Complexation Modulated Iron Redox Systems for Waste Water Treatment: A Natural Attenuation Model

Natural attenuation mimics nature's own cleansing mechanism and offers an effective solution for contaminant treatment under prevalent environmental conditions without generating secondary toxins. Despite obvious advantages, these processes are restricted by a narrow range of reduction potential available within natural water systems. Complexation reaction offers to modulate the redox potential range of transition metals allowing detoxification of persistent contaminants. Consequently, present work describes complexation modulated redox potential of iron systems with environmentally available ligands for degradation of contaminants (textile dyes, antibiotics and toxic metal ions) for a possible application in water treatment under natural attenuation concept. The observed spectrophotometric results are indicative of a significant ligand effect on degradation kinetics of studied contaminants by iron(II) complexes. The kinetic efficacies of iron(II) complexes for contaminant degradation were in the order: aqua (i) direct reduction of contaminants by iron(II) complexes (ii) and indirect degradation through reaction between iron(II) complexes and dissolved oxygen to produce reactive oxygen species. This modular study besides being an insight in environmental redox processes is also aimed for the impetus towards natural attenuation based treatments for degradation of contaminants, especially under aerobic conditions that are rich in both iron(II) and organic matter.