ALS2 Recovery Efficiency Across Fire-Assay And Solution Feeds

Recovery efficiency depends on far more than the nominal gold, silver or platinum content of a feed. Feed chemistry, particle size, impurity loading, moisture, residence time and the form in which precious metals are presented can all change the outcome. This is especially important when comparing a concentrated fire-assay product with a solution-based stream.

ALS2 acidless separation technology has been developed for precious-metals recovery from electronic waste and WEEE recycling streams. Its value is clearest when the process is assessed against the full recycling chain, including pre-treatment, concentration, separation, refining and residue management.

A fire-assay feed and a solution feed therefore represent two different operating cases. The first has already passed through a high-temperature concentration step, while the second presents metals in a dissolved form. A fair comparison should measure payable metal recovered per tonne of original e-waste, rather than focusing only on the final separation stage.

Feed type	Typical condition entering recovery	ALS2 efficiency opportunity	Main efficiency constraint
Fire-assay product	Concentrated bead, metallic phase, ash or assay-derived fraction	High-value finishing with a relatively small mass to process	Losses or dilution introduced during melting, sampling and slag handling
Solution-based feed	Precious metals dissolved in a process liquor	Direct separation from a controlled liquid stream with potentially high selectivity	Complexing agents, dissolved base metals, suspended solids and variable chemistry
Unprocessed WEEE concentrate	Mixed boards, connectors, components and fines	Lower-cost front-end recovery when pre-treatment is well controlled	Heterogeneous feed, plastics, ceramics, iron, copper and dust
ALS2-prepared concentrate	Mechanically and thermally conditioned material	More stable plant operation and improved material utilisation	Feed preparation quality and consistent specification

The Feed Form Sets The Starting Point

Fire assay is primarily an analytical and concentration method. A sample is fused so that valuable metals collect into a small metallic phase, while much of the gangue enters slag. When an assay bead or related concentrate is sent to a precious-metals separation unit, the recovery plant receives a much richer and more uniform feed than the original circuit material.

That apparent advantage can make fire-assay processing look more efficient. A high percentage recovery may be achieved from a small quantity of material, with less plastic, ceramic and base-metal interference. However, the result should be traced back to the original WEEE feed. Gold or silver lost in slag, cupels, furnace dust, sampling residues or non-representative portions of a batch is outside the final recovery calculation unless those streams are included.

A solution-based feed presents a different starting point. Precious metals may already be dissolved, but the liquor can contain copper, nickel, iron, tin, organic compounds, chloride, suspended solids or residual leaching reagents. ALS2 performance is then influenced by the chemistry of the solution and by how effectively the upstream leach has transferred target metals into the liquid phase.

For this reason, solution processing can offer excellent separation efficiency without necessarily delivering the highest whole-system recovery. If dissolution is incomplete, metals remain in solids and never reach the ALS2 stage. The correct comparison is therefore between total metal in the original feed and total metal recovered in saleable products.

Recovery Percentage Needs A Wider Definition

For fire-assay-derived material, the most visible metric is often the proportion of precious metal recovered from the metallic bead or concentrate. This is useful for checking the separation step, but it can conceal upstream losses. A proper mass balance should include furnace residues, slag, dust, cupel material, sampling rejects and any material returned for reprocessing.

Fire assay can also create a very concentrated feed that is easy to handle and assay. This reduces the amount of material moving through a compact plant and may improve throughput measured in grams of precious metal per hour. Yet concentration does not automatically mean better economics. Energy demand, furnace maintenance, emissions controls and the cost of handling high-temperature residues must be included in the comparison.

With a solution feed, recovery efficiency can be assessed through feed-liquor assays, raffinate assays, wash streams and final product analysis. A low precious-metal content in the raffinate indicates effective separation, but the result should be checked against entrained liquor, filter cake and precipitation residues. Valuable metal can be lost through solids carryover or poor washing even when the main separation reaction performs well.

ALS2’s acidless approach changes the environmental and operating profile of this assessment. Avoiding conventional aggressive acids can reduce some hazards associated with storage, corrosion and spent-acid management. It does not remove the need for chemical controls, ventilation, residue testing, operator training or compliant waste handling. Efficiency includes safe material utilisation, stable operation and the quantity of secondary waste generated.

Selectivity Affects Product Value

A recovery figure alone does not describe the quality of a precious-metals product. A fire-assay feed may have high gold or silver concentration, yet also carry copper, lead, bismuth or other metals that affect the value and next refining step. If the ALS2 output requires extensive downstream treatment, the headline recovery rate may overstate its commercial benefit.

Solution-based feeds can make selectivity easier to monitor because the process liquor is sampled continuously or at regular intervals. This supports tighter control of target-metal concentration and impurity rejection. On the other hand, dissolved base metals can compete for active sites or alter the chemistry of the separation stage, particularly when the solution comes from mixed electronic scrap rather than a narrowly defined material.

The best feed is often the one that matches the plant’s separation window. A cleaner, concentrated stream may produce a high-purity product with fewer treatment stages. A more diluted or contaminated stream may still be suitable if the system is designed for it, but it will require stronger front-end sorting, filtration and process control.

For recyclers, payable recovery should be calculated using the final product specification accepted by a refiner. This calculation can include deductions for moisture, impurities, treatment charges, transport and assay variation. Such a commercial measure is more useful than comparing laboratory recovery percentages from two feeds with very different preparation histories.

Australian Conditions Change The Comparison

Australia’s e-waste market combines large metropolitan collection systems with long transport distances. A recycler servicing Sydney or Melbourne may obtain regular quantities of printed circuit boards, mobile phones and computer equipment from commercial collection networks. A regional operator near Perth, Adelaide or Brisbane may face higher freight costs and less consistent batch sizes, making compact recovery equipment particularly relevant.

Households and businesses commonly hold obsolete phones, laptops, chargers and small appliances before taking them to council drop-off points or scheduled collection events. That behaviour creates a mixed and irregular feed rather than a steady industrial stream. Effective sorting at the collection or dismantling stage can improve ALS2 performance by separating high-grade connectors and boards from low-value plastics and bulky equipment.

The regulatory setting also matters. Australia’s National Product Stewardship Act provides a framework for shared responsibility across product life cycles, while state and territory environmental rules govern storage, transport, processing and disposal. Victoria’s landfill ban on e-waste and New South Wales restrictions on sending e-waste to landfill have increased the importance of compliant recovery routes, though requirements vary by jurisdiction.

A local plant must also account for worker safety, hazardous material controls and environmental authority conditions. Leaded components, mercury-containing items, batteries and contaminated dust may require separate handling. In remote areas, the cost of moving residues to an approved facility can materially affect the benefit of a high recovery percentage. A solution feed that reduces solid handling may be attractive, while a fire-assay route may suit a site with established thermal infrastructure.

Build A Like-For-Like Performance Test

A useful comparison begins with a shared basis: the same original WEEE feed, the same assay method, and a complete chain-of-custody record. One portion can be prepared through fire assay and another through a solution route, but both must be traced back to the initial metal inventory. Otherwise, the comparison measures different concentration levels rather than ALS2 separation efficiency.

The test should record gold, silver and relevant platinum-group metals at every major point. For fire-assay material, this includes the original feed, fused product, slag, dust and final ALS2 output. For solution processing, it includes the leached solids, pregnant liquor, raffinate, wash streams, residues and recovered product.

Useful indicators include overall recovery, stage recovery, product purity, reagent and energy use, throughput, residue mass, operator exposure and plant availability. It is also important to test variability. A single clean laboratory feed may produce an impressive result, while a month of mixed Australian WEEE may reveal interruptions caused by plastics, batteries, fine dust or changing copper content.

Pilot trials should therefore use representative batches from the intended supply chain. Samples from a Melbourne commercial dismantler may differ substantially from household collections in regional Queensland or a Western Australian mining camp. The ALS2 process should be evaluated against the feed that the plant can reliably obtain, not an idealised material that is rarely available.

ALS2 technology can provide a strong route for recovering precious metals without relying on conventional acid-based refining. Its comparative advantage is greatest when feed preparation, analytical control and residue management are designed together. Fire-assay products may offer concentration and simpler handling, while solution-based feeds may provide controllable chemistry and direct separation. Neither route is automatically superior in every application.

Australian recyclers, refiners and project developers can use ALS2Project to examine the technology, its sustainability objectives and its role in compact precious-metals recovery plants. Review the available project information, define a representative feed specification and arrange a technical discussion with Ikoi S.p.A. to assess recovery, product quality and operating requirements for your WEEE stream.