Heterogeneous catalytic oxidation of phenanthrene by hydrogen peroxide in soil slurry: Kinetics, mechanism, and implication

Abstract

The degradation of phenanthrene sorbed on soil has been carried out using a H2O2/ goethite heterogeneous catalytic oxidation process. The effect of operating variables, such as the goethite concentration, pH, H2O2 concentration, soil organic matter, and bicarbonate ions has been investigated. The reaction followed pseudo-first order kinetics. The rate constants were evaluated and varied between 2.0 x 10(-4) and 1.1 x 10(-3) min(-1) depending on the (HO2)-O-2 concentration. The highest rate of degradation of phenanthrene was observed at a (HO2)-O-2 concentration of 5 M and 134.0g/kg goethite. The intermediate product formed during the degradation of phenanthrene was identified to be salicylic acid that finally degraded to CO2 and H2O. H2O2 consumption continued as the OH radical attacked the salicylic acid. More than 80% consumption of the 5 M H2O2 took place within 30 min, and the degradation was almost complete after 3 h of reaction. Neutral pH was found to be effective in the removal of phenanthrene. Both soil organic matter (SOM) and bicarbonate ions in the soil inhibited the oxidation rate of phenanthrene.