Experimental study and modeling of Pb2+ sorption by calcined ni/mo hydrotalcite in a fixed-bed column

Abstract

This study investigates the continuous flow behavior of a fixed-bed column for Pb2+ removal using calcined Ni/Mo hydrotalcite. The sorbent was characterized using FTIR, XRD, TEM, and BET surface area analysis to evaluate its removal efficiency. Experiments explored different operating conditions, such as feed flowrate (5–20 mL/min), inlet Pb2+ concentration (20–50 mg/L), bed height (10–15 cm), and solution pH (3–8). Results show that exhaustion time increased with higher bed heights, while lower flowrates, and inlet Pb2+ concentrations extended the column’s lifespan. Enhanced removal capacities were observed at higher Pb2+ concentrations and bed heights, as well as with lower flowrates, particularly at an optimal solution pH of 6, due to an increased driving force. Regeneration tests demonstrated good sorbent reusability for up to five consecutive sorption–desorption cycles without affecting its removal efficiency. Therefore, calcined Ni/Mo hydrotalcite shows promising potential for treating Pb2+-containing wastewater. Analytical solutions for diffusion mechanisms were applied to predict the experimental data under various conditions, revealing that surface diffusion accurately describes the sorption kinetics (average percentage errors <5%), while pore diffusion can be neglected. The proposed model effectively predicts column performances for scaling up wastewater treatment operations.