Preparation and Evaluation of Alginate-Chitosan-Bentonite Based Beads for the Delivery of Pesticides in Controlled-Release Formulation

Abstract

The alginate-bentonite (SA-BT) bead, sodium alginate (SA) bead, alginate-chitosan (SA-CS) bead and alginate-chitosan-bentonite (SA-BT-CS) bead were prepared by extrusion into calcium chloride solution and characterized by FT-IR, SEM, thermogravimetry, water-up tests and release studies. Experimental results showed that the obtained hydrogel beads were 1.42-1.71 mm in diameters. Bentonite could improve the hydrogel beads' size and sphericity and make the drug loading rate and encapsulation efficiency of acetamiprid rise up from 4.16 and 36.36 % to 4.91 and 63.01 %, respectively. Chitosan and sodium alginate had formed the polyelectrolyte complexes by electrostatic interactions and made the drug loading rate and encapsulation efficiency of acetamiprid rise up 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 calcium alginate large swelling to improve the performance of their release.