The application of electrochemical technology for the degradation of organic pollutants often faces two main problems, related to the anode material and mass transport limitations. Although PbO2 electrode is inexpensive and provides satisfactory electrooxidation kinetics, in the form of plane electrodes it is unable to resolve the mass transfer problem that arises at low concentrations of organics. In this work, an electrochemical flow reactor was developed for the preparation of three-dimensional electrodes consisting of PbO2 films electrodeposited onto reticulated vitreous carbon. The electrodes were characterized in terms of the substrate coating, morphology, structure, and electrocatalytic activity in the decoloration reaction of Reactive Blue 19 dye. The results showed that it was possible to deposit a uniform film of PbO2 on the surface of the substrate after optimization of the current density and deposition time (0.7 mA cm-2 for 30 min). Comparison of the plane and three-dimensional electrodes revealed that the turbulence generated by the porous matrix significantly accelerated the dye decoloration kinetics, increasing 3.3-fold the first order kinetic constant (from 0.010 min-1 for VC/PbO2 to 0.033 min-1 for RVC/PbO2).

<p>In this work, copper electrowinning using a three-dimensional spouted-bed electrode (SBE) was studied in order to investigate the effects of current density (i), concentration of supporting electrolyte (Cs), pH, electrolyte temperature, and bed thickness on the process current efficiency (EC), energy consumption (CE) and space-time yield (Y). The results indicated that the SBE may be successfully used for the electrowinning of copper when the copper ion concentration is high and the pH is between 1 and 2. In this case, 100% CE, 2.7 kWh kg^-1 EC and 118 kg L^-1 h^-1 Y can be achieved. It was verified that an increase in the electrolyte temperature caused a decrease in the electrodeposition rate (from 3.97 g L^-1h^-1 to 1.17 g L^-1 h^-1), indicating that, despite the solution conductivity enhancement, temperature promoted the increase in the anodic dissolution kinetics. The results also showed that EC depends on the applied current density, whereby greater EC values can be obtained using high current densities. Finally, the copper particles were analyzed by scanning electron microscopy and it was confirmed that a smooth, uniform and compact electrodeposit can be obtained without using any chemical additives.</p>

This article reports the use of polyaniline (PAni), chemically and electrochemically synthesized, for copper removal from aqueous solutions. PAni films were electrodeposited on reticulated vitreous carbon (RVC). In all cases, p-toluenesulfonate anion (PTS-) was used as the dopant to obtain cation exchange properties. RVC/PAni showed no expressive copper removal due to the small amount of polymer in the film. Chemically synthesized PAni-PTS- was obtained in its reduced form (leucoesmeraldine). PAni degraded at neutral pH but remained stable at low pH, showing a very high ion-exchange capacity, which is superior to those observed for commercial resins.