Merits of polyoxotungstates as environmental remediation catalysts: A novel wet oxidation technology for refractory industrial pollutants

The catalytic effect of silicadodecatungstate (SiW₁₂O ₄₀^4-) on the oxidation of nitrobenzene in subcritical water (T = 100-300°C; P = 0.1-8.6 MPa, pH = 2.6) was examined. In the absence of SiW₁₂O₄₀^4- catalyst nitrobenzene oxidation slowed down significantly after a brief period of rapid degradation and an average of 40% nitrobenzene removal. The catalytic effect of SiW ₁₂O₄₀^4- becomes particularly pronounced after a temperature dependent induction period. Catalyzed wet air oxidation continued until the degradation of the parent compound was complete provided that experimental conditions were harsh enough (T > 200°C). Product distribution analysis suggested that the oxidation paths for catalyzed and uncatalyzed wet air oxidation of nitrobenzene are similar, but the analysis was not definitive.