Conclusions
Fluoride, iron (hydr)oxide such as goethite, and bicarbonate at
concentrations typically found in natural groundwater samples could play
an important role in sunlight photo-induced reactions in presence of
H2O2 (10 mg L-1) to
the abatement of organic pollutants. We have suggested that goethite
fluorination may take place leading to an increase of iron (hydr)oxide
photocatalytic activity while the reaction between photoinduced•OH radicals and bicarbonate
(HCO3-) could lead to the formation of
carbonate radicals (CO3-•) which may
exhibit an interesting oxidizing power able to degrade 2,4-D molecules
as well.
The implications of these findings are very important since it exhibits
the possibility to enhance natural abiotic sunlight photoinduced
processes by the simple addition of hydrogen peroxide to remove both
organic pollutants and bacteria from natural groundwater samples without
the further addition of iron salts, photocatalysts, and complexing
agents. Moreover, results also suggest that “natural” goethite
fluoridation in real groundwater could lead to the “natural” formation
of iron (hydr)oxides with enhanced photocatalytic activities.