A Unique Modified Eggshell Method as a Model to Reduce and Remove Copper(II) from Aqueous Solutions for Water Treatment

Abstract

The aim of this study was to investigate the removal of Cu2+ using eggshells and iron-modified eggshells. Batch adsorption experiments were conducted to assess the impact of various operational parameters, including contact time, pH, isotherms, and kinetics. The samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). XRD analysis confirmed the presence of crystalline phases, specifically trigonal and hexagonal structures, in both eggshell samples. The addition of iron resulted in a reduction in the average crystallite size from 33.157 nm to 16.086 nm. The FTIR spectra exhibited a carbonyl peak at 1804 cm-1. The results indicated that Cu2+ adsorption on eggshells occurred rapidly, reaching equilibrium within 80 min, with an optimal pH range of 6.0 to 7.0. Furthermore, the modified eggshells demonstrated superior Cu2+ removal compared to unmodified eggshells due to the increased external surface area. The copper concentration on the eggshell surface increased from 0% to 94.58%, suggesting an ion exchange between iron and copper within the modified eggshell. The experimental data exhibited a better fit with the Freundlich isotherm model, indicating the presence of heterogeneous adsorption sites for Cu2+. The kinetics of adsorption followed a pseudo-second-order rate equation. This study highlights the efficacy of using eggshells, particularly iron-modified eggshells, as a cost-effective and accessible method for the efficient removal of heavy metals like Cu2+ from drinking water or industrial wastewater.