Recovery of cobalt, nickel, and copper from sea nodules by their extraction with alkylphosphines

The paper describes a process for the recovery of pure Co(II), Ni(II), and Cu(II) from a hydrochloric acid solution of polymetallic sea nodules. An overnight contact of the nodule powder with 4 M HCl almost quantitatively leaches these metal ions. From the leachate, Co(II) and Cu(II) were recovered by their extraction with Cyanex 923 and Ni(II) by extraction with Cyanex 301. Co(II) and Cu(II) are partitioned in the organic phase as H 2CoCl 4·2 Cyanex 923 and CuCl 2·2 Cyanex 923, whereas Ni(II) is extracted in the form of NiR 2 (HR=Cyanex 301). A solution of 0.001 M H 2SO 4 is used for the stripping of Co(II) and Cu(II) and 5% NH 4Cl in 75% NH 3 for Ni(II). Both extractants are found to be stable toward prolonged contact with HCl and show negligible loss in their extraction capacity even after recycling them for 20 cycles. The partition data have been utilized in developing conditions for the separation of Co(II), Ni(II), and Cu(II) mutually and from other metal ions, namely Ti(IV), Al(III), Fe(III), Mn(II), and Zn(II). The procedure of separation thus developed has been extended for the recovery of around 90% Co(II), Ni(II), and Cu(II) from sea nodules. The purity of the metal ions thus obtained is around 99%.