Every concentrator buys mining flotation chemicals, but not every concentrator buys the right ones. The reagent scheme is the heart of a flotation plant: collectors select the mineral, frothers build the froth, and modifiers decide which minerals float and which are depressed. Getting the scheme wrong — or buying inconsistent quality — shows up immediately in recovery and concentrate grade. This guide sets out the standard flotation chemical lists for the three ore types that account for most of the world’s sulphide flotation: copper, gold, and lead-zinc.
The Four Functional Families
Before looking at individual ores, it helps to fix the four roles every reagent scheme must fill:
- Collectors — the chemistry that makes a mineral surface hydrophobic so it attaches to air bubbles. Xanthates dominate sulphide flotation.
- Frothers — surfactants that stabilise the bubble bed so collected minerals can be skimmed off.
- Activators — reagents that make a reluctant mineral responsive to the collector (typically copper sulfate for sphalerite).
- Depressants and pH regulators — reagents that stop unwanted minerals from floating: lime, sodium hydrosulfide, sodium sulfide, zinc sulfate, and cyanide in some flowsheets.
Copper Ore: The Classic Xanthate Scheme
For copper sulphide ores — chalcopyrite being the most common — the standard scheme is simple and robust:
- Collector: sodium butyl xanthate (SBX) or sodium isopropyl xanthate (SIPX), often supplemented with a small amount of a dithiophosphate where silver or gold values need scavenging.
- Frother: methyl isobutyl carbinol (MIBC), the workhorse for copper circuits.
- Depressant and pH control: lime, added to raise pulp pH to 10–12, which strongly depresses pyrite so it does not report to the copper concentrate.
A typical regime for a simple porphyry copper ore is SBX plus MIBC plus lime, with doses of tens to a few hundred grams per tonne, tuned by laboratory and plant trials. Where the ore contains molybdenum, the flowsheet later uses sodium hydrosulfide or sodium sulfide to depress copper sulphides during the molybdenum cleaning stage.
Gold Ore: Strong Collectors and Scavenging
Gold and gold-bearing pyrite respond to the same xanthate chemistry, but with two twists: gold often requires a more powerful collector, and losses tend to hide in the tailings.
- Collector: potassium amyl xanthate (PAX) is the classic choice for free and pyrite-associated gold; blends of PAX with dithiophosphate or thionocarbamate collectors improve recovery of fine and coarse gold.
- Frother: MIBC or a blend with higher-frothing alcohols where the ore is fine-grained.
- Modifiers: lime for pyrite depression where the gold is associated with other sulphides; in some refractory ores the gold is recovered with a bulk sulphide float first.
Gold circuits benefit from aeration and careful froth control: the value is dilute (a few grams per tonne is a rich ore), so losses of even a few percent of the contained gold dominate plant economics.
Lead-Zinc Ore: Selective Sequential Flotation
Lead-zinc ores are where flotation chemistry earns its reputation, because the circuit must separate three minerals — galena, sphalerite, and pyrite — from a single ore. The classic flowsheet is sequential:
- Lead flotation: sphalerite and pyrite are depressed with zinc sulfate plus lime (and, in many plants, a small addition of sodium sulfite or cyanide), while galena is floated with SEX or SBX.
- Zinc activation and flotation: copper sulfate is added to activate sphalerite, which is then floated with SEX or SBX into a zinc concentrate.
- Pyrite depression is maintained through the whole circuit with lime at high pH.
The quality of the zinc sulfate and copper sulfate is critical here: a consistent activator dose makes the difference between a clean zinc concentrate and one contaminated with iron sulphides.
Buying Mining Flotation Chemicals: The Checklist
Whatever the ore type, the same procurement rules apply:
- Buy against the flowsheet, not the price list. Choose the collector families and frother first, then match grades and doses by laboratory flotation tests on your own ore.
- Verify effective content per batch. Xanthate effective content and moisture, frother purity, and the assay of copper sulfate all drift between suppliers; require a certificate of analysis with every batch.
- Check packaging and logistics. Xanthates are flammable and moisture-sensitive; sodium hydrosulfide and sodium sulfide are hazardous solids. Waterproof packaging, correct UN classification, and dependable sea freight matter as much as the price per tonne.
- Plan the reagent budget together. A supplier who can provide the whole scheme — collectors, frothers, and modifiers — simplifies quality control and lets you negotiate one contract instead of three.
Conclusion
The right mining flotation chemicals are a matched set, not a shopping list: collectors, frothers, activators, and depressants selected together for the mineralogy in your mill. Copper calls for the classic SBX–MIBC–lime scheme, gold rewards stronger collectors and scavenging discipline, and lead-zinc demands a carefully sequenced activation and depression balance. For a fuller treatment of reagent families, see our complete guide to flotation reagents, and for copper and lead-zinc flowsheets in practice, our guide on xanthate collectors for copper and lead-zinc ores.