High selective separation of cobalt from nickel-cobalt mixtures

Environmentally friendly hydrometallurgical methods: Introduce a process for the high selective separation of cobalt from nickel-cobalt mixtures using an undiluted ionic liquid

Use a kind of undiluted ionic liquid extraction agent to separate cobalt and nickel in hydrochloric acid medium to achieve green solvent extraction.

Cobalt was extracted to the ionic liquid organic phase in a cobalt tetrachloride complex, while nickel, magnesium and calcium were left in the aqueous phase.

The advantage of this ionic liquid extraction process is that does not need to add any organic diluent to prepare the organic phase, can make the extraction process safe and environmentally friendly.

The cobalt/nickel separation coefficient will reach more than 50000 when the aqueous phase contains 8M chloride ions.

When cobalt is extracted into the ionic liquid phase, the cobalt can be easily extracted with water and the ionic liquid can be reused. Then the reaction process of continuous extraction can be realized.

The maximum capacity of cobalt can be up to 35 g/L-1 (In practical extraction process can’t use such high capacity).

When the distribution coefficient is more than 100, can use sodium chloride or sea water to supply the chloride ions.

Phosphorus ion liquid, such as three hexyl myristyl phosphorus chloride, tributyl myristyl phosphorus chloride, four (octyl) bromide phosphine, three hexyl alkyl brominated phosphorus 14. Now three octyl methyl ammonium chloride has been used in business experiment to extract cobalt from chloride medium, consider the commercial availability and comprehensive performance, finally choose three hexyl myristyl phosphorus chloride (Cyphos IL 101) as the best Ionic liquid extractant for cobalt and nickel.

Normally Ionic liquids is colorless, tasteless, non-flammable, stable substances, with a high viscosity at room temperature, for some metal ions has a high solubility (with a high distribution coefficient).

Only the physical properties of colorless, odorless and non-flammable, a lot of hydrometallurgical worker will be glad to use it.

We, Zhengzhou Deyuan Fine Chemicals Co., Ltd., had started small-scale production and offered to major domestic customers for pilot test.

Hope we will begin to do mass production soon, then will update the process greatly in metal extraction industry.

The effects of nitrate ion.

In acidic conditions, copper extractant (hydroxyl oxime) will be nitrated by nitrate, become to the corresponding nitro aldoxime or nitro ketoxime. The extraction ability of nitrated extraction reagent is very strong, but the back extraction ability is very weak, even use 200 g/L sulfuric acid, it is difficult to take down the loaded copper ion.
In normal back extraction system of electrolyte, nitrated extraction reagent cannot be regenerated, so the extraction ability has been lost absolutely. Nitrate not only make nitration with the extracting reagent, but also can oxidize extraction reagent, accelerate the degradation of extracting reagent. In the condition of higher acidity, the oxidative damage effect of NO3- is very strong for extraction reagent, some extraction reagent will be oxidized degradation before it is nitrated.

The influence of chloride ions.

In chloride system, copper will be the forms of Cu2+, CuCl+, CuCl3-, CuCl42-, when copper is leaching by oximes solvent, usually copper ions enter organic phase in the form of Cu2+, CuCl+. The experimental results show that when the concentration of chloride ion is not higher than 70 g/L, the extraction rate of copper will be not changed.
When the content of chloride ion in the system is higher than 70 g/L, will has large amount complex anion formation, it can reduce the ability of extraction system. Chlorine will be happened in the electrolytic tank; Chloride ions have adverse effect for the crystal growth of cathode copper, affect the cathode copper’s color and stripping. The allowed upper limit concentration of chlorine ion in the electrolyte system is 40-50 mg/L, it will be beneficial for the deposition of cathode copper, when the content of chloride ion is 20-25 mg/L in the electrolyte system.

The influence of iron ion.

If there is a lot of iron ion in the electrolyte system, even it is good for reducing manganese oxidized, But Fe2+ and Fe3+ is oxidized and reduced repeatedly in the cathode and anode respectively, not only can consume electricity directly, but also Fe3+ can dissolve sedimentary copper cathode, reduce the electrolysis efficiency.

The influence of manganese ion.

In electrolytic bath, manganese ion will be oxidized to MnO4- and Mn3+, these ions have strong oxidizing, can oxidize solvent oil and leaching solvent, make organic phase degradation badly. Some iron in electrolyte can control MnO4- happened, greatly reduce organic phase degradation by the reason of manganese. When manganese is turned to electrolyte that with rich copper, adjust the content of Fe:Mn to 8~10:1, to reduce the oxidation of leaching solvent by manganese.

The reason of third phase happened.

① The mixing speed of mixing tank is higher, to make organic phase emulsification.
② The clarification effect of lixivium is poor or filtration is not completely.
③ The residual oxidant in lixivium process make organic phase degradation.
④Impurity and suspended particles accumulate
Third phase is the emulsion phase of unite solid, little quantity can help phase separation and reduce entrainment.