Natural cellulose fibers (Agave Americana L. ASPARAGACEAE) impregnated with magnetite nanoparticles as a novel adsorbent of mercury (Hg) in aqueous solutions

Abstract

High mercury levels from industrial and natural sources necessitate effective water mercury removal methods owing to human and ecosystem toxicity risks. This study addresses the adsorption of Hg ions onto mixed-valent magnetite nanoparticles (MNPs) owing to their high surface area, reactivity, and magnetic recovery ability. The adsorption capacity of MNPs is influenced by the morphological characteristics. The influence of the vegetable fiber surface charge in magnetite, along with the change in pH, on the Hg ion adsorption process by MNPs remains an open question. The adsorption capacities of the synthesized MNPs and Cabuya fibers (Agave Americana L. ASPARAGACEAE) impregnated with magnetite nanoparticles (FC-MNPs) were compared. The synthesis and impregnation of MNps were performed using the chemical coprecipitation method with ferrous and ferric chloride as precursor solutions. The composition, surface properties, and morphology of the synthesized adsorbents were investigated by scanning electron microscopy (SEM) coupled with an energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and Raman spectroscopy (RS), which provided evidence that MNps reached an approximate diameter of 19 nm. Both adsorbents were used for the removal of Hg (II) at different initial pH values, times, temperatures, adsorbent dosages, and analyte concentrations. FC-MNPs and MNPs were able to achieve approximately 93% and 83% Hg (II) removal, respectively, under the following experimental conditions: the adsorbent dose 0.5 g, Hg (II) 10 mg/L, pH 5.0, stirring speed of 150 rpm, temperature of 25 °C, and equilibrium time of 4 h. Equilibrium data were evaluated by fitting the Langmuir and Freundlich isotherm models to the experimental conditions. Additionally, kinetic studies of pseudo-first and pseudo-second order were conducted to understand the mechanism of interaction between the adsorbent and the metal ions. The results show that FC-MNPs has a maximum adsorption capacity of Hg(II) of 4.95 mg/g of adsorbent, and that the reaction system follows pseudo-second order kinetics and the Freundlich isotherm model. Finally, the experimental results reported in this work show that cabuya fibers impregnated with MNPs have an important impact on the immobilization of aqueous contaminants. This offers a new method for developing novel nanocomposite adsorbents for the removal of metallic ions from wastewater.