Advanced oxidation methods of organic compounds lead to their partial mineralization and enhance of adsorption process efficiency on the surface of oxidized activated carbon.
For this purpose it has been studied the catalytic photo-oxidation process of compounds in the following mixture: direct brown dye (CD) - 200 mg / l ethylene glycol (ETG) - 60mg / l and anionic surfactant (sodium lauryl sulfate, SLS) - 60 mg / l . We have studied the oxidation process using model solutions containing this mixture (CD, ETG and SLS) under the action of Fenton’s reagent, in the presence and absence of UV irradiation or under the action of electric current (in the electrochemical cell). The same studies were performed by replacing the iron(II) ion with titanium dioxide.
As a result of laboratory research, we have found increasing of the oxidation degree and mineralization, by photocatalytic oxidation and thus decreased the concentration of organic compounds. Due to the oxidation of dye molecules and other auxiliary components, by strong oxidation ability of free OH* radicals, resulted carbon dioxide, water and low molecular organic compounds (alcohols, ketones, organic acids). The decrease of mixture of organic compounds concentration (for the values of COD-Cr) depends on the nature of catalysts and the presence of electric power. The oxidation degree is greater in the presence of iron (II) ions than in the presence of titanium dioxide after oxidation of the mixture of organic compounds with hydrogen peroxide in model solutions. One explanation is that UV irradiation increases the concentration of free OH* radicals as iron ions further decompose hydrogen peroxide, but in the presence of titanium dioxide, the leading band electrons are accepted by free OH* radicals, converting these radicals to ions, as shown in the mechanism by GARCIA, J., et al. This leads to lower concentration of OH* radicals in model solution and reducing of oxidation effect, respectively. On the contrary, in the presence of electric power, electrons are accepted by the electrode, and the OH* radicals concentration does not decrease, but increases, and this leads to the enhancement of the oxidation effect and mineralization of organic compounds.
After oxidation for 1 hour of the pattern solutions of dye CD, ethylene glycol, and anionic surfactant with photo-Fenton‘s reagent and electric power, the oxidation level was 91-95%.
It was established that the treatment with the titanium dioxide mixture (0.5g / l) and Photo-Fenton’s reagent, lead to an oxidation degree and digestion of 57-77%, using only electrochemical method - 64-75%.