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Title (Primary) Reagent or catalyst? – FeS as activator for persulfate in water
Author Sühnholz, S.; Kopinke, F.-D.; Mackenzie, K.
Journal Chemical Engineering Journal
Year 2020
Department TUCHEM
Volume 387
Page From art. 123804
Language englisch
Keywords Persulfate activationSulfate radicalsIron sulfideTCE oxidation
Abstract

FeS was evaluated as heterogeneous activator for peroxydisulfate (PS) with trichloroethene (TCE) chosen as model substance representing organic water pollutants prone to fast oxidation by sulfate radicals. The TCE degradation followed in most cases pseudo-first-order kinetics with a FeS-normalized maximum rate constant of k’TCE = 140 M−1min−1 (with cFeS,0 = 0.28 mM and cPS,0 = 5 mM).

Sulfate radicals were determined as predominant radical species formed during PS activation by FeS by evaluation of the kinetic isotope effect for oxidation of cyclohexanes C6H12 vs. C6D12 (kC6H12: kC6D12 = 2.22). Monitoring of sulfur and iron species during the course of the reaction revealed that sulfide is rapidly oxidized, whereas Fe(II)solid is rather stable over time.

The present study describes in detail the influence of the pH value on the reaction and the long-term performance of FeS as activator for PS with an optimum pH value of 5. On the basis of the radical yield from PS of 1.6 mols SO4 per mol S2O82− and the activation energy of EA = (31 ± 1) kJ mol−1 for the heterogeneous radical generation, a surface-assisted homolytic bond cleavage without simultaneous electron transfer is proposed as activation mechanism, which is contrary to the currently prevailing opinion.

Persistent UFZ Identifier https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=22715
Sühnholz, S., Kopinke, F.-D., Mackenzie, K. (2020):
Reagent or catalyst? – FeS as activator for persulfate in water
Chem. Eng. J. 387 , art. 123804