Theoretical Framework for Sensorless pH Monitoring in Hydrometallurgical Systems: A Voltammetric Overpotential Approach for Edge Computing

This paper introduces the “Hydro-Logics” protocol, a formal theoretical framework for indirect pH estimation in complex electrochemical systems. Traditional potentiometric sensors face severe degradation in both industrial and clinical environments due to chemical poisoning, mechanical abrasion, and biofouling. This framework proposes a “quasi-sensorless” alternative by analyzing the Hydrogen Evolution Reaction (HER) through linear sweep voltammetry. Validated through synthetic Monte Carlo simulations (R2 = 0.9979, RMSE = 0.138 pH units, 95.81% uncertainty coverage, excess kurtosis = 17.0810 indicating heavy-tailed perturbations from redox interferences), the protocol utilizes an ESP32-S3 platform for Edge Computing to identify the onset potential (Vonset) and apply an empirical-calibrated model corrected for cathodic overpotential (η), ohmic drop (iRu), reference drift (∆Eref), and activity coefficients. A Kalman filter provides sequential state estimation with rigorous uncertainty propagation. This allows for real-time monitoring of critical variables such as gastric acidity and metal electrodeposition (including Rare Earth Elements), providing a resilient baseline for global technological applications.