What gold leaching and gold cyanidation actually are
Gold leaching is the hydrometallurgical process of dissolving fine or finely disseminated gold from crushed or milled ore into a solution. Gold cyanidation is the dominant commercial route for doing this: a dilute cyanide solution contacts the ore, selectively dissolves gold, and the gold-bearing solution then moves to recovery. Xinhai reports that CIL/CIP recovery on suitable ores can reach 99%. On ores where physical separation would leave too much gold behind, leaching is usually the workhorse.
You'd use leaching when gold is too fine to respond to gravity or when the ore is low grade but large tonnage. A plant treating 1,200 t/d with finely disseminated gold, for instance, will often dissolve the gold rather than try to recover it physically. The choice between leaching and a physical route like gold recovery methods depends on liberation, grade and testwork.
Leach testwork is cheap compared with a failed plant.
Cyanidation: CIP and CIL circuit arrangements
Gold cyanidation uses a dilute sodium cyanide solution, typically in agitated tanks for milled ore. The two standard arrangements are carbon-in-pulp (CIP) and carbon-in-leach (CIL). CIP refers to a circuit where leaching takes place in dedicated leach tanks first, and the gold-bearing solution then moves to a separate train of carbon adsorption tanks. CIL, by contrast, runs leaching and carbon adsorption together in the same tanks, which suits slow-leaching ores because carbon competes for gold as soon as it dissolves.
Both routes end in elution, electrowinning and smelting to recover doré gold. The leaching tanks for these circuits can be as large as 20 m × 20 m, according to Xinhai's published equipment range, with dual impellers for agitation. For a closer comparison of when each arrangement pays off, read gold CIL vs CIP. If you're already settled on a cyanidation route, the CIL plant capability page shows the standard package.
Cyanide is toxic and its handling is governed by compliance and safety procedure, not by a catalogue choice. The International Cyanide Management Code is a voluntary industry programme covering production, transport, storage and use of cyanide at gold and silver mining operations. Signatory operations are certified through third-party audits. Any cyanidation design should account for cyanide management from the start.
| Feature | CIP | CIL |
|---|---|---|
| Leaching and adsorption | Separate tank trains | Same tanks |
| Suits | Fast-leaching ores | Slow-leaching ores |
| Carbon handling | Moves between trains | Stays in leach |
Heap leaching: lower cost, lower recovery
Heap leaching is a lower-capital route for low-grade, large-tonnage deposits. You crush the ore, stack it on a lined pad, and irrigate the pile with a leaching solution. The solution percolates through the heap, dissolves gold, and drains as pregnant solution to a collection pond for recovery. Because you skip fine grinding and agitated tanks, the capital and operating cost drop sharply. Recovery is typically lower than a milled cyanidation circuit, but the economics can still work on ore that would never justify a full agitation plant.
Heap leaching trades recovery for much lower operating cost. If you're evaluating a low-grade oxide deposit, compare heap leaching with agitated cyanidation. The decision rests on laboratory column leach tests before you commit capital. See heap leaching gold for the full circuit description.
Alternatives to cyanide
Where cyanide is restricted or the ore chemistry is unsuitable, alternatives include thiosulphate, thiourea and other lixiviants. These are less common. They get selected only when testwork shows the ore and the local conditions demand them, and they usually carry higher reagent cost or more complex recovery. A site that cannot permit cyanide may still reach a workable flowsheet, but you'd need pilot data before committing capital.
Cyanide alternatives are not drop-in replacements. Each lixiviant has its own kinetics, toxicity profile and downstream recovery route. If your jurisdiction restricts cyanide, ask the testwork team to run comparative leach tests before you lock the process.
Agitation and leaching equipment: what drives selection
Leaching equipment covers agitation, carbon adsorption, carbon separation, desorption electrolysis, zinc dust cementation and carbon regeneration. The main machines include dual-impeller leaching agitation tanks, carbon screens, air lifts, high-efficiency desorption electrolysis systems, carbon regeneration kilns, multi-layer washing thickeners, deaeration towers and carbon adsorption columns. Xinhai's manufacturing range includes more than 1,000 equipment types across three bases totalling about 110,000 m², according to the company's published figures.
For a leaching tank, the key variables are slurry throughput, gold grade, leaching time, carbon concentration, desorption batch size, and the local safety and environmental requirements. The tank's working volume must match the required residence time at the design throughput. For example, if a plant treats 1,200 t/d of slurry at 40% solids, the total leach volume follows directly from the residence time, not from a preferred tank size.
Select a leaching tank in three steps. First, define the circuit type—CIP, CIL or zinc dust cementation—because that sets whether carbon is present in the same tank. Second, calculate the total tank volume from the design slurry flow and the laboratory residence time. Third, check the impeller arrangement and air supply against the ore's settling behaviour and viscosity. Ore milling basics covers the upstream grind size that feeds this calculation.
Thickening and filtration: solid-liquid separation after leaching
After leaching, the slurry still needs solid-liquid separation before carbon adsorption or zinc cementation can run efficiently. Thickeners use gravity settling to raise slurry density and return clear water. The main types are high-efficiency improved thickeners, hydraulic centre-drive thickeners, peripheral-drive thickeners, vibrating inclined plate thickeners and deep-cone thickeners. Xinhai lists thickener diameters up to 100 m in its large equipment range. Selection depends on solids flux, settling test results, feed concentration, target underflow concentration, overflow clarity, flocculant regime, rake torque, tank diameter and tailings rheology.
Filtration is the final dewatering step for concentrate, tailings or sludge. The common machines are disc vacuum filters, ceramic vacuum filters, belt vacuum filters, filter presses, vertical filter presses and belt sludge dewatering machines. The same filter model can behave very differently on two ore types, so filter selection must rely on filterability tests, feed concentration, target cake moisture, throughput, pressure drop and filter cloth or ceramic plate selection.
Do not size a thickener or filter from a catalogue alone.
Testwork, design standards and laboratory support
Leaching route selection depends on ore grade, particle size, leaching kinetics and site conditions—all measured in the laboratory before design. Xinhai reports a CNAS-accredited laboratory and an industrial pilot base, running about 5,000 element analyses per month and roughly 200 mineral processing tests per year. The laboratory also performs Bond work index tests, which matter when you need to link grind size to leach response.
Before you fix a leaching route, run the ore through a proper testwork programme. How to test gold ore explains what a leach test programme should include.
Design work should follow recognised reporting and design standards where the project requires them. The JORC Code sets minimum standards for public reporting of exploration results, mineral resources and ore reserves in Australasia. NI 43-101 is the Canadian instrument governing disclosure for mineral projects. Xinhai's design institute holds a Class B metallurgical qualification in China; Chinese qualifications are not automatically valid in other jurisdictions. So use them as an engineering input, not as a substitute for local permitting.
Xinhai gold leaching project scope
Xinhai reports serving more than 2,500 mines and delivering over 600 mine EPC+M+O projects across more than 100 countries and 70 ore types. The group keeps more than 700 technical experts and supports plant capacities up to 50,000 t/d from three manufacturing bases. For gold specifically, the company's published project list includes a 15,000 t/d gold processing EPC in Guinea, a gold mining and processing contracting and operation in Ghana, and a 4,000 t/d gold carbon-in-pulp plant in Kyrgyzstan. You can see the regional pages for Ghana gold plant and Kyrgyzstan gold plant.
Those figures are company self-reported and should be read as context, not as a performance guarantee. Every ore body is different, and the right leaching route still depends on your own test results.
Not sure which leaching route fits your ore? See the CIL/CIP plant capabilities or ask the testwork team through the contact page.