Separation of Nickel and Cobalt by Porous Glass Packed Column using Methylamine as Eluent

Abstract

Separation experiments of nickel and cobalt were carried out using a porous glass packed column using methylamine as eluent at 298K. When methylamine concentration is maintained on 1mol/dm³, separation performance is completely accomplished in the pH region from 8 to 8.5, but it is reduced at pH above 8.5 because precipitate of nickel hydroxide is formed. Recovery of cobalt is a minimum of 70% at pH 8.5 when using dilute hydrochloric acid as a post-treatment material, while the recovery is not so much improved for use of dilute nitric acid, and is completely accomplished when using 0.1mol/dm³ EDTA. EDTA is very useful to completely recover cobalt when ammonium chloride is used as eluent. This shows that a slightly soluble cobalt complex similar to pentaammine cobalt (III) complex is formed in the column when methylamine is used as eluent. The two metals are completely separated over the methylamine concentration of 0.5mol/dm³ at pH 8. In this way nickel and cobalt can be separated over wider ranges of concentration when using methylamine than that of ammonium chloride.