Redox Technologies in Wastewater Treatment for Removal of Pharmaceutical (Cephalexin) Contaminants

Introduction

β-lactam antibiotics, including cephalosporin, are among the most widely used antibiotics in human and veterinary medicine. The most quantity of β-lactam antibiotics are excreted unchanged in wastewater and, since they are not biodegradable, can enter the aquatic environment. The presence of these compounds in the environment raises concerns about their toxicity to aquatic organisms and the emergence of antibiotic-resistant bacteria (Benarab et al., 2020).

Contamination of natural water by pharmaceutical wastewater plays an essential role in the anthropogenesis impacts. Under the action of different external factors, there comes to pass degradation of toxicants and the formation of new substances including the more toxic ones. Removal of pharmaceutical compounds from the aqueous environment is one of the most significant priorities in the field of wastewater treatment. Having a complex composition, these pollutants are difficult to remove by conventional or biological methods, and the application of photochemical methods is an effective alternative. From this point of view, various advanced oxidation processes (AOPs) have shown the potential to remove antibiotics from an aqueous solution. Due to high non-degradability, non-toxicity, universal viability, and acceptability AOPs have become a promising option for efficiently removing persistent pharmaceutical compounds. According to the studied references, it was concluded that catalytic and photocatalytic processes may be potential methods for the removal cephalexin (CEX) in optimal conditions at low concentrations of antibiotics. However, this process must be adapted to real substrate concentrations of CEX.

In this context, the main purpose of research is to study the degradation of CEX from aqueous solution by applying homogeneous and heterogeneous oxidation. Further studies are, however, required to optimize the operating conditions for maximum degradation of multiple pharmaceuticals in wastewater under realistic conditions and on an industrial scale. Frequently investigated operational parameters include pH of the solution, reaction time, catalyst and oxidant concentration, catalyst loading, initial concentration of the pharmaceutical under investigation, wavelength, and light intensity. After establishing the optimal conditions, it has released degradation/mineralization of the CEX antibiotic over the initial concentrations range of 50÷200 mg/L which represents the real concentrations in the residual effluents.

Background

As maintained by WHO and UNICEF, 780 million people do not have access to safe drinking water, of which 185 million use surface water to meet their daily needs. The risk associated with pollution with compounds derived from the pharmaceutical industry is highly topical. In the last decades, pollution by emerging contaminants has been paid more attention by the academic community (Gonta et al., 2022). On the one hand, the discharged pharmaceutical pollutants are toxic and are found in a considerable diversity, which makes the treatment of wastewater difficult (Verma et al., 2020; Mocanu et al., 2021). Concern about emerging contaminants, such as pharmaceutical compounds (PCs) has increased due to their negative impact on the ecosystem, as effluents from the pharmaceutical industries are discharged into the sewers of domestic wastewater, natural water flows, soil, etc. (Tran et al., 2018; Gonta et al., 2022; Vaseashta et al, 2021; Vaseashta et al, 2022). Also, it has been shown that pharmaceutical compounds in wastewater have negative environmental impacts. It was found that some bacteria and genes acquired resistance to antibiotics (Hansen et al., 2020,). Lethal effects on aquatic organisms, interference with the natural decomposition of organic matter, and a decrease in the diversity of microbial communities in various environments have been observed (Felis et al., 2019).