Liquid-liquid Extraction of Co (II) from Nitrate Solution Using the Mixture of TOPO and TOA

A large volume of waste is generated due to rapid growth of mining and metallurgical industries and the dissolution of heavy metals pollute the industrial belt water. Mostly copper, zinc, cadmium, arsenic, lead, nickel, cobalt etc. are responsible for environmental pollution. So, they should be removed before being discharged to surface water. Cobalt is most popular of metals because of its vast area of application. Cobalt is used in electroplating because of its appearance, hardness and resistance to oxidation. Cobalt is essential to the metabolism of all animals. But if present in excess amounts it may cause several toxic effects. In hydrometallurgical processes, liquid-liquid extraction is a well-established technique for the removal and separation of various metal ions after leaching and able to produce pure metal solutions which are used for electrowinning processes. In fact, the techniques can be applied for treatment of both concentrated and dilute solutions. In the present investigation attempts have been made to extract Co (II) from nitrate solution using mixture solutions of TOPO (tri-n-octyl phosphine oxide) and TOA (tri-n-octyl amine) in toluene. The effects of nitric acid concentration, equilibration time, concentration of aqueous phase and presence of salt have been studied. The extraction equilibrium was achieved in 15 minutes. The percentage of extraction of Co (II) decreased with increase in cobalt concentration in aqueous solution. The percentage of extraction of cobalt was found to be insignificant in the presence of salt. The extraction of cobalt using mixture of extractants, TOPO and TOA changed from antagonistic to synergistic with the increase in concentration of acid.

Author(s): Naresh Kumar Rauta1, Bhabani Shankar Panda2*, Nandita Swain1 and Mohammed Ansar Ahemad2

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