Mechanism and influence factors of chromium(VI) removal by sulfide-modified nanoscale zerovalent iron

Lv, Dan; Zhou, Jianwei; Cao, Zhen; Xu, Jiang; Liu, Yuanli; Li, Yizhou; Yang, Kunlun; Lou, Zimo; Lou, Liping; Xu, Xinhua

doi:10.1016/j.chemosphere.2019.02.109

Cited by 208 publications

(53 citation statements)

References 67 publications

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“…In this work, different amounts of sulfur were incorporated into NZVI particles using a previously described one‐step synthesis method. [ 40,41 ] The physicochemical properties of resulting SNZVI were extensively characterized, including morphology, crystalline structure, sulfur distribution and speciation, hydrophobicity, corrosion tendency, and electron transfer resistance. Differences in these properties explained well the observed reactivity of SNZVI with water and trichloroethylene (TCE).…”

Section: Figurementioning

confidence: 99%

“…Sulfidation of NZVI has been hypothesized to facilitate electron transfer in previous studies. [ 29,30,41,59,60 ] However, the impact of sulfur amount and speciation on the electrochemical properties of SNZVI, and on their reactivity and selectivity has not been reported. We prepared electrodes by pressing pellets of NZVI and SNZVI onto Ti mesh and performed several electrochemical tests.…”

Section: Figurementioning

confidence: 99%

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Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

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radionuclides. [12][13][14][15][16][17] However, NZVI is an indiscriminate reductant that also readily reduces water to form hydrogen gas (Fe 0 + 2H 2 O → Fe 2+ + 2OH − + H 2(g) ). [18] This unwanted side reaction consumes the reducing capacity of the NZVI, decreasing its reactive lifetime, and increases the amount and cost of NZVI required for remediation. Several approaches have been proposed to increase the reactivity or stability of NZVI during remediation, including encapsulating them with polymers or into silica matrices, [15,19] doping them with noble metals like Pd or Pt, [20,21] and supporting them onto carbon matrices like carbon nanotubes or graphene. [22,23] While these approaches improve the injectability of the materials into the subsurface, none have improved the selectivity of NZVI for contaminants over water while still maintaining high reactivity with the target groundwater contaminants. An ideal material for groundwater remediation should possess both high reactivity and selectivity, [24] where the contaminant outcompetes water for reactive sites.Recently, it was shown by us and others that the sulfidation of NZVI lowers its reactivity with water and other non-target hydrophilic contaminants (e.g., NO 3 − ), while increasing its reactivity with target contaminants like chlorinated solvents Sulfidized nanoscale zerovalent iron (SNZVI) is a promising material for groundwater remediation. However, the relationships between sulfur content and speciation and the properties of SNZVI materials are unknown, preventing rational design. Here, the effects of sulfur on the crystalline structure, hydrophobicity, sulfur speciation, corrosion potential, and electron transfer resistance are determined. Sulfur incorporation extended the nano-Fe 0 BCC lattice parameter, reduced the Fe local vacancies, and lowered the resistance to electron transfer. Impacts of the main sulfur species (FeS and FeS 2 ) on hydrophobicity (water contact angles) are consistent with density functional theory calculations for these FeS x phases. These properties well explain the reactivity and selectivity of SNZVI during the reductive dechlorination of trichloroethylene (TCE), a hydrophobic groundwater contaminant. Controlling the amount and speciation of sulfur in the SNZVI made it highly reactive (up to 0.41 L m −2 d −1 ) and selective for TCE degradation over water (up to 240 moles TCE per mole H 2 O), with an electron efficiency of up to 70%, and these values are 54-fold, 98-fold, and 160-fold higher than for NZVI, respectively. These findings can guide the rational design of robust SNZVI with properties tailored for specific application scenarios.Highly redox active materials are an important tool for the degradation of refractory organic water and soil contaminants. [1][2][3][4][5][6][7] Nanoscale zero valent (NZVI) has been used for in situ groundwater remediation for more than two decades. [8][9][10][11][12] NZVI is a strong reductant that readily dechlorinates chlorinated solvents and antibiotics, and reduces and immobilizes h...

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

et al. 2020

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“…Hexavalent chromium (Cr(VI)) pollution poses a serious crisis to human beings and the ecosystem, due to its high mobility, toxicity, and potential carcinogenicity [1,2]. It is extremely urgent to treat Cr(VI) contamination.…”

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Titanium Carbides (Ti3C2Tx) Functionalized by Poly(m-phenylenediamine) for Efficient Adsorption and Reduction of Hexavalent Chromium

Jin

Chai

Yang

et al. 2019

IJERPH

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Titanium carbides (MXenes) are promising multifunctional materials. However, the negative surface charge and layer-by-layer restacking of MXenes severely restrict their application in the field of anionic pollutants, including in hexavalent chromium (Cr(VI)). Herein, Ti3C2Tx MXenes was functionalized through in situ polymerization and intercalation of poly(m-phenylenediamine) (PmPD), then Ti3C2Tx/PmPD composites were obtained. Delightedly, Ti3C2Tx/PmPD composites exhibited positive surface charge, expanded interlayer spacing, and enhanced hydrophobicity. Furthermore, the specific surface area of Ti3C2Tx/PmPD composite was five and 23 times that of Ti3C2Tx and PmPD, respectively. These advantages endowed Ti3C2Tx/PmPD composite with an excellent adsorption capacity of Cr(VI) (540.47 mg g−1), which was superior to PmPD (384.73 mg g−1), Ti3C2Tx MXene (137.45 mg g−1), and the reported MXene-based adsorbents. The Cr(VI) removal mechanism mainly involved electrostatic adsorption, reduction, and chelation interaction. This study developed a simple functionalization strategy, which would greatly explore the potential of MXenes in the field of anionic pollutants.

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“…7). A possible reason is that with the increase of the initial Cr(VI) concentration, Cr(VI) rapidly occupied the active site on the nZVI surface and formed a Fe(Ⅲ )-Cr(Ⅲ ) (oxy)hydroxides passivation layer, which inhibited the release of Fe 2+ and the reduction of Cr(VI) subsequently [43,47]. increased (Fig.…”

Section: Effect Of Initial Cr(vi) Concentrationmentioning

confidence: 99%

“…At pH > 6.5, Cr(VI) speciation is predominantly CrO4 2-, and at pH < 6.5, HCrO4is the dominant form. As the pH decreases, the reduction of hexavalent chromium becomes easier [25,43,44]. On the other hand, the pH of zero point of charge (pHzpc) for Cu/Fe bimetallic nanoparticles was measured to be 4.6 (see Fig.…”

Section: Effect Of Initial Phmentioning

confidence: 99%

Removal of Hexavalent Chromium From Wastewater by Cu/Fe Bimetallic Nanoparticles

Wang

et al. 2020

Preprint

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BackgroundNanoscale zerovalent iron (nZVI) is a promising material for removing heavy metals from wastewater. However, passivation of nZVI hinders its efficiency in water treatment. Loading another catalytic metal has been found to improve the efficiency significantly. In this study, Cu/Fe bimetallic nanoparticles were prepared by liquid-phase chemical reduction for removal of hexavalent chromium (Cr(VI)) from wastewater. Purpose of this study was to clarify the effects and mechanisms of Cu loading on the removal efficiency of Cr(VI).ResultsThe results showed that Cu loading can significantly enhance the removal efficiency of Cr(VI) by 29.3% to 84.0%, and the optimal Cu loading rate was 3% (wt%). The removal efficiency decreased with increasing initial pH and Cr(VI) concentration. It was found that Cr(VI) removal followed a pseudo-first-order kinetic model. When the Cu loading rate was 3%, the initial concentration of Cr(VI) was 100 mg/L, the observed first-order rate coefficient (kobs) was 0.016 min-1 for Cu/Fe bimetallic nanoparticles at pH of 3.5, which was twice than that of nZVI (0.008 min-1). X-ray photoelectron spectroscopy (XPS) analysis indicated that Cr(VI) was completely reduced to Cr(Ⅲ) and precipitated on the particle surface as hydroxylated Cr(OH)3 and CrxFe1-x(OH)3 coprecipitation.ConclusionsIn this study, it was found that the loading of Cu can significantly increase the specific surface area and the Cr(VI) remove efficiency of nZVI, and the removal efficiency decreases with increasing pH and Cr(VI) initial concentration. Therefore, Cu loading can alleviate the passivation of nZVI effectively and can be beneficial for the application of iron-based nanomaterials in remediation of wastewater.

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Mechanism and influence factors of chromium(VI) removal by sulfide-modified nanoscale zerovalent iron

Cited by 208 publications

References 67 publications

Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

Sulfur Loading and Speciation Control the Hydrophobicity, Electron Transfer, Reactivity, and Selectivity of Sulfidized Nanoscale Zerovalent Iron

Two-Dimensional Titanium Carbides (Ti3C2Tx) Functionalized by Poly(m-phenylenediamine) for Efficient Adsorption and Reduction of Hexavalent Chromium

Removal of Hexavalent Chromium From Wastewater by Cu/Fe Bimetallic Nanoparticles

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