Dissolved ozone coupled permanganate based process for chemical decontamination of stainless steel surfaces

Highlights: • Modified permanganate process with dissolved ozone is more effective for stainless steel decontamination. • Coupling of DOz with ${\text{MnO}}_4^{-}$ reduced the total requirement of formulation chemicals. • DOz coupled ${\text{MnO}}_4^{-}$ process is effective in release of 'Fe', 'Co' and 'Ni' from chromite or chromia lattice. • The in-situ reconversion of MnO₂ to ${\text{MnO}}_4^{-}$ will the prevent sorption of radioactive metal ions and clogging of the system. Removal of passive/corrosion oxide film comprising radioactive nuclides from the alloy surfaces forms a decisive step during the chemical decontamination process development in the nuclear industry. Conventionally, permanganate based methods are used for stainless steel surface decontamination. We have modified this ${\text{MnO}}_4^{-}$ method by coupling with dissolved ozone (DOz). In DOz coupled ${\text{MnO}}_4^{-}$ method, DOz is used for the regeneration of permanganate from MnO₂ formed during the oxidation of chromium. For the DOz coupled ${\text{MnO}}_4^{-}$ process, parameters like DOz and ${\text{MnO}}_4^{-}$ concentration and solution temperature were optimized. Optimized parameters exhibited a reduction in the chemical requirement for simulated corrosion product oxide dissolution while maintaining the same dissolution efficiency. The process also helps in the release of iron, cobalt, and nickel to the solution from the oxide layer, thereby lowering the number of steps involved in the decontamination process as compared to the conventional ${\text{MnO}}_4^{-}$ process. The process effectively shrinks the radioactive waste volume generation, an essential factor in decontamination process development in the nuclear industry.