Online measurement and timely optimization of hydrogen peroxide concentration in photo-Fenton processes: Application of an Arduino device

The scale-up of photocatalytic processes for pollutant removal from water involves several critical aspects, including timely analytical control and optimization of operational parameters to maximize efficiency while minimizing reagent consumption. In advanced oxidation processes, reagent use represents a major cost. Specifically, in photo-Fenton processes, excess hydrogen peroxide (H₂O₂) can hinder pollutant degradation kinetics, making precise dosing crucial. Automation of H₂O₂ concentration monitoring and dosing is therefore essential to the development of reliable, rapid, and cost-effective devices. This study investigated the role of H₂O₂ dosing in the photo-Fenton degradation of two emerging contaminants (paracetamol and caffeine). A custom Arduino-controlled automated device was employed for online colorimetric H₂O₂ measurements and dosing. The kinetics of substrate degradation, organic carbon mineralization, and H₂O₂ consumption were compared to determine the optimal H₂O₂ dosing strategy for maximizing process efficiency. The H₂O₂ consumption profile was found to be substrate-dependent. Caffeine degradation exhibited distinctive behavior, warranting preliminary analysis of its by-products. The device also enabled online dissolved oxygen measurements to explore potential relationships with H₂O₂ concentrations. The results revealed faster substrate and organic carbon removal when a stoichiometric H₂O₂ dose was added initially, whereas successive additions of smaller H₂O₂ doses reduced overall H₂O₂ consumption.