Flotation: Collectors vs Frothers

How to use this guide

This guide is written for operations + procurement + EHS alignment. Use it to clarify what collectors and frothers actually do in a circuit, what data matters for selection, and how to write a practical RFQ that results in comparable offers (quality, packaging, compliance, and supply reliability).

Where it fits in a flotation circuit

• Rougher: maximize recovery at acceptable grade (fast kinetics; froth must carry high mass pull).
• Cleaner: upgrade concentrate (selectivity dominates; froth must drain gangue).
• Scavenger: capture remaining value (often stronger collector / different frother window).
• Regrind + cleaning: new surface area changes reagent demand and froth behavior.

Collectors: what they do (and what they don’t)

Collectors are surface-active molecules that adsorb (chemically or physically) onto mineral surfaces, making selected minerals hydrophobic. This increases attachment probability and speeds flotation kinetics. Collector choice is driven by mineralogy and the electrochemical environment (pH/Eh/ions).

Common collector families (high level)

• Xanthates (PAX/SAX/PBX, etc.): widely used for sulfides; strength and selectivity shift with chain length and circuit conditions.
• Dithiophosphates / dithiophosphinates: often used for selectivity improvements, precious metals association, and certain complex ores.
• Thionocarbamates / thiocarbamates: used where selectivity and kinetics need tuning for specific sulfide systems.
• Fatty acids / soaps: common for oxide minerals (e.g., apatite, fluorite) with strong dependence on water hardness and pH.
• Amines: typical for silica/silicate flotation in reverse circuits (e.g., potash/iron ore reverse flotation), sensitive to clays and water chemistry.

Collector selection cues

• If grade suffers (too much gangue): you may be over-collecting or collecting the wrong surfaces; check pH control, depressants, and froth entrainment first.
• If recovery suffers (slow kinetics): you may need stronger collector chemistry, better activation, improved conditioning, or better dispersion — but confirm bubble surface area and froth stability first.
• If consumption rises: check oxidation state, fines/clays, recycle water organics, and dosing location (collector lost to non-target surfaces).

Frothers: what they control

Frothers do not “make minerals float” by themselves; they shape the gas phase and froth structure: bubble size, coalescence, froth stability, and drainage rate. This strongly affects both recovery (bubble surface area and stability) and grade (entrainment and drainage).

Common frother families

• Alcohol-based (e.g., MIBC-type): often produce more mobile froths; typically lower persistence and easier drainage.
• Polyglycols / polypropylene glycols (PPG): can generate finer bubbles and more persistent froths; may increase entrainment if overdosed.
• Blended frothers: tuned for specific circuits (rougher vs cleaner) or water recycle conditions.

Frother selection cues

• Froth collapses / low mass pull: insufficient frother, too much coalescence, wrong air rate, or surfactant contamination issues.
• Froth too stable / “sticky” / high entrainment: overdosed frother, too fine bubbles, excessive slimes/clays, or high recycle organics.
• Unstable bubble size / patchy froth: changes in water quality (hardness, ions), frother dilution, or air distribution problems.

Collectors vs frothers: how they trade off grade and recovery

In practice, collectors and frothers are tuned together. Think in terms of the “attachment + transport” chain:

• Collector: increases attachment probability (kinetics) and defines selectivity (what attaches).
• Frother: determines bubble surface area and froth survival (how much attaches and makes it out).
• Water + air + solids: define the environment that can amplify or negate both.

Water quality effects (why recycle water changes everything)

Water chemistry can shift collector adsorption, frother coalescence control, and froth drainage. This is why lab tests should be run with plant water (or representative recycle blends), not only DI water.

What to watch

• pH and alkalinity: impacts collector ionization, mineral surface charge, and depressant performance.
• Hardness (Ca/Mg): critical for fatty acid/soap systems; can also affect froth and dispersion.
• Ionic strength (TDS): changes bubble coalescence, froth stability, and reagent partitioning.
• Sulfate/chloride and specific ions: can influence adsorption and redox behavior depending on ore type.
• Dissolved organics: can increase frother demand and raise entrainment; common in high recycle circuits.
• Clays/fines: increase viscosity, stabilize froth, and raise entrainment; can consume collectors via non-selective adsorption.

Practical dosing & addition points

Dosing strategy matters as much as product selection. Use your circuit’s conditioning time and mixing to your advantage.

Collectors

• Add where conditioning exists: adequate mixing and contact time before flotation improves adsorption consistency.
• Split dosing: can reduce over-collecting in the rougher while maintaining recovery downstream (rougher + scavenger split).
• Strength vs selectivity: “stronger” is not always better; stronger collectors can pull more gangue if depression and froth drainage are not tuned.

Frothers

• Add close to flotation: frother primarily controls bubble/froth in the cell; long conditioning is usually not necessary.
• Watch dilution water: frother dilution quality can change performance (hardness/ions).
• Control with air and level: reagent changes should be paired with air rate and froth depth setpoints.

Specification & acceptance checks (procurement-ready)

Flotation reagents vary by supplier route, purity, and blend consistency. These checks help you compare offers and avoid surprises:

• Identity: exact product name, chemistry family, grade, and intended use (collector/frother/depressant/activator).
• Active content / purity: stated assay range and test method where applicable (especially for collectors and blended frothers).
• Physical checks: appearance, density, and viscosity (important for metering and cold-weather handling).
• Water content: where relevant (affects actives and dosing).
• Impurity limits: sulfur species, ash, or specific contaminants only if they matter for your circuit and compliance.
• Packaging: drum/IBC/bulk, liner type, closures, labeling language, and palletization.
• Safety: current SDS (GHS/CLP), PPE guidance, spill handling, and transport classification.
• Logistics: lead time, Incoterms, shelf life, storage temperature window, and multi-origin availability for continuity.

Handling & storage

• Store sealed in original packaging; protect from moisture ingress where applicable (some collectors are sensitive).
• Use secondary containment and clear labeling in reagent areas.
• For transfers: verify pump/hoses for compatibility and viscosity; implement spill-control basics and operator training.

Troubleshooting: symptom → likely cause → first checks

• Recovery drops suddenly → air distribution change, froth collapse, water chemistry shift, or ore change → check air rate, froth depth, bubble size, recycle water blend, and frother dosing calibration.
• Grade drops (more gangue) → entrainment increase, froth too stable, clays/fines, over-collection → check froth drainage, solids %, frother dose, and clay management; verify depressant performance.
• Froth too persistent / hard to break → frother overdose, high organics, fine bubbles → step down frother, adjust air/level, review recycle organics and slimes.
• High reagent consumption → non-selective adsorption to clays/oxidized surfaces, wrong addition point, inconsistent actives → check ore oxidation, conditioning, dispersion, and COA/assay consistency.
• Scaling or deposits in reagent lines → incompatibility with hard water, precipitation, poor dilution practice → review dilution water hardness, temperature, and mixing; confirm material compatibility.

RFQ notes (what to include)

• Ore & circuit: sulfide/oxide mix, target minerals, rougher/cleaner/scavenger arrangement, and typical PSD.
• Operating window: pH, temperature, solids %, residence time, air rate ranges, froth depth targets.
• Water: recycle ratio, TDS, hardness, alkalinity, key ions, and known organic load issues.
• Current reagent suite: collectors, frothers, depressants, activators, dispersants (and typical doses).
• KPIs: recovery/grade targets, mass pull, froth stability constraints, downstream filtration/handling constraints.
• Supply: estimated monthly volumes, packaging preference (drum/IBC/bulk), delivery location and Incoterms.
• Documentation: SDS, COA, TDS, and any compliance requirements for your destination.

FAQ

Educational content only. Always follow site EHS rules and the supplier SDS for safe use. Validate reagent changes with plant trials and monitoring, especially under changing ore and water recycle conditions.