Solar Light-Driven Photocatalytic Degradation of Tetracycline Using Fe3+-Doped CdO/ZnS Nanocomposite

What is it about?

In recent years, studies on the efficient spatial charge separation for broad solar light absorption and water remediation have been a major priority. Moreover, the development of transition metal-doped nanocomposites for this purpose is a new endeavor in current research. Here, we constructed an Fe3+-doped CdO/ZnS nanocomposite with a low doping level and investigated the effect of doping on the charge transfer and recombination behavior for improved photocatalytic performance. The X-ray diffraction analysis results indicate that both materials, CdO and ZnS, exhibit a cubic phase structure with an average crystallite size of 35 nm. Morphology analysis of the Fe3+-doped CdO/ZnS nanocomposite confirms the formation of irregularly shaped particle-like structures. From the optical studies, the bandgap energies of CdO/ZnS and Fe3+-doped CdO/ZnS nanocomposites are 3.19 eV and 2.87 eV, respectively, which proved that the iron ions doping reduced the bandgap energy and extended the absorption to the visible range. The efficiency of photodegradation in the tested samples was evaluated using tetracycline under solar light exposure. The experimental results demonstrated that the Fe3+-doped CdO/ZnS nanocomposite outperformed the other samples, exhibiting a significantly higher photocatalytic activity. After 80 min, it achieved a remarkable degradation rate of 97.06%. The Fe3+-doped CdO/ZnS nanocomposite demonstrated good stability and recyclability after five cycles. Radical trapping experiments showed that hydroxyl (•OH) radicals play a key role in photodegradation

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Why is it important?

Aquatic environments, in particular, have become a repository for a range of diverse compounds, which are collectively known as emerging pollutants [1,2]. This intriguing category has attracted intense attention because of its potential ramifications for both ecological integrity and human well-being. Notably, a significant subset of these compounds exhibits remarkable resilience against conventional chemical oxidation methods. Furthermore, their inherent toxicity poses formidable obstacles to successful biodegradation processes. Consequently, the possibility of their release into the environment is a worrying conundrum [3,4]. In recent decades, there has been a notable surge in the demand for pharmaceutical products in developing nations, encompassing a spectrum of categories including analgesics, antibiotics, anti-inflammatory agents, lipid regulators, beta blockers, and tranquilizers [5,6]. Significant proportions of these pharmaceutical compounds exhibit robust stability, posing considerable challenges for their effective dismantling through conventional wastewater treatment methodologies [7]. Consequently, a substantial presence of these pharmaceutical compounds is consistently observed across diverse water sources, including sewage and surface water, as well as within drinking water, groundwater, soil, sediments, and sludge [8]. Tetracycline (TC) is a globally utilized antibiotic known for its extensive range of effectiveness. It proves to be effective against infections caused by both Gram-positive and Gram-negative microorganisms [9]. Moreover, TC is used in the medical, veterinary and agricultural fields due to its low cost and high antimicrobial activity [10].

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