Similar to the reactions between organic solutes and OH radicals, this recombination reaction can only occur in the interfacial zone, where OH radicals are present. Therefore, like Eq. (4), the overall rate of reaction must be proportional to the area of the plasma–liquid interface. However, unlike Eq. (4), the reaction is pseudo-zero-order and all reactants originate in the plasma interior; therefore, diffusion is negligible. These features are captured in the following kinetic model: