Synthesis of Chitosan/Halloysite Nanotubes Composite Aerogel as Adsorbents

Abstract

A novel chitosan/halloysite nanotubes composite aerogel (CS/HNTs) was prepared by incorporation of halloysite nantubes into crosslinked chitosan network via vacuum freeze drying. Nitrogen adsorption—desorption isotherms analysis show it has a specific surface area of 51.24 m2g–1 with an average pore diameter of 8.96 nm, the resulting CS/HNTs was used as an efficient adsorbent material for removal of Cr(VI) from water. The adsorption performance of CS/HNTs for Cr(VI) under different experimental conditions were studied. The adsorption experiments show that the adsorption capacity of CS/HNTs composite aerogel for Cr(VI) increases slightly with the increase of temperature and the optimum pH value for Cr(VI) adsorption is found at pH = 2. The maximum adsorption capacity of Cr(VI) was estimated to be 49.85 mg g–1 with the optimum adsorbent dose of 0.10 g at 30 °C. The adsorption kinetics of the assay exhibit a strong correlation with the mathematical model known as the pseudo—second—order equation. The experimental results exhibit a high level of conformity with the Langmuir isotherm, providing evidence of a state of equilibrium. Moreover, detailed computations have been conducted to ascertain crucial thermodynamic parameters such as the change in Gibbs free energy (ΔG°), modification in enthalpy (ΔH°), and variation in entropy (ΔS°). These calculated parameters provide compelling evidence that the adsorption of Cr(VI) onto CS/HNTs is a spontaneous process driven by thermodynamic favorability. Furthermore, the process is characterized by the absorption of heat from the surroundings, indicating an endothermic nature.