Nanocomposite of functionalized halloysite and Ag(0) decorated magnetic carbon dots as a reusable catalyst for reduction of dyes in water

A new magnetic, catalytic nanocomposite of Hal-MT-Cys-Ag/MNCD was fabricated and utilized for catalyzing reductive de-colorization of methyl orange and rhodamin B in aqueous media at room temperature. To prepare this material, Cl-functionalized halloysite nanoclay was successively reacted with melamine and 2,4,6-trichloro-1,3,5-triazine to furnish multi-nitrogen containing ligand on halloysite surface. Then, magnetic carbon dots were crafted through a facile method and decorated with Ag nanoparticles and cysteine to furnish Cys-Ag/MNCD species. The final nanocomposite was obtained via incorporation of this latter species onto functionalized halloysite. This new composite was characterized through the XRD, TEM, BET, FTIR, TGA, EDX, and mapping analyses. The catalytic experiments confirmed that low loadings of the Hal-MT-Cys-Ag/MNCD composite reduction of both dyes were performed in similar to 1 min. This material could also be readily collected from the reaction media magnetically and displayed excellent recyclability with a slight decrease in its activity of at most similar to 6% up to 8 cycles. The kinetic and thermodynamic study of de-colorization reactions emphasized high catalytic performances of the synthesized nanocomposite. More precisely, activation energy, enthalpy, and entropy were determined to be 48.15 kJ mol(-1), 45.65 kJ mol(-1), and -124.61 J mol(-1) K-1; respectively for the methyl orange while the corresponding values for the rhodamine B were found to be 11.03 kJ mol(-1), 8.53 kJ mol(-1), and -249.93 J mol(-1), K-1.