Ultrasound-assisted electrodeposition of indium from HCl stripped indium-loaded organic phase solutions by EQCM: Electrochemical behavior and nucleation mechanisms

In order to reduce the duration of the recovery process for indium from zinc oxide dust, an electrodeposition technique was employed, utilizing a hydrochloric acid stripping solution as the electrolyte. A study of the cyclic voltammetry-EQCM of conventionally electrodeposited indium and of ultrasound-assisted electrodeposition of indium was undertaken. The valence transition of conventionally electrodeposited indium was found to be In²⁺-In⁺, In³⁺-In; that of ultrasound-assisted electrodeposition of indium is In²⁺-In⁺-In, In³⁺-In. Furthermore, the Scharifker and Hills model underwent modification due to the negative values of the timed amperage curve currents, which resulted in the dimensionless processed timed amperage curve (j/j_max)²-(t/t_max) conforming to the specification. Concurrently, it was determined that ultrasound-assisted electrodeposition has the capacity to impede the precipitation of hydrogen, chlorine, and trivalent arsenic on the cathode deposition. The chronoamperometric study demonstrated that conventional electrodeposition exhibited transient nucleation at deposition potentials of -0.75 V, -0.78 V, -0.80 V, and -0.82 V. Conversely, ultrasound-assisted electrodeposition manifested transient nucleation at deposition potentials of -0.75 V, -0.78 V, and -0.82 V, along with gradual nucleation at the -0.80 V potential. Furthermore, at the same electrodeposition potential, ultrasound-assisted electrodeposition resulted in greater nucleation density values (N) than conventional electrodeposition. Furthermore, ultrasound-assisted electrodeposition has been shown to enhance current efficiency. In addition, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) analysis has revealed that the indium deposited on the cathode exhibits high purity. Moreover, the surface morphology of the indium layer deposited by conventional electrodeposition is characterized by flocculent structures, while the indium layer deposited by ultrasound-assisted electrodeposition demonstrates a spherical morphology. This provides a novel concept for the large-scale production of indium sponge.