Adsorption of acid red 114 and reactive black 5 in aqueous solutions on dendrimer-conjugated magnetic nanoparticles

Abstract

The adsorption of the dyes Acid Red 114 and Reactive Black 5 in aqueous solutions on polyhydroxyl dendrimer magnetic nanoparticles (Fe3O4@SiO2-TRIS) was studied in a batch system. The Fe3O4@SiO2-TRIS NPs were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. Experiments were performed under different conditions such as the initial dye concentration, adsorbent dose, and pH. The pseudo-second-order model provided a very good fit for the two anionic dyes. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherms at different temperatures, and the former agreed very well with the experimental data. However, the adsorption capacity of Fe3O4@SiO2-TRIS NPs was reduced during surface modification, which could be due to the dye occupying the binding sites of the dendrimer. Thermodynamic parameters, namely the change in free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0), were also determined.