A comparative evaluation of hexavalent chromium treatment in contaminated soil by calcium polysulfide and green-tea nanoscale zero-valent iron

Chrysochoou, Maria; Johnston, Chad P.; Dahal, Geeta

doi:10.1016/j.jhazmat.2011.11.003

Cited by 163 publications

(52 citation statements)

References 42 publications

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“…These results are in accordance with the observations of other authors such as Wang et al (2014b), who produced green nZVI with eucalyptus leaf extracts, and Kuang et al (2013) and Chrysochoou et al (2012), who used tea extracts to produce nZVI.…”

Section: Size Determination Of the Nanoparticlessupporting

confidence: 93%

Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts

Machado

Pacheco

Nouws

et al. 2015

Science of The Total Environment

199

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a b s t r a c t Keywords:Zero-valent iron nanoparticles Green synthesis method Tree leaves Size Reactivity AgglomerationIn the last decades nanotechnology has become increasingly important because it offers indisputable advantages to almost every area of expertise, including environmental remediation. In this area the synthesis of highly reactive nanomaterials (e.g. zero-valent iron nanoparticles, nZVI) is gaining the attention of the scientific community, service providers and other stakeholders. The synthesis of nZVI by the recently developed green bottom-up method is extremely promising. However, the lack of information about the characteristics of the synthetized particles hinders a wider and more extensive application. This work aims to evaluate the characteristics of nZVI synthesized through the green method using leaves from different trees. Considering the requirements of a product for environmental remediation the following characteristics were studied: size, shape, reactivity and agglomeration tendency. The mulberry and pomegranate leaf extracts produced the smallest nZVIs (5-10 nm), the peach, pear and vine leaf extracts produced the most reactive nZVIs while the ones produced with passion fruit, medlar and cherry extracts did not settle at high nZVI concentrations (931 and 266 ppm). Considering all tests, the nZVIs obtained from medlar and vine leaf extracts are the ones that could present better performances in the environmental remediation. The information gathered in this paper will be useful to choose the most appropriate leaf extracts and operational conditions for the application of the green nZVIs in environmental remediation.

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Section: Size Determination Of the Nanoparticlessupporting

confidence: 93%

Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts

Machado

Pacheco

Nouws

et al. 2015

Science of The Total Environment

199

View full text Add to dashboard Cite

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“…22,23 Much work has already been done to investigate the use of ZVI and nZVI to reduce Cr(VI) over the common environmental pH range of mildly acidic to moderately alkaline conditions. [22][23][24][25][26][27] In acidic conditions the reaction is relatively fast, but the rate of reaction is slower in neutral and mildly alkaline conditions. 28 The primary objective of this study is to extend understanding of the reaction between ZVI and Cr(VI) to alkaline conditions characteristic of COPR leachate.…”

Section: Introductionmentioning

confidence: 99%

Chromate Reduction in Highly Alkaline Groundwater by Zerovalent Iron: Implications for Its Use in a Permeable Reactive Barrier

Fuller

Stewart

Burke

2013

Ind. Eng. Chem. Res.

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It is not currently known if the widely used reaction of zero valent iron (ZVI) and Cr(VI) can be used in a permeable reactive barrier (PRB) to immobilise Cr leaching from hyper alkaline chromite ore processing residue (COPR). This study compares Cr(VI) removal from COPR leachate and chromate solution by ZVI at high pH. Cr(VI) removal occurs more rapidly from the chromate solution than from COPR leachate. The reaction is first order with respect to both [Cr(VI)] and the iron surface area, but iron surface reactivity is lost to the reaction.Buffering pH downwards produces little change in the removal rate or the specific capacity of iron until acidic conditions are reached. SEM and XPS analysis confirm that reaction products accumulate on the iron surface in both liquors, but that other surface precipitates also form in COPR leachate. Leachate from highly alkaline COPR contains Ca, Si and Al that precipitate on the iron surface and significantly reduce the specific capacity of iron to reduce Cr(VI). This study suggests that although Cr (VI) reduction by ZVI will occur at hyper alkaline pH, other solutes present in COPR leachate will limit the design life of a PRB. 4

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“…For instance, XPS analysis carried out on reacted Fe-Ni nanoparticles revealed that ratio between adsorbed Cr III and Cr VI was 7.87 [92]. Therefore, in addition to the heterogeneous reduction mechanism occurring at the surface of Fe 0 , dissolved Fe II and H/H 2 , both products of Fe 0 corrosion, may also be involved in the mechanism of Cr VI removal in Fe 0 /H 2 O system [62,67,86,91,[102][103][104][105][106][107][108]. Even though these reduction pathways have been suggested much earlier by several pioneering works in this field [15,18,21], they were often overlooked in articles describing the removal of Cr VI with Fe 0 -based PRBs, as well as in numerous more recent papers.…”

Section: More Recent Laboratory-scale Reports (Post Elisabeth City Prb)mentioning

confidence: 99%

Progress in Understanding the Mechanism of CrVI Removal in Fe0-Based Filtration Systems

Gheju¹

2018

Water

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Hexavalent chromium (Cr VI ) compounds are used in a variety of industrial applications and, as a result, large quantities of Cr VI have been released into the environment due to inadequate precautionary measures or accidental releases. Cr VI is highly toxic to most living organisms and a known human carcinogen by inhalation route of exposure. Another major issue of concern about Cr VI compounds is their high mobility, which easily leads to contamination of surface waters, soil, and ground waters. In recent years, attention has been focused on the use of metallic iron (Fe 0 ) for the abatement of Cr VI polluted waters. Despite a great deal of research, the mechanisms behind the efficient aqueous Cr VI removal in the presence of Fe 0 (Fe 0 /H 2 O systems) remain deeply controversial. The introduction of the Fe 0 -based filtration technology, at the beginning of 1990s, was coupled with the broad consensus that direct reduction of Cr VI by Fe 0 was followed by co-precipitation of resulted cations (Cr III , Fe III ). This view is still the dominant removal mechanism (reductive-precipitation mechanism) within the Fe 0 remediation industry. An overview on the literature on the Cr geochemistry suggests that the reductive-precipitation theory should never have been adopted. Moreover, recent investigations recalling that a Fe 0 /H 2 O system is an ion-selective one in which electrostatic interactions are of primordial importance is generally overlooked. The present work critically reviews existing knowledge on the Fe 0 /Cr VI /H 2 O and Cr VI /H 2 O systems, and clearly demonstrates that direct reduction with Fe 0 followed by precipitation is not acceptable, under environmental relevant conditions, as the sole/main mechanism of Cr VI removal in the presence of Fe 0 .

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A comparative evaluation of hexavalent chromium treatment in contaminated soil by calcium polysulfide and green-tea nanoscale zero-valent iron

Cited by 163 publications

References 42 publications

Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts

Characterization of green zero-valent iron nanoparticles produced with tree leaf extracts

Chromate Reduction in Highly Alkaline Groundwater by Zerovalent Iron: Implications for Its Use in a Permeable Reactive Barrier

Progress in Understanding the Mechanism of CrVI Removal in Fe0-Based Filtration Systems

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