@MASTERSTHESIS{Rui_Fun_2018,
author = "Ruiz Bravo, Lisette Dyanna",
title = "Funcionalización del silicato laminar de alta carga (Na-2-Mica) para la liberación controlada de los herbicidas MCPA y Paraquat",
abstract = "In this work, a high charge synthetic mica (Na-2-Mica) has been modified through of intercalated and pillaring process with the Keggin´s polycation and the functionalization with thiol and silanol groups were successfully obtained. Their potential application in controlled release of 2-methyl-4-chlorophenoxyacetic acid (MCPA) and N,N′-dimethyl-4,4′-bipyridinium dichloride (PARAQUAT) was investigated. The characterization techniques (XRD, FTIR, Elemental Analysis, XRF, TG - DTA and N2 isotherms) allowed to determine that the pillared materials had an expanded basal spacing (2.05 nm) even after the thermal treatment at 400 ° C for 2 hours, indicating effective incorporation of Al2O3 pillars covalently bonded to the sheets of the structure building pore networks with 40-fold higher specific surface than that of the starting material (79.246 Vs. 2.562 m2/g). Intercalated mica was treated with tetraethyl orthosilicate (TEOS) followed by calcination at 550 ° C for 6 hours generated mixed pillars Al2O3 - SiO2 and increasing the amount of silanol groups (SiOH) promoted to the hydrophobic character of this material; the characterization by XRD, FTIR and isotherms of N2 allowed to corroborate that the structure of the mica Al - Si pillared exhibited a basal spacing of 2.03 nm with a significant increase in the specific surface area 100-fold higher than that Na-2-Mica of the order of 274.125 m2/g . Functionalization of mica Al/Si pillared carried out via grafting using 3-Mercaptopropyltrimethoxysilane (MPTMS) allowed the obtaining of a material with molecules of organosilane covalently bonded to the Al - Si pillar improving its hydrophobic properties in comparison with the intercalated mica functionalized with TEOS.
The set of synthesized materials were studied for their application in the design of controlled release formulations of MCPA and Paraquat herbicides through adsorption isotherms from aqueous solutions measured over a range of solute concentrations of 0.075 – 1.000 mM and leaching in soil columns. Adsorption equilibrium Isotherm of MCPA onto the Al-pillared mica and the functionalized with thiol groups - mica showed greater affinity than the functionalized with silanol groups – mica. While the last showed greater affinity adsorption by the herbicide Paraquat. The leaching study in soil columns showed that the formulations
obtained through material - herbicide complexes allowed the reduction of the leaching of MCPA and Paraquat herbicides on the soil profile; in such a way that complexes of pillared mica - MCPA and functionalized with groups thiol mica - MCPA allowed the reduction of leaching in 54.6 and 19.0 % respectively compared to a commercial formulation of MCPA and the complex functionalized with silanols mica - Paraquat allowed the reduction of 21.8 % compared to the commercial formulation of Paraquat.",
year = 2018,
institution = "UPTC, Universidad Pedagógica y Tecnológica de Colombia",
url = "https://repositorio.uptc.edu.co/handle/001/2495",
}