Rapid in situ identification of arsenic species using a portable Fe<sub>3</sub>O<sub>4</sub>@Ag SERS sensor

Du, Jingjing; Cui, Jinli; Jing, Chuanyong

doi:10.1039/c3cc46920d

Cited by 85 publications

(39 citation statements)

References 16 publications

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“…The EXAFS data analysis was performed using the ATHENA and ARTEMIS programs in the Demeter computer package. 15,16 The analysis procedure was similar to our previous studies 17,18 and is detailed in the Supporting Information. In Situ Flow Cell ATR-FTIR Study.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study

Shi

Chan

et al. 2015

ACS Appl. Mater. Interfaces

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Rare earth-modified adsorbents (REMAs) have been widely used to remove oxyanion pollutants from water, including arsenic (As). However, the molecular-level structural information and reactions at the liquid/solid interface are still murky, which limits the design of applicable REMAs. Herein, a lanthanum-impregnated activated alumina (LAA) was synthesized as a representative REMA, and its As uptake mechanisms were explored using multiple complementary characterization techniques. Our adsorption experiments showed that LAA exhibited 2−3 times higher As adsorption capacity than AA. In contrast to the bidentate configuration formed on most metal oxide surfaces, our EXAFS and DFT results suggest that As(III) and As(V) form monodentate surface complexes on LAA through As-O-La coordinative bonding. In situ flow cell ATR-FTIR observed a strong dependence of As-O peak positions on pH, which could be interpreted as the change in the fractions of As(V) surface complexes with zero-to double-protonation on LAA, AA, and LaOOH. As(V) on LAA existed as singly and doubly protonated surface species, and the pK a of transition from double to single protonation (∼5.8) was lower than that for its soluble counterpart (6.97). The surface reaction and structural configuration were incorporated in a CD-MUSIC model to satisfactorily predict macroscopic As adsorption behaviors. The insights gained from the molecular-level reactions shed light on the design and application of REMAs in environmental remediation for As and its structural analogues.

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Section: ■ Materials and Methodsmentioning

confidence: 99%

Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study

Shi

Chan

et al. 2015

ACS Appl. Mater. Interfaces

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“…Had aqueous Cd−As(III) complexes formed, the As(III) symmetry and the As−O bond energy would be changed accordingly, which should result in a peak shift or split. 24 Arsenic K-Edge EXAFS Analysis. EXAFS spectroscopy was employed to determine the As local coordination environment on TiO 2 in the presence of Cd.…”

Section: Methodsmentioning

confidence: 99%

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂

Chan

et al. 2015

Environ. Sci. Technol.

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Insights from molecular-level mechanisms of arsenite [As(III)] and cadmium (Cd) co-adsorption on TiO 2 can further our understanding of their synergistic removal in industrial wastewaters. The motivation for our study is to explore the interfacial interactions of neutrally charged As(III) and cationic Cd 2+ on nanocrystalline TiO 2 using multiple complementary techniques. The results of adsorption edge, ζ potential, and surface complexation modeling suggest that coexistence of As(III) and Cd 2+ enhanced their synergistic adsorption on TiO 2 and, consequently, resulted in the formation of a ternary surface complex. This ternary surface complex, in turn, inhibited the metal release into the aqueous phase and, therefore, facilitated the immobilization of the heavy metals. Our in situ flow-cell attentuated total reflectance Fourier transform infrared (ATR−FTIR) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy evidence showed that, regardless of the order of contact, As(III) was preferentially adsorbed on TiO 2 rather than Cd. In agreement with our spectroscopic analysis, quantum chemistry calculations also illustrated that the Cd−As(III)−TiO 2 ternary surface complex should be formed with the adsorbed As(III) as the bridging molecule. At high As(III) concentrations, the formation of the Cd−As(III)−TiO 2 complex is responsible for the Cd removal. The simultaneous removal mechanisms will further our understanding of the removal of multiple pollutants in industrial wastewaters. ■ INTRODUCTIONCoexistence of arsenic (As) and cadmium (Cd) with extremely high concentrations in mining and smelting wastewaters presents a major challenge to the environment. 1,2 Arsenate [As(V)] is the primary As species in oxic environments, whereas under reducing conditions and especially in industrial wastewaters, the more toxic and mobile arsenite [As(III)] is predominant.3−5 Simultaneous adsorptive removal of As(III) and Cd can be successfully achieved using regenerable TiO 2 . 6 However, the molecular-level interactions between cationic Cd and neutrally charged As(III) on the TiO 2 surface are poorly understood.The rapid increase in industrial mineral exploration and extraction over the past 2 decades 7 has motivated extensive studies on the interactions of metals and oxyanions on solids.8−10 The synergistic uptake of cationic metals and anionic ligands on metal oxide surfaces is generally attributed to the electrostatic effect, formation of ternary surface complexes, and surface and bulk precipitation, as evidenced by spectroscopic analysis.11−14 However, no clear boundaries exist distinguishing ternary surface complexes and surface precipitation, and these two terms sometimes are even used interchangeably.12 For example, surface precipitation was used to describe elevated As(V) removal in the presence of Zn 11 and Cu 15 on goethite. On the other hand, more recent reports use ternary surface complexation to describe the co-adsorption of cations and anions on a surface where the newly formed cation...

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“…The lack of change in band position in the presence of HA suggests that no HA-As(V) complex was formed under the experimental conditions. Had aqueous HA-As(V) complexes formed, the As(V) symmetry and the As-O banding energy would be changed accordingly which should result in peak shift or split (Du et al, 2014). The conclusion was further supported by the observation of peak shift from 785 cm −1 in As(V) solution to 810 cm −1 in calcium arsenate solution (Fig.…”

Section: Sers Studymentioning

confidence: 99%

Removal of arsenate with hydrous ferric oxide coprecipitation: Effect of humic acid

Jing

Duan

et al. 2014

Journal of Environmental Sciences

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a b s t r a c tInsights from the adverse effect of humic acid (HA) on arsenate removal with hydrous ferric oxide (HFO) coprecipitation can further our understanding of the fate of As(V) in water treatment process. The motivation of our study is to explore the competitive adsorption mechanisms of humic acid and As(V) on HFO on the molecular scale. Multiple complementary techniques were used including macroscopic adsorption experiments, surface enhanced Raman scattering (SERS), extended X-ray absorption fine structure (EXAFS) spectroscopy, flow-cell attenuated total reflectance Fourier transform infrared (ATR-FTIR) measurement, and charge distribution multisite complexation (CD-MUSIC) modeling. The As(V) removal efficiency was reduced from over 95% to about 10% with the increasing HA concentration to 25 times of As(V) mass concentration. The SERS analysis excluded the HA-As(V) complex formation. The EXAFS results indicate that As(V) formed bidentate binuclear surface complexes in the presence of HA as evidenced by an As-Fe distance of 3.26-3.31 Å. The in situ ATR-FTIR measurements show that As(V) replaces surface hydroxyl groups and forms innersphere complex. High concentrations of HA may physically block the surface sites and inhibit the As(V) access. The adsorption of As(V) and HA decreased the point of zero charge of HFO from 7.8 to 5.8 and 6.3, respectively. The CD-MUSIC model described the zeta potential curves and adsorption edges of As(V) and HA reasonably well.

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Rapid in situ identification of arsenic species using a portable Fe₃O₄@Ag SERS sensor

Cited by 85 publications

References 16 publications

Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study

Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂

Removal of arsenate with hydrous ferric oxide coprecipitation: Effect of humic acid

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Rapid in situ identification of arsenic species using a portable Fe3O4@Ag SERS sensor

Cited by 85 publications

References 16 publications

Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study

Arsenic Adsorption on Lanthanum-Impregnated Activated Alumina: Spectroscopic and DFT Study

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO2

Removal of arsenate with hydrous ferric oxide coprecipitation: Effect of humic acid

Contact Info

Product

Resources

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Rapid in situ identification of arsenic species using a portable Fe₃O₄@Ag SERS sensor

Molecular Insights into Ternary Surface Complexation of Arsenite and Cadmium on TiO₂