Mechanistic modeling of solar photo-Fenton process with Fe 3+ -EDDS at neutral pH

Abstract

This paper presents, for first time, a mechanistic model of the solar photo-Fenton process at neutral pH with the Fe 3+ -EDDS complex for micropollutant removal, taking into account irradiance and reactor geometry. Due to its high photon absorptivity, this biodegradable complex allows high percentages of micropollutant removal to be achieved for short reaction times. Nonetheless, no model of the process with the Fe 3+ -EDDS has yet been developed, meaning the proposed mechanism relies on photochemical reactions with the complex previously reported, and hypotheses deduced from experimental observation. The data for acetamiprid (ACTM) removal (100 μg L −1 ) in stirred tank reactors with different liquid depths, under controlled conditions of irradiance and temperature, was used to obtain the model parameters. The model successfully fitted the experimental results obtained outdoors in a raceway pond reactor (RPR), with a change of scale from 0.85 to 19 L. For the calculation of the average volumetric rate of photon absorption (VRPA), the effect of the two components of solar UV radiation (direct and diffuse) as a function of the environmental conditions and the reactor layout was considered. The results showed an important contribution by diffuse radiation, even at noon under spring conditions (≈40% of the total VRPA). In addition, the applicability of the model has been demonstrated in water matrices containing organic matter and HCO 3 −/CO 3 2− ions, usually found in secondary wastewater treatment plant (WWTP) effluents. This approach allows for the development of control and optimization tools for the photo-Fenton process at neutral pH in low-cost photoreactors.