The removal of molybdates and tungstates from aqueous solution by organo-smectites

Sorption of Molybdates and Tungstates on Functionalized Montmorillonites: Structural and Textural Features

“…First, the clay-size fraction (<2 μm) was separated from bentonite by a sedimentation process [25]. XRD confirmed that the only phase occurring after the separation procedure was Ca-montmorillonite and that all impurities from the initial sediment had been removed [12]. A strong 001 diffraction peak at 15.2 Å indicates that Ca 2+ is the predominant cation in the montmorillonite interlayer positions [25,26].…”

“…However, natural smectites exhibit a weak affinity for the anionic forms of metals, which limits their use [9]. Modification of smectite with organic compounds such as quaternary ammonium salts yields a material with improved sorption properties in terms of anionic form [6,10,11,12].…”

“…The aim of this paper is to investigate the structural and textural features of organically-modified montmorillonites with adsorbed anions. In our earlier studies, we analyzed the influence of surfactant amount, kinetics, pH, and initial concentration of Mo, W on the sorption of molybdates and tungstates by organo-smectites [12]. However, the proper understanding of the changes in structural and textural properties of used sorbents are crucial to finding an effective method for the disposal of both compounds.…”

Biogeochemistry of trace elements in anaerobic digesters

“…MoS 2− 4 showed the greatest propensity for Fe minerals, thus suggesting a possible mechanism of Mo immobilization under sulfidogenic and iron-rich conditions. In addition, MoS 2− 4 was shown to strongly interact with organically modified montmorillonite (organo-smectite) at low pH (,5), displaying a maximum sorption capacity of 705 mmol kg −1 (Muir et al, 2017). The main sorption mechanisms proposed are chemisorption and ion exchange.…”

“…Another study investigated the interaction of tungsten with hematite showing strong adsorption and, similarly to pyrite, increased adsorption capacity with decreasing pH (Rakshit et al, 2017). Tungstate was also shown to adsorb onto organically modified montmorillonite and the main sorption mechanisms involve chemisorption and ion exchange (Muir et al, 2017). The sorption capacity was high at acidic pH (pH , 5), while at pH .…”