ABSTRACT
Electrochemical techniques have been used for the discolouration of synthetic textile industrial wastewater by Fenton's process using a parallel plate reactor with a reticulated vitreous carbon (RVC) cathode. It has been shown that RVC is capable of electro-generating and activating H2O2 in the presence of Fe(2+) added as catalyst and using a stainless steel mesh as anode material. A catholyte comprising 0.05â M Na2SO4, 0.001â M FeSO4.7H2O, 0.01â M H2SO4 and fed with oxygen was used to activate H2O2.The anolyte contained only 0.8â M H2SO4. The operating experimental conditions were 170â mA (2.0â V < ΔECell < 3.0â V) to generate 5.3â mM H2O2. Synthetic effluents containing various concentrations (millimolar - mM) of three different dyes, Blue Basic 9 (BB9), Reactive Black 5 (RB5) and Acid Orange 7 (AO7), were evaluated for discolouration using the electro-assisted Fenton reaction. Water discolouration was measured by UV-VIS absorbance reduction. Dye removal by electrolysis was a function of time: 90% discolouration of 0.08, 0.04 and 0.02â mM BB9 was obtained at 14, 10 and 6â min, respectively. In the same way, 90% discolouration of 0.063, 0.031 and 0.016â mM RB5 was achieved at 90, 60 and 30â min, respectively. Finally, 90% discolouration of 0.14, 0.07 and 0.035â mM AO7 was achieved at 70, 40 and 20â min, respectively. The experimental results confirmed the effectiveness of electro-assisted Fenton reaction as a strong oxidizing process in water discolouration and the ability of RVC cathode to electro-generate and activate H2O2 in situ.
Subject(s)
Carbon/chemistry , Coloring Agents/chemistry , Electrochemical Techniques/instrumentation , Hydrogen Peroxide/chemistry , Wastewater/chemistry , Water Purification/methods , Coloring Agents/analysis , Electrochemical Techniques/methods , Electrodes , Hydrogen Peroxide/chemical synthesisABSTRACT
This study was conducted to evaluate the ozone, UV and O3/UV processes for the reuse of sewage treatment plant effluent (Universidad Autonoma Metropolitana Azcapotzalco wastewater treatment plant). The ozone/UV process was compared to individual ozone and the UV processes and control parameters were total and fecal coliforms. Different ozone concentrations (6-12 mg O3/min) and different UV fluencies (6.7-20.12 mJ/cm²) were tested. It is possible to conclude than none of the processes achieved the disinfection levels required to comply with the Mexican standard NOM-003-SEMARNAT-1997. The continuous ozone process offered the lower total and fecal coliforms reductions, while UV light resulted a disinfection agent with higher germicide power than ozone. The maximum logarithmic reduction achieved due to the combined ozone/UV process was of 2.04 for fecal coliforms and of 2.17 for total coliforms. The next 8 combinations showed lower removal efficiencies, but always higher than those obtained with the single ozone or UV processes. The ozone/UV process was highly effective for the disinfection and a synergistic effect was observed.