Green-Synthesized Nanoparticles for Efficient Dye Degradation: Mechanisms, Applications, and Future Perspectives

The acceleration of industrialization in many countries, driven by increasing societal demands, has led to a substantial rise in dye consumption and associated environmental concerns. Dye wastewater constitutes a significant pollution source, with certain dyes exhibiting high toxicity and carcinogenicity, posing serious threats to human health and ecosystem integrity. Current dye removal techniques face notable limitations: adsorption methods often entail high costs and restricted applicability, whereas biological treatments impose specific requirements on the physicochemical properties of wastewater. Nanoparticles, characterized by their distinct physical, chemical, and biological properties, offer promising alternatives due to their high surface-to-volume ratios, which render them effective as both catalysts and adsorbents. This review systematically categorizes the mechanisms of nanoparticle-mediated dye degradation into three primary pathways, with a specific focus on the application of green-synthesized metal nanoparticles within each category. It elucidates the fundamental reaction mechanisms of green synthesis and provides an in-depth analysis of how bioactive components regulate the final morphology, crystal structure, and surface properties of the resulting nanoparticles. Furthermore, strategies to enhance degradation efficiency are discussed, including nanoparticle modification, bimetallic doping, and immobilization on suitable substrates. The incorporation of magnetic properties, either through intrinsic design or by supporting nanoparticles on magnetic carriers, also improves recyclability and practical utility. These advances underscore the considerable potential of nanoparticles to address the challenges of dye pollution.