Influence of Bentonite on the Performance of Sodium Alginate-Chitosan Hydrogel Beads

To obtain an acetamiprid pesticide carrier with high loading rate and good sustained-release properties,the acetamiprid hydrogel beads were prepared by the extrusion-exogenous gelation method,using bentonite as adsorbent and taking advantage of the film-forming properties of chitosan.The structure,morphology and performance of those hydrogel beads were characterized by means of Fourier transform infrared spectroscopy(FTIR),scanning electron micrograph(SEM),thermogravimetry(TG),water-up tests and release studies.The experimental results show that the obtained hydrogel beads were 1.42~1.71 mm in diameter.Bentonite could improve the hydrogel beads′ size and sphericity and enable the drug loading rate and encapsulation efficiency of acetamiprid to increase from 4.16% and 36.36% to 4.91% and 63.01%,respectively.Chitosan and sodium alginate had formed polyelectrolyte complexes by electrostatic interactions,and those complexes assisted the crosslinking by calcium ion and made the drug loading rate and encapsulation efficiency of acetamiprid increase from 4.16% and 36.36% to 5.23% and 54.29%,respectively.Bentonite contains a lot of hydroxyl groups on the surface that could form the hydrogen bonds with the sodium alginate and chitosan,which could effectively inhibit the mass swelling of calcium alginate so as to improve their release performance.