Photochemical Oxidation of Hexacyanoferrates in Aqueous Solutions

• Published in: Russian Journal of Physical Chemistry A Vol. 97; no. 7; pp. 1445 - 1452
• Main Authors: Tsybikova, B. A., Batoeva, A. A., Sizykh, M. R., Aseev, D. G.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.07.2023; Springer Nature B.V
• Subjects: Anions; Aqueous solutions; Bicarbonates; Chemistry; Chemistry and Materials Science; Degradation; Hydroxyl radicals; Industrial wastes; Oxidation; Oxidizing agents; Photolysis; Physical Chemistry; Physical Chemistry of Solutions; Radiation; Solar radiation; Wastewater; oxidative degradation; solar radiation; persulfates; free cyanides; hexacyanoferrates; reactive oxygen species
• ISSN: 0036-0244; 1531-863X
• DOI: 10.1134/S0036024423070294

The main kinetic laws governing the photochemical degradation of stable cyanide compounds are studied using the example of hexacyanoferrates (HCFs) in the combined {Solar/S 2 O } oxidation system under the action of solar radiation. The efficient oxidation of intermediate products (toxic free cyanides) to nontoxic final products proceeds in the combined {Solar/S 2 O } system, in addition to the complete degradation of [Fe(CN) 6 ] 3− complex. The high efficiency of HCFs oxidation in the combined system is attributed to a conjugated ion-radical mechanism that includes (along with direct photolysis) oxidation with the participation of highly reactive oxygen species (ROSes)—reactive secondary oxidizing agents consisting mostly of hydroxyl radicals generated in situ during the simultaneous alkali and light activation of persulfate with solar radiation. The effect anions (chlorides, sulfates, bicarbonates) and associated organic pollutants (xanthates, phenol) most characteristic of cyanide-containing industrial wastewater have on HCF oxidation in the {Solar/S 2 O } system is studied. The studied anions promote HCF photochemical oxidation in a wide range of concentrations (1–10 mM).