Rapid and effective removal of heavy metal ions from aqueous solution using nanostructured clay particles

Abstract

Natural mineral clays were extracted from the Syahkalahan mine and used as adsorbent matrices with the aim of removing lead ions (Pb) from drinking water. In this study, the chemical structure, surface morphology, and surface area of prepared clays were characterized using various techniques, including inductively coupled plasma-mass spectrometry, powder X-ray diffraction, field emission scanning electron microscopy (FE-SEM), and Brunauer–Emmett–Teller surface porosity analysis. Characterization results revealed that silica is the dominant chemical component of the clay. FE-SEM images of clay samples confirmed that the average size of clay’s particles is in the nanoscale range. The results for two different clays showed ion removal efficiency of > 92% under the following experimental conditions: clay weight = 1 g, [Pb(II)] =100 ppm, pH = 7, and time = 120 min. Additionally, for the clay samples exhibiting the best removal efficiency, the ion removal efficiency was studied as a function of reaction parameters such as pH, and concentration of both adsorbent and metal ions. To evaluate the adsorption kinetics and mechanism of ion adsorption, kinetic modeling and isotherm models (Langmuir and Freundlich) were performed under the optimized conditions. Based on the fitting analysis, it can be inferred that the adsorption kinetic follows a pseudo-first-order model and the Langmuir isotherm accurately describes the adsorption mechanism of Pb(II) ions on the clays’ surface. These findings further highlight that these inexpensive natural clays can be used as excellent matrices for the adsorption of heavy metal ions in various water treatment systems.

Keywords

• Natural clays
• Heavy metal ions
• Natural adsorbent
• Adsorption capacity
• Langmuir and Freundlich isotherms