Use of real-time <i>in situ</i> monitoring as a tool for comparing electrochemical advanced oxidation processes for the decolourisation of triarylmethane dyes

This study explores a phosphate-based electrochemical advanced oxidation process (EAOP) for the decolourisation of synthetic dyes in wastewater. A real-time <i>in situ</i> UV-Vis spectrophotometric system enabled continuous monitoring of dye decolourisation, allowing for high-throughput optimisation of reaction conditions using phenol red as a model compound. The optimised system demonstrated superior performance compared to anodic oxidation and electrochemically activated persulphate systems. Further analysis of six triarylmethane dyes revealed that structural features, such as substitution near the central carbon and halogenation, significantly impact decolourisation efficiency. Among the dyes studied, bromocresol purple exhibited the fastest decolourisation, reaching 99% colour removal in 19 min, while tetrabromophenol blue was the slowest, requiring 34 min to reach a smilar level of decolourisation. Overall, this system offers an effective, pH-stable, and environmentally conscious alternative for wastewater remediation.