Layered Double Hydroxide as a Potential Matrix for Controlled Release Formulation of Phenoxyherbicides

Abstract

Phenoxyherbicides, namely 4-(2,4-dichlorophenoxy)butyrate (DPBA), 2-(2,4-dichlorophenoxy) propionate (DPPA) and 2(3-chlorophenoxy)propionate (CPPA) were intercalated separately into the interlamellae of Zn/Al layered double hydroxides (LDHs) by direct co-precipitation method for the formation of their nanohybrids, DPBA-LDH, DPPA-LDH and CPPA-LDH, respectively. Powder x-ray diffraction patterns of the sample show that the interlayer spacing expended from 8.9 Å in LDH to 28.14, 21.44 and 20.05 Å for DPBA-LDH, DPPA-LDH and CPPA-LDH nanocomposite, respectively. Release study of the phenoxyherbicides, DPBA, DPPA and CPPA anion from their respective nanohybrids were carried out at different concentrations of sodium phosphate. The maximum percentage release of DPBA, DPPA and CPPA into 0.008 M sodium phosphate was found to be different; 51, 76 and 87 %, respectively. Rapid release of the phenoxyherbicides was observed at the beginning  of the process followed by a slower one near to the equilibrium. Kinetic study shows the release behavior for all the phenoxyherbicides from their nanohybrids is governed by pseudo second order.