Comparative analysis between the biological and electrochemical methods for removal of 4-nitrophenol from aqueous media
- Category: Volume 21 No.5 (September 2011)
Sustain. Environ. Res., 21(5), 321-328 (2011)
Silvia Reyna, José L. Sánchez, Erick R. Bandala, Juan Manuel Peralta-Hernández, Carlos A. Martínez-Huitle and Marco A. Quiroz
Biodegradation, electrooxidation, 4-Nitrophenol, Pb/PbO2 anodes, nitrocompounds elimination
The elimination of 4-nitrophenol (4NPh) from aqueous solutions by electrooxidation and biodegradation methods was investigated. Electrochemically, the process was studied in alkaline media on Pb/PbO2 anodes at a current density of 20 mA cm-2 and 60 °C. The biological process was carried 2 out in mineral medium of pH 7 with 4NPh as the only carbon and nitrogen source. The strains chosen for the study were isolated from soils close to contaminated industrial aqueous streams, identified and characterized as Neisseria sp. and Acinetobacter sp. The removal of aqueous 4NPh by electrooxidation and biodegradation was monitored by UV spectroscopy and by high performance liquid chromatography (HPLC). All the kinetic studies showed that in the biological process the 4NPh concentration began to diminish in the first steps of the log phase and is stable at the end of the stationary phase. HPLC results have demonstrated that the 4NPh concentration was reduced from 50 to 8.5 mg L-1 in 10.5 h and to 4.9 mg L-1 after 31 h. By electrooxidation, the best 4NPh elimination (97%) was obtained in 7 h of electrolysis. Under the latter conditions, almost complete chemical oxygen demand removal was attained, which suggests a high level of 4NPh mineralization (> 80%), a percentage of 4NPh elimination from the solution greater than 95% and a scarce formation of aliphatic acids (e.g., maleic acid and/or formic acid).