Electrochemical Decolorization and Removal of Indigo Carmine Textile Dye from Wastewater

<p>The present paper discusses an integrated electrochemical decolorization/degradation treatment procedure of indigo carmine dye, which comprises electrocoagulation, electrooxidation and advanced electrochemical oxidation using the electro-Fenton process.</p> <p>The electrocoagulation process is performed by sacrificial iron electrodes, the indirect electrooxidation process by dimensionally stable Ti/Pt and graphite electrodes in NaCl electrolyte solution, and the electro-Fenton process by iron electrodes and added amounts of H₂O₂. All electrochemical experiments are conducted in the same electrochemical cell with the same apparent electrode surface and inter-electrode distance.</p> <div> <p>The three different electrochemical processes are discussed, their efficiencies compared and evaluated. The initial dye concentration of 100 mg l^-1 was fast and efficiently removed in only a few minutes of electroprocessing time. The electro-Fenton treatment is the fastest, most efficient and economical process operated at very low current densities of 0.33 and 0.66 mA cm^-2 and consuming only 4.75x10^-3 and 5.23x10^-3 kWh m^-3 of treated solution respectively. The electrocoagulation treatment with iron electrodes and the electrooxidation process with Ti/Pt electrodes conducted at applied current densities of 5 mA cm^-2 consumed 0.511 and 0.825 kWh m^-3 of treated solution respectively. The proposed procedure is a safe, economical and efficient method for removal of indigo carmine dye from aqueous solutions and dye house effluents.</p> </div> <p>&nbsp;</p>

Degradation of P-Nitrophenol Affected by Synergy of Indirect and Direct Electrooxidation

The synergy of indirect and direct electrooxidation of p-nitrophenol (PNP) at Ti/PbO2 anode was studied with linear sweeping voltammetry and galvanostatic electrolysis. The concentration of PNP and the form of redox medium were detected by high performance liquid chromatography (HPLC) and ion chromatography. The results indicated that Ti/PbO2 electrode can electrocatalyze the degradation of PNP effectively. The degradation ratio of 1.0 mmol/L PNP is 64.5% after 1 h electrolysis when the temperature is 35°C, the current density is 40 mA•cm-2. When the electrolyte containe 1.0 mmol / L Cl-, the degradation ratio of PNP is 81.0% after 1 h electrolysis under the same conditions. Cl-, ClO-, and ClO3- were detected simultaneously in the electrolyte, and their concentrations showed nonlinear oscillation with electrolysis time. These indicated that Cl- cause indirect electrooxidation of PNP, and the redox medium Cl-/Cl2 has a good reversibility.