Isotherm Investigation and Assessment of the Adsorption Efficacy of Zinc Ions on Natural Zeolite and Zeolite Modified with Anionic (SDS) and Cationic (CTAB) Surfactants

Abstract

This investigation examines the efficacy of natural clinoptilolite zeolite and its modified variants, utilizing the cationic surfactant  hexadecyltrimethylammonium bromide (CTAB) and the anionic surfactant sodium dodecyl sulfate (SDS), for the removal of zinc ions  from aqueous solutions. Solutions containing zinc at varying concentrations were formulated, and the residual ion concentrations  post-adsorption were assessed utilizing atomic absorption spectroscopy. The findings demonstrate that surface modification with  anionic SDS surfactant dramatically enhances adsorption performance, achieving an exceptional capacity of 18.56 mg/g at 200 mg/L initial concentration. This represents a substantial threefold enhancement compared to natural zeolite (5.57 mg/g) and a notable  fivefold superiority over CTAB-modified zeolite (3.85 mg/g), highlighting the crucial influence of surfactant charge characteristics. The  adsorption isotherm analyses suggested that the adsorption process conformed to a monolayer model. Nonlinear regression analysis of the empirical data against various isotherm models indicated that the Fritz-Schlunder model offered the most accurate representation for the natural zeolite, while the Weber-van Vliet model exhibited optimal conformity for both surfactant-modified  systems. In summary, the results of this study indicate that the modification of clinoptilolite zeolite with the anionic surfactant SDS constitutes a promising  approach for augmenting the efficiency of zinc ion removal from aqueous systems.