Enrichment of Precious Metals from Wastewater with Core–Shell Nanoparticles of Iron

Ling, Lan; Xiaoyue, Huang; Zhang, Wei‐xian

doi:10.1002/adma.201705703

Cited by 116 publications

(50 citation statements)

References 52 publications

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“…[ 8–12 ] NZVI is a strong reductant that readily dechlorinates chlorinated solvents and antibiotics, and reduces and immobilizes heavy metals and radionuclides. [ 12–17 ] 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.…”

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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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%

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

et al. 2020

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“…Due to rapid increase in water pollution throughout the world, wastewater treatment has become a popular topic [1]. Over the past few decades, numerous materials and methods, such as bio-remediation [2], physical methods [3][4][5], and chemical methods [6,7] including processes with zero valent metals [8], Fenton catalysis [9][10][11], ozonation [12], and photocatalysis [13][14][15], have been developed for wastewater treatment. Among the chemical methods, zero valent iron (ZVI) technology is considered to be one of the most promising approaches because of its low cost, natural abundance, good performance, and ease of operation.…”

Section: Introductionmentioning

confidence: 99%

Excellent long-term reactivity of inhomogeneous nanoscale Fe-based metallic glass in wastewater purification

et al. 2019

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Metallic glasses (MGs) have attracted great attention in wastewater treatment because of their high reactivity arising from amorphous structure, large residual stress and high density of low coordination sites. However, the reactivity of MGs would gradually slow down with time due to the passivation of active sites by corrosion products, resulting in limited long-term reactivity, which is also an unsolved key issue for established crystalline zero valent iron (ZVI) technology. Here, such problems are successfully overcome by introducing nanoscale chemical inhomogeneities in Fe-based MG (Fe-MGI), which apparently contributes to local galvanic cell effect and accelerates electron transfer during degradation process. More importantly, the selective depletion of Fe 0 causes local volume shrinkage and crack formation, leading to self-peeling of precipitated corrosion products and reacted regions. Thereby fresh low coordination sites could be continuously provided, counteracting the mass transport and reactivity deteriorating problem. Consequently, Fe-MGI demonstrates excellent long-term reactivity and self-refreshing properties even in neutral solution. The present results provide not only a new candidate but also a new route of designing ZVI materials for wastewater treatment.

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“…纳米零价铁与无氧 Ag(I)溶液反应 10 s 后仍保持完整的球形"核-壳"结构, 但颗粒表面附着大量 1～5 nm 的 Ag 小颗粒(图 6a). 随着反应的继续进行, 更多的 Ag 被纳米零价铁还原并沉积在表面, Ag 作为晶核继续长大至团聚状 [26] . Au(III)与纳米零价铁反应的表面化学与 Ag(I)相似, Au(III)与纳米零价铁反应 10 s 后, 颗粒保持"核-壳"结构, 但壳层氧化物外层点缀着 1～5 nm 更加明亮的纳米颗粒(图 6b).…”

Section: 纳米零价铁表面化学和晶相结构unclassified

Surface Chemistry and Phase Transformation of Nanoscale Zero-Valent Iron (nZVI) in Aquatic Media

Liu¹,

Gu²,

Wang³

et al. 2019

Acta Chim. Sinica

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The unique "core-shell" structure endows nanoscale zero-valent iron (nZVI) rich aquatic surface chemistry properties. Transformation of surface chemistry and crystal phase of nZVI affect its reactivity and environmental transport and fate. Recent advances on the surface chemistry and phase transformation of nZVI in aqueous media are highlighted in this paper focusing on a basic theory of nZVI for pollution control and environmental application. Surface chemistry and phase of both fresh and reacted nZVI are presented. The structure, composition and properties of nanoparticles are determined not only by reaction time but also by environmental conditions. Specifically, the influences of dissolved oxygen, hydraulic conditions (static and stirring), types and concentrations of heavy metals (U(VI), Cr(VI), Se(IV)) and anions (HPO − and 3 HCO − ) are investigated. In addition, the effect of surface modification with polyelectrolytes, including anionic polyacrylamide (APAM) and carboxymethylcellulose sodium (CMC), on microstructure, morphology and composition of nanoparticles in aqueous phase was discussed. Results demonstrate that environmental conditions have significant impacts on particles structure, composition and properties, consequently on nZVI performance for pollutant removal. After corrosion under different aqueous conditions, the core-shell structured nZVI are distorted and the metallic iron core is transformed into different iron oxides/hydroxides, such as γ-Fe 2 O 3 , Fe 3 O 4 and γ-FeOOH. These iron (hydr)oxides exhibit different surface complexation and affinity proprieties, thus eventually affecting the pollutant removal performance and the environmental fate of reaction products. More research on the effect of dynamic structure transformation by different types of pollutants, and a reaction model between the surface chemistry/phase transformation and removal performance are needed to deepen our understanding on nZVI surface chemistry, and develop more effective technologies of environmental applications. Keywords nanoscale zero-valent iron; aquatic media; surface chemistry; crystal phase; transformation 1 引言铁的标准氧化还原电位为-0.44 V, 零价铁材料 (Zero-Valent Iron, ZVI)因其强还原能力、良好的电化学和配位化学特性 [1～4] , 在环境修复领域被广泛应用. 纳米零价铁(nanoscale Zero-Valent Iron, nZVI)不但具有零

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Enrichment of Precious Metals from Wastewater with Core–Shell Nanoparticles of Iron

Cited by 116 publications

References 52 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

Excellent long-term reactivity of inhomogeneous nanoscale Fe-based metallic glass in wastewater purification

Surface Chemistry and Phase Transformation of Nanoscale Zero-Valent Iron (nZVI) in Aquatic Media

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