Which Chemical is Used to Separate Gold from Rock

1. Cyanidation Leaching Chemicals (CIP/CIL)

Think of cyanide as dissolving gold. Crush rock small, mix with water, add cyanide solution (usually sodium cyanide). Gold sticks to the cyanide, makes a gold soup. Then throw in activated carbon (made from stuff like coconut shells) – that carbon soaks up the gold soup. Finally, burn the carbon to get rid of the cyanide and leave the gold.

Two main ways:

• CIP (Carbon-in-Pulp): Mix ore with cyanide first. Leach it. Then add the carbon. Works well for ore with less gold.

• CIL (Carbon-in-Leach): Add the carbon while you're leaching with cyanide. Faster, better for ore with more gold.

Chemicals:

Cyanide Based:

• Sodium Cyanide (NaCN): The go-to. Dissolves gold: 4Au + 8NaCN + O₂ + 2H₂O → 4Na[Au(CN)₂] + 4NaOH

• Potassium Cyanide (KCN): Does the same job as NaCN, but not used as much.

Non-Cyanide Alternatives:

• Thiourea: Works fast in acid, but eats metal pipes – nasty stuff.

• Thiosulfate: Easier on the environment, but needs copper and ammonia to help it work.

Brands (Cyanide Alternatives): Brands like CNLITE, JINCHAN, ECO GOLDEX. These are trying to replace sodium cyanide. Less toxic, work in CIP, CIL, or heap leach. Get about the same gold as cyanide, less risky for the land and water.



Xinahi Guinea 15,000tpd Gold Gravity Separation and CIP Plant

2. Heap Leaching Chemicals

Heap leaching? Like a big pile acting like a sponge for gold. Save money – don't crush the rock so fine. Pile the crushed ore up. Spray a weak cyanide mix over the top. It trickles down, dissolves the gold, collects in a pond at the bottom. Later, you use carbon or zinc to pull the gold out of that solution.

Chemicals:

Main Chemical: Sodium Cyanide (NaCN) – use about 60–150 grams per ton of ore. Gotta keep the pH high (9.5–10.5), so you add lime.

Eco-friendly chemicals: CNLITE works here too.

Rare Stuff: Thiourea or Thiosulfate – sometimes thought about, but usually too expensive or complicated to bother.

Key Requirements:

Crush ore no bigger than 25mm so the solution can flow through.

Let the pile sit ("cure") for at least 3 days (72 hours) before you start spraying – gives the chemicals time to start working right.

Brands in Africa: 

• Senmin (South Africa) sells cyanide and lime. They're active in places like Ghana and Tanzania.

xinhai gold leaching plant

3. Flotation Chemicals

Flotation? Like a bubble bath for gold. Needed when gold is stuck inside sulfide minerals (like pyrite) – crushing alone won't free it. Mix crushed ore with water and special chemicals:

• Collectors: Make the gold particles sticky so they grab onto air bubbles.

• Frothers: Make stable bubbles (like soap makes bubbles).

• Modifiers: Adjust the pH or stop other junk minerals from getting sticky.

Blow air through the mix. The sticky gold grabs the bubbles, floats to the top as a froth. Skim off that froth. Process that froth to get the gold out.

Chemicals:

• Collectors: Xanthates are common. Sodium ethyl xanthate is a big one.

• Frothers: MIBC (Methyl isobutyl carbinol) is popular.

• Brands: BASF makes frothers and collectors. Common in plants dealing with sulfide ores, like in Zimbabwe.

xinhai flotation plant

Picking Chemicals - Quick Thoughts

• Safety: Cyanide works great, but it's deadly poison. If your mine is near people or water, really think hard about the non-cyanide options like CNLITE.

• Ore Type: Oxide ore? Cyanide leaching usually best. Sulfide ore? You probably need flotation first.

• Test It before buy: Small miners – always try the chemicals on a sample of your ore first. Don't waste money buying stuff that doesn't work for what you've got.