Comparison of a novel electro-Fenton method with Fenton's reagent in treating a highly contaminated wastewater

Abstract

This study applied a novel electrochemical process called the Fered-Fenton method to treat a highly concentrated wastewater. By combining electrochemical reduction and chemical oxidation, the process can remove organic compounds and heavy metals in a batch reactor. A PVC-stabilizer processing wastewater was treated in this investigation owing to its high heavy metal concentration (Pb = 7,500 mg/l) and high organic concentration (COD = 11,000 mg/l). The major organic component was acetate. Direct anodic oxidation showed no effect on COD removal. Fenton's method only removed 36% of COD using 4,000 mg-Fe2+/l and 28,000 mg-H2O2/l dosage. In the Fered-Fenton process, about 89% of COD was removed with 2,000 mg-Fe3+/l and 28,000 mg-H2O2/l. Furthermore, the COD removal attained an efficiency of about 98% for 56,000 mg-H2O2/l used. Results presented herein demonstrate that the Fered-Fenton method is superior to direct anodic oxidation and Fenton's method in this case. Furthermore, the changes of the intermediate compounds including acetate, oxadate, and formate during the reaction were analyzed, which provided us with the information to propose degradation reactions of the wastewater in this system.

Microbial decolorization of reactive black-5 in a two-stage anaerobic–aerobic reactor using acclimatized activated textile sludge

“…Chemical treatments, aerobic and anaerobic biological treatment, anaerobic-aerobic processes in tandem, have been attempted for color removal from textile wastewater (Reife & Freeman 1996). Chemical treatments like adsorption (Ramakrishna & Viraraghavan 1997), flocculation-coagulation and precipitation ( Vandevivere et al 1998), electrochemical oxidation (Lin &Peng 1994), photocatalytic oxidation (Davis et al 1994;Zielinska et al 2001), electro-Fenton oxidation (Bose 2002, Huang et al 2001) though successful in COD reduction and color removal, are not yet affordable.…”

Dye wastewater treated by Fenton process with ferrous ions electrolytically generated from iron-containing sludge

“…Electrochemical regeneration of Fe(II) via reduction of Fe(III), denoted as Fered-Fenton process by Huang et al [3], as EF-FeRe process by Qiang et al [2], and as Fenton sludge recycling (FSR) process by Gnann et al [4], was proposed to alleviate the sludge problem associated with Fenton process.…”

“…Concentration of electrolytically-generated Fe(II) depends on initial ferric concentration, pH, temperature, cathodic potential, electrolysis time, cathode area, and cathode-to-anode area ratio [2][3][4][5][6]. Amount of Fe(II) generated and electrolytic current efficiency increase with increasing initial ferric concentration, but are drastically decreased at pH higher than 2.5 because of Fe(OH) 3 precipitation [2,6].…”

“…Fe(II) [4]. Increasing concentration of Fe(II) was also observed with increasing cathodic surface area [2], and cathode-to-anode area ratio higher than 8 has been employed [3,6]. Cathodic potential ranging from −0.1 to −0.9 V has little impact on amount of Fe(II) generated, although electrolytic current efficiency decreases with decreasing cathodic potential due to electricity wasted through H 2 evolution [2].…”

“…The majority of the above-mentioned studies demonstrated electro-regeneration efficiency of Fe(II) using dissolved ferric salts (e.g., ferric sulfate or ferric nitrate) as the iron sources in batch reactors [2,3,6,7]. Although, electro-regeneration of Fe(II) using precipitated iron oxides as the iron source has been investigated by Gnann et al [4] and Qiang et al [2], treated water quality and properties of iron sludge after long-term repeated use had not been elaborated.…”