Mechanism of Ozone Oxidation of Polycyclic Aromatic Hydrocarbons During the Reduction of Coking Wastewater Sludge

Abstract

Activated coking wastewater sludge is a significant problem, due to the content of adsorbed hydrophobic organic micro-pollutants which are adsorbed. Here we discuss an O 3 fluidized bed reactor (FBR) process able to stabilize and reduce the coking sludge, and also removing 16 target polycyclic aromatic hydrocarbons (PAHs) adsorbed onto the sludge. The degradation efficiencies and influential factors affecting the sludge ozonation, such as the concentration of O 3 and of H 2 O 2 , UV irradiation, and the initial pH were investigated. The results indicate that the target PAHs present in the activated coking sludge, especially those with high molecular weight can be effectively removed by O 3 FBR. However, the concentration of O 3 plays an important role in the degradation of the target PAHs because a low concentration can generate an increase in the concentrations of PAHs in the liquid phase of the activated coking sludge. Due to the synergistic effect (S > 0), increasing the concentration of H 2 O 2 and increasing the pH value, can improve the removal of most of the target PAHs. The degradation kinetics of the target PAHs are assigned to a pseudo first-order model. In this process, the solubilization rate of the activated coking sludge reached about 68.2% and the target PAHs adsorbed on it were removed by >95% at 500 mg O 3 g À1 SS.

Study of adsorption-oxidative degradation of PAHs over organic–inorganic hybrid layered double hydroxides

“…The ozone dissolved in water is adsorbed to the surface of the catalyst functional group, which produces free radicals that attack large organic molecules, resulting in chain breaking, ring opening, and other reactions. 31 The destroyed organic matter produces various small organic molecules, which are further mineralized into smaller inorganic molecules under the action of free radicals. Free radicals contributing to degradation include hydroxyl radical (˙OH), singlet oxygen radical ( 1 O 2 ), and superoxide anion radical (˙O 2− ).…”