Adsorption of arsenate by hexadecylpyridinium bromide modified natural zeolite

Abstract

The presence of arsenate (As(V)) anions in various sources of water is a prominent issue since the toxicity of this species can result in death if this species are taken either over a long period of time or present in high concentrations. In this study, a natural zeolite of the mordenite type was modified by cationic surfactant hexadecylpyridinium bromide (HDPB) to make more efficient sites for adsorption of As(V) from aqueous solutions. The natural zeolite and surfactant-modified natural zeolite (HDPB-zeolite) were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FTIR), and BET specific surface area. The analysis of XRD revealed that the natural zeolite consists of quartz and mordenite phases, while the FTIR analysis revealed that HDPB cations has been incorporated into the natural zeolite’s structure via electrostatic interaction and van der Waals forces. The results showed that the unmodified natural zeolite had little affinity for the As(V) anionic species, while the HDPB-zeolite showed significant ability to remove this anion from the aqueous solutions. The highest arsenates adsorption efficiency was obtained from the solution of pH 7 because of the dominance of the univalent species of anion. The adsorption equilibrium data were analyzed by both Freundlich and Langmuir isotherm models and the data were best fitted with the Freundlich isotherm model. The study concluded that the HDPB-zeolite can be used as alternative sorbent to remove As(V) species from water.