PHENOL OXIDATION PROMOTED BY CHELATED IRON: INFLUENCE OF THE CHELATING AGENT
Sustainable process-product development & green chemistry
Sustainable & Clean Technologies - Ia: Extraction & Remediation (T1-4a)
Keywords: phenol, oxidation, iron, EDTA
Destruction of organics compounds from wastewater is of interest due to their biotoxic properties. Several catalyzed oxidation techniques carried out at low temperature present some limitations in their operational use. To over come this inconvenient a chelator is added in the reaction system; as a result, the oxidation potential of the catalyst decreases (Miller et al., 1999). One of the most important group of organic compounds able to capture metal ions are aminopolycarboxylic acids (e.g. Ethylenediaminetetraacetic acid (EDTA)). These compounds contain several carboxylate groups linked to one or several nitrogen atoms and they are able complex the metal ion by forming one or more stable heteroatomic rings around it (Egli, 2001). These metal complexes are stable and water-soluble and restrict the metal ions from playing their normal chemical role. This simple method could be applied to the degradation of refractory aromatics compounds such as phenol or its derivatives (Noradoun et al., 2003). This work will present the preliminary results obtained for oxidation of phenol using metallic iron in presence of differents chelating agents as Ethylene Diamine Tetraacetic Acid (EDTA), Ethylene Diamine Diacetic Acid (EDDA), Nitrilo Triacetic Acid (NTA), Imino Diacetic Acid (IDA), Diethylene Triamine Pentaacetic acid (DTPA), and Hydroxyethyl Ethylene Diamine Triacetic Acid (HEDTA).
The reaction was carried out in a stirred tank reactor under extremely mild conditions, temperature of 20ºC and atmospheric pressure, in the presence of 150 ppm of the organic compound, metallic iron particles (10 g), a chelating agent (EDTA, EDDA, NTA, IDA, DTPA or HEDTA, 0.3 mM) and air. The samples were filtered and analyzed by HPLC using a tailored method. The efficiency of the process has been evaluated based on the degree of conversion. The pH value was monitored throughout the experiment.
The experimental results of this study demonstrate that the feasibility of the process depends on the chelating agent used to promoted the reaction. The best results are obtained using NTA reaching a 99% of conversion and only a 37% when DTPA is the chelating agent used under the same operation conditions. Studies about the influence of the carboxylate groups and the nitrogen atoms of the different chelating agents on the reaction are currently on progress.
References
Egli, T. (2001). J. Biosci. Bioeng. 92(2): 89-97.
Miller, D. M., Buettner, G.R., Aust, S.D. (1990). Free Radic. Biol. Med. 8: 95-108.
Noradoun, C., Engelmann, M. D., McLaughlin, M., Hutchenson, R., Breen, K., Paszczynski, A. and Cheng, I. F. (2003). Ind. Eng. Chem. Res. 42: 5024-5030
Presented Wednesday 19, 11:54 to 12:12, in session Sustainable & Clean Technologies - Ia:Extraction-Remediation (T1-4a).
