Xanthate Collector Selection Chart: SEX vs SIPX vs SIBX vs PAX

Choosing a xanthate collector comes down to two variables: the chain length (which sets the balance between collecting power and selectivity) and the ore and target mineral. This page pulls that into one selection chart you can use to shortlist a collector before lab testing. The four common xanthates are sodium ethyl (SEX), sodium isopropyl (SIPX), sodium isobutyl (SIBX) and potassium amyl (PAX).

1. The one rule that decides most of it

Longer chain = stronger collector, less selective. Shorter chain = more selective, weaker collector.

Collector	CAS	Chain	Strength	Selectivity
SEX (sodium ethyl xanthate)	140-90-9	C2 (shortest)	Weakest	Highest
SIPX (sodium isopropyl xanthate)	140-93-2	C3	Moderate	High
SIBX (sodium isobutyl xanthate)	25306-75-6	C4	Strong	Moderate
PAX (potassium amyl xanthate)	2720-73-2	C5 (longest)	Strongest	Lowest

2. Selection chart by target mineral

Typical first choices – use them to shortlist, then confirm by flotation test on your ore.

Target mineral	Typical ore	First choice	Also used	Notes
Chalcopyrite (CuFeS₂)	Porphyry copper	SIBX	PAX (rougher), SIPX (cleaner)	Strong collector for copper; SIPX where a cleaner concentrate matters
Galena (PbS)	Lead-zinc	SIPX	SIBX	Selectivity helps in Pb-Zn separation
Sphalerite (ZnS)	Zinc / Pb-Zn	SIBX	PAX	Requires activation (typically CuSO₄); depress zinc in the lead circuit
Pyrite, gold-bearing (FeS₂)	Gold	PAX	SIBX	Strong collector to float the gold-bearing sulphide
Pentlandite (Ni sulphide)	Nickel	SIBX	PAX
Free / gravity gold	Gold	PAX	SIBX	Used in flotation of the fine/free gold fraction
Chalcopyrite + sphalerite (Cu-Zn)	Copper-zinc	SIPX	SIBX	Pair with a zinc depressant to keep Zn out of the copper concentrate
Molybdenite (MoS₂)	Copper-molybdenum	Hydrocarbon oil (not a xanthate)	–	Molybdenite is floated with oil; xanthate is used for the copper

3. Selection chart by ore type

Ore type	Typical approach
Porphyry copper (single sulphide)	SIBX in the rougher; SIPX or SEX in the cleaner for a cleaner concentrate
Lead-zinc (two sulphides)	Selective collector (SIPX); depress sphalerite with zinc sulphate + metabisulfite
Copper-zinc	SIPX with zinc depression; SIBX if recovery is limiting
Gold in sulphide (refractory or pyritic)	PAX or SIBX to maximise sulphide (and gold) recovery
Nickel sulphide	SIBX, with controlled pH and non-selective conditions
Complex polymetallic	Stage the dosing: strong collector early (bulk), selective later (clean)

4. Rougher / scavenger vs cleaner

Stage	What you want	Collector to reach for
Rougher	Maximise recovery – float as much as possible	PAX or SIBX (strong)
Scavenger	Recover the last of the target mineral	PAX or SIBX
Cleaner	Reject gangue and unwanted sulphides	SIPX or SEX (selective)

5. Typical dosage

Collector	Typical dose (starting point)
SEX	About 10 – 80 g/t
SIPX	About 10 – 80 g/t
SIBX	About 10 – 100 g/t
PAX	About 10 – 100 g/t

Dosage is ore- and stage-specific. These are starting points for a lab programme, not a specification.

6. Quick decision rules

Maximise recovery of a single valuable sulphide -> long chain (PAX, SIBX).
Cleanest concentrate / separation between sulphides -> short chain (SEX, SIPX).
Split the stages: strong collector in the rougher, selective collector in the cleaner.
Sphalerite needs activation (CuSO₄) and a depressant (zinc sulphate + metabisulfite) in lead circuits.
Oxidised or partly oxidised ore usually needs higher dosage, a sulphidisation step, or a combination – test it.
Always confirm by flotation test on your ore; chain length shortlists the collector, the test picks it.

7. Other factors that change the choice

Factor	Effect
Pulp pH	Strongly affects selectivity; xanthates are alkaline-stable but vary in performance by pH
Degree of oxidation	Oxidised surfaces float poorly; may need sulphidising or more collector
Grind size and liberation	Finer grind can change selectivity and dose
Flotation time and circuit design	Longer times and multi-stage circuits favour staged dosing
Water quality	Hard process water and ions can consume collector or depress

Frequently Asked Questions

How do I choose between SEX, SIPX, SIBX and PAX?

By what you need most: the strongest recovery favours PAX or SIBX (long chains), the cleanest or most selective separation favours SEX or SIPX (short chains). Confirm with a flotation test on your ore.

What is the difference between SIBX and PAX?

SIBX is C4 (sodium isobutyl xanthate) and PAX is C5 (potassium amyl xanthate). PAX is the stronger but less selective collector; SIBX is strong and more selective.

Why use a strong collector in the rougher and a selective one in the cleaner?

The rougher should recover as much of the target mineral as possible, so a strong collector is used; the cleaner should reject unwanted minerals, so a selective collector is used.

Can two xanthates be used together?

Yes – staged dosing (strong then selective) and collector blends are both common practice. Confirm the combination in lab tests.

Does sphalerite need a different collector?

Sphalerite usually has to be activated (typically with copper sulphate) before it will float with a xanthate; in lead-zinc circuits it is also depressed in the lead stage.