Cobalt Extractant (Dimethylglyoxime / DMG Organic Phase) Storage & Tank Compatibility

Storing Cobalt Extractant (Dimethylglyoxime / DMG Organic Phase)? Start Here

A “cobalt extractant (DMG)” is not a single pure chemical but a solvent-extraction organic phase: the chelating dioxime dimethylglyoxime dissolved in a hydrocarbon diluent (kerosene or an aromatic such as toluene or xylene), usually with a phase modifier or alcohol co-solvent. In hydrometallurgical circuits the dioxime selectively complexes nickel and cobalt out of an aqueous leach liquor, and the loaded organic layer is then separated and stripped to recover the metal. Because the working fluid is a flammable organic liquid — the diluent typically being a petroleum or aromatic cut — material of construction is governed by the solvent, not the dioxime. The hydrocarbon phase attacks polyethylene by absorption and swelling, so tank selection follows flammable-solvent practice: steel, stainless, or a hydrocarbon-rated lined/FRP system, with full ignition-source control. Always verify the supplier SDS for the specific diluent and modifier before specifying a tank.

Is Polyethylene (HDPE / XLPE) Safe for the DMG Organic Extractant Phase?

No — polyethylene is not recommended. The dimethylglyoxime reagent is carried in a hydrocarbon or aromatic diluent (kerosene, toluene, xylene and similar cuts). Published polyethylene chemical-resistance data rate aromatic hydrocarbons such as toluene and xylene as “Severe Effect / Not Recommended” for HDPE: these solvents absorb into the polyethylene matrix, swell and soften the wall, and promote environmental stress cracking and permeation. Even predominantly aliphatic kerosene diluents cause gradual swelling and weight gain over time. On top of the chemical attack, the finished organic phase is a flammable liquid, which adds an ignition and static-discharge concern that polyethylene atmospheric tanks are not built to manage. Specify steel (UL-142 or lined), stainless steel, or a fiberglass system whose resin is specifically rated for the aromatic content of the chosen diluent.

Material compatibility at a glance

Store and handle the DMG organic extractant phase in steel (UL-142 or lined), stainless steel, or a hydrocarbon-rated FRP system — never in HDPE or XLPE polyethylene. The aromatic/aliphatic diluent plasticizes and stress-cracks polyethylene, and the blend is a flammable liquid requiring bonding, grounding, venting and ignition-source control.

Ratings: S suitable · C conditional / limited · U unsuitable. Verify against the cited resistance charts and your concentration/temperature before specifying.

The safety that actually matters

• Flammable liquid: the hydrocarbon/aromatic diluent (and any alcohol modifier) ignites readily; keep away from heat, sparks, static and open flame, and bond and ground all transfer equipment.
• Aspiration hazard: low-viscosity hydrocarbon diluents can be fatal if swallowed and drawn into the lungs — do not induce vomiting.
• Toxic dioxime component: dimethylglyoxime is classified toxic if swallowed (acute oral Category 3); avoid ingestion and wash thoroughly after handling.
• Vapor inhalation: solvent vapors may cause respiratory irritation, drowsiness and dizziness; use local exhaust ventilation and keep containers closed.
• Skin and eye irritation: wear chemical-resistant nitrile or fluoroelastomer gloves, splash goggles and a face shield; the solvent defats skin on repeated contact.
• Loaded organic / metal complex: the stripped and loaded phases carry dissolved nickel/cobalt complexes — manage spills and waste per the SDS and local metals-waste regulations.

Common questions

Is the DMG cobalt extractant a single chemical?

No. It is a formulated organic phase: dimethylglyoxime (a solid chelating dioxime) dissolved in a hydrocarbon or aromatic diluent, usually with a phase modifier or alcohol co-solvent. There is no single CAS number for the finished blend, so always rely on the supplier SDS for the specific formulation.

Can I store this extractant in a polyethylene (HDPE or XLPE) tank?

No. The hydrocarbon/aromatic diluent absorbs into polyethylene, causing swelling, softening and stress cracking, and aromatic cuts like toluene and xylene are rated “Not Recommended” for HDPE. The blend is also a flammable liquid. Use steel, stainless steel, or a hydrocarbon-rated lined/FRP system instead.

What tank material should I use?

Carbon steel (UL-142 or lined) and stainless steel (304/316) are the standard choices for flammable solvent-extraction organic phases. FRP can work if the resin and liner are specifically rated for the aromatic content of your diluent — confirm with the resin supplier.

Why does the diluent, not the dimethylglyoxime, drive tank selection?

The dioxime is present at relatively low concentration; the bulk of the fluid is the organic diluent. Its flammability and its plasticizing attack on polyethylene set both the fire-code and the materials-of-construction requirements for the tank.