits feed each other instead of exporting an intermediate.
Electrolyte service life extended by purification instead of replacement. Impurity ions are removed and the electrolyte returned, so the plant is not continually making up fresh solution and discarding a metal-bearing liquid. Result: lower reagent cost and a smaller spent-liquor volume to treat.
Water and dissolved metal recovered together. Cascade washing sends first wash back to the electrolyte as make-up and reuses second wash as the next batch’s first wash. Result: a sharply reduced effluent volume with the metal it would have carried returned to the circuit.
Working inventory of metal reduced. High current density means less electrolyte volume, and less electrolyte volume means less gold or silver immobilised in solution at any moment. Result: less capital tied up in metal that is neither product nor feed.
Purity reached by a specified number of passes. One pass delivers 99.99%, meeting the Au99.99 Shanghai Gold Exchange Grade I standard and national-standard No. 1 silver; a second pass reaches 99.999%. The pass count comes from the anode assay and is written into the flowsheet. Result: a purity commitment that can be checked against the certificate, not a ceiling quoted for marketing.
One platform for anode refining and dilute-solution recovery. The same cell family covers cast anode plates and the cyclone electrowinning duty for low-concentration liquor, and the electrowinning cells handle copper-bearing waste water down to 0.062 mg/L Cu²⁺. Result: a plant that can recover the metal in its waste streams on the equipment it already owns.
Recovery verified on a closed balance. Each batch closes on a weighed metal balance supported by anode, electrolyte, slime and product assays. Result: environmental and economic performance that a buyer, an auditor or a toll-refining counterparty can reproduce.
Built to be extended. The layout is modular, so a single cell that validates a flowsheet becomes a multi-cell line by adding cells to the same rectifier circuit and electrolyte loop rather than by replacing the installation. Result: an entry point that does not become stranded capital.

Service Process

Step 1 — Enquiry and feed review. You provide the feed type, an assay or typical analysis, the monthly metal volume and any site constraints. We confirm which cell family the material suits, whether it needs desilverising or another pretreatment first, and what the anode specification should be. Output: preliminary route and a clear scope statement.

Step 2 — Laboratory test and small-batch verification. A representative sample is run through anode casting, electrolysis at the candidate current density, harvesting, washing and melting. The operating window, the achievable purity and the number of passes required are established on your material. Output: test report and a returned product sample for your own assay.

Step 3 — Process design and flowsheet. We issue the process flow diagram, the material and reagent balance, the metal balance by element, the cell count and current density, the rectifier rating, the electrolyte circuit and its heat balance, the equipment list and the utility schedule. Output: process design package and mass balance.

Step 4 — Equipment manufacture and factory testing. Cells, electrode assemblies, rectifier, circulation, cooling, extraction, scrubbing and control panel are fabricated, assembled and function-tested before shipment, with material certificates retained. Output: factory acceptance test record.

Step 5 — Layout and site interface design. Cell arrangement, maintenance access for anode and cathode changes, civil loading, power supply, water, cooling, compressed air, extraction ducting and floor drainage are defined against your building drawings. Output: layout and utility interface drawings.

Step 6 — Shipment, installation and commissioning. Equipment ships with its documentation set, and our engineers supervise installation, leak and pressure testing, electrical and control checkout, and water commissioning of the electrolyte circuit before any metal is charged. Output: mechanically complete line ready for process commissioning.

Step 7 — Operator training and SOP handover. Starting and stopping a run, anode and cathode handling, electrolyte make-up and titration, temperature and current set-points, harvest, washing and melting, slime handling, and routine maintenance are taught on the installed equipment. Output: trained operators and a signed SOP set.

Step 8 — Production trial and performance acceptance. The line is run on your feed and the agreement is confirmed against measured current density, product purity, recovery and the effluent figures. Output: performance test certificate and the first certificate of analysis.

Step 9 — Ongoing technical support. Process troubleshooting, flowsheet revision as your feed mix changes, spare parts at cost, and consumables such as anode bags, filter elements and reagent supply on request. Output: continuing production support.

Warranty & After-Sales Service

Warranty period. Twelve months from successful commissioning or eighteen months from shipment, whichever falls earlier, covering design, manufacture and assembly defects of the supplied equipment. Excluded: consumables such as anode bags, filter elements, gaskets and reagents, and damage from misuse or from feed outside the agreed specification.
Performance commitment. Where the feed matches the tested sample, we stand behind the agreed current density, product purity, recovery and effluent figures established in the process design package, with the performance test as the reference point. Output: documented performance acceptance.
Spare parts. Wear and critical spares are quoted with the order and held available afterwards, with a recommended on-site stock list issued at handover. Output: spare parts list and supply at cost.
Remote support. Telephone, email and messaging support for operating questions, alarm interpretation and process troubleshooting whenever your cells are running. Output: same-day response on operating issues.
On-site service. Engineer attendance for warranty faults, process problems and periodic check-ups, with response and attendance times agreed in the contract according to your location. Output: on-site intervention and a service report.
Electrolyte and process audit. Periodic review of electrolyte analysis, current density, temperature records and slime assays against the flowsheet, with recommendations where the feed or the product specification has moved. Output: process audit report with corrective actions.
Operator retraining and refresher visits. Additional training and refresher sessions as your feed mix, product specification or staffing changes. Output: updated training and procedure revisions.
Documentation set. Operation and maintenance manuals, process flow diagram, piping and instrumentation diagram, equipment layout, electrical drawings, spare parts catalogue, reagent safety data and the emergency response plan. Output: complete documentation handover.
Compliance support. Assistance with emission and effluent parameter declarations, extraction and absorption performance verification, and the handling, storage and disposal requirements for nitric acid, hydrochloric acid and other reagents used in the process. Output: technical data for your permit applications.
Lifetime technical support. The process design remains yours, and our engineering team remains available for modification and expansion advice for the operating life of the plant. Output: long-term engineering continuity.

Frequently Asked Questions

Q1. What is precious metal electrolysis equipment used for?

It refines impure precious metal into saleable metal by passing a controlled direct current through a cell. A cast crude-metal anode is dissolved in an electrolyte, the purified metal deposits on the cathode, and the impurities either stay in solution or report to the anode bag as slime. In practice the equipment turns crude gold, silver or copper of 75–98% purity into 99.99% product in one pass, with 99.999% available from a second pass, and it also recovers metal from dilute solutions and waste waters where precipitation would be uneconomical.

Q2. Which metals can be refined by electrolysis?

Gold, silver and copper are the three commercial anode-plate systems, and tellurium and indium are refined on the same equipment platform. Gold runs in a chloroauric acid electrolyte, the chloride route known in the industry as the Wohlwill process, silver in silver nitrate, copper in copper sulphate with sulphuric acid, and each has its own feed gate and its own deposits. The platinum group metals are the deliberate exception: platinum, palladium, rhodium, iridium and ruthenium are finished by hydrometallurgical separation — selective precipitation, solvent extraction and ion exchange — because their electrode potentials are too close for electrolysis to separate them cleanly, and molten-salt platinum electrolysis has never been industrialised. This equipment family therefore delivers the electrolytic metals, and the PGM residue that leaves the anode bag is handed to a wet-chemical refining line.

Q3. What feed purity does the anode plate need?

Gold anodes should be at least 90% gold by the process requirement and 92–95% in practice, with silver below 6% and copper below 2%. Above 6% silver, silver chloride forms on the anode face and passivates it, the anode stops dissolving cleanly and the cell loses current efficiency; above 2% copper, copper deposits on the cathode and dilutes the gold. Silver anodes need at least 75% silver by the process requirement, and in commercial practice crude silver runs at 97% or above. Copper anodes are typically about 98% copper. Material below its gate is not rejected — it is routed to a pretreatment, most often desilverising, and then returned to the cell.

Q4. How does electrolysis reach 99.99% and 99.999% purity?

Purity comes from selectivity plus repetition. Even at the first pass, only the target metal is reduced at the cathode within the cell’s voltage window, so the base metals that dissolved with it stay in the electrolyte and the insoluble fraction stays in the anode bag. That yields 99.99%, which is enough for the Au99.99 Shanghai Gold Exchange Grade I standard and for national-standard No. 1 silver. Repetition is what removes the last order of magnitude: the 99.99% product is melted, cast into a fresh anode and run again, and the second pass reaches 99.999%. How many passes your feed needs is established in the laboratory test and written into the flowsheet.

Q5. What does high current density actually buy, and what does it cost?

It buys throughput per unit of floor area and per unit of money held in metal. The silver cell runs at 750 A/m² against 250–350 A/m² for conventional silver cells, which cuts the time needed to dissolve a given anode mass by about 60%, and the gold cell reaches 1,000 A/m². The cost is real and has to be designed away rather than wished away: denser current steepens concentration polarisation at the cathode, encourages dendritic growth that can bridge to the anode and short the cell, raises the resistive voltage drop through the electrolyte, and magnifies any impurity capable of co-depositing. The answers are structural — parallel-flow circulation to thin the boundary layer, automatic scraping to stop bridging, titanium-clad copper busbars and screwed joints to hold the current path cool, and an anode bag to keep slime away from the cathode.

Q6. What electrolyte and temperature does each cell run?

Gold runs in chloroauric acid with free hydrochloric acid, holding 120–150 g/L Au, at 60–70 °C, automatically controlled. Silver runs in silver nitrate with 10–18 g/L free nitric acid and 60–150 g/L silver, at a 40 °C set point held by a chiller that starts and stops on electrolyte temperature — warm enough for efficient deposition, cool enough that the electrolyte does not volatilise and acid consumption stays under control. Copper runs in copper sulphate with sulphuric acid at 300 A/m². Free acid is titrated and corrected on a schedule, and the electrolyte is purified and returned to the cell rather than being replaced when impurity ions accumulate.

Q7. How is silver powder harvested from the cathode?

Automatically. Scrapers sit on both faces of the cathode and strip the deposit as it forms, and a mechanical conveyor carries the powder across the sloped front section of the cell and discharges it into the washing and drying unit. This is not a convenience feature: manual scraping is the usual cause of short circuits between cathode and anode, and powder left to accumulate in the cell degrades in quality and eventually blocks the discharge path. Removing both problems is what allows the cell to run continuously between clean-outs, and the electrolyte drain valve lets the electrolyte be taken off before the solids so that the first wash is not diluted.

Q8. What happens to the anode slime and the silver chloride?

They are a product stream, not waste. Silver-cell anode slime runs at roughly 8% of the anode mass and typically carries 50–70% gold with 30–40% silver — too rich in silver to melt directly into a gold anode, so it is desilvered with nitric acid until the gold grade passes 90%, and then cast into anode plates for the gold cell. The silver dissolved by that acid goes to the silver circuit. Gold-cell anode bags collect silver as silver chloride, which is reduced and returned to the silver circuit as anode metal. What neither circuit claims — platinum group metals and refractory phases — leaves as a concentrate for hydrometallurgical separation.

Q9. How is the electrolyte kept in specification?

Partly by design and partly by routine. Circulation in parallel flow across the electrode array keeps the electrolyte moving over every cathode face and holds the bulk composition uniform; the cooling circuit holds the temperature window; filtration removes suspended slime and particulate; level and concentration are held by metered make-up. Free acid and metal concentration are titrated and corrected on a schedule rather than in response to a quality excursion. When impurity ions reach their limit, the electrolyte is purified and returned to the cell instead of being thrown away, which reduces both the cost of new electrolyte and the volume of spent metal-bearing liquor that has to be treated.

Q10. How are nitrogen oxides and acid mist controlled?

At the source first. Cells are closed with a transparent cover and extraction is taken from the side of the cell body rather than from an open hood above it, so a small, well-directed air volume captures the mist, the workshop floor stays clean and less acid reaches the absorber. Vapour passes a condenser that returns volatilised electrolyte — and the metal in it — to the cell. Electrolyte make-up and melting are ducted into the same acid-mist and nitrogen-oxide absorption train, and where the recovered acid is strong enough it goes back into the process. The reference extraction figure on the high-current-density silver cell is 7,000 m³/h, and the emission parameters are logged with the batch record.

Q11. Can the plant treat dilute solutions and waste water rather than anode plates?

Yes, on the electrowinning side of the family. Cyclone electrowinning units handle metal concentrations from a fraction of a gram per litre to several hundred grams per litre, including PCB acidic etching liquor at 110–180 g/L copper, and they separate copper from nickel and copper from silver selectively. Desorption electrowinning sets recover gold from loaded-carbon eluate in a CIL/CIP circuit. For waste water, electrolysis on composite titanium electrodes breaks the complex that holds the metal and deposits it as metal: copper-bearing chemical plating waste water has been taken from 450 mg/L to 0.062 mg/L Cu²⁺ and from 50 mg/L to 0.093 mg/L Ni²⁺, with the metal recovered rather than landfilled as hydroxide sludge.

Q12. What capacity, power and floor space do I need?

Those follow from your anode assay and your daily metal target, so they are engineered rather than selected from a size list. What determines the answer is the metal content of the anode, the current density the flowsheet sets, the number of cells needed to run the anode change and harvest cycle without starving the rectifier, and the electrolyte volume that goes with them. Two installations with the same nominal cell size can have very different daily output depending on feed grade. We size the cells, rectifier, circulation, cooling, extraction and scrubbing from your assay and monthly volume and state the resulting figures in the process design package, and because the layout is modular a pilot cell can be extended rather than replaced if throughput grows.

Q13. Is a sample test carried out before the equipment is quoted?

Yes, and it is the step that decides the flowsheet. A representative sample is taken through anode casting, electrolysis at the candidate current density, harvesting, washing and melting at bench scale. That establishes the achievable purity, the number of passes your feed needs, the current density the deposit will tolerate, the expected recovery and the slime yield. Part of the recovered product is returned to you so that you can verify it with your own assay, and the equipment quotation is based on that result rather than on an assumption about your material.

Q14. How is the purity of the finished metal verified?

By assay of a sample taken from the released batch, cross-checked across the anode, the electrolyte and the product, using XRF and ICP-OES with wet-chemical titration support for the electrolyte. The batch is not released until the certificate of analysis confirms the specified purity, and the test results are held with the weighed metal balance for that run. That traceability is what allows a buyer, an auditor or a toll-refining counterparty to reproduce the result independently, and it is also what makes a purity commitment defensible rather than promotional.