Experimental and theoretical calculation investigation of 2,4-dichlorophenoxyacetic acid adsorption onto core-shell carbon microspheres@layered double hydroxide composites

Layered double hydroxides (LDHs) usually aggregate irregularly and hardly redisperse in water. Moreover, the affinity of LDHs is poor for organic compounds. In this study, three different core-shell composites, i.e. CMS@MgAl-LDH, CMS@NiAl-LDH, and CMS@ZnAl-LDH, were synthesized by direct fabrication of LDH nanoplatelets onto carbon microspheres (CMS) for the removal of the adsorbed 2,4-dichlorophenoxyacetic acid (2,4-D). The CMS@LDH composites show good water-dispersity due to the 3D hierarchical sphere structure and high affinity for 2,4-D due to the organic carbon cores that possess abundant hydrophobic compounds. It was found that the adsorption process was rapid, and the time required to reach the sorption equilibrium was within 100 min. The theoretical DFT calculation analysis suggested that the adsorption of 2,4-D on the CMS@LDH composites was dominated by pi-pi interactions, ion-exchange, and hydrogen bonding. The core-shell CMS@LDH composites can serve as a promising adsorbent that offers a rapid and effective adsorption capacity for the removal of 2,4-D in an aqueous solution.