Adsorption of Pb(II) from Water onto ZnO, TiO₂, and Al₂O₃: Process Study, Adsorption Behaviour, and Thermodynamics

Abstract

This study is aimed at comparing the use of zinc oxide (ZnO), titanium dioxide (TiO2), and aluminium oxide (Al2O3) for removing lead ions from water through adsorption. The point of zero charge was obtained for ZnO, TiO2, and Al2O3 and was found to be 7.3, 7.1, and 9.0, respectively. The effect of pH, adsorbent dose, contact time, initial concentrations, and temperature was investigated in batch experiments. The optimal conditions obtained were 7, 2 g/L, 120 mins, 100 ppm, and 41°C, respectively, where the optimal removal efficiencies were 98.43%, 96.45%, and 85.50% for ZnO, TiO2, and Al2O3, respectively. In addition, analyses of adsorption kinetics, mechanisms, isotherms, and thermodynamics were performed. The adsorption kinetics of Pb(II) were compared to popular models, and it was found that the pseudo-second-order (PSO) model best fitted the Pb(II) uptake for all adsorbents at correlation coefficient ( R 2 ≥ 0.96 ). The adsorption isotherms of Pb(II) were also compared to popular models, and it was found that the Pb(II) uptake by TiO2 and ZnO was well-described by the Langmuir model ( R 2 ≥ 0.96 ) with maximum adsorption capacities of 55.04 and 58.88 mg/g, respectively. On the other hand, the behaviour of Al2O3 is described more accurately by the Dubinin-Radushkevich (D-R) model ( R 2 = 0.96 ), and the maximum adsorption capacity was 53.64 mg/g. The isotherm analysis proved that the limiting step of the adsorption process is the film diffusion mechanism. In addition, studying the heat of adsorption of Pb(II) implied that the adsorption is endothermic due to the positive values of enthalpy ( Δ H ° ≥ 30 ) for all adsorbents. The absorbents were characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to study the morphology of surfaces and the chemical characterization of the adsorbents to ensure that adsorption is achieved. ZnO showed better performance for the uptake of lead followed by TiO2 then Al2O3.

Inhibitory Effect of Chromium Shock Loads on Integrated Fixed-Film Activated Sludge (IFAS)

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Synthesis of Low Cost Activated Carbon from Agriculture Wase for Wastewater Treatment

“…Although biological wastewater is considered the most widely used system to treat wastewater, it is not suitable for many industrial wastes that contain inhibitory substances for the growth of bacteria [1]. Therefore, adsorption is considered an vital process in industrial wastewater treatment and can be regarded as the most cost-effective and easy process for removing heavy metals from industrial wastewater [2,3]. Activated carbon has been the adsorbent extensively used over the past years.…”

Template-Free Synthesis of Phosphorus/Nitrogen-Doped Mesoporous Titania Materials with Excellent Adsorption for Lysozymes

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