Lead-zinc ore is separated by what method?

For global mine owners, understanding the most effective ways to process raw zinc ore and separate lead-zinc ore is crucial. In the world of mining, two primary methods stand out: the cyanide method and the non-cyanide method.

Cyanide Method: A Balance of Efficiency and Caution
The cyanide method has long been a staple in lead-zinc flotation. It uses a relatively small dosage, offers a stable process that is easy to operate and control, and provides excellent process indicators. This is why many factories still rely on it. However, the toxicity of cyanide and its tendency to dissolve gold and silver have raised concerns. As a result, many mines are now exploring alternatives or reducing cyanide usage.

Take, for example, a processing plant that combines sodium cyanide with zinc sulfate. By doing so, they have managed to reduce the cyanide amount to 20 – 30g/t, with some even achieving a remarkable drop to 3 – 5g/t. In a specific lead-zinc deposit, a metasomatic deposit in dry carbonate rocks, the lead mineral is galena with a bit of lead alum, and the main ores of zinc are sphalerite and a small amount of smithsonite. Iron sulfide is present as pyrite, and the gangue consists of calcite, quartz, feldspar, etc. When separating lead and zinc using the cyanide method, due to the similar buoyancy of part of sphalerite to galena and the floatability of hard-to-float sphalerite to pyrite, an “iso-floating” process is adopted. During lead flotation, under the principle of floating net lead, some easily floatable sphalerite is also floated. Then, the tailings from lead flotation are mixed with zinc and sulfur for further processing.

Selection indicator	Raw ore grade (%)	Concentrate grade (%)	Capacity（%）
Pb	2.35	71	90
Zn	2.96	53	92
S	11.14	36	74

Non-Cyanide Method: Gaining Traction with Superior Results
The non-cyanide method is emerging as a viable and often superior alternative. In a lead-zinc sulfide ore, a high-quality flotation process using ZnSO4 + Na2CO3 (14:1) to suppress sphalerite during lead flotation has shown remarkable results. Compared to the cyanidation method, the grade of lead concentrate increased from 39.12% to 41.80%, the recovery rate rose from 74.59% to 75.60%, the grade of zinc concentrate increased from 43.59% to 48.43%, and the recovery rate climbed from 88.5% to 90.30%. This plant has also experimented with Na2SO3 + ZnSO4 and ZnSO4 alone to suppress sphalerite, achieving favorable indicators.

Internationally, innovative techniques are being employed. When lead-sulfur is mixed, the ore is ground to 45%-0.075mm, SO gas is introduced to suppress zinc, and the tailings are reground for zinc flotation. The lead-sulfur mixed concentrate is further reground for lead-sulfur separation, with cyanide then used to suppress sulfur and float the lead.

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