Enhanced Degradation of Phenol by a Fenton-Like System (Fe/EDTA/H2O2) at Circumneutral pH

Abstract

This work deals with the degradation of phenol based on the classical Fenton process, which is enhanced by the presence of chelating agents. Several iron-chelating agents such as ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), diethylenetriamine pentaacetic acid (DTPA), and ethylenediamine-N,N’-diacetic acid (EDDA) were explored, although particular attention was given to EDTA. The effect of the molar ligand to iron ratio, EDTA:Fe, initial pH, and temperature on the oxidation process was studied. The results demonstrate that the proposed alternative approach allows the capacity for degrading phenol to be extended from the usual acidic pH (around 3.0) to circumneutral pH range (6.5–7.5). The overall feasibility of the process depends on the concentration of the chelating agent and the initial pH of the solution. The maximum phenol conversion, over 95%, is achieved using a 0.3 to 1 molar ratio of EDTA:Fe, stoichiometric ratio of H2O2 at an initial pH of 7.0, and a temperature of 30 °C after 2 hours of reaction, whereas only 10% of phenol conversion is obtained without EDTA. However, in excess of ligand (EDTA:Fe > 1), the generation of radicals seems to be strongly suppressed. Improvement of the phenol removal efficiency at neutral pH also occurs for the other chelating agents tested.

Insights into the generation of hydroxyl radicals from H2O2 decomposition by the combination of Fe2+ and chloranilic acid

“…In this case, CAA degradation by Fenton oxidation was less sensitive to pH due to the enhanced production of OH radicals by Fe 2+ /Fe 3+ organo-complexation. It should be noted that similar results have been reported related to the presence of organic ligands susceptible to form complexes with Fe 2+ /Fe 3+ ions (Messele et al 2019). The results illustrated in Table 1 present the effect of initial pH on the degradation of some aromatic compounds including CAA, phenol, benzoic acid, and hydroquinone by Fenton oxidation.…”

UV/FeⅡNTA as a novel photoreductive system for the degradation of perfluorooctane sulfonate (PFOS) via a photoinduced intramolecular electron transfer mechanism

“…The inefficiency of Fe 2+ in this study can be ascribed to three aspects. 1) Fe 2+ /Fe 3+ is only stable in strong acidic condition [35], while at pH above 4-5 the catalytic reaction cannot proceed because of formation of inactive and insoluble iron precipitation.…”

“…However, Fe(H2O)6 2+ and Fe(H2O)6 3+ are only stable in very acidic conditions (pH<4). Under neutral or alkaline conditions, Fe 2+ and Fe 3+ ions are easy to precipitate in the form of oxyhydroxide iron species [35]. Thus, under normal condition in the absence of chelation, the catalytic effects of Fe 2+ /Fe 3+ is only applicable at low pH [33,36,37].…”

Bathophenanthroline as Turn-off Fluorescence Sensors for Selective and Sensitive Tetection of Fe(II)

“…The use of BPhen as a sensitive chromophore to detect iron was initially described by the Smith method. After this, various modi cations have been made to increase the effectiveness of the Fe(III) to Fe(II) conversion in the original method described by Smith et al [22]. These colorimetric-based procedures to detect Fe(II) with BPhen include an organic extraction step, as Fe(II) is generally an aqueous medium.…”