Enhanced Treatment of Municipal Wastewater Effluents by Fe-TAML/H2O2: Efficiency of Micropollutant Abatement

Combining iron with a tetraamido-macrocyclic ligand (Fe-TAML) as a catalyst and with hydrogen peroxide (H2O2) as the bulk oxidant is a process that has been suggested for the oxidative abatement of micropollutants during water treatment. In this study, the reactivity of the Fe-TAML/H2O2 system was evaluated by investigating the degradation of a group of electronrich organic model compounds with different functional groups in a secondary wastewater effluent. Phenolic compounds and a polyaromatic ether are quickly and substantially abated by FeTAML/H2O2 in a wastewater effluent. For tertiary amines, a moderate rate of abatement was observed. Primary and secondary amines, aromatic ethers, aromatic aldehydes, and olefins are oxidized too slowly in the investigated Fe-TAML/H2O2 systems to be significantly abated in a secondary wastewater effluent. Trichlorophenol is readily oxidized to chloromaleic acid and chlorofumaric acid, which support a one-electron transfer reaction as the initial step of the reaction between Fe-TAML/H2O2 and the target compound. Fe-TAML/H2O2 does not oxidize bromide to hypobromous acid; however, iodide is oxidized to hypoiodous acid, and as a consequence, the H2O2 consumption is accelerated by a catalytic reaction in iodide-containing water. Overall, Fe-TAML/H2O2 is a rather selective oxidant, which makes it an interesting system for the abatement of electron-rich phenolic-type pollutants.

Automated summary

The Fe-TAML/H2O2 system is effective in degrading electron-rich phenolic compounds and polyaromatic ethers in wastewater, but shows slower oxidation rates for other types of compounds. Trichlorophenol is readily oxidized by the system, and iodide is oxidized to hypoiodous acid, accelerating H2O2 consumption.