The quality of life has been adversely affected by the rapid urbanization and industrialization of modern society, leading to increased contamination of groundwater, air, and fossil fuels through conventional industrial waste disposal methods [1, 2]. Consequently, major environmental issues, such as pollution and climate change, have emerged as significant threats to ecosystems and human health [3–8]. According to recent reports by the World Health Organization, environmental pollution has resulted in 3.7 million deaths in the twenty-first century alone, with 92% of the global population living in areas with severe air and water pollution [9, 10]. As a result, the safe disposal of hazardous waste in both water and the atmosphere has become a critical national and international priority [11–14]. Advanced Oxidation Processes (AOPs) have been extensively employed for the removal of organic contaminants from water and air, with heterogeneous photocatalysis being one of the most promising AOPs due to its ability to degrade organic pollutants [15, 16].
Semiconductor-based photocatalysts, especially metal oxide-based ones, have garnered significant attention for their efficient and cost-effective applications in water pollution treatment and disinfection [17–24]. Titanium dioxide (TiO2) has been widely studied due to its low cost, non-toxicity, and chemical inertness, but its photocatalytic activity is mainly confined to UV light irradiation, limiting its effectiveness under visible light [25–28]. Consequently, there is a pressing need to design and synthesize effective visible-light-driven photocatalysts [29]. Various metal oxides, including La2O3, CdO, CeO2, CaO, and ZnO, have been explored as promising co-catalysts to enhance the photocatalytic activity of TiO2 [30–32].
Scientists are incorporating magnetic nanoparticles into photocatalysts. These nanoparticles, including hematite, maghemite, magnetite, and various ferrites, give the photocatalyst magnetic properties. This allows the photocatalyst to be easily separated from a solution using a magnet [33]. Adding these magnetic nanoparticles doesn't significantly affect the surface area or how the photocatalyst spreads in water because the photocatalyst remains a powder. Even better, some of these magnetic nanoparticles can absorb visible light and act as photocatalysts themselves, which can help break down pollutants even faster [34].
One of the most exciting frontiers in combating water pollution lies in the development of magnetic visible-light-active nanocomposites. These innovative materials are grabbing the attention of researchers due to their immense potential for photocatalytic environmental cleanup. This article delves into the applying these powerful tools for water treatment.
Covellite CuS is a fascinating material for photocatalysis due to its visible-light absorption. This p-type semiconductor with a narrow bandgap (1.2-2.0 eV) boasts several advantages: low cost, non-toxicity, easy production, and excellent stability. Its potential as a photocatalyst is further bolstered by broad visible light absorption, plasmon absorbance, and even near-infrared (NIR) absorption. Studies on CuS for organic dye degradation have shown promise.However, challenges remain. The photocatalytic efficiency of CuS is influenced by factors like morphology, size, and surface area. Additionally, bare CuS suffers from rapid recombination of photoexcited charges and low quantum yield. Furthermore, CuS nanoparticles tend to aggregate in water, hindering their effectiveness.Researchers are addressing these limitations by creating CuS-based nanoheterostructures. These structures can modify CuS properties, leading to enhanced charge separation, improved stability, and ultimately, better photocatalytic performance[35–36]. An example of this approach is the work by Sohrabnezhad et al., who embedded CuS nanospheres within an MCM-41 matrix [37]. This nanocomposite exhibited superior performance in degrading methylene blue under visible light, highlighting the potential of CuS-based materials for water treatment.
With its unique properties and the promise of further improvement through nanoheterostructure design, CuS presents a compelling avenue for developing powerful photocatalysts for clean water applications.
Silver (Ag) doping has emerged as a promising strategy to enhance the photocatalytic activity of semiconductor photocatalysts. By incorporating Ag into the crystal lattice, it effectively lowers the recombination rate of holes and electron pairs, thereby improving the efficiency of photocatalysis [38–40]. Moreover, Ag doping can modify the band gap energy of the semiconductor, making it more active under visible light [43]. This property of Ag-doped materials is particularly advantageous for wastewater treatment applications.
Introducing Fe3O4 (magnetite) as a base material for the photocatalyst adds another dimension to its functionality. Magnetite is a naturally occurring iron oxide mineral with magnetic properties, making it an excellent candidate for various applications. In the context of photocatalysis, Fe3O4 serves as a stable and robust support material for semiconductor photocatalysts like CuS[41].
The utilization of Fe3O4 in CuS-based nanocomposites offers several advantages. Firstly, Fe3O4 provides a high surface area and facilitates the dispersion of CuS nanoparticles, thereby enhancing the accessibility of reactants to the catalytic sites. Additionally, Fe3O4 imparts magnetic properties to the nanocomposite, allowing for easy separation and recovery of the catalyst from the reaction mixture using an external magnetic field. This magnetic recyclability significantly reduces the operational costs and simplifies the catalyst retrieval process, making it more environmentally friendly.
Furthermore, Fe3O4 exhibits excellent stability and biocompatibility, making it suitable for applications in environmental remediation and biomedical fields. Its chemical inertness ensures that it does not interfere with the catalytic activity of CuS, while its biocompatibility is advantageous for potential biomedical applications, such as drug delivery systems.
Combining Fe3O4 with CuS and Ag to form ternary nanocomposites (CuS@Fe3O4/Ag) not only enhances the photocatalytic performance but also provides multifunctionality. The synergistic effects between CuS, Fe3O4, and Ag result in improved charge separation efficiency, extended light absorption range, and enhanced catalytic activity.
Therefore, the incorporation of Fe3O4 as a base material in CuS-based photocatalysts holds significant promise for addressing environmental pollution and advancing various technological applications[42–43]. However, the introduction of silver doping into CuS@magnetite (CuS@Fe3O4) nanocomposites presents a unique opportunity. The incorporation of Ag into the CuS@magnetite structure not only enhances the photocatalytic activity but also provides magnetic properties, enabling easy separation and recycling of the catalyst from the reaction medium. This dual functionality of CuS@Fe3O4/Ag nanocomposites makes them highly desirable for environmental remediation applications [44].
In this study by incorporating Ag NPs and CuS into the Fe3O4 matrix, we aim to enhance light absorption and charge separation, leading to improved photocatalytic performance. Additionally, the magnetic properties of the nanocomposite facilitate easy separation and recyclability, making it a promising candidate for practical applications in water treatment processes. Through this research, we contribute to the development of efficient and recyclable photocatalysts for the removal of pharmaceutical contaminants from water resources.