Extraction of Co(II) from aqueous solution using emulsion liquid membrane.

Area of Science:

• Chemical Engineering
• Hydrometallurgy
• Separation Science

Background:

• Cobalt(II) recovery from thiocyanate solutions is crucial for various industrial processes.
• Cyanex 923, a phosphine oxide extractant, shows promise for selective metal ion separation.
• Emulsion liquid membrane (ELM) technology offers an efficient method for metal extraction and concentration.

Purpose of the Study:

• To investigate the extraction equilibrium of Cobalt(II) from thiocyanate media using Cyanex 923.
• To evaluate the performance of ELM for cobalt removal and concentration.
• To determine the optimal conditions for cobalt extraction and stripping.

Main Methods:

• Solvent extraction equilibrium studies using Cyanex 923 in cyclohexane.
• Slope analysis method to determine extraction stoichiometry and constants.
• Emulsion liquid membrane experiments with Cyanex 923 as carrier and SPAN 80 as surfactant.
• Investigation of various parameters affecting ELM stability and efficiency: stirring speed, surfactant concentration, pH, carrier concentration, stripping acid concentration, initial cobalt concentration, and temperature.

Main Results:

• The stoichiometry of cobalt(II) extraction was determined, and the extraction constant (Kex) was calculated.
• Stripping efficiency of cobalt(II) increased with higher sulfuric acid concentrations.
• Emulsion liquid membrane process achieved 95% cobalt recovery within 10 minutes.
• A concentration factor of 5 was achieved for cobalt(II) using the ELM process.

Conclusions:

• Cyanex 923 is an effective extractant for cobalt(II) from thiocyanate solutions.
• The ELM process using Cyanex 923 and SPAN 80 is a viable method for cobalt removal and concentration.
• Optimized ELM parameters lead to high cobalt recovery and significant concentration factors.