Date of Award
Civil and Environmental Engineering
CC BY-NC-ND 4.0
Nitroaromatic compounds (NACs) are major environmental pollutants and their degradation is difficult to achieve. Using zero-valent iron reduction of the NACs coupled with peroxidase-catalyzed capture of the resulting anilines, a two-step strategy for removal of NACs from waste- and process-water, is investigated here. The concentration range of NACs studied was that which would be present in industrial wastewater streams (millimolar, 123 ppm), a concentration range considerably higher than those studied previously with groundwater by other researchers. Zero-valent iron (Fe0) has been successfully employed to reduce nitrobenzene, o-, m- and p-nitrotoluenes to corresponding anilines in synthetic wastewater in both batch and continuous flow reactors. Anaerobic conditions were maintained in the reactors by including Na2SO 3 as an oxygen scavenger in the presence of CoCl2.6H 2O, which acted as a catalyst. Batch reactors exhibited adsorption of aniline on the Fe0, which could be described by a Langmuir isotherm. A 200 g Fe0 (particle size: 1--2 mm) bed completely converted 1 mM of NAC flowing upward for about 600 pore volumes before experiencing flow reduction due to clogging by corrosion products. A green-black precipitate was formed at the influent end of the column, an Fe0 corrosion product identified as maghemite. The enzymatic treatment following the zero-valent iron reduction was done in a plug-flow reactor (PFR) using a crude preparation of the enzyme soybean peroxidase extracted from soybean hulls. The complete reaction time for the two steps was 5--51/2h. Parameters like pH, peroxide to substrate ratio, enzyme concentration and alum concentration were optimized. At pH 7--7.2, the optimum H2O2 to substrate ratio was found to be 1.5 for the aryl amines, aniline, o-, m- and p-toluidines, investigated in this study. Alum concentrations between 50--100 mg/L were useful in removing the end-color from the treated water. NACs were quantitatively reduced to their corresponding amines, which were completely removed from the wastewater in the enzymatic treatment step.Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2001 .M365. Source: Dissertation Abstracts International, Volume: 63-04, Section: B, page: 2007. Advisers: N. Biswas; K. E. Taylor. Thesis (Ph.D.)--University of Windsor (Canada), 2001.
Mantha, Ramkrishna., "Continuous flow system for combined chemical and enzyme-catalyzed removal of nitroaromatics from synthetic wastewater." (2001). Electronic Theses and Dissertations. 1564.