Abstract
Laboratory wastes containing Cd2+ and water polluted by pharmaceuticals represent an environmental concern. In this work, a proof concept, consisting of the use of teaching-laboratory wastes to synthesize CdS and its subsequent use as a photocatalyst to degrade fluoroquinolone antibiotics, was developed. The CdS was prepared by extraction with thioacetamide and calcination (at 450 °C) and characterized using several techniques. The photocatalytic activity of the CdS, to degrade levofloxacin and norfloxacin, was tested, and the routes involved in the process and the primary transformations of the fluoroquinolones were established. Moreover, the ability of CdS-photocatalysis to eliminate levofloxacin in simulated matrices of fresh urine and hospital wastewater was evaluated. The characterization analyses indicated that the CdS semiconductor was synthesized successfully. Effectively, the CdS acted as a photocatalyst toward degradation of levofloxacin, involving the action of superoxide anion radical, holes, and singlet oxygen mainly. The process induced transformations on the methyl-piperazyl moiety, plus hydroxylation of the fluoroquinolone nucleus on levofloxacin. Additionally, CdS-photocatalysis was highly selective for the elimination of the target pollutant in both tested matrices. Our research indicated the good potentiality of recycling teaching-laboratory wastes to generate photocatalysts to degrade organic pollutants. This work was presented at 4° Congreso Colombiano de Procesos Avanzados de Oxidación (4CCPAOx).
Highlights
The circular economy has appeared as a possible solution to make better use of resources and to minimize environmental pollution
The Scanning electron microscopy (SEM) micrograph, at the 1 μm scale (Figure 1c), revealed that the surface morphology of the solid was characterized by large amounts of voids
In the Transmission electron microscopy (TEM) images, the shape of these nanoparticles was in agreement with that observed in the SEM images
Summary
The circular economy has appeared as a possible solution to make better use of resources and to minimize environmental pollution. This is an actual trend, which proposes the reuse and/or the generation of value-added products from wastes [1]. Since the 1980s of the last century, aqueous solutions containing metals such as cadmium are considered hazardous wastes, even if the metal concentrations are low [3]. In this sense, wastewater containing cadmium represent a serious risk for both the environment and humans
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