Green Synthesis of 2% g-C3N4/SnS2-V3/CQD1 Composite Photocatalyst: A Sustainable Solution for Uranium Removal

Heavy metal pollution, particularly uranium [U(VI)] contamination in wastewater, presents serious environmental and health risks due to its radiotoxicity and chemical toxicity. The accumulation of uranium in water not only disrupts aquatic ecosystems but also poses significant health hazards to humans through the food chain. The effects of uranium contamination on human health are profound, as prolonged exposure can lead to kidney damage, cancer, and other chronic illnesses. While conventional methods of removing uranium, such as adsorption, membrane separation, and chemical extraction, have demonstrated some success, they come with various limitations, including inefficiency, secondary pollution, and high operational costs. These drawbacks have made it necessary to explore alternative methods for uranium removal that are both effective and environmentally sustainable. Photocatalysis, a process that uses light to drive chemical reactions, has emerged as a promising solution for the removal of pollutants, including heavy metals like uranium. Unlike conventional treatment methods, photocatalysis is an energy-efficient and environmentally friendly technique that could potentially overcome many of the limitations associated with traditional methods. However, the practical application of photocatalytic systems has been hampered by several issues, such as the reliance on toxic reagents, the need for high energy inputs, and the limited use of UV light sources, which restrict the scalability and effectiveness of these systems. To address these challenges, a groundbreaking study led by Professor Longshan Zhao’s team from Shenyang Pharmaceutical University has introduced a novel Z-scheme photocatalytic system, 2% g-C₃N₄/SnS₂-V3/CQD1, which shows exceptional efficiency in uranium removal while adhering to the principles of green chemistry. This new composite photocatalyst offers a sustainable, cost-effective, and highly efficient approach to uranium removal from wastewater.

The key innovation in this study lies in the green synthesis of carbon quantum dots (CQDs) derived from waste plant soot, a byproduct that would otherwise contribute to environmental pollution. By utilizing waste plant soot, the researchers were able to reduce the environmental impact of the synthesis process and promote the reuse of waste materials, aligning perfectly with the principles of sustainable development. The CQDs, once synthesized, were incorporated into a composite with SnS2, a material known for its photocatalytic properties. The SnS2 was further modified by doping with vanadium (V), which significantly enhanced its photocatalytic performance. The combination of SnS2 and g-C3N4 created a synergistic effect that optimized charge separation and minimized electron-hole recombination, further enhancing the overall photocatalytic efficiency. This composite material, 2% g-C₃N₄/SnS₂-V3/CQD1, operates efficiently in aqueous environments at low temperatures, avoiding the use of harmful solvents or toxic reagents. This represents a significant step forward in the development of photocatalysts that can be used in real-world applications without posing additional environmental or health risks. Under visible light, the 2% g-C₃N₄/SnS₂-V3/CQD1 composite exhibited a uranium [U(VI)] removal efficiency of 98.84% within 30 minutes at pH 3, an outstanding result that highlights the material’s potential for large-scale environmental remediation. This exceptional performance can be attributed to the advanced Z-scheme photocatalytic mechanism, which enhances charge carrier separation, facilitates the efficient transfer of electrons, and boosts redox reactions, all of which are critical for the effective degradation of pollutants such as uranium. Additionally, the reaction rate constant of 0.09972 min⁻¹ observed for the composite is significantly higher than that of many traditional photocatalysts, underscoring the superior performance of this material in uranium removal. One of the most notable aspects of the 2% g-C₃N₄/SnS₂-V3/CQD1 composite is its remarkable stability and durability. The composite maintained over 80% of its initial photocatalytic efficiency over four recycling cycles, demonstrating its potential for long-term practical applications in environmental remediation. The carbon quantum dots (CQDs) play a crucial role in enhancing the photocatalytic efficiency of the composite. The CQDs extend the light absorption spectrum into the visible range, enabling the material to harness solar energy more effectively. The upconversion photoluminescence property of the CQDs also facilitates the activation of the photocatalysts under longer wavelengths, further improving the system’s overall performance. Additionally, the CQDs contribute to the structural stability of the composite by enhancing charge carrier mobility, ensuring that the material can continue to perform efficiently over multiple cycles. The use of CQDs in this system not only improves the photocatalytic activity but also plays a significant role in stabilizing the material, ensuring that it remains functional for extended periods without a significant decrease in performance. This makes the 2% g-C3N4/SnS2-V3/CQD1 composite an ideal candidate for large-scale environmental remediation projects that require both efficiency and long-term reliability.

The 2% g-C₃N₄/SnS₂-V3/CQD1 composite represents a breakthrough in sustainable photocatalytic technology. Its low energy requirements, use of renewable resources, and exceptional efficiency make it an attractive solution for large-scale implementation in environmental remediation. Beyond uranium removal, this composite material has the potential to treat other heavy metal pollutants and organic contaminants, further expanding its applications across various industries, including water treatment, packaging, and materials science. The scalability of this technology is also a key advantage, as the use of waste plant soot in the production process reduces costs and minimizes the environmental impact of manufacturing. By eliminating the need for toxic solvents and high-temperature processing, the composite offers a more environmentally friendly and cost-effective alternative to traditional photocatalytic systems. The affordability of this method could also lead to its widespread adoption, particularly in regions where access to advanced technologies is limited due to cost and resource constraints. The adoption of this approach could accelerate the transition toward sustainable practices in industries where water and air pollution are major concerns. In conclusion, the 2% g-C₃N₄/SnS₂-V3/CQD1 composite represents a transformative advancement in photocatalytic technology. Its exceptional performance in uranium removal, coupled with its sustainability, versatility, and cost-effectiveness, positions it as a leading solution for environmental remediation. As industries and governments increasingly prioritize eco-friendly and sustainable practices, materials like the 2% g-C₃N₄/SnS₂-V3/CQD1 composite could play a crucial role in achieving cleaner, safer, and more sustainable environmental management. This study underscores the importance of integrating green chemistry into material science, demonstrating the potential of sustainable technologies to address pressing environmental challenges. Furthermore, it sets a precedent for future research and development in the field of photocatalysis and eco-friendly materials, paving the way for the next generation of sustainable solutions to combat environmental pollution on a global scale.