Electrochemical recovery of tin and palladium from the activating solutions of the electroless plating of polymers -: Potentiostatic operation

An electrochemical reactor having a ceramic diaphragm was applied to recover tin and palladium from the activating solutions of the electroless plating of polymers. The different figures of merit (fractional conversion, current efficiency, space-time yield and specific energy consumption) for the electrochemical reactor were analysed. In the absence of palladium, as the electrode potential was shifted towards more negative values, the space-time yield of tin (eta) and tin fractional conversion (X) were increased because of the increase in the electrode roughness and the hydrogen turbulence-promoting action. Simultaneously, current efficiency for the tin deposition (phi) was decreased, and subsequently the specific energy consumption (E,,) was increased due to the hydrogen cathodic reaction. When experimental conditions are very cathodic, i.e. around -1 V with respect to a standard Ag/AgCl saturated KCl reference electrode, Sn(IV) electrochemical reduction takes place with the formation of Sn(II). The Pd(II) effect on Sn(IV) electrochemical deposition and the related figures of merit were also evaluated. At -0.4 V, the recovery of both metals separately was possible. The presence of Pd(II) enhanced Sn(IV) deposition for more positive potential values than -0.6 V. At -0.6 V, low values of total energy consumed in addition to the maximum global current efficiency (>70%) were obtained. On the other hand, quite good values of fractional conversion were obtained for both tin (100%) and palladium (>90%). (C) 2005 Elsevier B.V. All rights reserved.