Adsorption characteristics of Zn (ii), Pb (ii) and Cd (ii) ions from aqueous solution onto natural clay minerals

Abstract

Heavy metal contamination represents a significant environmental issue with adverse implications on ecosystems and human health. Natural clay minerals have unique properties providing good binding sites that make them effective in the removal of metal ions from water and other solutions. Information on the type of clay and sorption of heavy metal ions onto local natural clay minerals from Itu is scarce. Since the adsorption capacities vary depending on the metal and the type of clay, this study focuses on the nature of clay and the sorption mechanisms of Zn, Pb and Cd ions onto clay minerals. Analytical techniques, including X-ray diffraction, X-ray fluorescence (XRF) spectroscopy, and atomic absorption spectroscopy were employed to determine some quality parameters, mineral composition and concentration of clay mineral under investigation. The preliminary analysis, the XRD data revealed the dominance of kaolinite and quartz in the clay samples. Results of elemental analysis - CHNS showed significant levels ranging from 41.06 to 49.85% for Carbon, 3.60 to 4.97% for Hydrogen, 0.51 to 1.74% for Nitrogen and 0.23 to 0.89 % for Sulphur, and varies between 45% and 20%. Results showed that the Freundlich equation characterized Zn²⁺, Pb²⁺ and Cd²⁺ sorption data with the regression coefficient, R² values ranging between 0.1960 - 0.8655, 0.0106 - 0.8878 and 0.5852 - 0.9368 respectively for all four clay samples. Since the choice among model equations is often made based on the goodness of fit data, therefore, the Freundlich isotherm model provided the best choice for Zn, Pb and Cd sorption calculation against that of Langmuir model. Therefore, this study lays a solid foundation for investigating the efficacy of these minerals in adsorbing heavy metals such as Zn, Pb and Cd ions, vital for developing effective strategies in environmental remediation and water purification.