Fabrication and characterization of a porous gas-evolving anode constituted of lead dioxide microfibers electroformed on a carbon cloth substrate

Electrochemical incineration of glyphosate wastewater using three-dimensional electrode

Anodic oxidation of recalcitrant organic compounds is still challenging concerning to the anode material and mass transport limitations imposed by the low concentration. In this work, we studied the degradation of a real wastewater containing glyphosate using an electrode of PbO2 electrodeposited on a three-dimensional matrix of reticulated vitreous carbon (RVC). The high mass transfer rate provided by the RVC/PbO2 anode is demonstrated. A Box-Behnken factorial design was used for a systematic analysis of the effects of current density, flow rate and temperature on the degradation and mineralisation kinetics, current efficiency and specific energy consumption. The optimised degradation performance was achieved applying 30 mA cm-2, 3000 mL min-1 and 50°C. As the flow rate increases from 150 to 1500 mL min-1, the current efficiency increases from 18% to 65% and the energy consumption dropped from 72 to 33 kWh kg-1 due to the mass transfer enhancement promoted by the porous matrix. The efficacy of the electrochemical process for the treatment of real effluents using the three-dimensional PbO2 has been demonstrated.

Electrochemical oxidation of gaseous benzene on a Sb-SnO2/foam Ti nano-coating electrode in all-solid cell

An all-solid cell with a solid polymer electrolyte was applied to electrochemical oxidation of low-concentration indoor gaseous aromatic pollution. Antimony-doped tin dioxide nanocoatings deposited on a titanium foam substrate (Ti/Sb-SnO₂) with different Sb/Sn ratios (4.8-14.0 mol%) and loading weight of Sb-SnO₂ (4.4-7.7 mg cm^-2) were used as dimensionally stable anodes. Sn and Sb were homogeneously dispersed on the substrate, and a crack-free nanocoating was built when the loading of nanocoating was increased to 6.3 mg cm^-2. The activity tests for oxidation of benzene showed that 40 ppm gaseous benzene was converted to CO₂ with high selectivity (85%) at the low cell voltage of 2.0 V in this all-solid cell. The conversion of benzene was greatly increased from 30% to 100% upon increasing the Sb/Sn ratio of the nanocoating from 4.7 mol% to 14.0 mol%. With the increase of nanocoating loading (Sb/Sn = 14.0 mol%) from 6.3 to 7.7 mg cm^-2, the conversion of 100 ppm benzene was increased from 70% to 100%. Cyclic voltammetry revealed that high Sb content in the oxide nanocoating increased the overpotential and current intensity of the oxygen evolution reaction. The large outer charge q_o^∗ related to the electroactive surface of the SS-7.7/Ti3 electrode was up to 305.3 mC cm^-2, which were responsible for its excellent electrochemical performance in the benzene oxidation process. Our studies provide a potential method for removal of indoor VOCs at ambient temperature.

Electrocatalytic degradation of methylene blue on PbO2-ZrO2 nanocomposite electrodes prepared by pulse electrodeposition

PbO2-ZrO2 nanocomposite electrodes (P) were prepared by pulse electrodeposition and used for the electrocatalytic degradation of methylene blue (MB). The SEM and XRD tests show that PbO2-ZrO2 nanocomposite electrodes (P) possess more compact structure and finer grain size than PbO2-ZrO2 nanocomposite electrodes (D) prepared by direct electrodeposition. The electrochemical measurements show that PbO2-ZrO2 nanocomposite electrodes (P) have higher oxygen evolution overpotential and the oxidation regions of MB and water are significantly separated. The experimental parameters on electrocatalytic degradation of MB by PbO2-ZrO2 nanocomposite electrodes (P) were evaluated, such as initial MB concentration, current density, pH value and supporting electrolyte concentration. The results indicate that MB and COD removal efficiency of PbO2-ZrO2 nanocomposite electrodes (P) reach 100% and 72.7%, respectively, after 120 min electrolysis at initial 30 mg L(-1) MB concentration at current density of 50 mA cm(-2) in 0.2 mol L(-1) Na2SO4 supporting electrolyte solution, and the degradation of MB follows pseudo-first-order kinetics. Compared with PbO2-ZrO2 nanocomposite electrodes (D), PbO2-ZrO2 nanocomposite electrodes (P) show higher COD removal efficiency and instantaneous current efficiency with MB degradation. The experimental results demonstrate that PbO2-ZrO2 nanocomposite electrodes (P) possesses the excellent electrocatalytic properties and show great potential applications in refractory pollutants.