SEX in Selective Flotation: Where the Shortest Xanthate Wins

Sodium ethyl xanthate (SEX, CAS 140-90-9) is the shortest-chain common xanthate – the most selective and the weakest. That trade-off is exactly what makes it valuable: SEX is the collector you reach for when the problem is separating sulphides cleanly, not maximising recovery. This page covers where SEX wins and how to use it.

1. Why SEX

Property	Consequence in the circuit
Shortest chain (C2)	Highest selectivity, lowest collecting power
Fast but selective adsorption	Floats the most readily floatable sulphides and leaves the rest
Low dosage effective	Works at low addition on responsive ores
Cheapest xanthate	Made from ethanol – the lowest-cost alcohol

2. Where SEX wins

Situation	Why SEX
Separating sulphides that must not co-float	High selectivity keeps unwanted sulphides in the tailings
Ores whose sulphides float readily	Little collecting power is needed; selectivity is what matters
Cleaner / selective stages	Cleans the concentrate without pulling extra gangue sulphide
Fine-tuning a collector blend	Blended with a stronger xanthate to shift the recovery/selectivity balance

3. The limitation, and how plants handle it

SEX alone is too weak to drive recovery on many ores. The usual solution is staged dosing:

Strong collector (SIBX/PAX) in the rougher/scavenger to recover the values.
SEX (or SIPX) in the cleaner to reject unwanted sulphides and upgrade the concentrate.

Used this way, SEX improves concentrate grade without sacrificing overall recovery – each stage gets the collector that suits it.

4. Dosage

Stage	Typical dosage (starting point)
Selective / cleaner stage	Low addition (about 10 – 80 g/t overall range for xanthates; set by the ore)
Combination	Usually less SEX than the strong collector it is paired with

Because SEX is weak, dosage is often adjusted to fine-tune grade rather than to drive recovery – small changes shift selectivity.

5. SEX vs SIPX

Collector	Chain	Selectivity	Note
SEX	C2	Highest	Weakest; for the most demanding separations
SIPX	C3	High	A step stronger while still selective – often the practical compromise

In many plants SIPX is the selective workhorse and SEX is used where even more selectivity is needed. See SEX vs SIPX.

6. Practical notes

Pair it. SEX rarely works alone – combine with a stronger collector for recovery.
Control pH. Selectivity depends on pH and on depressants as much as on the collector.
Degradation. Like all xanthates, SEX decomposes with moisture, heat and time – make up solutions fresh.
Screen it. Confirm the SEX/strong-collector split by flotation testing on the ore.

Frequently Asked Questions

What is SEX used for?

As a highly selective sulphide collector – for separating sulphides that must not co-float, in cleaner stages, and in blends where more selectivity is needed.

Is SEX weaker than the other xanthates?

Yes – it has the shortest chain, so the lowest collecting power, but the highest selectivity. It is normally paired with a stronger collector.

Should I replace SIPX with SEX?

Only if you need more selectivity than SIPX gives. SIPX is the more common selective choice; confirm both on the ore.

How much SEX is used?

Low additions, set by the ore; it is used to fine-tune grade rather than to drive recovery.