Sodium-Modified Vermiculite for Calcium Ion Removal from Aqueous Solution

Abstract

The treatment and recuperation of hydric resources portray recurrent challenges and demand alternative processes and technologies. The removal of hardness and metal ions from water are necessary in certain sources of human consumption and for industrial purposes. In this work, sodium-modified vermiculite was investigated toward the removal of calcium ions in aqueous medium. The effects of adsorbent dosage, contact time, initial concentration of calcium ions, initial pH, and temperature were systematically studied for both raw and modified vermiculite. pH 10 was shown to be the most appropriate to conduct the experiments. Raw, sodium-modified, and postadsorption vermiculite were characterized by microstructure analysis (scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray fluorescence, and X-ray diffraction). The maximum adsorption capacity was found in sodium-modified vermiculite, resulting in about 80 mg g–1. Kinetic studies were carried out to relate the experimental data to pseudo-first-order, pseudo-second-order, and Elovich models. Isotherm models (Freundlich, Langmuir, and Redlich–Peterson) were employed to describe the softening process, and thermodynamic parameters ΔG°, ΔH°, and ΔS° were determined. Results revealed a spontaneous endothermic adsorption process with pseudo-second-order kinetics and corroborated the sodium-modified vermiculite adequacy for water softening.

Ion exchange and adsorption of cadmium from aqueous media in sodium-modified expanded vermiculite

“…In this case, previously, there were predominantly divalent ions (Mg 2+ ) that were replaced by monovalent ions (Na + ). Similar XDR patterns were obtained in works that aimed the investigation of vermiculite and modified vermiculite (Lima et al 2019;Moraes et al 2019 andAnjos et al 2014). After sample contamination by cadmium (Fig.…”

“…The sodification process of the EV leading to the VNa formation decreases the structural organization of the solid, inducing decreases in the reflections intensity and clay crystallinity in its sodified form (VNa). This fact probably occurs due to the insertion of the hydrated ion of the alkali metal that causes an enlargement in the clay interlayer space, which can be observed by the increase of the basal space of EV and VNa: 1.42 and 1.45 nm, respectively Lima et al 2019;Moraes et al 2019;Anjos et al 2014). The observed changes confirm that the sodification process was successfully carried out by leaching and ion exchange of the ions present in the region between layers.…”

“…Almeida also observed that the clay treatment with sodium improved the adsorptive properties in the nickel and copper ion removal, since there was an increase of exchangeable Na + in the Bofe bentonite surface. Lima et al (2019) achieved better adsorptive capacities for Ca 2+ removal with sodiummodified vermiculite, compared with raw vermiculite. The authors applied a different sodification process from the one applied in the present work, sodifying the raw vermiculite only in saline solution, and the water softening process was performed at pH 10.…”

“…The FTIR spectra are characteristic of trioctahedral phyllosilicates such as vermiculite (Russell and Fraser 1994). The peaks in the ranges 3411-3483 cm −1 and 1631-1644 cm −1 are observed due to the stretching and bending vibration of the O-H of water molecule adsorbed by hydrogen bonds (Moraes et al 2019;Lima et al 2019;Marcos and Rodríguez 2014). Other ranges are observed between 1002 to 1004 cm −1 that occur because of Si-O-Si and Si-O-Al stretching bond vibrations, 665 to 673 cm −1 that is related to bending vibration of Si-O, and 441 to 459 cm −1 which is attributed to bending of Si-O-R vibrations (considering R metals like Mg, Al, Fe, and Si) (Marcos and Rodríguez 2014).…”

Poly(lactic acid)/vermiculite‐g‐polyisoprene nanocomposites based on thiol‐ene click chemistry: performance, shear crystallization and Rheonaut technology analysis

“…One of the significant nanolayered silicate materials is expandable vermiculite (VMT) formed by mica alteration in nature, which is composed of an aluminium oxide octahedral sheet and two adjacent tetrahedral sheets. VMT has the functions of good heat resistance, flame retardancy, cation exchange property, 1 easy thermal exfoliation and adsorption performance; these are mainly due to its large surface which has more active sites and can be used as an adsorbent of water hardness ions 2 . The advantages of VMT are low cost, ecological friendliness, renewable reuse and so on.…”