Long-term electrode behavior during treatment of arsenic contaminated groundwater by a pilot-scale iron electrocoagulation system

Bandaru, Siva; Roy, Abhisek; Gadgil, Ashok; Genuchten, Case M. van

doi:10.1016/j.watres.2020.115668

Cited by 69 publications

(30 citation statements)

References 28 publications

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“…The results of this work also provide critical information to help guide the operation of As drinking water treatment. Coprecipitation of magnetite with As has been reported during the operation of a variety of modular Fe(0)-based systems, including the SONO filter , and Fe(0) electrocoagulation . The safe handling, storage, and ultimate disposal of the As-rich waste generated from As removal remains one of the most important challenges for sustainable As treatment, especially for household or community-scale plants deployed in rural, low-income regions.…”

Section: Discussionmentioning

confidence: 89%

“…Following published protocols, , each batch of As-CoPPT-Mag was generated by dosing a total of 3 mM Fe(II) by Fe(0) electrolysis open to the atmosphere using a charge dosage rate of 200 mA and an electrolysis time of 10 min, which equates to an Fe(II) dosage rate of 300 μM/min. The initial As/Fe ratios were 1 mol % for the As(V) experiments and 0.5 mol % for the As(III) experiments, which match the As/Fe ratios of drinking water treatment residuals . During the electrolysis stage, electrochemically generated Fe(II) consumed DO from the initial value of 3.0 mg/L to <0.1 mg/L.…”

Section: Methodsmentioning

confidence: 98%

“…Coprecipitation of magnetite with As has been reported during the operation of a variety of modular Fe(0)-based systems, including the SONO filter 14,15 and Fe(0) electrocoagulation. 26 The safe handling, storage, and ultimate disposal of the As-rich waste generated from As removal remains one of the most important challenges for sustainable As treatment, especially for household or community-scale plants deployed in rural, lowincome regions. The observation that As-CoPPT-Mag is a highly stable solid reaction product resistant to As release over prolonged periods is a key finding in the context of long-term waste storage.…”

Section: Persistence Of Structural Fe(ii) Andmentioning

confidence: 99%

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The Enhanced Stability of Arsenic Coprecipitated with Magnetite during Aging: An XAS Investigation

Genuchten

2022

Ind. Eng. Chem. Res.

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The coprecipitation of magnetite (Fe3O4) with arsenic (As) is a potential remediation technique for As-contaminated groundwater that can be applied to meet increasingly stringent As drinking water limits. However, knowledge of the fate of As coprecipitated with magnetite during aging for extended periods is lacking, which is critical to predict the long-term efficiency of this As treatment strategy. In this work, I combined aqueous As measurements with solid-phase characterization by synchrotron-based Fe and As K-edge X-ray absorption spectroscopy (XAS) to track the transformation of magnetite and the speciation of coprecipitated As(V) or As(III) for up to a year in oxic or anoxic conditions. It was determined that the initial magnetite particle increased in crystallinity for all aging experiments, but some differences in solid-phase Fe speciation were detected depending on aging conditions. For the anoxic aging samples with initial As(V), a significant fraction (15% of the total Fe) of maghemite (a magnetic Fe oxide spinel with formula γ-Fe2O3) was identified, which was coupled to As(V) reduction [As(III) was ∼30% of the total sorbed As], suggesting electron transfer between magnetite and particle-bound As(V). In the oxic aging experiments, the initial particle crystallized, with a large fraction of Fe(III) (oxyhydr)oxides (i.e., maghemite and lepidocrocite, γ-FeOOH) in the final products. Despite increased crystallinity suggested by Fe XAS analysis, sorbed As was not released from the particles in any experiment (aqueous As never exceeded 1 μg/L). This remarkable stability of As coprecipitated with magnetite was revealed by As K-edge XAS to be largely due to the formation of distinct multinuclear As uptake modes [i.e., As(V) incorporation; hexanuclear 3C As(III) complexes]. These results demonstrate the unique potential of magnetite for long-term As sequestration.

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Section: Discussionmentioning

confidence: 89%

Section: Methodsmentioning

confidence: 98%

Section: Persistence Of Structural Fe(ii) Andmentioning

confidence: 99%

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The Enhanced Stability of Arsenic Coprecipitated with Magnetite during Aging: An XAS Investigation

Genuchten

2022

Ind. Eng. Chem. Res.

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“…Electrodes and sludge characterization showed that silica is removed through charge neutralization with polyaluminum hydroxide, and hardness is removed through a coprecipitation reaction on the surface of cathode. The resistance of the anode and cathode decreased with an increase in applied current density, thus allowing faster charge transfer. − When compared to the removal obtained through chemical coagulation, EC removes almost 50% more silica at the same aluminum charge loading. Furthermore, EC eliminates the higher salinity associated with chemical coagulation, and additional chemicals are not required for pH adjustment.…”

Section: Discussionmentioning

confidence: 99%

Electroprecipitation Mechanism Enabling Silica and Hardness Removal through Aluminum-Based Electrocoagulation

et al. 2022

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We evaluate the effectiveness of an aluminum-based electrocoagulation pretreatment system to remove dissolved silica and hardness. Silica and hardness limit water recovery during membrane-based desalination applications when silica and hardness exceed the solubility limit and generate scale on the membrane surface. We show that simultaneous removal of nearly all silica (95 ± 4%) and a significant amount of hardness (40–60%) occurs with a hydraulic residence time of 2 h and a charge loading between 0 and 1200 C/L. Increasing the residence time maximized the hardness removal (58 ± 8%) via the formation of larger flocs, which allowed for more constituent removal by gravity settling. We highlight the trade-offs between improved energy efficiency at lower charge loadings and an improved removal rate at a higher charge loading. We further compare the percente of silica and hardness removed in multicomponent solutions and compare this to single component feed solution. We discuss the implications that operational considerations have in terms of cost and treatment capacity. Finally, a cost–benefit analysis comparing chemical coagulation with electrocoagulation indicates that electrocoagulation could be half the cost of chemical coagulation and could produce more stable effluent pH and conductivity.

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“…The functional unit is 1.0 kg of As.For reference of conventional water treatment volumes, on average, approximately 90,000 m 3 /d is produced for a US water treatment plant serving over 50,000 people 52. For decentralized treatment, an As removal plant currently serving a school of 2500 students in West Bengal, India has the capacity to treat 1700 m 3 (1.0 kg As generated) in less than 6 months 3,53.…”

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confidence: 99%

LCA of Disposal Practices for Arsenic-Bearing Iron Oxides Reveals the Need for Advanced Arsenic Recovery

Genuchten

Etmannski

Jessen

et al. 2022

Environ. Sci. Technol.

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Iron (Fe)-based groundwater treatment removes carcinogenic arsenic (As) effectively but generates toxic As-rich Fe oxide water treatment residuals (As WTRs) that must be managed appropriately to prevent environmental contamination. In this study, we apply life cycle assessment (LCA) to compare the toxicity impacts of four common As WTR disposal strategies that have different infrastructure requirements and waste control: (i) landfilling, (ii) brick stabilization, (iii) mixture with organic waste, and (iv) open disposal. The As disposal toxicity impacts (functional unit = 1.0 kg As) are compared and benchmarked against impacts of current methods to produce marketable As compounds via As mining and concentrate processing. Landfilling had the lowest non-carcinogen toxicity (2.0 × 10–3 CTUh), carcinogen toxicity (3.8 × 10–5 CTUh), and ecotoxicity (4.6 × 103 CTUe) impacts of the four disposal strategies, with the largest toxicity source being As emission via sewer discharge of treated landfill leachate. Although landfilling had the lowest toxicity impacts, the stored toxicity of this strategy was substantial (ratio of stored toxicity/emitted As = 13), suggesting that landfill disposal simply converts direct As emissions to an impending As toxicity problem for future generations. The remaining disposal strategies, which are frequently practiced in low-income rural As-affected areas, performed poorly. These strategies yielded ∼3–10 times greater human toxicity and ecotoxicity impacts than landfilling. The significant drawbacks of each disposal strategy indicated by the LCA highlight the urgent need for new methods to recover As from WTRs and convert it into valuable As compounds. Such advanced As recovery technologies, which have not been documented previously, would decrease the stored As toxicity and As emissions from both WTR disposal and from mining As ore.

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Long-term electrode behavior during treatment of arsenic contaminated groundwater by a pilot-scale iron electrocoagulation system

Cited by 69 publications

References 28 publications

The Enhanced Stability of Arsenic Coprecipitated with Magnetite during Aging: An XAS Investigation

The Enhanced Stability of Arsenic Coprecipitated with Magnetite during Aging: An XAS Investigation

Electroprecipitation Mechanism Enabling Silica and Hardness Removal through Aluminum-Based Electrocoagulation

LCA of Disposal Practices for Arsenic-Bearing Iron Oxides Reveals the Need for Advanced Arsenic Recovery

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