Biosorption of Heavy Metals with Eggshell

Abstract

The main objective of this study was to determine the heavy metal (Pb, Zn, Cd) remediation capacity in synthetic aqueous solutions using thermally transformed eggshell residues, and to establish a rigorous technical comparison between the analytical methodologies used for monitoring: complexometric titration (EDTA) and instrumental spectrometry (AAS). For this purpose, poultry biomaterial was collected and processed, undergoing a calcination process at 900°C to obtain activated Calcium Oxide (CaO). A batch factorial experimental design was applied, evaluating critical variables: pH (6.5, 7.5, 8.5), adsorbent dosage (2.0, 4.0, 6.0 g/L), and contact time (30, 90, 150 min). The quantification of residual metal ions was performed using a dual strategy differentiated by concentration and toxicity levels.Through statistical characterization and data analysis, removal schemes and adsorption kinetics were developed, allowing for the identification of maximum efficiencies of 88.1% for Pb, 84.07% for Cd, and 79.2% for Zn under alkaline conditions (pH 8.5), driven by synergistic mechanisms of chemical precipitation and electrostatic attraction on the biosorbent surface. Finally, based on the characteristics observed during the experimental phase and analytical validation, it was concluded that while Atomic Absorption Spectroscopy (AAS) is indispensable for detecting Cadmium traces due to its high sensitivity and selectivity regarding the calcic matrix, Complexometric Titration with EDTA remains a robust and economically viable alternative for controlling processes with high Zinc and Lead loads, provided that interferences are strictly managed through chemical masking protocols.