Adsorption Potential, Kinetic, and Thermodynamic Studies of Halloysite-Based Magnetic Field-Responsive Adsorbent

Despite the excellent potential of halloysite nanotubes (HNT) as an adsorbent for water-soluble molecules, their high aqueous dispersity makes it difficult to separate them from the aqueous media after adsorption. This study explores the potential of developing HNT-based magnetic field-responsive adsorbent to facilitate the separation of the HNT from aqueous media after adsorption. Fe 3 O 4 was successfully synthesized from iron salt precursors using maize leaves extracts as reducing and capping agents after which different weight percentages were used to develop Fe 3 O 4 –HNT composites. The developed composite materials were characterized using x-ray diffraction, ultra violet–visible light spectrophotometry, scanning electron microscopy-energy dispersive x-ray spectroscopy, Fourier-transform infrared spectroscopy, and thermal gravimetric analysis. The adsorption capacity of the Fe 3 O 4 –HNT composite was examined using methylene blue dye and found to be dependent on the percentage of HNT in the Fe 3 O 4 –HNT composite. The adsorption kinetics of methylene blue by Fe 3 O 4 –HNT was best fitted with the pseudo-second-order adsorption kinetic model. The equilibrium adsorption of methylene blue was best described by the Freundlich isotherm model and the inter particle diffusion model describes the rate-controlling steps. The thermodynamic analysis of the adsorption process revealed that ΔG° , ΔH° , and ΔS° values were dependent on temperature and the amount of HNT in the Fe 3 O 4 –HNT composite. The results from the study revealed the potential application of HNT-based magnetic f ield responsive adsorbent in water treatment technologies.