Wavelength dependence of the efficiency of photocatalytic processes for water treatment

•Novel methodology for evaluation of action spectra using monochromatic LED sources.•TiO2 and Fe-citrate action spectra for methanol oxidation and E. coli inactivation.•Quantitative correlation between photonic efficiency and absorption spectrum.•Higher energy efficiency at 365nm at for TiO2 and near visible for Fe-citrate.•Prediction of process efficiency under solar light successfully validated.