Wet Oxidation of Pharmaceutical Sludge for the Treatment and Production of Value-Added Materials

Abstract

The wet oxidation of pharmaceutical sludge for the treatment and production of value-added materials was investigated. The experiments were carried out in a stainless-steel autoclave reactor with chemical synthetic pharmaceutical sludge. The highest removal rate of total suspended solids (90.1%) and volatile suspended solids (98.4%) was achieved at 260 °C for 60 min with an initial oxygen pressure of 0.8 MPa. Simultaneously, the total chemical oxygen demand removal rate (78.7%) and the soluble chemical oxygen demand removal rate (81.6%) were obtained. The volatile fatty acid concentration—including acetic acid, propanoic acid, isobutyric acid and isovaleric acid—increased to 4819 mg/L with pH 12.56, which indicated the possibility of improving the quality of wet oxidized sludge solution as a potential carbon source by adding reagents. Scanning electron microscopy images showed that the sludge became a loose porous structure after wet oxidation, which is beneficial for dewatering performance. Energy dispersive spectroscopy images illustrate that carbon elements in sludge migrate from solid to liquid phases during the wet oxidation process. These results provide meaningful data for the design of further works and demonstrate that wet oxidation is a promising method for the treatment of pharmaceutical sludge, and the produced volatile fatty acids, including acetic acid and propanoic acid, are potential carbon sources for the biological treatment of wastewater.