Fixed-Bed Adsorption of As and Pb Using Carbon Nanotubes, Activated Carbon and Zeolite: Solids Characterization and Kinetic Analysis.

This study presents a fixed-bed column packed with zeolite, activated carbon, and carbon nanotubes synthesized by chemical vapor deposition, which were used to adsorb heavy metals (As and Pb) from water. Water containing 50 mg/L of the target heavy metal was filtered through the column. The materials were characterized before and after their use in the column by X-ray diffraction (XRD) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). The analyses confirmed the structural stability and functional efficiency of each adsorbent material. A removal efficiency of 100% was achieved within the first 15 min for both metals, decreasing to 45% for As and 95% for Pb. The experimental data were evaluated using the Thomas, Yoon-Nelson, and Adams-Bohart models. For arsenic, an R2 value of 0.934 was obtained, whereas better fits were observed for Pb, with all three models achieving R2 values greater than 0.98. Dynamic adsorption analysis indicated that the mass and height of the fixed bed are suitable for the operating concentration. The column arrangement proved to be more efficient for Pb retention than for As retention.