Isotope Techniques in Chemical Wastewater Treatment: Opportunities and Uncertainties

A comprehensive and in-depth analysis of reaction mechanisms is essential for advancing chemical water treatment technologies. However, due to the limitations of conventional experimental and analytical methods, the types of reactive species and their generation pathways are commonly debatable in many aqueous systems. As a highly sensitive diagnostic tool, applications of isotopes as tracers and reactive probes offers deeper insights than conventional methods with minimal interference from reaction conditions. Nevertheless, precise interpretations of isotope results remain a significant challenge. Herein, we first scrutinized the fundamentals of isotope chemistry and highlighted key changes induced by the isotope substitution. Next, we discussed the application of isotope techniques in kinetic isotope effects (KIE), presenting a roadmap for interpreting KIE in sophisticated aqueous redox systems. Furthermore, we summarized the applications of isotope techniques in qualitative and quantitative elemental tracing to pinpoint reaction sites and identify dominant reactive species in chemical treatment processes. Lastly, we propose future research directions, highlighting critical considerations for the rational design and interpretation of isotope experiments in environmental chemistry and related fields.