Kinetic study of hydroxyl radical formation in a continuous hydroxyl generation system

Abstract

A novel and simple apparatus for the continuous generation of hydroxyl radicals has been constructed for the first time. In this paper, we focused on the investigation into the kinetic study of hydroxyl radical formation in the preparation process. The effects of the process parameters (such as the electrolyte solution concentration, graphite dosage, the applied current strength, and air flow rate) on the concentration of hydroxyl radicals were investigated in detail. The concentration of hydroxyl radicals first increased with the concentration of sodium dodecyl benzene sulfonate electrolyte solution, graphite dosage, applied current strength, and air flow rate, and then decreased. The concentration of ·OH and time well fit a third-order model of {C(·OH) = B₁ × t + B₂ × t² + B₃ × t³ + intercept}. The highest concentration of hydroxyl radicals was 7.98 × 10⁻³ mol L⁻¹ under the following conditions: sodium dodecyl benzene sulfonate concentration 10.0% (w/v), graphite dosage 5.0 g, applied current strength 10 mA, and air flow rate 1.0 L h⁻¹. Our hydroxyl radical generation method can achieve the preparation of higher-concentration hydroxyl radicals continuously without using strong acid reagents. Moreover, our method has low energy consumption by using milliampere-level current. It is a green and efficient method for the generation of hydroxyl radicals. The kinetic study of hydroxyl radical generation can quantitatively predict the concentration changes with process parameters and provide a good prediction of hydroxyl radical generation, which is crucially important in industrial applications.