Depending on their origin and structure, humic acids (HAs) have a remarkable ability to absorb light and transfer this energy to other substrates and in some cases strongly affect photolysis of xenobiotics. This search exhibits several examples of spectral and fluorescent study of humics acids with different genesis. The group of studied HAs was isolated from an unditourified high-moor peat with different humidity in the Mezensky District of the Arkhangelsk Region. The standard commercial preparation of humic acids Aldrich was also studied. For photochemical studies, an excilamp on working molecules KrCl with λrad = 222 nm, developed at the Institute of High Current Electronics of the SB RAS, was used as sources of UV radiation. The results of direct and sensitized (in the presence of HAs) photolysis are discussed. For samples of HAs from the Arkhangelsk region, the dependence of the absorption spectra and fluorescence on the duration of drying and the depth of occurrence was found. The longer is the duration of drying of the samples, the lower is the optical density of the absorption spectra. In the process of humification and with the duration of peat drying, the fluorescence intensity of the HAs increases. The dependence of the fluorescence spectra of the studied samples on the wavelength of fluorescence excitation was found.
Spectroscopy and photochemistry of humic acids are discussed. The samples of HAs fractions were obtained from Fluka Chemical Co and prepared from peat of Western Siberia region. The comparative analysis of these acids with the sample of humic acids allocated from brown coal is carried out. A specific feature of the reactor is the use of barrier discharge excilamp (KrCl) with radiation wavelength λ = 222 nm. Influence of the received humic acids on process of photodegradation of herbicide - 2.4-dichlorophenoxyacetic acid is considered.
Investigation of the destruction of 2,4-dichlorophenoxyacetic acid (2,4-D) under the influence of UV radiation from the KrCl excilamp with the use of additives of hydrogen peroxide, the Fenton reagent. Effective rate constants of degradation reactions of the initial compound were calculated. The estimation of efficiency of both each system separately, and together is given. The use of hydrogen peroxide additives and Fenton's reagent is due to the fact that the use of direct photolysis in some systems is ineffective. Addition of hydrogen peroxide in such cases increases the efficiency, due to the formation of active forms of oxygen in aqueous solutions. Thus, studies have been carried out to find the most effective amount of hydrogen peroxide additive and to create the most effective system for the destruction of chlorinated phenoxy acids when excited by a KrCl excilamp (222 nm).