Adsorption and removal of cationic and anionic surfactants using zero-valent iron nanoparticles

Abstract

This study is dedicated for adsorption of surfactants on Zero-Valent Iron (nZVI). As a nano-adsorbent, nZVI is synthesized by simple and economic method then characterized using various surface and structural techniques. These include; transmission electron micrograph (TEM), field emission scanning electron microscopy (FE-SEM), X-ray diffraction spectroscopy (XRD), BET surface area determination and Zeta potential (ζ–potential) of the nZVI. Nano-ZVI is tested as potential adsorbent for the removal of a cationic surfactant, hexadecylpyridinium chloride surfactant (HDPCl) and anionic surfactant, sodium dodecylbenzene sulfonate (DBS) from dilute solutions. The effects of different experimental parameters such as the amount of nZVI, the initial surfactant concentration, pH, shaking speed, and temperature on the system performance have been studied. The equilibrium adsorption isotherms of the HDPCl and DBS on the nZVI have been fitted with Langmuir model. The obtained thermodynamic parameters demonstrate the easiness and spontaneity of the adsorption process with favorable adsorption extent to the HDPCl compared to the DBS. This was attributed to the difference in the molecular structures. Kinetic studies show that the experimental data for HDPCl and DBS follows the Lagergren first-order kinetics. Reusing of spent nZVI is possible with adequate removal efficiencies of the surfactant molecules through multiple regeneration cycles.