Ethyl xanthate (SEX) and isopropyl xanthate (SIPX) are the two most common short-chain xanthate collectors in sulfide flotation. They look similar — both are pale yellow sodium xanthates — but the one-carbon difference in their alkyl chains changes collecting strength, selectivity and cost. This article compares SEX and SIPX so mill operators can choose the right collector (or combination) for their ore.
1. The Xanthate Family and Chain Length
Xanthates are ranked by alkyl chain length: the longer the chain, the stronger the collecting power and the weaker the selectivity. The short-chain pair is:
- SEX (sodium ethyl xanthate, CAS 140-90-9): C2 chain — the shortest commercial xanthate, most selective, weakest collecting power.
- SIPX (sodium isopropyl xanthate, CAS 140-93-2): C3 branched chain — a step stronger than SEX, the industry workhorse.
2. Side-by-Side Comparison
| Property | SEX (Ethyl) | SIPX (Isopropyl) |
|---|---|---|
| Alkyl chain | C2 (shortest) | C3 (branched) |
| Collecting power | Weakest | Moderate |
| Selectivity (esp. vs pyrite) | Highest | High |
| Recovery of slow-floating minerals | Lower | Better |
| Typical dose | 20-80 g/t | 10-100 g/t |
| Relative cost | Lowest | Low |
| Typical uses | Selective circuits, simple ores, fine particles | Bulk Cu/Pb/Zn flotation, general purpose |
3. When to Choose SEX
- Selectivity-critical circuits: where pyrite and gangue must be strongly rejected, SEX’s weak collecting power works in your favor.
- Simple, well-liberated ores: where a strong collector is unnecessary.
- Fine or slow-floating mineral handling: some plants find SEX’s gentle action gives cleaner froths on specific minerals.
- Cost-sensitive simple circuits: SEX is the cheapest xanthate per kilo.
4. When to Choose SIPX
- Copper-lead-zinc bulk flotation: SIPX is the standard workhorse, balancing recovery and selectivity.
- Where recovery of middlings matters: SIPX’s slightly stronger collecting power recovers slow-floating particles SEX misses.
- Zinc flotation after activation: the stronger SIPX dose on activated sphalerite gives better zinc recovery.
- General-purpose simplicity: one collector for multiple stages reduces reagent inventory.
5. Using Them Together
Many plants use both: SEX (or a weak dose) in the more selective stage and SIPX in the recovery-oriented stage, or a SEX/SIPX blend in a single stage to tune selectivity against recovery. Jar testing a blend ratio (e.g. 70:30 or 50:50) on your ore is the fastest way to find the balance.
6. Practical Selection Checklist
- Identify the value minerals and the main gangue (especially pyrite content).
- Define the bottleneck: is the problem grade (selectivity) or recovery?
- Test SEX vs SIPX vs a blend at the same dose on your ore; compare grade and recovery.
- Consider circuit pH: both work in alkaline circuits; test at your operating pH.
- Check cost per ton of concentrate, not per kilo of reagent.
7. FAQ
Is SEX stronger than SIPX?
No — SIPX is stronger. SEX has the shortest chain and the weakest collecting power, which is why it is the most selective.
Can I replace SEX with SIPX directly?
Not without re-testing. SIPX is stronger; a direct swap will likely increase recovery but may reduce selectivity. Run a jar test and adjust the dose.
Which is cheaper, SEX or SIPX?
SEX is typically the cheapest xanthate per kilo; SIPX costs slightly more but usually less per ton of concentrate because of its stronger collecting power.
Do SEX and SIPX mix well together?
Yes — blends are common. Test ratios on your ore to tune selectivity vs recovery.
8. References and Further Reading
- Peer-reviewed literature on xanthate chain length and flotation selectivity
- Plant practice reviews for copper and lead-zinc circuits
This article is published for industrial and technical reference by PolyblueChem. Selection should always be confirmed by flotation test work.
PolyblueChem supplies SIPX (CAS 140-93-2) and related flotation reagents with COA and MSDS. See also our SIBX vs SIPX vs PAX comparison and SIPX circuit practice guide. Contact us for specifications and quotations.