Results in Surfaces and Interfaces (Aug 2024)
The efficient elimination of lead ions from aqueous solution using MgCuAl-Layered double hydroxides@montmorillonite composite: A kinetic, isotherm and statistical analysis
Abstract
In this study, a MgCuAl-layered double hydroxide (MCA-LDH)-based montmorillonite cationic clay (MMT) composite was synthesized via a co-precipitation method and then characterized using various analytical techniques, including BET surface area, TEM, XRD, FT-IR, and SEM/EDS analysis, to confirm the successful loading of LDH onto MMT. The material was subsequently used as a novel adsorbent for Pb2+ ion removal from aqueous solution in batch mode experiments. The effects of important variables on Pb2+ adsorption were investigated, and the values of these variables were optimized using the central composite design (CCD) of the response surface methodology (RSM). The results showed that the favorable conditions for the adsorption of Pb2+ onto the MCA-LDH@MMt composite were pH 5, an initial Pb2+ concentration of 85 mg/l, and an adsorbent dose of 0.225 g/100 ml. Under these conditions, the maximum adsorption efficiency was 89.1%. Using the RSM methodology, a quadratic polynomial equation was obtained that expresses the relationship between the adsorption efficiency and the effective parameters. The results show that pH and temperature had a greater effect on the adsorption efficiency. The pseudo-second-order model kinetically well fitted the adsorption process, while external mass transfer and intra-particle diffusion controlled the adsorption mechanics. The Langmuir isotherm model fitted the isotherm to the adsorption process, yielding a capacity of 132.83 mg/g. The thermodynamic study showed that the spontaneous adsorption of Pb2+ onto MCA-LDH@MMt composites is exothermic in nature. Moreover, there was a mere 30% reduction in the removal efficiency after five consecutive regeneration cycles. In conclusion, this work demonstrated that the MCA-LDH@MMt composite could be a promising adsorbent for the treatment of aqueous solutions contaminated with heavy metals.
