Wanda Gumowska

The influence of phase structure on the dissolution of Cu–Co–Fe alloys in sulphuric acid solution and the metals recovery

Abstract Investigations of Cu–Co–Fe alloys dissolution in sulphuric acid solution were conducted. The phase compositions were identified before electrochemical experiments. Anodic dissolution was found to give about 100% current efficiency and was independent of anode composition. Passivation of anodes was not observed. Dissolution was selective; iron and cobalt were transferred into the electrolyte, while copper was left in anodic slimes and/or deposited on the cathode.

Structure and magnetic properties of Co nanowires electrodeposited into the pores of anodic alumina membranes

Cobalt nanowires were obtained in the process of electrodeposition into pores of an alumina membrane. Structural research (XRD, TEM) of Co revealed the face-centered cubic structure. However, the existence of the hexagonal structure cannot be excluded due to strong texture. The influences of an external magnetic field and Al2O3 membrane geometry on magnetic properties of obtained wires were examined. It was found that cobalt nanowires exhibit pronounced shape anisotropy in a direction parallel to the wire axis. The highest influence on the magnetic properties is ascribed to the nanowires geometry i.e., height, diameter, and distances between single wires. Application of an external magnetic field in a perpendicular direction to the sample surface during cobalt electrodeposition increases magnetic anisotropy with a privileged direction along the wire axis. Application of the magnetic field in a parallel direction to the sample surface changes the direction of magnetization.

Influence of the lead and oxygen content on the passivation of anodes in the process of copper electro-refining

Abstract It has been found that up to 2% lead in copper anodes does not markedly influence the passivation process. Oxygen, when it is in a stoichiometric surplus in relation to lead, promotes passivation of anodes. A cathodic reduction method was adapted to determine, qualitatively and quantitatively, the lead compounds remaining on the surface of anodically dissolving CuPb electrodes. It was proven that lead is present in the form of PbSO4 and PbO. No PbO2 was found. Only a small fraction of lead present in the dissolved layer of the CuPb anode remains on its surface. The results indicate that lead can influence the passivation process in two ways: (1) lead compounds remaining on the anode surface hinder diffusion of the Cu2+ into solution and promote passivation; (2) lead compounds which fall off the anode cause convection in the electrolyte layer close to the anode. This promotes the transport of the Cu2+ and hinders passivation. This second effect seems to prevail.