Layered double hydroxides as adsorbents and carriers of the herbicide (4-chloro-2-methylphenoxy)acetic acid (MCPA): Systems Mg-Al, Mg-Fe and Mg-Al-Fe

摘要

Hydrotalcite-like compounds [Mg3Al(OH)8]Cl·4H2O; [Mg3Fe(OH)8]Cl·4H2O; [Mg3Al0.5Fe0.5(OH)8]Cl·4H2O (LDHs) and calcined product of [Mg3Al(OH)8]Cl·4H2O, Mg3AlO4.5 (HT500), were studied as potential adsorbents of the herbicide MCPA [(4-chloro-2-methylphenoxy)acetic acid] as a function of pH, contact time and pesticide concentration, and also as support for the slow release of this pesticide, with the aim to reduce the hazardous effects that it can pose to the environment. The information obtained in the adsorption study was used for the preparation of LDH-MCPA complexes. The results showed high and rapid adsorption of MCPA on the adsorbents as well as that MCPA formulations based on LDHs and HT500 as pesticide supports displayed controlled release properties and reduced herbicide leaching in soil columns compared to a standard commercial MCPA formulation. Thereby, we conclude that the LDHs employed in this study can be used not only as adsorbents to remove MCPA from aqueous solutions, but also as supports for the slow release of this highly mobile herbicide, thus controlling its immediate availability and leaching.