A pH-responsive production of hydroxyl radical in Fenton process.

Efficient management of temporal latency and spatial heterogeneity remains a critical challenge in sensor-based pH regulation for smart water management, primarily due to inherent response delays and mass transfer constraints. In oxidation systems with dynamic pH environments, delayed responses can lead to issues such as cyanide release, unwanted side reactions, or pipe damage. To address these challenges, we propose a "pause-then-adjust" control strategy, exploiting the pH-responsive generation of hydroxyl radicals (OH) in a modified Fenton reaction system. This system utilizes hydroxylamine as an electron donor and ethylenediaminetetraacetic acid (EDTA) as a stabilizer for iron ions. Within the pH range of 7.0-10.0, the coexistence of [Fe-EDTA] and [Fe-OH-EDTA] complexes facilitates efficient electron transfer, resulting in the selective and sustained production of OH radicals. The inherent pH-responsiveness of this strategy enables rapid and spatially coherent adjustments, offering a robust supplementary method for addressing complex and evolving requirements in advanced water treatment systems.