Electroflotation is receiving more and more attention for wastewater treatment. This electrochemical process employs the oxygen and hydrogen gas bubbles evolved from the surfaces of anode and cathode during water electrolysis. The lack of ideal electrodes that can service as both anode and cathode has been a problem since the very beginning of the study of this process. This dissertation reports a kind of unique electrode that can partly solve this problem. _{x 3-x 4 x 3-x 4} ...[ Read more ]

Electroflotation is receiving more and more attention for wastewater treatment. This electrochemical process employs the oxygen and hydrogen gas bubbles evolved from the surfaces of anode and cathode during water electrolysis. The lack of ideal electrodes that can service as both anode and cathode has been a problem since the very beginning of the study of this process. This dissertation reports a kind of unique electrode that can partly solve this problem.

After careful examination of 16 different materials including metal oxides of Ir, Ru, Rh, Pt, Sb, Sn, Ti, Cu, Pd, Ni and Co, the Cu_xCo_3-xO₄ combination was found to be the candidate for the one material electrode. The Ti/Cu_xCo_3-xO₄ electrode (x = 0~1.5) developed in the present work was much more stable compared with the other electrodes. All the electrodes were prepared by thermal decomposition at 550 °C from metal chloride salts precursors which were dissolved in a mixture of 37 % HCl and isopropanol solution. The stability of Ti/Cu_0.3Co_2.7O₄ electrode was found to be the best, lasting for 1080 h under daily alternative anodic and cathodic polarization in 1 M NaOH electrolyte.

The Ti/Cu_xCo_3-xO₄ electrodes were characterized by different techniques such as scanning electron microscopy connected with energy-dispersive X-ray (SEM-EDX), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry and quasi-steady state polarization curves. The effect of crystallographic properties and surface morphology have been analyzed systemically before and after this one material electrodes used in water electrolysis process. Under hydrogen evolution condition, cobalt oxide could be reduced to amorphous metal Co and Co(OH)₂. The formation of the amorphous Co is the key process for this kind of electrode to be served as both anode and cathode under alternative current. It is also the main reason leading to the failure of the electrode eventually.