Flotation Reagents: Selection Guide

A flotation circuit is a system of reagents, each with a job: collectors make target minerals float, frothers stabilise the froth, depressants hold unwanted minerals back, activators switch a mineral on, and pH modifiers set the chemistry. This page is the selection guide – what each class does, when to use it, and where our products fit. Use it to shortlist, then follow the links for the detail.

1. The reagent classes

Class	Job	Typical reagents	Products we supply
Collectors	Make target minerals hydrophobic so they attach to bubbles	Xanthates, dithiophosphates, thionocarbamates, MBT	SEX, SIPX, SIBX, PAX; MBT
Frothers	Stabilise the froth so mineralised bubbles can be recovered	MIBC, pine oil, glycols	Speciality frothers (quoted per circuit)
Depressants	Hold unwanted minerals in the tailings	Zinc sulphate, sodium metabisulfite, sodium cyanide, starch, lime	Sodium metabisulfite
Activators	Switch on a mineral that will not float by itself	Copper sulphate, lead nitrate	Quoted per circuit
pH modifiers	Set the pulp chemistry that makes selectivity possible	Lime, soda ash, caustic	Caustic potash / quoted per circuit
Flocculants	Thicken tailings and dewater concentrate	Polyacrylamide	Polyacrylamide (PAM)

2. Collectors: the xanthate family

Xanthates are the workhorse sulphide collectors. The chain length sets the balance between collecting power and selectivity:

Collector	Chain	Strength	Selectivity	Best for
SEX	C2	Weakest	Highest	Selective separations; cleaner stages
SIPX	C3	Moderate	High	Copper and lead-zinc; cleaner concentrates
SIBX	C4	Strong	Moderate	General-purpose sulphide flotation
PAX	C5	Strongest	Lowest	Rougher/scavenger recovery (gold, copper)

Full decision tables: xanthate selection chart and SIBX vs SIPX vs PAX. For non-sulphide and oxide ores, MBT is a thiol collector used where xanthates struggle (MBT in flotation).

3. Selection by target mineral

Target mineral	Collector	Typical depressant / modifier
Chalcopyrite (Cu)	SIBX, PAX; SIPX in the cleaner	Lime for pH
Galena (Pb)	SIPX, SIBX	Zinc sulphate to depress sphalerite
Sphalerite (Zn)	SIBX after activation	Copper sulphate activator; depress in the lead stage
Pyrite / gold-bearing sulphide	PAX, SIBX	pH control; pyrite depression where unwanted
Pentlandite (Ni)	SIBX	Controlled pH, non-selective conditions
Oxidised / partly oxidised	MBT (after sulphidisation)	Sodium sulphide for sulphidisation
Sulphide depression	–	Sodium metabisulfite; zinc sulphate

4. Selection by stage

Stage	What you want	Reagent choice
Rougher	Maximum recovery	Strong collector (PAX/SIBX), frother, pH modifier
Scavenger	Recover the last of the values	Strong collector, additional frother
Cleaner	Reject gangue and unwanted sulphides	Selective collector (SIPX/SEX), depressant, pH control
Tailings handling	Water recovery and containment	Flocculant (PAM)

5. Quick selection rules

Maximise recovery? Strong collector (PAX/SIBX) in the rougher.
Cleanest concentrate? Selective collector (SIPX/SEX) in the cleaner.
Two sulphides to separate? Selective collector plus a depressant (zinc sulphate, metabisulfite).
Zinc not floating? It needs activation (copper sulphate) before the collector will work.
Oxidised ore? Sulphidise first, then use a thiol collector (MBT) or a xanthate.
Thickening tailings? Flocculant (PAM), graded to the slurry.
Confirm by flotation test – the scheme is developed on the actual ore, not on a chart.

Frequently Asked Questions

Which collector should I use?

Start from the target mineral and the stage: strong collectors (PAX/SIBX) for recovery in the rougher, selective collectors (SIPX/SEX) for concentrate cleaning. Confirm with flotation tests on the ore.

What depressant do I need for lead-zinc separation?

Typically zinc sulphate to depress sphalerite in the lead circuit, with metabisulfite also used as a depressant/modifier. The exact scheme is set by testwork.

When is MBT used instead of a xanthate?

For oxidised and partly oxidised ores (after sulphidisation) and some complex sulphides where xanthates under-perform.

Do you supply frothers?

We quote frothers per circuit; collectors (xanthates, MBT), metabisulfite and flocculants (PAM) are standard products.