Photo-fenton and UV photo degradation of naphthalene with zero- and two-valent iron in the presence of persulfate

• Published in: Chemical engineering communications 2019-01, Vol.206 (1), p.1-11
• Main Authors: Benincá, Cristina, Charao Boni, Eduardo, Gonçalves, Fabio Ferreira, Primel, Ednei Gilberto, Freire, Flavio Bentes, Zanoelo, Everton Fernando
• Format: Article
• Language: English
• Subjects: Experiments; Hydrogen peroxide; Iron; Naphthalene; Organic chemistry; Persulfate; Photo degradation; Photo-Fenton; Photodegradation; Rate constants; Reaction kinetics; Two-valent iron; Wastewater treatment; Zero-valent iron
• ISSN: 0098-6445; 1563-5201
• DOI: 10.1080/00986445.2018.1469015

An initial set of 12 kinetic experiments was carried out to remove naphthalene from an aqueous effluent by photo-Fenton involving Fe 0 and Fe 2+ at two different concentrations of H 2 O 2 (150 and 300 mg L −1 ) and three different pHs (3, 5, and 7) (2 2 ×3 1 experiments). The rate constants (k) for the reaction of naphthalene degradation by involving Fe 2+ as reactant were in general higher than those with Fe 0 , but the use of Fe 2+ increased the concentration of naphthalene at equilibrium (C e ) when compared with the same response obtained with Fe 0 at analogous conditions. A second set of twelve kinetic experiments of photo-Fenton degradation was also performed with persulfate as additive at the conditions already reported, but at a constant concentration of H 2 O 2 of 150 mg L −1 (2 1 ×3 1 experiments with NaCl +2 1 ×3 1 experiments without NaCl). In almost all the runs in which only the source of iron was varied, k from the kinetic data involving Fe 2+ was higher than that involving Fe 0 , but no difference was observed in terms of C e that was always zero. The addition of persulfate to treat the effluent either containing or not containing salt enhanced the chemical kinetics, and shifted the equilibrium toward the full removal of naphthalene. A final set of nine experiments of UV photo degradation of naphthalene by involving persulfate without iron, with Fe 0 and Fe 2+ in the pH range from 3 to 7 (3 2 experiments) mainly showed that the use of H 2 O 2 may be avoided to remove rapidly and completely naphthalene from wastewater.