NO removal using oxidation of free radicals produced from Fe²⁺ and heat synergic activation of oxone

The NO removal using oxidation of free radicals produced from Fe²⁺ and heat synergic activation of oxone in a gas-liquid impinging stream reactor was investigated. The effects of several main process parameters (solution temperature, Fe²⁺ concentration, oxone concentration, solution pH value, NO inlet concentrations) on NO removal were examined. The reaction products and free radicals were also detected and analyzed. Based on the comparative study of different systems, detection of reaction products and capture of active free radicals, the mechanism and reaction pathways of NO removal process were revealed. The results indicate that the increase in oxone concentration, solution temperature or Fe²⁺ concentration elevates the NO removal efficiency, but the increase in the solution pH value or NO inlet concentration reduces the NO removal efficiency. A synergistic effect between Fe²⁺ and heat, which activates the oxone to generate sulfate radicals and hydroxyl radicals, was observed. It reveals that the sulfate radicals and hydroxyl radicals are the primary reactive oxidants, and oxone is the complementary oxidant for NO removal. The synergistic activation system of Fe²⁺ and heat has much higher NO removal efficiency than other systems.