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

Abstract

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<acetate<oxalate<NTA (nitrilotriacetate)<IDA (iminodiacetate)<EDTA (ethylenediamine tetraacetate). This observed reactivity order of iron(II)complexes corroborates well with their oxidation propensity under the given ligand field (E°=+0.131 to+0.771 V in case of EDTA and aqua ligand respectively). The influence of reaction conditions, nature of contaminant and identification of electroactive species was investigated by using spectro‐electrochemical experiments with selected systems. Two plausible mechanisms of contaminant degradation were proposed:(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.

Photocatalytic evaluation of CuO and ZnO crystallites synthesized hydrothermally using binary eugenol/iso-eugenol mixtures: isomer effects on the capping propensity of biogenic agents

“…In continuation of our interests in photocatalysis and designing organic synthesis and waste water treatment applications, [37][38][39][40][41] in this work we evaluated the effect of eugenol and isoeugenol mixtures on the photocatalytic characteristics of ZnO and CuO photocatalysts synthesized hydrothermally. The data from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques were used to evaluate the comparative effect of five different molar ratios of eugenol and isoeugenol mixtures on the surface morphology and structural, optical and electrochemical characteristics of CuO and ZnO materials.…”

Dye contaminated wastewater treatment through metal–organic framework (MOF) based materials

“…1 Contamination of natural water resources has been increasing day-by-day due to the disposal of waste organic and inorganic by-products mainly from industries, mining activities, wastewater irrigation, and agricultural output. [2][3][4] Among these toxic waste products, industrial effluents contain many poisonous metals (such as Cr, Se, Cu, Ar, Hg, and Cd) and organic moieties. Organic hazardous waste mainly includes organic dyes, detergents, plasticizers, grease, surfactants, and pesticides.…”