Effect of magnetite particle size on adsorption and desorption of arsenite and arsenate

Abstract

Numerous studies have examined arsenic adsorption on varying adsorbents including iron oxides, aluminum hydroxides, alumina, and carbon as a means of arsenic removal in drinking water treatments. The objectives of this study were to evaluate the effect of magnetite particle size on the adsorption and desorption behavior of arsenite and arsenate, and to investigate the competitive adsorption between natural organic matter (NOM) and arsenic. Increases in adsorption maximum capacities for arsenite and arsenate were observed with decreasing magnetite particle size. Arsenic desorption is hysteretic, more so with the smaller nanoparticles. Such desorption hysteresis might result from a higher arsenic affinity for magnetite nanoparticles. In the presence of NOM, substantial decrease in arsenic sorption to magnetite nanoparticles was observed. It would be beneficial to thoroughly investigate adsorption and desorption of arsenic on magnetite nanoparticles for further practical purposes.

The effect of nanocrystalline magnetite size on arsenic removal

“…This work also uses commercially available nanoscale iron oxides. While these materials are more polydisperse, large amounts are available and the two sizes (20 and 300 nm) are readily suspended in water [12,13]. In addition to a difference in size, these commercial materials are also more aggregated in suspension than the laboratory-prepared materials.…”

XAFS study of starch-stabilized magnetite nanoparticles and surface speciation of arsenate

“…Magnetite (Fe 3 O 4 ) nanoparticles have shown great potential for sorption of arsenic in contaminated soil and water because of the small particle size, large specific surface area, and high sorption capacity and affinity (Yean et al, 2005;Yavuz et al, 2006;Shipley et al, 2009;An et al, 2011). To prevent nanoparticles from aggregating, and thus, to enhance sorption capacity and soil deliverability, various particle stabilization strategies have been reported (Ponder et al, 2001;Raveendran et al, 2003;Zhao, 2005, 2007;Pan et al, 2010).…”

“…Previous studies have reported that magnetite particle size (Yean et al, 2005) and starch coating (He and Zhao, 2005) could strongly influence the arsenic adsorption capacity. However, a molecular level understanding has been lacking pertaining to the mechanisms of particle stabilization, effect of starch on the structure of SMNP, and the mode of arsenic complexation on the nanoparticles.…”

Synthesised magnetic nanoparticles coated zeolite (MNCZ) for the removal of arsenic (As) from aqueous solution

“…Apparently, the magnetic nanoparticles possess the advantages of large surface area, high number of surface active sites and magnetic properties, which lead to high adsorption efficiency, removal rate of contaminants, easy and rapid separation of adsorbent from solution via magnetic field, in addition to, the regeneration of magnetic nanoparticles and the potential reuse of the removed harmful components [14]. Investigators have shown that the magnetite nanocrystals can absorb both arsenate and arsenite at a special size range of 6-20 nm and are easily removed from solution by low-field magnets [15,16]. The nanoparticles have several advantages, such as their magnetic properties, high adsorption capacity and observed desorption hysteresis [15][16][17].…”

“…Investigators have shown that the magnetite nanocrystals can absorb both arsenate and arsenite at a special size range of 6-20 nm and are easily removed from solution by low-field magnets [15,16]. The nanoparticles have several advantages, such as their magnetic properties, high adsorption capacity and observed desorption hysteresis [15][16][17].…”