Adsorption of Pb2+ ions by MgCuAl-layered double hydroxides@montmorillonite nanocomposite in batch and circulated fluidized bed system: Hydrodynamic and mass transfer studies

In this study, montmorillonite cationic clay coated with MgCuAl-Layered double hydroxides nanoparticles was investigated for its capacity to adsorb lead ion (Pb 2 + ) from aqueous solutions. Montmorillonite, MgCuAl-LDH, and the prepared MgCuAl- Layered double hydroxides/montmorillonite nanocomposite (MCA - LDH @MMt) were characterized using various mechanism including BET surface areas, XRD, FTIR, and SEM/EDS analysis. The adsorption behavior of MCA - LDH @MMt toward Pb 2 + ion was studied using batch and continuous flow systems. pH, contact time, initial Pb 2 + concentration, MCA - LDH @MMt dose and particle size, agitation speed, and temperature were examined in the batch system. The higher removal efficiency of Pb 2 + was reported at pH 6 at 70 mg/l initial concentration and 0.2 g/100 ml as best adsorbent dose. Temperature affects the efficiency of Pb 2 + removal and decreases as temperature increases, this mean it is exothermic in nature. The negative value of Delta G degrees increases with increasing temperature, demonstrating that the removal process of Pb 2 + on MCA - LDH @ MMt becomes unfavorable at high temperature. The Langmuir model displays that the maximum adsorption capacity was 132.85 mg/g. While the pseudo-second-order model better simulates the lead kinetics data, and sorption rate parameters value showing that adsorption process was chemisorption. A three-phase circulated fluidized bed column, commonly known as a gas-liquid-solid circulating fluidized bed, was adopted in continuous elimination of Pb 2 + , four influencing variables were studied, including: liquid and air flow rate, bed height, and initial concentration. Minimum fluidized velocity (U mlf ) is affected by particles size and density, gas velocity, and bed height, while the mass transfer coefficient of this system increases as U l increases. The adsorption efficiency of Pb 2 + in a continuous system increased when the liquid flow rate decreased and the bed height increased. The time required for MCA - LDH @MMt to reach saturation increases as the bed height increases as well as the air flow rate.