Adsorption Kinetics of Acid Dye Acid Red 88 onto Magnetic Multi‐<scp>W</scp>alled Carbon Nanotubes‐<scp>F</scp>e₃<scp>C</scp> Nanocomposite

Abstract

Magnetic multi‐walled carbon nanotubes‐Fe 3 C nanocomposite was synthesized by chemical vapor deposition process and was used as an adsorbent for the removal of acid dye Acid Red 88 (AR88) from aqueous solution. The effects of various parameters such as initial AR88 concentration (10–58 mg L −1 ), pH (3.1–11.3) and temperature (20–60°C) were investigated. The properties of this adsorbent were characterized by X‐ray diffraction, high‐resolution transmission electron microscopy, energy dispersive X‐ray analysis, fourier transform IR, N 2 adsorption/desorption isotherms, and particle size distribution by laser diffraction. The experimental data were analyzed by the Langmuir and Freundlich models of adsorption. Equilibrium data fitted well with the Freundlich model. Kinetic adsorption data were analyzed using the Lagergren pseudo‐first‐order kinetic model, the pseudo‐second‐order model and the intraparticle diffusion model. The regression results showed that the adsorption kinetics was more accurately represented by pseudo‐second‐order model. Thermodynamics parameters, Gibbs free energy (Δ G 0 ), enthalpy (Δ H 0 ), and entropy (Δ S 0 ), were calculated. All Δ G 0 values were negative. The values of Δ H 0 and Δ S 0 were −4.70 and −7.98 J mol −1 K −1 , respectively, indicating that adsorption of AR88 onto magnetic multi‐walled carbon nanotubes nanocomposites was spontaneous and exothermic in nature.