Graphitic carbon−TiO 2 nanocomposites with different carbon loadings were synthesized by a one-pot hydrothermal method. The prepared catalysts were characterized by X-ray diffractometry (XRD), scanning electron microscopy, UV−vis diffuse reflectance spectrophotometry, and Brunauer−Emmett−Teller surface area analysis. The XRD results confirmed the presence of graphite in the composite without alteration of the TiO 2 structure. The photocatalytic efficiencies of the synthesized composites were determined by the degradation of aqueous nitrobenzene (NB) under UV irradiation. Because of the presence of graphitic carbon in the composite, there was an increase in the adsorption of NB (24%) on the composite surface, which led to a higher photocatalytic yield (up to 96% in 4 h at a graphitic carbon content of 1%). NB degradation was corroborated by chemical oxygen demand determinations.

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Wet air oxidation of aqueous solutions of poly(vinyl alcohol) (PVA) has been studied in a batch autoclave reactor at temperatures ranging from 175 to 250°C in an excess of oxygen of 0-300% and at oxygen partial pressures (P O 2 ) of 0.53-2.11 MPa. No destruction of PVA was observed below 175°C. The decomposition of PVA and the removal of total organic carbon (TOC) and chemical oxygen demand (COD) rapidly increased at reactor temperatures above 200°C. PVA decomposition was more sensitive to the reaction temperature than to P O 2 or the excess oxygen ratio. About 90% destruction of PVA occurred in 90 min at 200°C, 0% excess oxygen, and 0.7 MPa oxygen partial pressure. Whereas the amount of excess oxygen had little effect on PVA destruction, it accelerated COD and TOC removal. The main intermediates analyzed were carboxylic acids, in particular formic and acetic acids. Further oxidation of these acids resulted in carbon dioxide (CO 2 ) and carbon monoxide (CO). The conversions of PVA to CO 2 and CO were 78% and 5%, respectively, after 4 h of reaction at 200°C and 100% excess oxygen. Our experimental results indicate that, of the two main intermediates, formic acid was short-lived, whereas acetic acid limited the wet oxidation process. Biodegradability of the solution substantially increased upon wet oxidation.