Effect of humic acids on phototransformation of methylphenols in water

We have studied photolysis of a mixture of 2-methylphenol (2-MP) and 4-methylphenol (4-MP) in distilled water and in water containing humic acids. The samples were irradiated under different conditions: by monochromatic light with λ ∼ 222, 283, and 308 nm; by polychromatic light from a mercury lamp in the wavelength region 290–600 nm. We have shown that a mixture of methylphenols is efficiently degraded with irradiation by a KrCl exciplex lamp (λrad ∼ 222 nm). Preliminary treatment of peat before extraction of the humic acids has an effect on the extent of photoconversion of the methylphenols. Regardless of the type of humic acids, their presence in solution inhibits photoconversion. The greatest extent of degradation of the methylphenols in aqueous solutions with humic acid additives is detected for irradiation by a KrCl exciplex lamp or a mercury lamp, but it is lower than the extent of degradation of the mixture of methylphenols in water.