ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Thermal release of thymol encapsulated into sodium, organic and pillared modified clay matrixes

M. El Miz, M. Loutou, M. Aaddouz, A. Tahani, E. Mejdoubi, S. Jodeh, K. Azzaoui, and B. Hammouti

Laboratory of Molecular Chemistry, Materials and Environment (LCM2E), Multidisciplinary Faculty of Nador, Mohammed First University, Nador, Morocco

E-mail: sjodeh@najah.edu

Received: 27 June 2023  Accepted: 26 October 2023

Abstract:

This study investigated the controlled-release properties of thymol, a biological insecticide, encapsulated within sodium purified (Na-Mont), pillared modified with Al₁₃ (Mont-Pil-Al₁₃) and organophilic (modified with cetyl pyridinium (Mont-CPC)) montmorillonites clay matrices. The clays were characterized using elemental analysis, XRD, FTIR, and TGA. Na-Mont, Mont-Pil-Al₁₃, and Mont-CPC exhibited maximum thymol adsorption of 177 mg/g, 319 mg/g, and 183 mg/g, respectively. Thermal analysis revealed thymol release from the microcapsules followed zero-order kinetics and was dependent on temperature (20–120 °C), time (0–240 min), encapsulated concentration, and clay matrix. Mont-Pil-Al₁₃ microcapsules showed the fastest release, with 50% thymol released after 610s and 100% after 1386s at 35 °C. Mont-CPC and Na-Mont microcapsules released 50% thymol after 1579 s and 2019s and 100% after 3597s and 3882s, respectively. Activation energies calculated using the Friedman method were 26 kJ/mol for Mont-Pil-Al₁₃, 78 kJ/mol for Mont-CPC, and 120 kJ/mol for Na-Mont, correlated to their release rates. Kinetic models demonstrated thymol release primarily followed zero-order diffusion, with the rate modulated by interactions between thymol and the clay matrices. Thus, thymol encapsulation within modified clay microcapsules provides a means for controlled insecticide release tuned by carrier material and thermal conditions.

Keywords: Modified clay; Thymol; Adsorption; Thermal release; Kinetic studies; Organophilic clay

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-023-03186-4

Chemical Papers 78 (3) 1585–1599 (2024)