Dithiophosphate collectors — widely known as aerofloats — are the quiet workhorses of selective sulphide flotation. Where xanthates deliver brute recovery, a dithiophosphate collector buys you grade: cleaner lead concentrates, better copper-lead separation, and fewer depressed minerals reporting to the wrong stream. For a concentrator engineer, the practical question is rarely whether to use them, but which grade to specify and which dithiophosphate collector supplier can hold that specification batch after batch. This guide covers the chemistry in plain terms, the main product types, the specification sheet you should demand, and the checks that separate a reliable manufacturing partner from a trader with a drum.
How Dithiophosphate Collectors Work
A dithiophosphate collector is an O,O-dialkyl dithiophosphoric acid derivative, normally supplied as a sodium or ammonium salt so that it dissolves readily in the pulp. The molecule carries a polar dithiophosphate head that chemisorbs onto sulphide mineral surfaces, and two alkyl tails that render the mineral hydrophobic. Because the head group is bulkier and less reactive than a xanthate’s, adsorption is more selective: dithiophosphates attach readily to galena, chalcopyrite and activated sphalerite, but respond weakly to pyrite and to minerals that have been deliberately depressed.
That selectivity is why aerofloats are common in sequential circuits. They are often used ahead of xanthate in lead roughers, in copper-lead separation, and as a secondary collector where a xanthate alone would float too much iron sulphide. Typical additions run from roughly 10 to 100 g/t, fed as a dilute solution; the exact figure depends on head grade, pH and the degree of oxidation of the ore. Because the reagent is a weak acid salt, it performs best in mildly alkaline to neutral circuits and loses efficiency in strongly limed pulps.
The Main Aerofloat Types and Their Fit
Suppliers usually offer dithiophosphates by alkyl group and by salt form, and the differences matter in the plant.
- Cresylic types are the traditional general-purpose grade. They are relatively strong for a dithiophosphate and are used where a little extra pulling power is needed without going all the way to xanthate.
- Ethyl types are the most selective of the family. They suit clean lead-copper separation and circuits that are sensitive to pyrite reporting into the concentrate.
- Butyl and higher alkyl types give stronger collecting power and better performance on coarser or more heavily locked particles, at some cost in selectivity.
- Ammonium salts dissolve quickly and are convenient in plants that prepare reagent solutions on demand, while sodium salts are common where alkalinity control is handled separately.
In practice, most operations standardise on one primary grade and keep a second on hand for campaign changes. If you are still mapping collector classes against ore types, the site’s overview of flotation reagents and the guide to xanthate collectors provide the surrounding context.
Dithiophosphate vs Xanthate: A Selectivity Trade-Off
Comparing the two families is mostly a question of what the circuit can afford to lose. Xanthates are stronger and cheaper per unit of collecting power, which makes them the default for roughing. Dithiophosphates cost more per tonne of ore and generally recover less of the target mineral in a single pass. What they return is a cleaner concentrate and a more stable separation, which often pays for itself downstream in smelter penalties, transport costs and dewatering performance.
A useful rule of thumb: if your problem is recovery, add or increase xanthate; if your problem is grade, pyrite rejection or an unstable copper-lead split, a dithiophosphate is the more direct lever. Many plants run both — a dithiophosphate in the selective head and a xanthate scavenger downstream — and treat the split as a tuning parameter rather than a fixed recipe.
Specifications to Demand From a Dithiophosphate Collector Supplier
A dithiophosphate is not a single pure substance, and two drums labelled with the same grade name can behave differently. The specification sheet should pin down at least the following:
- Active content, expressed as the mass fraction of the dithiophosphate salt, with the analytical method named.
- Alkyl distribution, since a supplier blending C4 and C6 tails will not match a pure grade in flotation response.
- pH of a standard solution, which affects how the reagent behaves when diluted in plant water.
- Water insolubles and sediment, the usual cause of plugged reagent lines and erratic dosing.
- Appearance and colour, useful as a fast incoming-goods check against a retained reference sample.
- Batch number and production date, so that a drift in plant performance can be traced to a specific lot.
Ask for a certificate of analysis per batch rather than a one-off laboratory report, and keep a retained sample from each delivery. When concentrate grade moves, the first question should be whether the reagent changed, and a retained sample answers it in an afternoon.
Packaging, Storage and Shipping
Dithiophosphates are supplied in 200 L drums, 1000 L IBCs or, for large consumers, in ISO tanks. The salts are water-based and should not be allowed to freeze; prolonged exposure to high temperatures accelerates decomposition and produces the characteristic sulphidic odour that signals degradation. Store under cover, out of direct sun, and rotate stock so that older material is consumed first.
For export, the reagent is normally shipped as a non-hazardous or mildly regulated industrial chemical depending on concentration and salt form. Confirm the correct classification and documentation with your freight forwarder rather than relying on a generic description, and check that the supplier can provide an SDS in the language your customs broker requires.
Qualifying a Dithiophosphate Collector Supplier
Price per drum is the least informative number in a tender. A supplier worth shortlisting can answer four questions without hesitation: which grade, at what active content, produced in which plant, and with what batch-to-batch tolerance. Ask for the plant’s quality control routine, not just its certificate template; ask how it handles a customer complaint about off-spec material; and ask for two references in comparable circuits.
Then run a plant trial. Dose the candidate reagent against your current supplier at the same addition rate, hold the rest of the reagent scheme constant, and compare concentrate grade and recovery over a full shift rather than a single assay. A dithiophosphate that looks identical on paper frequently separates two concentrates apart in practice — and that difference is the only specification that ultimately matters.
Conclusion
Choosing a dithiophosphate collector is a two-part decision: select the grade that matches your separation problem, then select the supplier that can reproduce it. Cresylic, ethyl and butyl grades each occupy a distinct place in the selectivity ladder, and the specification sheet — active content, alkyl distribution, insolubles, batch traceability — is what turns a grade name into a predictable reagent. Get both right and the reward is a cleaner concentrate, a steadier circuit and fewer surprises in the thickener.