Evaluation of solar photo-Fenton parameters on the pre-oxidation of leachates from a sanitary landfill

Abstract

The main purpose of this work is to study the treatment of a leachate after preliminary aerated lagooning by a solar photo-Fenton process, using a photocatalytic reactor with compound parabolic collectors (CPCs). The influence of different process parameters in the reaction rate was evaluated, such as, the type of acid used in the acidification step (H2SO4, HCl, H2SO4+HCl); type of iron salt (FeSO4, FeCl3) and respective iron concentration (60, 80, 100 and 140mg Fe2+/L); temperature; and ratio of illuminated to total volume (25L/35L; 25L/72L). DOC abatement in the acidification procedure is independent of the type of acid used and temperature, and is related principally with the precipitation of humic acids. The use of HCl alone or in combination with H2SO4 leads to a substantially increase of the chloride ions, leading to the formation of less reactive chloride radicals when compared with sulfate radicals, decreasing the photo-Fenton reaction rate. The use of ferrous ions instead of ferric ions influenced positively the photo-Fenton reaction. Meteorological conditions favoring higher temperature of the leachate enhance the photo-Fenton reaction. Alternating dark and illumination intervals has shown a negligible effect on the illumination time needed to achieve the same mineralization, indicating that the Fenton process that takes place in dark zones is not efficient, even in the degradation of intermediate compounds resulting from the light-enhanced reaction. According to biodegradability tests, the optimum energy dose, necessary to obtain a biodegradable effluent, is 57.4kJUV/L, consuming 120mM of H2O2 and leading to a final DOC of 284mg/L which corresponds to approximately 66% of mineralization.