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Flotation reagent

Also known as
reagent scheme, mineral processing reagent

A flotation reagent is any chemical added in froth flotation to control which minerals float and how the froth behaves. The main groups are collectors, frothers and modifiers such as depressants, activators and pH regulators; together they make up the plant's reagent scheme.

What are flotation reagents?

Froth flotation depends on chemistry. Without reagents, most minerals would not attach to air bubbles, and those that did would not separate cleanly. Flotation reagents are the chemicals that make the process selective and controllable. Their doses are small relative to the ore treated, but they strongly affect metallurgical recovery, concentrate grade and cost.

Main types

TypeRoleExamples
CollectorsMake target minerals water-repellent so they attach to bubblesXanthates, dithiophosphates, fatty acids, amines
FrothersCreate small bubbles and a stable frothMIBC, polyglycol ethers
DepressantsStop specific minerals from floatingLime, sodium silicate, starch, cyanide
ActivatorsHelp specific minerals respond to the collectorCopper sulfate for sphalerite
pH regulatorsControl the pulp chemistryLime, soda ash, sulfuric acid
DispersantsControl fine particles and claysSodium silicate, polymers

The reagent scheme

The combination of reagents, their doses, where they are added in the circuit, and the conditioning time before flotation make up the reagent scheme. It is designed for a specific ore and adjusted as the ore changes. Because reagents interact, changing one often affects the performance of the others.

Evaluating new reagents

Plants are cautious about changing reagents, because a change that performs well in the laboratory can behave differently at plant scale or on different ore. A typical evaluation path is:

  1. Laboratory flotation tests on representative ore, comparing grade-recovery curves.
  2. Pilot or locked-cycle tests that simulate recirculating streams.
  3. Plant trials, often alternating periods with and without the new reagent, with careful sampling and statistical analysis.

Drop-in reagents that fit the existing scheme without other changes are easier to trial and adopt.

Flotation reagents and Locus

Locus Mining develops biosurfactant-based flotation reagents that it describes as integrating with existing reagent programs, and supports evaluation through structured laboratory, pilot and plant testing.

Frequently asked questions

Collectors, frothers and modifiers. Modifiers include depressants, activators, pH regulators and dispersants.

Because ore changes. Differences in mineralogy, grade, oxidation and clay content, along with water quality and metal prices, all affect which reagents and doses give the best result.

  • Collector

    A collector is a flotation reagent that adsorbs onto the surface of a target mineral and makes it water-repellent, so that the mineral particles attach to air bubbles and float into the froth. Xanthates, dithiophosphates, fatty acids and amines are common collectors.

  • Frother

    A frother is a surface-active flotation reagent that helps create small, stable air bubbles and a froth that can hold mineral particles long enough to be collected. Common frothers include MIBC and polyglycol ethers.

  • Depressant

    A depressant is a flotation reagent that stops a particular mineral from floating, usually by making its surface more water-attracting or by preventing the collector from attaching to it. Depressants are used to reject gangue or to separate one valuable mineral from another.

  • Activator

    In froth flotation, an activator is a reagent that changes a mineral's surface so that a collector can attach to it, making a mineral float that otherwise would not. The classic example is copper sulfate, which activates sphalerite, the main zinc mineral, for flotation with xanthate collectors.

  • Froth flotation

    Froth flotation is a mineral separation process in which valuable mineral particles are made water-repellent so they attach to air bubbles and rise into a froth, while unwanted minerals stay in the water. It is the most widely used method for concentrating sulfide and many other ores.

Sources

  1. Wills' Mineral Processing Technology, 8th edition, B. A. Wills and J. A. Finch, Butterworth-Heinemann, 2016
  2. SME Mineral Processing and Extractive Metallurgy Handbook, Society for Mining, Metallurgy and Exploration, 2019