Use of Natural and Modified Magadiite As Adsorbents to Remove Th(IV), U(VI), and Eu(III) from Aqueous Media — Thermodynamic and Equilibrium Study

Abstract

The contamination of aquatic environments by toxic metals such as radionuclides is of great concern because of the tendency of those metals to accumulate in the vital organs of humans and animals, causing severe health problems. The objective of this study was to investigate the use of natural and modified magadiite clay as an adsorbent to remove Th(IV), U(VI), and Eu(III) from aqueous solutions. Magadiite from the Amazon region, Brazil, was modified chemically with 5-mercapto-1-methyltetrazole (MTTZ) using a multi-step or heterogeneous synthesis pathway. The natural and modified materials were characterized using 29Si and 13C nuclear magnetic resonance, scanning electron microscopy, nitrogen gas adsorption, and elemental analysis. The physical-chemical properties of the chemically modified magadiite sample were modified, e.g. the specific surface area changed from 35.0 to 678.9 m2 g−1. The ability of the magadiite to remove Th(IV), U(VI), and Eu(III) from aqueous solution was then tested by a series of adsorption isotherms adjusted to a Sips equation. The effects of properties such as pH, contact time, and metal concentration on the adsorption capacity were studied. The adsorption maxima were determined to be 7.5 × 10−3, 9.8 × 10−3, and 12.9 × 10−3 mmol g−1 for Th(IV), U(VI), and Eu(III), respectively. From calorimetric determinations, the quantitative thermal effects for all these cations/basic center interactions gave exothermic enthalpy, negative Gibbs free energy, and positive entropy, confirming the energetically favorable conditions of such interactions at the solid/liquid interface for all systems.

Characterization of organo-kenyaites: thermal stability and their effects on eosin removal characteristics

“…Layered silicates such as magadiite (NaSi 7 O 13 (OH) 3 . 4H 2 O), kenyaite (Na 2 Si 22 O 41 (OH) 8 .6H 2 O) and kanemite (NaHSi 2 O 5 .3H 2 O) have recently become the subject of great interest due to their adsorptive and catalytic properties (Alarcón et al, 2005; Kalvachev et al, 2006; Park et al, 2009; Royer et al, 2010; Guerra et al, 2012; Kim et al , 2012; Chen et al, 2016). The structure of kenyaite is composed of silica layers and interlayer hydrated cations; each silica layer is built from three silica sheets instead of two, as in the case of magadiite (Wang et al, 2006).…”

Parameters Synthesis of Na-Magadiite Materials for Water Treatment and Removal of Basic Blue-41: Properties and Single-Batch Design Adsorber

“…On the other hand, different silica sources were used to prepare Na-magadiite, and there was not a systematic reason as to why one source was favored over the others. For example, by using silica gel as a source of silica, a pure magadiite phase was obtained at 150 • C for 3 days [14]; however, the same phase required 8 days of reaction at 150 • C using colloidal silica (40% in water) [15]. The reaction time was reduced to 3 days using Ludox-HS40 [16].…”

Remediation of copper ions from aqueous solution using hybrid magadiite: kinetics, isotherm and mechanism of removal

“…To solve this problem, several researchers introduce different organic ligands into the solid matrix to increase their extraction capacities [7 10]. Guerra et al [11] reported the use of natural and modified magadiite as adsorbents to remove Th(IV), U(VI), and Eu(III) from aqueous media in thermodynamic and equilibrium study. In most cases, the amount of heavy metal absorbed onto these organo-modified clays was much greater than that adsorbed onto the unmodified clays under the same experimental conditions [12,13].…”