Saponin-mediated synthesis of silica nano-reservoirs

Mesoporous silica nanoparticles are synthesized by sol-gel route, using green porogen agent saponin. Two sets of nanoparticles are synthesized using different alkoxides, tetrapropyl orthosilicate (TPOS) and tetraethyl orthosilicate (TEOS) in different reaction media. In each set, the amount of saponin has varied in the range 100-500 mg. Samples are characterized by TEM analysis and N2 adsorption/desorption measurement. The results show that the used alkoxide, the reaction medium and the amount of saponin has a significant effect on the textural properties of the sample. All synthesized particles show a complex pore architecture, with a central cavity and meso-nanoporous walls. The central cavity communicates with the external environment through micro/meso channels. This structure, composed of an accessible central nanometric reservoir, appears particularly suited for applications in different fields, such as biomedical and water remediation. Obtained mesoporous silica nanoparticles are tested to bioremediate wastewater, focusing particularly on the removal of Cu2+ model cation. The results reveal a correlation between the textural properties of the particles and their adsorption capability. All samples exhibit high kinetics and efficiency against Cu2+, particularly those obtained using TPOS, characterised by greater surface area and more negative ζ -potential. The sample with the best performance has been prepared with the highest amount of saponin and managed to absorb 100% Cu2+ in 10 min, even when it is present in wastewater.