Simultaneous removal of phenoxy herbicides, 2-methyl-4-chlorophenoxyacetic acid and 2,4-dichlorophenoxyacetic acid from aqueous media by magnetized MgAl-LDH@Fe3O4 composite: application of partial least squares and Doehlert experimental design

Abstract

Today, the excessive and increasing use of phenoxy family herbicides such as 2-methyl-4-chlorophenoxyacetic acid (MCPA) and (2,4- dichlorophenoxy) acetic acid (2,4-DCPA) for reasons such as indestructibility and pollution of groundwater resources is one of the most important environmental problems. Pesticide adsorbents like layered double hydroxides (LDHs) are commonly utilized due to their straightforward synthesis, substantial specific surface area resulting from their layered structure, and the potential for surface modification. These natural minerals serve as effective options for adsorption. In this study, a co-precipitation approach was used to create an MgAl-LDH@Fe₃O₄ magnetic adsorbent for the simultaneous removal of MCPA and 2,4-DCPA herbicides from aqueous solution. Using different techniques such as TGA, XRD, FESEM, EDS and zeta potential, we investigated the properties of the prepared adsorbent. The partial least squares method measures the concentration of each herbicide in their mixture. The optimization of MCPA and 2,4-DCPA simultaneous adsorption by LDH was achieved through Doehlert experimental design and the response surface method. The optimal conditions for absorption were determined to be an adsorbent dose of 40.20 mg L^-1, a pH of 6.8, and an initial concentration of 28.35 mg L^-1. In this work, the equilibrium, kinetic, and thermodynamic absorption data of the absorption process were studied, and the obtained results were well described by the Freundlich model, and the pseudo-second-order model, respectively, and showed the spontaneity of the absorption process in this research. The highest absorption capacities of MCPA and 2.4-DCPA herbicides on the prepared adsorbent were 134.50 and 131.30 mg g^-1, respectively.

Graphical abstract