Insights into the adsorption of lead ions by Mg-Al LDH doped activated carbon composites: Implications for fixed bed column and batch applications

In this study, we developed granular activated carbon-doped Mg-Al LDH composites (MgAl@AC) with an Mg:Al molar ratio of 3:1 using the co-precipitation method. The MgAl@AC was characterized using FE-SEM, BET-SA, TGA, XRD, and FT-IR, before and after lead adsorption. Through fixed-bed column and batch adsorption methods, we evaluated the impact of pH, adsorbent amount, initial Pb(II) concentration, temperature, duration of contact, and presence of competing ions, on the adsorption capacity of MgAl@AC. The MgAl@AC demonstrated a maximum Langmuir adsorption capacity of 94.6 mg/g for Pb(II). Through characterizing the Pb(II)-loaded material, the ion exchange, inner-sphere complexation, and electrostatic attraction were identified as the potential mechanisms of Pb(II) adsorption by MgAl@AC. The Yoon-Nelson and Clark models fit the breakthrough curve well, suggesting that adsorption occurs in surface and pore diffusion-controlled manners. Our findings indicated that MgAl@AC had excellent adsorption capacity, good selectivity, and fast kinetics, highlighting its potential for water treatment applications.