At a glance
Liquid-Liquid Extraction
ScopePartition coefficient
CAPEX$200k-$1.5M
Best forHydrophobic small molecule recovery
vs
Crystallization
ScopeSolubility-driven
CAPEX$200k-$1.5M
Best forHigh-purity solid recovery
Decision criteria
| Criterion | Liquid-Liquid Extraction | Crystallization | Verdict |
|---|---|---|---|
| Separation principle | Hydrophobic small molecule recovery | High-purity solid recovery | Partition vs solubility curve |
| Throughput / scale | 100-10,000 L/hr | 10-1,000 kg/hr | Similar |
| Capital cost | $200k-$1.5M | $200k-$1.5M | LLE lower |
| Operating cost | Solvent cost + recovery | Cooling / seeding | Application-dependent |
| Product purity ceiling | 70-90% per stage | 98-99.9% | Crystallization wins |
Quick verdict
LLE concentrates and recovers. Crystallization purifies and packages. They're a complementary pair, not alternatives.
Rule of thumb: Dilute aqueous feed needing recovery? LLE. Concentrated solution needing pure solid? Crystallize.
Frequently Asked Questions
When should I choose Liquid-Liquid Extraction over Crystallization?
Use LLE for bulk recovery from dilute aqueous feeds — penicillin extraction, organic acid concentration. Continuous, mass-transfer-limited.
When should I choose Crystallization over Liquid-Liquid Extraction?
Use crystallization for the final pure-form step — sharp purification, marketable solid product.
Can these two techniques be used together?
Yes — LLE concentrates, then back-extraction or evaporation, then crystallization. The penicillin process is exactly this train.
Which has lower OPEX at scale?
LLE costs depend on solvent inventory and recovery; crystallization costs depend on cooling load and yield.
Read more on each technique
Try both in your flowsheet
Build a process with each option side by side and compare yield, purity, and cost.
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