Waste-to-wealth strategies for the synthesis of silica nanoparticles from mine solid wastes and their biomedical applications.

The increasing accumulation of mine solid wastes poses significant environmental and economic challenges, necessitating the development of sustainable waste management strategies that enable resource recovery and value addition. In this study, a waste-to-wealth strategy is developed for the synthesis of silica nanoparticles (SiO2 NPs) from mining overburden (OB), and these NPs are further used for antibacterial, antifungal and algal applications. This approach diverts industrial waste from landfills and converts it into high-value nanomaterials via a cost-effective, environmentally benign process. The crystalline structure, optical properties, chemical composition, bonding, microstructure, elemental profile, thermal behaviour, and surface morphology of the synthesized silica have been examined. The X-ray diffraction patterns reveal the amorphous nature of the prepared silica NPs. Furthermore, the X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy results confirm the high purity of the extracted silica. However, the Fourier-transform infrared spectrum exhibits the characteristic vibrational stretching of silica, confirming the successful formation of SiO2 NPs. The synthesized silica has an average particle size in the nanometer range (∼65 nm) as observed through dynamic light scattering, high-resolution scanning electron microscopy, and transmission electron microscopy image analysis. Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analyses demonstrate a high specific surface area of 560 m2 g-1, a pore volume of 0.80 cm3 g-1, and a well-defined pore size distribution for the SiO2 NPs. Thermogravimetric analysis and differential scanning calorimetry showed high thermal stability of the silica particles. Additionally, the synthesized SiO2 NPs demonstrate strong potential for antibacterial, antifungal, and algal applications in agriculture, such as soil conditioning, nutrient delivery, and crop protection. Overall, the proposed waste-to-wealth strategy provides a scalable and sustainable pathway for circular economy implementation, addressing both environmental remediation and advanced material development.