Characterization and utilization of clay-based construction and demolition wastes as adsorbents for zinc (II) removal from aqueous solutions: an equilibrium and kinetic study.

Clay-based masonry materials such as brick and tile constitute a significant part among construction and demolition debris. These bulky materials, if not reused or recycled, are mostly landfilled for disposal. In this study, three types of these waste materials including hand-made bricks (H-bricks), machine-made bricks (M-bricks), and ceramic tiles were employed and their capability for adsorption of Zn²⁺ was investigated through batch experiments. The characterization of the adsorbents was performed by using X-ray diffraction, X-ray fluorescence, optical microscopy, scanning electron microscopy imaging, and Brunauer-Emmett-Teller analysis. The effect of initial zinc concentration, contact time, solution pH, and adsorbent particle size on Zn²⁺ adsorption onto the adsorbents was studied. The results indicated that the removal efficiency is reduced by increasing initial zinc concentration. Furthermore, M-brick and tile showed better adsorption capacity for finer sizes, whereas uptake capacity of H-brick decreased by size reduction. Both linear and nonlinear regression were then applied to the data and revealed that adsorption onto M-brick followed Redlich-Peterson isotherm, whereas the data of H-brick and tile were best modeled by Koble-Corrigan isotherm. The maximum Zn²⁺adsorption capacities for M-brick, H-brick, and tile were obtained as 3.9, 2.45, and 1.76 mg g⁻¹, respectively. Moreover, the kinetic data were modeled by using four well-known models. The adsorption kinetics of Zn²⁺ onto M-brick and tile was best represented by Elovich, and kinetic behavior of H-brick was found to obey the pseudo-second-order model. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 777-789, 2014 [ABSTRACT FROM AUTHOR]