Preparation of well-structured hybrid material through ion exchange of chloride by 2,4,5-trichlorophenoxyacetic herbicide in a layered double hydroxide

The [Zn-2-Al-Cl] layered double hydroxide (LDH) was used to successfully exchange chloride ions by 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), as a model of the carboxylate herbicide family. The total exchange was obtained after 6 h of stirring with a 2,4,5-T/Cl molar ratio of 10 and a pH of 7. The characterization by various techniques (XRD, FTIR, TG-DTG and SEM) indicates that this exchange led to the production of a new stable hybrid LDH phase intercalated by the herbicide. The structural analysis of the material, based on the interlayer distance of 1.855 nm, indicates that the 2,4,5-T anion takes a vertical arrangement in a double layer. The cohesion of the structure is ensured by hydrogen bonds between the carboxylate group of the herbicide and the hydroxyl groups of the LDH sheets. The exchange causes a modification of the type of symmetry from a 3R stacking mode for [Zn-2-Al-Cl] (space group R3m) to a 2H for [Zn-2-Al-2,4,5-T] (space group P63/mmc). This result confirms the already proven use of LDH materials as efficient anion exchangers for the trapping and elimination of this type of pollutant from wastewater.