Arsenic(III) and Arsenic(V) Reactions with Zerovalent Iron Corrosion Products

Abstract

Zerovalent iron (Fe0) has tremendous potential as a remediation material for removal of arsenic from groundwater and drinking water. This study investigates the speciation of arsenate (As(V)) and arsenite (As(III)) after reaction with two Fe0 materials, their iron oxide corrosion products, and several model iron oxides. A variety of analytical techniques were used to study the reaction products including HPLC-hydride generation atomic absorption spectrometry, X-ray diffraction, scanning electron microscopy-energy-dispersive X-ray analysis, and X-ray absorption spectroscopy. The products of corrosion of Fe0 include lepidocrocite (gamma-FeOOH), magnetite (Fe3O4), and/or maghemite (gamma-Fe2O3), all of which indicate Fe(II) oxidation as an intermediate step in the Fe0 corrosion process. The in-situ Fe0 corrosion reaction caused a high As(III) and As(V) uptake with both Fe0 materials studied. Under aerobic conditions, the Fe0 corrosion reaction did not cause As(V) reduction to As(III) but did cause As(III) oxidation to As(V). Oxidation of As(III) was also caused by maghemite and hematite minerals indicating that the formation of certain iron oxides during Fe0 corrosion favors the As(V) species. Water reduction and the release of OH- to solution on the surface of corroding Fe0 may also promote As(III) oxidation. Analysis of As(III) and As(V) adsorption complexes in the Fe0 corrosion products and synthetic iron oxides by extended X-ray absorption fine structure spectroscopy (EXAFS) gave predominant As-Fe interatomic distances of 3.30-3.36 A. This was attributed to inner-sphere, bidentate As(III) and As(V) complexes. The results of this study suggest that Fe0 can be used as a versatile and economical sorbent for in-situ treatment of groundwater containing As(III) and As(V).

Removal of arsenate from water by using an Fe–Ce oxide adsorbent: Effects of coexistent fluoride and phosphate

“…The second peak could be fit with 2.3 Fe atoms at R As-Fe = 3.32 Å and 1.1 Fe atoms at R As-Fe = 3.55 Å from the central As atom, respectively (Table S2). Similar As-Fe distances at 3.32 Å (43-45) and 3.55 Å [38,39] were previously reported, respectively. The results suggested that bidentate binuclear and monodentate mononuclear inner-sphere complex species coexisted at the Fe-Ce surface, which corresponded to an As-Fe distance of 3.32 and 3.55 Å, respectively.…”

Adsorption behavior of arsenic onto protonated titanate nanotubes prepared via hydrothermal method

“…Arsenic exists in natural water predominantly as inorganic arsenate, As (V) and arsenite, As (III) [3][4][5][6][7]. Elevated concentrations of arsenic are found in groundwater in many regions around the world, which are caused by the release of arsenic from As-bearing sediments or anthropogenic sources [8][9][10].…”

“…Many different technologies have been developed to remove arsenic from water, such as adsorption, coagulation/precipitation, ion-exchange, and so on [3,6,7]. Among them, adsorption is considered to be one of the most promising technologies for its simplicity in operation and cost-effectivity [3].…”

“…Among them, adsorption is considered to be one of the most promising technologies for its simplicity in operation and cost-effectivity [3]. Natural materials such as zeolite [11], natural iron ores [7,12,13], siderite [14] and red mud [15] have been examined intensively for arsenic removal. Although these materials are regarded as cheap and effective adsorbents, there are several problems (their impurities, unknown stability and regeneration, low adsorption capacity and slow kinetics) associated with their use [4,13,16].…”

Arsenic Removal from Contaminated Water by Various Physicochemical Processes

“…An acceptable norm in many countries, including India, for arsenic (expressed as total arsenic) in drinking water is 10 μg/L [1]. Various technologies practiced for arsenic removal from ground water based on various principles are namely, chemical coagulation and precipitation [2]; oxidation [3]; biological process [4]; electrocoagulation [5]; adsorption on various materials such as alumina [6], Fe or Mn oxi-hydroxides [7] or zerovalent iron corrosion products [8] etc. ; reverse osmosis [9]; membrane filtration/ nanofiltration [10]; and ion exchange [11].…”