Circular Economy in Action: Green Synthesis of Mesoporous Silica Nanoparticles from Rice Husk Waste for Biomedical and Industrial Applications

Mesoporous silica nanoparticles (MSNs) are highly prized for their large surface area, low density, and unique structure, making them ideal for applications in fields such as drug delivery, tissue engineering, biosensing, catalysis, and the elastomer industry. As demand for MSNs grows, there is an urgent need for more sustainable, cost-effective production methods. This study presents a sustainable and efficient method for synthesizing hierarchical MSNs from rice husks (RHs), utilizing phosphonium ionic liquids (PILs) as environmentally benign solvents. The PILs enable the dissolution of lignocellulose (LC) in rice husks through hydrogen-bonding (H-bonding) interactions, and the PILs can be regenerated by adding an anti-solvent. This process not only facilitates the extraction of valuable LC components but also removes detrimental metal cations, such as potassium (K⁺), which could otherwise affect the quality of the MSNs. By extracting LC prior to MSN synthesis, we maximize the utilization of rice husks, converting agricultural waste into valuable resources. This approach aligns with the principles of a circular economy by reducing waste, enhancing resource recovery, and promoting the sustainable production of MSNS. The synthesized MSNs were thoroughly characterized, and their properties position them for diverse applications in both industrial and medical fields, supporting sustainability and green chemistry initiatives.