Modification of montmorillonite by ball-milling method for immobilization and delivery of acetamiprid based on alginate/exfoliated montmorillonite nanocomposite

The objective of this study was to develop a sustained drug release system based on alginate/exfoliated montmorillonite nanocomposite for acetamiprid, a neonicotinoid insecticide, to improve its sustained release performance. Montmorillonite (MMT) was modified with cetyl trimethyl ammonium bromide (CTAB) using a ball-milling method. Then, acetamiprid was immobilized into the modified MMT layers through freeze-drying technology. Subsequently, the drug-loaded alginate-exfoliated MMT composite beads were prepared by dropwise addition of the mixture of the drug-loaded modified MMT and the alginate solution into the calcium chloride and chitosan blended solutions. The structure and surface morphology of the modified MMT and composite materials were determined by the means of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), BET-specific surface area measurements, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) analysis. The experiments on immobilization and release of acetamiprid were performed to examine the effect of the modified MMT on the properties of the composite beads. Experimental results showed the intercalation of CTAB into MMT has been successfully achieved during the ball-milling process, which was beneficial to the formation of exfoliated MMT nanocomposites in alginate matrix. The intensive force supplied during the superfine pulverization of the ball-milling process was effective to increase the modified MMT’s specific surface areas and decrease its particle size, consequently improving the drug-loading rate (DL) and encapsulation efficiency (EE) of the composite beads. The alginate/exfoliated MMT nanocomposite formulation exhibited a slow and sustained release property, which was demonstrated as a promising carrier material to promote the efficient use of organic pesticide, and thereby reduce environmental pollution.