Synthesis of ZnO/SiO₂-modified starch-graft-polyacrylate superabsorbent polymer for agricultural application

A bio-based superabsorbent polymer (SAP) for agricultural application was synthesized from modified starch (MS) to enhance its antibacterial property and biodegradability. The starch was modified by zinc oxide and tetraethyl orthosilicate via a sol-gel reaction under an acidic condition. Structural and morphological examinations were used to confirm the modification. The MS showed a good antibacterial activity against Staphylococcus aureus and Escherichia coli with 61.9 % and 99.9 % reduction in viable cells, respectively, after a 1 h exposure. The MS was then graft copolymerized with potassium acrylate monomer to synthesize a new MS-g-polyacrylate (PA) SAP. The grafting reaction was confirmed and the main factors for agricultural applications along with its biodegradation and antibacterial properties were achieved. The MS-g-PA SAP exhibited an excellent reusability and biodegradation. Importantly, the MS-g-PA SAP did not impose growth inhibition of mung bean (Vigna radiata), but provided some transient drought relief.