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 (H 2 O 2 ) can hinder pollutant degradation kinetics, making precise dosing crucial. Automation of H 2 O 2 concentration monitoring and dosing is therefore essential to the development of reliable, rapid, and cost-effective devices. This study investigated the role of H 2 O 2 dosing in the photo-Fenton degradation of two emerging contaminants (paracetamol and caffeine). A custom Arduino-controlled automated device was employed for online colorimetric H 2 O 2 measurements and dosing. The kinetics of substrate degradation, organic carbon mineralization, and H 2 O 2 consumption were compared to determine the optimal H 2 O 2 dosing strategy for maximizing process efficiency. The H 2 O 2 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 H 2 O 2 concentrations. The results revealed faster substrate and organic carbon removal when a stoichiometric H 2 O 2 dose was added initially, whereas successive additions of smaller H 2 O 2 doses reduced overall H 2 O 2 consumption.