Enhancement of Cd2+ removal on CuMgAl-layered double hydroxide/montmorillonite nanocomposite: Kinetic, isotherm, and thermodynamic studies
Fatin A. Alnasrawi, Ahmed A. Mohammed
Abstract
In recent decades, great progress has been made in the application of adsorption processes to mitigate water pollution by hazardous metals. However, developing a highly efficient adsorbent is essential if the adsorption process is to be successfully applied in practical applications. In this study, a CuMgAl-layered double hydroxides/montmorillonite nanocomposite (CuMgAl-LDH/MMt) was prepared, characterized, and then used as a novel adsorbent for adsorption of Cd2+ ions from wastewater. The effects of initial pH, adsorbent dosage, agitation speed, particle size, contact time, initial Cd2+ concentration, and temperature on the pollutant removal efficiency were analyzed. An isotherm model reading revealed that the results of the experimental work were a good fit with the Freundlich model. The maximum adsorption capacity was reached at 174.87 mg/g under optimal conditions (pH 5, dosage of 0.02 g/l, agitation speed of 150 rpm, and particle size of 87 μm) at 50 ppm after 120 min of adsorption time. Kinetic studies showed that pseudo-second-order models were best fitted to the adsorption data, indicating heterogeneous adsorption of Cd2+ ions onto multilayer CuMgAl-LDH/MMt sites, and that the adsorption process is primarily chemical adsorption. Thermodynamic parameters (ΔSo, ΔHo, and ΔGo) demonstrated that Cd2+ adsorption onto adsorbent was exothermic and spontaneous. Moreover, the synthesized adsorbent can be recovered after five consecutive cycles with a minimal reduction in the adsorption ability of 29.56 %. The study showed that specific heavy metals can be removed from aqueous solution by a newly prepared adsorbent due to its excellent morphology, high stability under a wide range of conditions, recyclability, and high adsorption capacity.