Nanoscale iron particles for complete reduction of chlorinated ethenes

doi:10.1016/S0927-7757(01)00767-1

Colloids and Surfaces A: Physicochemical and Engineering Aspects

Volume 191, Issues 1–2, 31 October 2001, Pages 97-105

https://doi.org/10.1016/S0927-7757(01)00767-1 Get rights and content

Abstract

This paper examines the potential for using laboratory synthesized nanoscale Pd/Fe bimetallic particles to reduce chlorinated ethenes. Rapid and complete dechlorination was achieved for six chlorinated ethenes: tetrachloroethene (PCE, C₂Cl₄), trichloroethene (TCE, C₂HCl₃), 1,1-dichloroethene (1,1-DCE, C₂H₂Cl₂), cis- and trans-1,2-dichloroethene (c-DCE, t-DCE, C₂H₂Cl₂), and vinyl chloride (VC, C₂H₃Cl). The chlorinated ethenes (20 mg l⁻¹) were completely reduced within 90 min at a metal loading of 5 g l⁻¹. Ethane was the primary product from these reactions, amount to 60–90% of the total carbon. Ethene (3–20%) was produced during the transformation of TCE, DCEs and VC. No chlorinated intermediates or final products were detected above the method detection limit (<5 μg l⁻¹). The remarkable performance of the nanoscale particles can be attributed to: (1) High specific surface area of the nanoscale metal particles, approximately 35 m² g⁻¹, tens to hundreds of times higher than commercial grade micro- or milli-scale iron particles; (2) Increased reactivity per unit metal surface area, largely due to the presence of the noble metal (Pd) on the surface. Values of the surface-area-normalized rate coefficients (k_SA) were two orders of magnitude higher than those reported in the literature for larger iron particles. Due to their small particle size and high reactivity, the nanoscale bimetallic particles may be useful in a wide array of environmental applications including subsurface injection for groundwater treatment.

Introduction

The rediscovery of zero-valent iron for the transformation of chlorinated organic compounds has led to the development and proliferation of a number of environmental applications, particularly in so far as groundwater remediation is concerned. Research in the past few years has demonstrated that metals such as iron and zinc can effectively reduce a broad array of organic compounds such as chlorinated aliphatics [1], [2], [3], [4], [5], [6], nitro aromatics [7], polychlorinated biphenyls (PCBs) [8], pesticides and related compounds [9], [10]. Applications of zero-valent iron for remediating contaminated soils, sediments and aquifers have received particular attention. An attractive feature is that it can be readily incorporated into reactive subsurface barriers via the ‘funnel and gate’ approach [11], [12], [13]. As contaminated water passes through the permeable wall of iron particles, organic contaminants react with iron to form primarily non-toxic end products such as hydrocarbons and chloride ion.

Bimetallic particles (e.g. Pd/Fe, Pd/Zn) have been shown to exhibit a high efficacy for the transformation of many chlorinated compounds. For example, palladized iron has been demonstrated to rapidly dechlorinate chlorinated ethenes such as PCE, TCE, 1,1-DCE, c-DCE, and t-DCE [14]. These compounds can be completely reduced to ethane in just a few minutes. The palladized iron was also noted for its effective transformation of PCBs [15]. Ni/Fe and Cu/Fe were used to transform 1,1,1-trichloroethane [16]. Other bimetals such as Pt/Fe, Pd/Zn have been reported for the degradation of chlorinated benzenes [17].

We reported using nanoscale metallic particles for transformation of TCE, chlorinated benzenes and polychlorinated biphenyls (PCBs) [18], [19]. The nanoscale metallic particles, with diameter on the order of 1 to 100 nm, were synthesized in the laboratory. A small amount (∼0.05% wt.) of Pd was deposited on the iron surface to enhance the reactivity of the metal particles. Preliminary experimental results suggest that reactivity of Pd/Fe particles is significantly higher than that of commercial grade iron particles. Due to their small particle sizes and high reactivity, the nanoscale metal particles may be useful in a wide array of environmental applications. For example, the metal particles could be injected directly into contaminated soils, sediments and aquifers [20], [21] for in situ treatment of chlorinated hydrocarbons, offering a relatively low-cost alternative to such conventional technology as pump and treat, air sparging or reactive barriers.

In this paper, systematic laboratory studies applying the nanoscale bimetallic particles for transformation of chlorinated ethenes (PCE, TCE, t-DCE, c-DCE, 1,1-DCE, VC) are presented. These compounds are among the most prevalent contaminants in soils and aquifers [22], [23]. They have been listed as priority pollutants by the US Environmental Protection Agency, and also on the Superfund National Priority List. These compounds are known or potential threats to public health and the environment so there is an urgent need to develop effective control methods. This study was aimed to: (1) characterize and quantify reaction intermediates and final products; (2) assess the stability of the nanoscale metal particles; and (3) examine their reactivity compared to larger commercial grade iron particles. This information is essential for exploring the possible environmental applications of the nanoscale metal particles.

Section snippets

Preparation of nanoscale metal particles

Synthesis of nanoscale iron particles was achieved by adding 1:1 volume ratio of NaBH₄ (0.25 M) into FeCl₃ · 6H₂O (0.045 M) [17], [18], [19]. The solution was mixed vigorously under room temperature for 5 min (22±1 °C). Ferric iron was reduced by borohydride according to the following reaction: $4 Fe^{3+} +3 BH^{−}_{4} +9 H_{2} O→4Fe^{0} ↓ +3 H_{2} BO_{3}^{−} +12 H^{+} +6 H_{2}$ The borohydrate to ferric iron ratio added was 7.4 times of the stoichiometric requirement according to Equation 1. Excessive borohydrate was the key factor for rapid

Reactions of chlorinated ethenes with nanoscale metallic particles

Reactions of the six chlorinated ethenes with the nanoscale Pd/Fe bimetallic particles are shown in Fig. 1(a–f). Concentrations in the figure are expressed as the molar ratio to initial organic concentrations. As shown in Fig. 1(a), 20 mg l⁻¹ PCE was completely dechlorinated within 90 min. We observed the immediate appearance of ethane corresponding to the disappearance of PCE. Average yield of ethane was 89% after 1 h. Trace amounts of TCE were detected briefly (<1 h). The amount of TCE was

References (31)

W. Zhang et al.
Catalysis Today
(1998)
R. Muftikian et al.
Wat. Res.
(1995)
K. Cantrell et al.
J. Haz. Mat.
(1995)
R.W. Gillham et al.
Ground Water
(1994)
L.J. Matheson et al.
Environ. Sci. Technol.
(1994)
S.W. Orth et al.
Environ. Sci. Technol.
(1996)
D. Burris et al.
J. Envir. Eng.
(1996)
D.P. Siantar et al.
Wat. Res.
(1996)
A. Agrawal et al.
Environ. Sci. Technol.
(1996)
F. Chuang et al.
Environ. Sci. Technol.
(1995)

G.D. Sayles et al.

Environ. Sci. Technol.

(1997)

G.R. Eykhol et al.

Environ. Sci. Technol.

(1998)

R.C. Starr et al.

Ground Water

(1994)

S.F. O'Hannesin et al.

Ground Water

(1998)

A.R. Gavaskar, N. Gupta, B.M. Sass, R.J. Janosy, D. O'Sullivan, Permeable Barriers for Groundwater remediation: Design,...

Cited by (337)

Nitrate reduction to ammonia in Fe/Fe<sup>2+</sup> system: A case study on the mechanism of green rust generation
2024, Separation and Purification Technology
The synthesis of ammonia through nitrate reduction has received increasing attention due to its ability to simultaneously achieve wastewater treatment and energy production. This study investigated the mechanism of high concentration nitrate reduction processes using Fe/Fe²⁺ process. Batch tests were carried out in high level nitrate reduction in Fe/Fe²⁺ system with different particle size iron powder to investigate the evolution of nitrate, nitrite, ammonium, nitrogen balance, and pH in the liquid phase. The characterization results showed that the solid products were γ-FeOOH when ZVI and nitrate react with lower activity. With the increasing of reduction reactivity, green rusts (GRs) generated and divided the reduction process into two phases. ZVI transformed into GRs and finally produced Fe₃O₄. The generation pathways of GRs in this study were mainly consist of the partial oxidation of Fe²⁺ and the hydrolysis of Fe²⁺ combing with the oxidation of Fe(OH)₂. The reactivity between ZVI and nitrate plays a pivotal role in the formation of GRs. This study has provided a more comprehensive exploration of the formation mechanism of green rust during nitrate reduction.
Nitrogen amended graphene catalyses fast reduction of vinyl chloride by nano zerovalent iron
2023, Water Research
Vinyl chloride (VC) is a dominant carcinogenic residual in many aged chlorinated solvent plumes, and it remains a huge challenge to clean it up. Zerovalent iron (ZVI) is an effective reductant for many chlorinated compounds but shows low VC removal efficiency at field scale. Amendment of ZVI with a carbonaceous material may be used to both preconcentrate VC and facilitate redox reactions. In this study, nitrogen-doped graphene (NG) produced by a simple co-pyrolysis method using urea as nitrogen (N) source, was tested as a catalyst for VC reduction by nanoscale ZVI (nZVI). The extent of VC reduction to ethylene in the presence of 2 g/L of nZVI was less than 1% after 3 days, and barely improved with the addition of 4 g/L of graphene. In contrast, with amendment of nZVI with NG produced at pyrolysis temperature (PT) of 950 °C, the VC reduction extent increased more than 10-fold to 69%. The reactivity increased with NG PT increasing from 400 °C to an optimum at 950 °C, and it increased linearly with NG loadings. Interestingly, N dosage had little effect on reactivity if NG was produced at PT of 950 °C, while a positive correlation was observed for NG produced at PT of 600 °C. XPS and Raman analyses revealed that for NG produced at lower PT (<800 °C) mainly the content of pyridine-N-oxide (PNO) groups correlates with reactivity, while for NG produced at higher PT up to 950 °C, reactivity correlates mainly with N induced structural defects in graphene. The results of quenching and hydrogen yield experiments indicated that NG promote reduction of VC by storage of atomic hydrogen, thus increasing its availability for VC reduction, while likely also enabling electron transfer from nZVI to VC. Overall, these findings demonstrate effective chemical reduction of VC by a nZVI-NG composite, and they give insights into the effects of N doping on redox reactivity and hydrogen storage potential of carbonaceous materials.
The effect of Fe–Zn mole ratio (2:1) bimetallic nanoparticles supported by hydroxyethyl cellulose/graphene oxide for high-efficiency removal of doxycycline
2023, Environmental Research
In this research, Hydroxyethyl cellulose – graphene oxide HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1) nanocomposite as adsorbents were fabricated by crosslinking ethylene glycol dimethacrylate (EGDMA) to study the thermodynamic, kinetic and isotherm of doxycycline antibiotic adsorption. The morphology and structure of the adsorbents were analyzed by Fourier transform infrared spectroscopy (FT-IR), Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (FE-SEM- EDX), and Transmission electron microscopy (TEM). The adsorption behavior of doxycycline (DOX) was studied with different parameters including doxycycline concentration, pH, the dose of adsorbent (HEC-GO and HEC-GO/Fe–Zn, mole ratio (2:1)), contact time, and temperature. The optimal conditions for the removal of DOX are pH = 3.0, contact time 100 min, and 20 min for HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1). The removal percentage for HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1) was 97% and 95.5%, respectively. Equilibrium adsorption isotherms such as the Langmuir, Freundlich, and Temkin models were analyzed according to the experimental data. Also, four adsorption kinetics were investigated for removing DOX. The Langmuir isotherm and pseudo-second-order kinetic models provided the best fit for experimental data for HEC-GO and HEC-GO/Fe–Zn mole ratio (2:1). Thermodynamic data showed that negative values of Gibbs free energy (ΔG°) and the negative value of enthalpy (ΔH°) of the adsorption process for adsorbents. It means that DOX removal was a spontaneous and exothermic reaction.
Recent advances in sustainability science for environmental conservation
2023, Role of Green Chemistry in Ecosystem Restoration to Achieve Environmental Sustainability
Mankind is on the brink of an ecological crisis, sitting behind the wheel itself. Sustainability science is concerned with the interactions between humans and the environment to foster long-term sustainable development. It focuses on the prediction and assessments of faults all over the globe and their appropriate remediation with the aid of best-fitting knowledge for the resilience of the global natural systems, social systems, and human systems. The primary goal of sustainability science is the restoration of ultimate functionality to Earth’s ecosystems and landscapes. Climate change, acidification of the oceans, loss of biodiversity, pollution of the environment, deforestation, and changes in the use of land are just a few of the global environmental concerns that are now manifesting on a planetary scale. Pollution is the root and the leading cause of every liability in the ecosystem, it is no less than a bane on the planet. In the ladder of sustainability science, pollution control serves as the side wood that holds all other steps. Here all the plausible sustainable techniques have been discussed that can help out in controlling all types of pollution.
Nanoparticle assisted environmental remediation: Applications, toxicological implications and recommendations for a sustainable environment
2022, Environmental Nanotechnology, Monitoring and Management
Increased consumer demands backed with a rising population has led to an increase in industrial installations and productions. However, these advancements come at the cost of the environment. Pollution of the environment through toxic contaminants released from various anthropogenic sources is a topic of major concern and demands immediate attention. Nanotechnology offers several cost-effective and efficient tools to limit the spread of toxic pollutants in the environment. Environmental remediation employing nanoparticles is one of the latest developments to occur in this regard. The lack of sufficient studies and proper understanding of the interactions of nanoparticles with the environmental components has made the use of nanotechnology a debatable topic. Despite several advantages, the toxicological aspects concerning the use of nanoparticles in the environment are being seriously looked upon. The work in its current form highlights the role of nanoparticles in the remediation of environmental pollutants. It aims to update readers about the successful applications of different nanoparticles and nanoscale materials for environmental clean-up. The toxicological implications of these nanomaterials on living entities of the environment have been briefly discussed. Efforts have been made to address the concern regarding the adverse effect of nanoparticles on the environment by providing certain suggestive measures. The authors suggest the use of biological synthesis methods over other physical and chemical methods of nanoparticle synthesis. Utilizing engineered nanoparticles as one of the remedial options has also been discussed. The article concludes by narrowing down on the relevance of strict regulatory measures that will ensure high environmental standards.
Catalytic hydrolysis: A novel role of zero-valent iron in haloacetonitrile degradation and transformation in unbuffered systems
2021, Science of the Total Environment
Citation Excerpt :
Therefore, the HAN may undergo considerable degradation in the presence of ZVI, which may reduce HAN related health risks before user consumption. In addition, cast iron pipe, rich in ZVI, is widely used in drinking water distribution systems (Agrawal and Tratnyek, 1996; Al-Jasser, 2007; Alowitz and Scherer, 2002; Arnold and Roberts, 2000; Bae and Hanna, 2015; Bae and Lee, 2010; Bond et al., 2011; Bull et al., 1985; Chen et al., 2018; Chu et al., 2010, 2016; Fang et al., 2011; Glezer et al., 1999; Guan et al., 2015; Hancock, 1999; Hozalski et al., 2001; Huang et al., 2018; Johnson et al., 2009; Krasner et al., 1989, 2006; Le Curieux et al., 1995; Lien and Zhang, 2001; Matheson and Tratnyek, 1994; Muellner et al., 2007; Muller-Pillet et al., 2000; Orth and Gillham, 1995; Plewa et al., 2008, 2010, 2017; Rossman et al., 2001; Shah and Mitch, 2012; Simmon et al., 1977; Song and Carraway, 2005, 2006; Stucki, 1981; Sun et al., 2006; Wagner and Plewa, 2017; Wang et al., 2015, 2018; Wei et al., 2010; Yun and Reckhow, 2015; Zhang et al., 2017, 2020). Exploring the attenuation of HANs in ZVI system can also provide a view for the fate of HANs in the water distribution system.
Efforts to remove highly toxic haloacetonitriles (HANs) is an important step to reduce health risks associated with disinfection by product exposure. Zero valent iron (ZVI) is a versatile material, whose reductant, sorbent and coagulant role has been well understood. However, their catalytic role is less known. In this study, the degradation and transformation of HANs in ZVI system were investigated. Significant decreases of the four HANs in ZVI system were observed, and haloacetamides and haloacetic acids (hydrolysis products of HANs) were the dominant transformation products of HANs. However dehalogenated HANs, Fe (II) and Fe (III) were rarely detected after reaction, indicating that the ZVI acted as a catalyst to promote the hydrolysis of HANs, rather than other previously reported causes (dehalogenation or redox reaction). The HAN degradation rates were dramatically affected by the initial pH, ZVI doses and initial HAN concentration. Kinetic analysis indicated that HAN removal was enhanced with the increase of initial pH (5–9), ZVI doses (1–10 g/L), and initial HAN concentration (25–200 μg/L). ZVI induced the transformation of HANs to haloacetamides, haloacetic acids and other de-halogenated compounds, which reduced the cytotoxicity and genotoxicity by 88% and 85%, respectively. This study helped to understand the fate of HAN during the transmission in cast iron pipes, and provided a theoretical foundation for future HAN control and monitoring efforts.

View all citing articles on Scopus

View full text

Nanoscale iron particles for complete reduction of chlorinated ethenes

Abstract

Introduction

Section snippets

Preparation of nanoscale metal particles

Reactions of chlorinated ethenes with nanoscale metallic particles

Catalysis Today

Wat. Res.

J. Haz. Mat.

Ground Water

Environ. Sci. Technol.

Environ. Sci. Technol.

J. Envir. Eng.

Wat. Res.

Environ. Sci. Technol.

Environ. Sci. Technol.

Environ. Sci. Technol.

Environ. Sci. Technol.

Ground Water

Ground Water