Degradation and toxicity variations of pyrazolone pharmaceuticals by homogeneous oxidation processes for reclaimed water reuse: A review

Abstract

Large-scale consumption of pyrazolone pharmaceuticals (PyACs), commonly used as non-steroidal anti-inflammatory and analgesic drugs, has led to their widespread presence in surface water, groundwater and wastewater, primarily originating from human metabolism and pharmaceutical wastewater. Owing to the resistance to conventional sewage treatment processes, PyACs potentially threaten humans, the natural environment and reclaimed water safety. Regarded as the key part in wastewater treatment, the homogeneous oxidation processes (HOPs) could effectively remove the PyACs by producing highly reactive species (RSs) to ensure the safety of reclaimed water and the aquatic environment. Hence, the review systematically summarized the performance, effects of environmental factors, mechanisms of PyACs degradation by various HOPs. Among the PyACs, it was found that aminopyrine (AMP) could be most efficiently degraded by different HOPs due to its unique tertiary amine substituents. The pH and water matrix would further alter the compositions and contributions of RSs, subsequently affecting the degradation efficiency of PyACs by different HOPs. In addition, the degradation pathways, eco-toxicity variations and energy cost evaluation are emphatically reviewed and compared. The degradation products and toxicity depended heavily on the structure of PyACs, as well as whether HOPs contained chlorine. Finally, the conclusion and future perspectives were also discussed. Overall, this review could provide valuable insights into the degradation behavior of PyACs by conventional and novel HOPs.