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An apparatus for real‐time in‐situ monitoring of electrochemical advanced oxidation processes using visible spectrophotometry has been developed. Central to the design is a 3D‐printed sleeve that interfaces commercially available electrochemical and spectrophotometry units. Using the anodic oxidation of Acid Orange 7 as a test bed, the apparatus has been used for probing the impact of varying electrode composition, current density, electrolyte concentration, and stirring speed on the rate of decolorization. In addition, the unit was used to prove that decolorization can continue after electrolysis has been stopped, thereby showing the inherent value of real‐time monitoring. Given that a significant challenge in the field of advanced oxidation processes is the inability to compare different reported systems, our approach, using commercially available equipment and a printable interface may open avenues for more standardized data collection. [ABSTRACT FROM AUTHOR]

The widespread use of synthetic dyes has led to the release of substantial amounts of dye-contaminated wastewater, posing significant environmental and health concerns. This study focuses on the use of anodic and electrochemically activated persulfate oxidation for the degradation of organic contaminants. Specifically, the structural variations of nine dyes in the indigoid and azo families, and their impact on the efficiency of electrochemical oxidation were analysed. An in situ continuous monitoring apparatus with a UV-visible detector was employed to collect data in real-time. The electrochemically activated persulfate system demonstrated higher efficiency compared to the anodic oxidation approach. In both systems the efficiency of decolourisation was highly dependent on the structure of the pollutant. Electron-withdrawing substituents in direct conjugation with the chromophore, bulky auxochromes, and extended aromatic systems significantly decreased the decolourisation efficiency. Conversely, changing the location of electron-withdrawing groups and adding electron-donating substituents increased the decolourisation efficiency, even overcoming the detrimental effects of bulky groups and extended conjugation. This type of systematic structural comparison study is essential for highlighting the interconnected nature of pollutant structure and degradation speed so that efficient electrochemical oxidation systems can be designed for the treatment of genuine wastewater effluent containing more than one pollutant., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)