Abstract
This work reports the behavior of montmorillonite–magnetite mixtures of varying composition in aqueous dispersions and evaluates their adsorbing properties using a cationic organic pollutant, methylene blue (MB+), and an anionic inorganic pollutant, arsenate (As(V)), as the adsorbing species. The effects of the presence of montmorillonite on the As(V) adsorption by magnetite and the effects of magnetite on the MB+ adsorption by the clay were specially addressed. The simple mixture of a montmorillonite dispersion with a magnetite dispersion led to the spontaneous formation of montmorillonite–magnetite co-aggregates. These co-aggregates showed a unimodal electrophoretic mobility distribution, with no evidence of the presence of separate populations of montmorillonite or magnetite. The application of a magnetic field confirmed the formation of co-aggregates and showed that their separation rate increased as the magnetite content increased. Adsorption studies as a function of the aggregate composition demonstrated that MB+ uptake was mainly controlled by the content of montmorillonite, while As(V) adsorption was mainly controlled by the content of Fe3O4. This permits an easy tuning of the adsorbing properties of cations and anions by controlling the composition of the system.
Highlights
Extensive research has been carried out in the field of environmental remediation in the last decades, aiming to develop efficient, economical, and versatile water remediation technologies
Magnetic modification of inexpensive adsorbents, such as clays, can lead to the formation of magnetic particles that can be and rapidly removed from solutions by applying an external magnetic field [5,6], capturing organic and inorganic pollutants. Clays, such as montmorillonite, have been used since the beginning of civilization and have maintained their position among the most important industrial raw materials since. They are well known as adsorbents of heavy metals, and of drugs, pesticides, organic matter, etc. [7,8,9,10,11] On the other hand, magnetic nanoparticles, such as Fe3 O4, have generated considerable repercussion in adsorption technologies and, in the remediation field [12,13], due to their stability, large surface area, high number of surface active sites, and, unlike montmorillonite which is paramagnetic, the particular advantage of being able to be separated by applying an external magnetic field
MBAs(V), ing it easy tune properties of theofsystem by controlling the composition making it to easy to the tuneadsorptive the adsorptive properties the system by controlling the compoof the co-aggregates
Summary
Extensive research has been carried out in the field of environmental remediation in the last decades, aiming to develop efficient, economical, and versatile water remediation technologies In this context, magnetic separation has been applied recently in many areas for preconcentration and quantification in analytical chemistry [1,2], to capture and separate pollutants from aqueous environments [3,4], and to adsorb and degrade undesired substances [5]. Magnetic modification of inexpensive adsorbents, such as clays, can lead to the formation of magnetic particles that can be and rapidly removed from solutions by applying an external magnetic field [5,6], capturing organic and inorganic pollutants Clays, such as montmorillonite, have been used since the beginning of civilization and have maintained their position among the most important industrial raw materials since . They are well known as adsorbents of heavy metals, and of drugs, pesticides, organic matter, etc. [7,8,9,10,11] On the other hand, magnetic nanoparticles, such as Fe3 O4 , have generated considerable repercussion in adsorption technologies and, in the remediation field [12,13], due to their stability, large surface area, high number of surface active sites, and, unlike montmorillonite which is paramagnetic, the particular advantage of being able to be separated by applying an external magnetic field
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