CONTROLLED RELEASE OF FERTILISER USING MESOPOROUS SILICA NANOPARTICLES

Abstract

Nanostructured delivery systems for fertilizers could minimize leaching and consequently reduce the amounts applied. In this study, Mesoporous Silica Nanoparticles (MSNs) were explored as controlled release carriers for fertilizers. A series of MSNs with particle sizes, Barrett-Joyner-Halenda (BJH) pore diameters, Brunauer-Emmett- Teller (BET) surface areas and BJH total pore volumes ranging between 50 nm – 900 nm, 2.4 nm - 4.4 nm, 589 m2g-1 - 1013 m2g-1 and 0.61 cm3g-1 – 0.81 cm3g-1 respectively were synthesized via Liquid Crystal Templating Mechanism (LCT). Urea was used as a model fertilizer to access the fertilizer loading and controlled release behaviour of MSNs. Loading was achieved by a simple immersion technique using concentrated aqueous urea solution. As much as 19.8 % - 78.2 % of the MSNs surface areas and 16.8 % - 99.0 % of the mesopore volumes were loaded with urea molecules, mainly by physisorption. In vitro release studies of urea-loaded MSNs (UMSNs) in water indicated a burst release (32 % - 91 %) within the 1st day attributed to the urea adsorbed on the external surfaces, followed by a slow and sustained release for up to 6 days when all urea was released (100 %), ascribed to urea molecules entrapped in the mesopores. The release profiles were found to vary with the physical properties of MSNs. Great potential for the development of fertilizer nanocarrier systems based on MSNs was revealed.