Chemical Engineering Communications, Vol.206, No.1, 1-11, 2019
Photo-fenton and UV photo degradation of naphthalene with zero- and two-valent iron in the presence of persulfate
An initial set of 12 kinetic experiments was carried out to remove naphthalene from an aqueous effluent by photo-Fenton involving Fe-0 and Fe2+ at two different concentrations of H2O2 (150 and 300mgL(-1)) and three different pHs (3, 5, and 7) (2(2)x3(1) experiments). The rate constants (k) for the reaction of naphthalene degradation by involving Fe2+ as reactant were in general higher than those with Fe-0, but the use of Fe2+ 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 H2O2 of 150mgL(-1) (2(1)x3(1) experiments with NaCl +2(1)x3(1) experiments without NaCl). In almost all the runs in which only the source of iron was varied, k from the kinetic data involving Fe2+ 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 Fe2+ in the pH range from 3 to 7 (3(2) experiments) mainly showed that the use of H2O2 may be avoided to remove rapidly and completely naphthalene from wastewater.