Synthesis and characterization of hexagonal Mg[sbnd]Fe layered double hydroxide/grapheme oxide nanocomposite for efficient adsorptive removal of cadmium ion from aqueous solutions: Isotherm, kinetic, thermodynamic and mechanism

Abstract

Heavy metal pollution in water is a major concern due to its bioaccumulation, non-biodegradability, and high toxicity. Long-term cadmium (Cd(II)) ion exposure could have an adverse impact on human health. Because, natural water bodies contain Cd(II) pollution at low concentrations, the treatment of Cd(II)-polluted water should be treated as micro-polluted water. It is critical to develop an effective water purification procedure to remove Cd(II) from micro-polluted water. In the present research, Mg[sbnd]Fe binary layered hydroxide/graphene oxide (Mg[sbnd]Fe LDH/GO) nanocomposite was synthesized, characterized and used for efficient Cd(II) adsorption. The adsorption process was investigated in terms of pH influence, kinetic behavior, isotherm equilibrium curves, and estimation of thermodynamic parameters. The characterization results showed that Mg[sbnd]Fe LDH/GO, which is composed of crystalline Mg[sbnd]Fe binary hydroxide and amorphous GO structures, has a considerable surface area (223 m2/g) and has a plate-like hexagonal structure with even forms and lamellar aggregates. Cd(II) adsorption was favoured on the Mg[sbnd]Fe LDH/GO surface in neutral circumstances at 25 °C. The pseudo-second-order kinetic behavior was adequately described, although the isotherm equilibrium curves fitted the Langmuir isotherm, with a high maximum uptake capacity of 174.83 mg/g. Chemisorption-controlled spontaneous and endothermic reactions occurred, which was confirmed by thermodynamic studies. Further, the surface interaction mechanism was investigated using the XPS analysis of spent catalyst. The Mg[sbnd]Fe LDH/GO nanocomposite is efficient to treat Cd(II) with a removal percentage of 99%. It can be reused more than four times without losing its original capacity and stability. Overall, the Mg[sbnd]Fe LDH/GO nanocomposite exhibited high potential to be utilized as an adsorbent for the removal of pollutants from actual contaminated water samples.