Recovering valuable metals from complex process streams is rarely just a matter of extracting as much metal as possible. In hydrometallurgy, the more difficult requirement is often selectivity—separating a target metal from large amounts of chemically similar or competing ions.

This is where Kelex-100, a long-chain alkylated 8-hydroxyquinoline extractant, has attracted attention. Its ability to form metal complexes makes it useful in solvent extraction systems designed for the recovery and separation of gallium, copper, germanium and other metal ions.

Kelex-100 Chemical Profile

Kelex-100 is identified by CAS No. 73545-11-6 and is also known as:

7-(4-Ethyl-1-methyloctyl)-8-hydroxyquinoline

7-(4-Ethyl-1-methyloctyl)-8-quinolinol

7-(1-Methyl-4-ethyloctyl)quinoline-8-ol

7-(5-Ethylnonan-2-yl)quinolin-8-ol

Kelex-100

Its molecular formula is C20H29NO, with a molecular weight of 299.45 g/mol. The long alkyl substituent gives the molecule strong organic-phase compatibility, while the 8-hydroxyquinoline functional group provides the metal-binding site.

SHLZ Pharma describes its Kelex-100 product as a deep red/brown liquid and lists storage at 2–8°C.

Why Kelex-100 Works as a Metal Extractant

The key feature of 7-(4-Ethyl-1-methyloctyl)-8-hydroxyquinoline is not simply its hydrocarbon chain. The functional 8-hydroxyquinoline group can coordinate with metal ions and promote their transfer from an aqueous phase into an organic phase.

The hydrophobic alkyl chain, meanwhile, improves the compatibility of the metal-containing complex with the organic extraction phase.

This combination gives Kelex-100 a useful balance between:

metal-ion coordination + organic-phase solubility + extractant selectivity

That is why Kelex-100 is more appropriately viewed as a specialized chelating extractant rather than a conventional solvent.

1. Gallium Recovery from Bayer Process Liquor

One of the best-established applications of Kelex-100 is gallium recovery from Bayer process liquor.

Gallium occurs as a minor component in bauxite-derived Bayer liquor, where it exists in a highly alkaline chemical environment dominated by sodium and aluminum species. Recovering gallium therefore requires an extraction system capable of distinguishing the target metal under demanding process conditions.

A study published in Minerals Engineering investigated gallium solvent extraction from concentrated Bayer process liquor using 7-alkyl-substituted-8-hydroxyquinoline (Kelex-100) together with isodecanol as modifier and kerosene as diluent. The research examined the influence of extractant concentration, modifier concentration and stripping conditions on gallium recovery.

Further research investigated Kelex-100-based gallium extraction in the presence of surfactants and reported improved extraction kinetics under specific formulation conditions.

Therefore, Bayer liquor gallium recovery remains one of the most recognizable industrially relevant applications associated with Kelex-100.

2. Copper Solvent Extraction

Kelex-100 is also relevant to copper separation.

Unlike a general-purpose extractant, Kelex-100 can interact strongly with copper under appropriate acidic conditions, making it useful for developing selective copper transfer systems.

Research published in Hydrometallurgy studied the transfer of copper from hydrochloric acid solution into sulfuric acid solution using Kelex-100. The process included copper extraction, chloride scrubbing, stripping and regeneration/conditioning of the extractant.

This demonstrates an important feature of Kelex-100: its application is not limited to simply loading metal into an organic phase. The overall process must also consider scrubbing, stripping, phase behavior and extractant regeneration.

For copper solvent extraction projects, these process parameters can be as important as the nominal purity of the extractant itself.

3. Germanium and Rare-Metal Separation

Another important application is germanium extraction and separation.

Research on liquid-liquid extraction of germanium with oxine derivatives identified Kelex-100 as an effective commercial oxine derivative for germanium extraction from acidic solutions. The study reported rapid extraction kinetics under suitable conditions and investigated the chemical forms of the extracted germanium species.

Later research also explored Kelex-100-functionalized adsorbents for germanium removal from aqueous solutions, highlighting the broader potential of the Kelex-100 ligand beyond conventional solvent extraction.

Its application in germanium systems is particularly relevant where the target metal is present alongside competing elements and selective separation is required.

From Extractant Molecule to Process Reagent

For industrial users, the performance of Kelex-100 should not be evaluated in isolation.

Extraction efficiency depends on the complete chemical system, including:

Aqueous-phase composition

pH and acidity/alkalinity

Kelex-100 concentration

Organic diluent

Phase modifier

Organic-to-aqueous phase ratio

Contact time

Temperature

Scrubbing conditions

Stripping chemistry

The published studies on gallium, copper and germanium demonstrate that changing these variables can significantly affect extraction kinetics, recovery and selectivity.

For this reason, laboratory-scale testing should normally precede large-scale process implementation.

What to Evaluate When Buying Kelex-100

For buyers sourcing Kelex-100 CAS 73545-11-6, several points deserve attention.

Chemical identity:
Confirm the CAS number, molecular formula and molecular weight against the required specification.

Appearance and physical condition:
SHLZ Pharma lists the material as a deep red/brown liquid. Because physical appearance can vary with storage and formulation conditions, buyers should rely on the supplier’s current batch specification and COA rather than color alone.

Purity:
The required purity should be established according to the extraction process and target metal. For industrial hydrometallurgy, consistent batch composition can be more important than simply purchasing the lowest-cost material.

Storage:
SHLZ Pharma recommends storage at 2–8°C for its listed product.

Supply continuity:
For solvent-extraction operations, replacing an established extractant source can require additional qualification work. Stable batch-to-batch supply is therefore an important procurement consideration.

Kelex-100 Supply from SHLZ Pharma

SHLZ Pharma lists Kelex-100 CAS 73545-11-6 as a regular production product and states that it can supply requirements ranging from small samples to tonnage-scale quantities.

For companies developing or operating metal extraction processes, this provides a practical supply path from:

laboratory testing → pilot-scale evaluation → process validation → larger-volume procurement

The supplier’s product information also identifies Kelex-100 within its extractant portfolio, supporting its positioning as a specialty chemical for metal separation rather than a general-purpose commodity reagent.

Final Perspective

Kelex-100 (7-(4-Ethyl-1-methyloctyl)-8-hydroxyquinoline), CAS 73545-11-6, is a specialized alkylated hydroxyquinoline extractant with a well-documented history in hydrometallurgical research.

Its most important application areas include gallium recovery from Bayer process liquor, copper solvent extraction, and germanium/rare-metal separation. The underlying value comes from combining a metal-coordinating hydroxyquinoline group with a hydrophobic alkyl structure suitable for organic-phase extraction.

For process developers and industrial buyers, the right Kelex-100 supplier should therefore be evaluated not only on price, but also on chemical identity, batch consistency, documentation, storage requirements and scalable supply capability.