Floatation of Palladium(Ⅱ) as a Ternary Association Complex in Presence of Sodium Nitrate

A water-insoluble ternary ionic association complex Pd(SCN)2-4·2CTMAB+ was formed in a weakly acidic solution between the anionic complex Pd(SCN)2-4 and cation CTMAB+ ,and after shaking with a definite amount of solid sodium nitrate (e.g.0.5 g),the association complex was floated on the surface of the water phase forming a clear interface between the liquid and solid phases.Based on these facts,quantitative separation of Pd(Ⅱ) from Cr(Ⅲ),Mn(Ⅱ),Ni(Ⅱ),Al(Ⅲ),Mo(Ⅵ),Zn(Ⅱ) and Fe(Ⅱ) by floatation was achieved on the following optimized conditions:① acidity of solution:pH 3.0,② cCTMAB 1×10-3mol·L-1,③ cNH4SCN 1.5×10-2mol·L-1,④ ρNaNO3 50 g·L-1 and ⑤ total volume of water solution:10 mL.Rate of floatation of 100% and 99.6% were obtained in tests of separation of Pd(Ⅱ) from binary ion mixtures and multi-ion mixtures containing the above mentioned metal ions respectively.The proposed method was applied to the separation and determination of palladium in Pd-Ni electroplating waste solution containing 1.434 g·L-1 of Pd(Ⅱ) and 2.715 g·L-1 of Ni(Ⅱ).After the floatation separation,Pd(Ⅱ) was determined by the dithizone photometric method.Average amount of Pd(Ⅱ) found by 7 separations and determinations was 1.423 g·L-1,with value of RSD (n=7) 1.8%.