Sabine Göb

Modeling the kinetics of a photochemical water treatment process by means of artificial neural networks

Abstract We have investigated the kinetics of the degradation of 2,4-dimethyl aniline (2,4-xylidine), chosen as a model pollutant, by the photochemically enhanced Fenton reaction. This process, which may be efficiently applied to the treatment of industrial waste waters, involves a series of complex reactions leading eventually to the mineralization of the organic pollutant. A model based on artificial neural networks has been developed for fitting the experimental data obtained in a laboratory batch reactor. The model can describe the evolution of the pollutant concentration during irradiation time under various conditions. It has been used for simulating the behavior of the reaction system in sensitivity studies aimed at optimizing the amounts of reactants employed in the process — an iron(II) salt and hydrogen peroxide. The results show that the process is much more sensitive to the iron(II) salt concentration than to the hydrogen peroxide concentration, a favorable condition in terms of economic feasibility.

Oxidative degradation of poly vinyl alcohol by the photochemically enhanced Fenton reaction

Abstract The effective degradation of polyvinyl alcohol (PVA) was achieved by the application of the photochemically enhanced Fenton reaction. This ‘Advanced Oxidation Process’ was studied in a batch reactor (V = 0.75 1) using a mercury medium pressure light source. The accuracy of the DOC measurements in function of irradiation and reaction time was remarkably enhanced by the addition of a reduction and precipitation agent, consisting of an aqueous solution of Na3PO4, Na2SO3 and Kl. Effective oxidation was observed when employing low iron(II) concentrations of approximately 1 equivalent of iron(II) per 20 PVA-units (C2H4O) and a stoichiometric amount of H2O2 with respect to the PVA-units to be oxidized.

Oxidative degradation of polyvinyl alcohol by the photochemically enhanced Fenton reaction. Evidence for the formation of super-macromolecules

The reaction mechanism of the oxidative degradation of polyvinyl alcohol (PVA) by the photochemically enhanced Fenton reaction has been studied. Fast and efficient degradation was observed in a batch reactor, using a medium pressure mercury arc in a Pyrex envelope and employing 80% of the stoichiometric amount of H2O2 required for the total oxidation of PVA and a concentration ratio as low as 1 mole of iron(II) sulfate per 20 moles of PVA sub-units (C2H4O) Model PVA polymers of three different molecular weights (15,000, 49,000 and 100,000 g mol−1) were found to follow identical degradation patterns. Strong experimental evidence supports the formation of super-macromolecules (MW: 1–5 × 106 g mol−1) consisting of oxidized PVA and trapped iron(III) at an early reaction stage. Low molecular weight intermediates, such as oxalic acid, formic acid or formaldehyde were not found during the PVA degradation, and we may deduce that the manifold of degradation reactions is mainly taking place within the super-macromolecules from which CO2 is directly released.