Accelerated the continuous production of ROS at the concentrated alkaline solution driven by O2 microbubbles

Abstract

Reactive oxygen species (ROS) play a central role in degrading many environmental pollutants and oxidizing low-valence metal ions due to their high oxidation potential and environmental sustainability. However, due to the influence of the solution coordination environment, it is always difficult to regulate the species and concentration of short-lived ROS. In this work, we first qualitative and quantified the ROS species including ·O₂⁻, HO₂⁻, and ·OH, with the concentrations as high as 147 μM. DFT calculation suggested that inducing O₂ molecule can intensify charge depletion around NaOH and then accelerate the single electron reduction of O₂, where the concentration of ROS elevated from 0.12 mM to 5.34 mM after employing a fine-bubble diffuser to form O₂ microbubbles. Additionally, it was found the addition of Fe²⁺/Fe³⁺ can regulate the formation of ·OH and ·O₂⁻ by Fenton-like reactions and stabilize the concentration of ·O₂⁻ at 25.67 to 37.07 μM. Based on this, a micro-bubbles reactor was manufactured to increase the oxidation and leaching efficiency of low-valence V(III) and Cr(III) by 17.5 ∼ 41 times, realize the efficient recovery of V(V) and Cr(VI) from vanadium slag. This study provides a comprehensive ROS profile in concentrated alkaline solutions, establishing a foundation for innovative approaches to enhance, control, and apply ROS production.