Photochemical behaviour of humic acid synthesized from phenol

Abstract

A humic-like material was synthesized by photo-oxidation of phenol at 253.7 nm, and its ability to photoproduce reactive species was compared with that of commercial humic acids. Irradiation at 253.7 nm of homogeneous solutions of humic acids leads to the formation of e−aq which are converted into hydroxyl radical in aerated or oxygenated solutions. At this wavelength, synthetic and commercial humic acids have similar behaviours. At λ⩾300 nm, production of e−aq is not observed. The formation of singlet oxygen was investigated over the range 365–434 nm. It is shown that commercial humic acids produce singlet oxygen whereas synthetic humic acid does not. Thus the formation of singlet oxygen can be attributed to chromophoric groups present in commercial humic acids but not in the synthetic humic acid.