In this work, wet oxidation and catalytic wet oxidation of pharmaceutical sludge using homogeneous and heterogeneous catalysts were investigated. The results indicate that wet oxidation is a promising method for the highly efficient degradation of pharmaceutical sludge. Under optimal conditions, the highest removal efficiencies of volatile suspended solids (VSS) 86.8% and chemical oxygen demand (COD) 62.5% were achieved at 260 °C for 60 min with an initial oxygen pressure of 1.0 MPa. NaOH exhibited excellent acceleration performance on the VSS removal. The highest VSS removal efficiency of 95.2% was obtained at 260 °C for 60 min with an initial oxygen pressure of 1.0 MPa and 10 g·L⁻¹ of NaOH. By using a Cu–Ce/γ-Al₂O₃ catalyst, the highest removal rates of VSS 87.3% and COD 72.6% were achieved at 260 °C for 60 min with an initial oxygen pressure of 1.0 MPa and 10 g·L⁻¹ of catalyst. The wet oxidation reaction can be maintained itself owing to the exothermic heat. The produced low-molecular-weight carboxylic acids have potential commercial utilization as organic carbon sources in the biological wastewater treatment processes. The inorganic residues can be utilized for the building materials production. These results implied that the catalytic wet oxidation is a promising method for the volume reduction and resource utilization of pharmaceutical sludge.

Pharmaceutical sludge is considered as a hazardous material with high treatment and disposal costs. In the present study, the catalytic wet oxidation (CWO) of pharmaceutical sludge by CuO-CeO₂/γ-Al₂O₃ as the catalyst was investigated. The catalyst was prepared by traditional wet impregnation. The catalyst was characterized using X-ray Powder Diffraction (XRD) and Scanning Electron Microscopy (SEM). CWO was performed in an experimental batch reactor. Several parameters that could affect the catalytic degradation efficiency, including catalyst dose, temperature, time, oxygen pressure and pH, were investigated. Under optimum conditions, the highest removal rate of volatile suspended solids (VSS) was 87.3% and was achieved at 260°C for 60 min with an oxygen pressure of 1.0 MPa and 10 g/L of catalyst. At the same time, the chemical oxygen demand (COD) removal rate reached as high as 72.6%. This work implies that catalytic wet oxidation is a promising method for the highly efficient degradation of pharmaceutical sludge.

In the present study, the catalytic wet oxidation of pharmaceutical sludge by molecular sieve loaded with Cu/Ce as catalyst was investigated. Experiments were performed in an experimental batch reactor. Reaction parameters including catalyst dose, temperature, time, and oxygen pressure were discussed. The results showed that the catalysts prepared by co-precipitating method have good catalytic performance. Under optimum conditions, the highest volatile suspended solids (VSS) removal rate approximately 92% and chemical oxygen demand (COD) removal rate of 75% were obtained at 260 °C for 60 min with initial oxygen pressure 1.0 MPa and the catalyst 10 g/L. These results implied that the catalytic wet oxidation of pharmaceutical sludge by molecular sieve loaded with Cu/Ce is a promising method for the highly efficient degradation of the sludge.

Catalytic conversion of formic acid into methanol was investigated with Cu as a catalyst and Al as a reductant under hydrothermal conditions. It was found that formic acid can be converted into methanol by such means. The highest yield of methanol (30.4%) was attained with a temperature of 300 °C and a reaction time of 9 h. The AlO(OH) formed from Al oxidation may also play a catalytic role in the formation of methanol. This process may provide a promising solution to producing methanol from carbohydrate biomass combined with the process of converting the carbohydrate into formic acid, which is expected to emit no CO2.

In the present study, enhanced wet oxidation of excess sludge from pharmaceutical wastewater by NaOH as an alkaline homogeneous catalyst was investigated. The experiments were carried out in a stainless-steel batch autoclave reactor. The highest volatile suspended solids (VSS) removal rate, 95.2%, was achieved at 260 °C within 60 min with an initial oxygen pressure of 1.0 MPa and NaOH 0.5 g·L⁻¹. Simultaneously, the chemical oxygen demand (COD) removal rate of 57.3% was reached. The increase in volatile fatty acids (VFAs) demonstrated that the degradation of sludge was greatly accelerated by NaOH. Interestingly, the production of acetic acid, an intermediate by-product generated from the oxidation of organic compounds, increased significantly. These results illustrated that NaOH is a promising catalyst for the utilization of wet oxidation liquid of excess sludge as a carbon source for the treatment of wastewater.