Arsenite removal from groundwater by iron–manganese oxides filter media: Behavior and mechanism

Abstract

Arsenic, a common contaminant in groundwater environments, usually coexists with other contaminants, for example, ammonium, iron, and manganese. In our previous studies, an iron-manganese (Fe-Mn) oxides filter media was developed for catalytic oxidation removal of ammonium, iron, and manganese. In this study, batch oxidation/ adsorption kinetic experiments revealed that the filter media could easily oxidize arsenite (As(III)) to arsenate (As(V)). And the sorption kinetics was found to follow the pseudo-second-order kinetic model. X-ray powder diffraction (XRD) and Fourier transform infrared spectra (FTIR) along with X-ray photoelectron spectroscopy (XPS) were used to analyze the surface change in the Fe-Mn oxides. Based on sorption and spectroscopic measurements, the mechanism of As(III) removal by the Fe-Mn oxides filter media was found to be an oxidation coupled with sorption approach. As(III) in the aqueous solution was firstly oxidized to As(V) on the surfaces of the Fe-Mn oxides filter media. Then the converted As(V) was attracted to the Fe-Mn oxides filter media surfaces and bounded with the active sites (−OH groups), through weak intermolecular H-bondings. Our results indicated that the novel Fe-Mn oxides filter media could be applied for the simultaneous removal of ammonium, iron, manganese, and As(III) in drinking water treatment and environmental remediation. • Practitioner points• A novel iron-manganese oxides filter for efficient As(III) removal was established. • The exhausted filter media could be easily regenerated by NaHCO 3 solution.• Mn(III) related to surface lattice oxygen species was responsible for As(III) oxidation. • The oxidation and adsorption processes were involved in As(III) removal. • The filter media could be successfully applied to simultaneous removal of ammonium, manganese, iron, and arsenic.

Laterite as a low-cost adsorbent in a sustainable decentralized filtration system to remove arsenic from groundwater in Vietnam

“…These results were very consistent with studies done on other natural laterites (Maiti et al, 2013;Mitra et al, 2016). With arsenic being intensively reported in the literature, the abundant presence of hydroxyl groups on the adsorbent's surface was expected to form the complexation reaction with arsenic ions in aqueous solution (Cheng et al, 2019;Siddiqui and Chaudhry, 2017;Zhao et al, 2018). As(III) to As(V) (Cheng et al, 2019;Partey et al, 2008).…”

“…Similarly, the relatively low S BET (m 2 /g) and V Total (cm 3 /g) values of other kinds of laterite derived from different geographical regions were reported in the literature, such as 17.5-18.5 m 2 /g and 0.02-0.05 cm 3 /g (Maiti et al, 2012) and 71-182 m 2 /g and 0.07-0.35 cm 3 /g (Maiti et al, 2013). Because the natural adsorbent is a nonporous material, the adsorption mechanism of arsenic ions in solution involved in pore filling might be less important than some surface interactions, i.e., complexation (Cheng et al, 2019).…”

“…With arsenic being intensively reported in the literature, the abundant presence of hydroxyl groups on the adsorbent's surface was expected to form the complexation reaction with arsenic ions in aqueous solution (Cheng et al, 2019;Siddiqui and Chaudhry, 2017;Zhao et al, 2018). As(III) to As(V) (Cheng et al, 2019;Partey et al, 2008). In their study, Zhao et al (2018) found that iron (hydro)oxides (i.e., ferrihydrite, hematite, and magnetite) can act as a promising catalyst in simulating the oxidation of As(III) onto As(V).…”

“…This outcome suggests the existence of competition. In fact, As(III) was possibly partly oxidized into As(V) ions in solution through particular oxidants, i.e., FeOOH, Fe 2 O 3 , MnO 2 , and TiO 2 (Cheng et al, 2019;Guan et al, 2012;Lenoble et al, 2004;Siddiqui and Chaudhry, 2017;Simeonidis et al, 2016;Zhao et al, 2018) that are available in the structure of the NLTT (see Section 3.2). Subsequently, the adsorption rate gradually decreased until the plateau was reached at around 120-360 min.…”

“…Notably, referring to the adsorption of As(V), the surface interaction possibly involved weak electrostatic attraction (outersphere complexation) and surface complexation (inner-sphere complexation) (Kalaruban et al 2019). Meanwhile, the oxidation of arsenite As(III) to arsenate As(V) and the complexation between arsenic ions in solution and the -OH groups on the surface of NLTT might be dominant reactions for the adsorption of As(III) (Cheng et al, 2019;Partey et al, 2009;Pozdnyakov et al, 2016;Zhao et al, 2018).…”