| 1. |
- Antelo, Juan, et al.
(author)
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Stability of naturally occurring AMD–schwertmannite in the presence of arsenic and reducing agents
- 2021
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In: Journal of Geochemical Exploration. - : Elsevier. - 0375-6742 .- 1879-1689. ; 220
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Journal article (peer-reviewed)abstract
- Secondary iron oxides formed in acid mine drainage, such as schwertmannite, are scavengers for metal(loid)s in mining environments. Increasing the understanding of the geochemical transformations of these minerals, as well as knowing how metal(loid)s affect these transformations, is crucial to ultimately predict the fate of these trace elements in acidic mine drainage and to minimize the potential environmental risk. In this study, transformation experiments have been conducted with a schwertmannite-rich sediment collected from a mining area and with synthesized schwertmannite as a reference material. The transformation of schwertmannite into goethite was studied as a function of the presence of arsenic, pH value, and redox conditions. Arsenic delayed the mineral transformation from pseudo-stable amorphous phases to more stable crystalline forms, especially at higher arsenic loadings and more acidic pH. Experiments in the presence of Fe(II) and ascorbic acid have proven that both components promote the mineral transformation or reductive dissolution of schwertmannite under anoxic conditions. The presence of arsenic reduced the catalytic effect of Fe(II), stabilizing the schwertmannite particles. On the other hand, arsenic had no effect on the reductive dissolution at these conditions when ascorbic acid was used as a reducing agent. © 2020 Elsevier B.V.
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| 2. |
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| 3. |
- Carabante, Ivan, et al.
(author)
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Adsorption of As (V) on iron oxide nanoparticle films studied by in situ ATR-FTIR spectroscopy
- 2009
-
In: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 346:1-3, s. 106-113
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Journal article (peer-reviewed)abstract
- Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. Fundamental studies are needed to establish under which conditions the complexes formed are stable. In the present work, a powerful technique, viz. ATR-FTIR spectroscopy, is adapted to studies of adsorption of arsenate species on iron oxides. This technique facilitates acquisition of both quantitative and qualitative in situ adsorption data.In the present work, about 800 nm thick films of 6-lineferrihydrite were deposited on ZnSe ATR crystals. Arsenate adsorption on the ferrihydrite film was studied at pD values ranging from 4 to 12 and at an arsenate concentration of 0.03 mM in D2O solution. The amount of adsorbed arsenate decreased with increasing pD as a result of the more negatively charged iron oxide surface at higher pD values. The adsorption and desorption kinetics were also studied. Arsenate showed a higher adsorption rate within the first 70 minutes and a much lower adsorption rate from 70 up to 300 minutes. The low adsorption rate at longer reaction times was partly due to a low desorption rate of already adsorbed carbonate species adsorbed at the surface. The desorption of carbonate species was evidenced by the appearance of negative absorption bands. The desorption of adsorbed arsenate complexes was examined by flushing with D2O at pD 4 and 8.5 and it was found that the complexes were very stable at pD 4 suggesting formation of mostly inner-sphere complexes whereas a fraction of the complexes at pD 8.5 were less stable than at pD 4, possibly due to the formation of outer-sphere complexes.In summary, the ATR technique was shown to provide in situ information about the adsorption rate, desorption rate and the speciation of the complexes formed within a single experiment, which is very difficult to obtain using other techniques.
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| 4. |
- Carabante, Ivan
(author)
-
Arsenic (V) adsorption on iron oxide : implications for soil remedeation and water purification
- 2012
-
Doctoral thesis (other academic/artistic)abstract
- Addition of iron oxide based adsorbents to arsenic contaminated soils has been proposed as a mean to reduce the mobility of arsenic in the soil. However, the conditions in the soil such as pH value, the presence of phosphate after addition of fertilizer to the soil or the presence of Zn (II) as a co-contaminant may affect the adsorption of arsenate on the iron oxide and may therefore have implications for the mobility of arsenic in the remediated soil.In the present work, a new flow method was developed to study the adsorption of arsenate on synthetic iron oxide with high surface area (ferrihydrite) in situ by means of Attenuated Total Reflection – Fourier Transform Infrared (ATR – FTIR) spectroscopy and the method was used for studying how the adsorption of arsenate was affected by the pH/pD value, the presence of phosphate and Zn (II) in the system. The highest adsorption of arsenate was found at pD 4 and decreased as the pD value increased. The arsenate complexes formed on ferrihydrite appeared to be very stable at pD 4, while the stability decreased as the pD value increased. Arsenate showed a higher adsorption affinity than phosphate on ferrihydrite under the conditions studied. However, phosphate was able to replace about 10 % of pre-adsorbed arsenate on ferrihydrite at pD 4 and about 20 % of the pre-adsorbed arsenate at pD 8.5 in equimolar concentrations of phosphate and arsenate. Phosphate replaced 30 % of pre-adsorbed arsenate at pD 4 and up to 50 % of pre-adsorbed arsenate at pD 8.5 when the concentration of phosphate in the system was 5 times higher than that of arsenate. Batch adsorption experiments indicated an enhancement in the arsenate removal from a ferrihydrite suspension in the presence of Zn (II) at pH 8 in accordance with previous reports. However, no adsorption of arsenate on ferrihydrite in the presence of high concentrations of Zn (II) in the system was observed by infrared spectroscopy. Instead, precipitation of zinc hydroxide carbonate followed by arsenate adsorption on the zinc precipitate was found to be the most likely explanation of these results.Although iron oxides are selective towards arsenate, high specific surface areas are required to achieve sufficiently high adsorption capacity. A method of increasing the specific surface area of coarse hematite particles to obtain a good adsorbent was also developed in the present work. The method comprises an acid treatment to produce iron ions followed by hydrolysis to precipitate an iron oxy-hydroxide coating on the hematite particles. While the arsenate adsorption capacity of the original coarse hematite particles was found to be negligible, the sintered coarse hematite particles showed good potential as an adsorbent for arsenate with an adsorption capacity of about 0.65 mg[As]/g.The method developed for studying adsorption on iron oxides by in situ ATR - FTIR spectroscopy was further developed for studying the adsorption of flotation collectors on iron oxides. Iron ore is often separated from gangue minerals by means of reverse flotation in which a surfactant should selectively adsorb on the gangue mineral rendering it hydrophobic. However, unwanted adsorption of the surfactants on the iron oxide has been reported to affect the production of iron ore pellets. A method was developed to study the adsorption of the surfactant Atrac 1563 on synthetic hematite in situ by means of ATR - FTIR spectroscopy. The adsorption of Atrac 1563 on hematite at pH 8.5 was found to mostly occur via interactions between the polar ester and ethoxy groups of the surfactant and the hematite surface.
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| 5. |
- Carabante, Ivan, et al.
(author)
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In situ ATR-FTIR studies on the competitive adsorption of arsenate and phosphate on ferrihydrite
- 2010
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In: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 351:2, s. 523-531
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Journal article (peer-reviewed)abstract
- In the present study, in-situ ATR-FTIR spectroscopy was used for the first time to study the competitive adsorption of phosphate and arsenate on ferrihydrite. Deuterium oxide was used as solvent to facilitate the interpretations of recorded infrared spectra.It was found that arsenate and phosphate adsorbed more strongly at lower pD values, showing similarities in the adsorption behavior as a function of pD. However, arsenate complexes were found to be more strongly adsorbed than phosphate complexes in the pD range studied. About five times higher concentration of phosphate in solution was needed to reduce the absorbance due to pre-adsorbed arsenate to the same relative level as for pre-adsorbed phosphate, which was desorbed using a solution containing equal (molar) concentrations in arsenate and phosphate. At pD 4, two phosphate complexes were adsorbed on the iron oxide, one deuterated and one de-deuterated. When phosphate was pre-adsorbed and arsenate subsequently added to the system, the deuterated phosphate complex desorbed rapidly while the de-deuterated phosphate complex was quite stable. At pD 8.5, only the de-deuterated phosphate complex was adsorbed on the iron oxide. Moreover, the arsenate adsorbed was also predominantly de-deuterated as opposite to the arsenate adsorbed at pD 4. During the substitution experiments the configuration of these complexes on the iron oxide surface did not change. To the best of our knowledge, this is the first time this difference in stability of the different phosphate complexes is reported and shows the power of employing in-situ spectroscopy for this kind of studies.
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| 6. |
- Carabante, Ivan, et al.
(author)
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Influence of Zn(II) on the adsorption of arsenate onto ferrihydrite
- 2012
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 46:24, s. 13152-13159
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Journal article (peer-reviewed)abstract
- Addition of iron oxide to arsenic-contaminated soil has been proposed as a means of reducing the mobility of arsenic in the soil. Arsenic and zinc are common coexisting contaminants in soils. The presence of zinc therefore may affect the adsorption properties of arsenic on iron oxide, and may thus affect its mobility in the soil. The influence of Zn(II) on the adsorption of arsenate ions on iron oxide was studied. Batch adsorption experiments indicated that Zn(II) increased the arsenate removal from a solution by ferrihydrite at pH 8. However, ATR-FTIR spectroscopy showed that no adsorption of arsenate on a ferrihydrite film occurred at pD 8 in the presence of Zn(II). Precipitation of zinc hydroxide carbonate followed by arsenate adorption onto the precipitate was found to be a plausible mechanism explaining the arsenate removal from a solution in the presence of Zn(II) at pH/pD 8. The previously suggested mechanisms attributing the enhanced removal of arsenate from solution in the presence of Zn(II) to additional adsorption on iron oxides could not be verified under the experimental conditions studied. It was also shown that at pH/pD 4, the presence of Zn(II) in the system did not significantly affect the adsorption of arsenate on ferrihydrite.
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| 7. |
- Carabante, Ivan, et al.
(author)
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Reciprocal influence of arsenic and iron on the long-term immobilization of arsenic in contaminated soils
- 2018
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In: Environmental Arsenic in a Changing World. - London : Taylor & Francis. ; , s. 467-469
-
Conference paper (peer-reviewed)abstract
- The main aim of this work was to evaluate the fate of arsenic associated with iron minerals in contaminated soils. The ageing behavior of synthetic arsenic-bearing poorly crystalline minerals – ferrihydrite and schwertmannite – was studied. Arsenic showed a passivation effect on poorly crystalline minerals, delaying their transformation towards more crystalline iron oxides. These results agreed well with studies performed on contaminated soils and sediments. These results are relevant in order to understand the long-term mobility of arsenic in contaminated soils and sediments. Iron oxides sequesters arsenic efficiently and, reciprocally, arsenic stabilize the mineral, delaying its transformation towards more crystalline phases.
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| 8. |
- Carabante, Ivan, et al.
(author)
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Reutilization of porous sintered hematite bodies as effective adsorbents for arsenic(V) removal from water
- 2014
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 53:32, s. 12689-12696
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Journal article (peer-reviewed)abstract
- A method was developed to enhance the arsenic adsorption capacity of porous bodies of sintered hematite. The method comprised the formation of a coating of 1 wt % iron oxide nanoparticles on the raw material. The nanoparticles showed two distinct habits: spherical habit, likely ferrihydrite, and acicular habit, likely goethite and/or akaganéite. The specific surface area of the hematite raw material increased from 0.5 to 3.75 m2/g, and the adsorption capacity increased from negligible to 0.65 mg of [As]/g as calculated from equilibrium and breakthrough adsorption data. Equilibrium adsorption data of arsenate on the adsorbent from a solution at pH 5 followed the Langmuir model, while breakthrough adsorption data for a 500 μg/L arsenate solution at pH 5 followed the Thomas model. The adsorbed arsenic could be desorbed using distilled water at pH 12. These results show the potential for the reutilization of waste products comprising coarse hematite bodies as adsorbents.
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| 9. |
- Carabante, Ivan
(author)
-
Study of arsenate adsorption on iron oxide by in situ ATR-FTIR spectroscopy
- 2009
-
Licentiate thesis (other academic/artistic)abstract
- Stabilization of arsenic contaminated soils by iron oxides has been proposed as a remediation technique to prevent leaching of arsenate into the environment. However, fundamental studies are needed to establish under which conditions the complexes formed are stable. A new method based on ATR-FTIR spectroscopy was adapted to study the adsorption of arsenate species on iron oxides. The measurements required the use of D2O as solvent. The amount of arsenate complexes adsorbed on the iron oxide increased with decreasing pD in the range studied, viz. pD 4-12. Arsenate complexes adsorbed at pD 4 desorbed from the film to some extent as the pD was increased to 8.5 or 12. The stability of arsenate complexes adsorbed on the iron oxide evidently changed with the change in pD, most likely due to the electrostatic repulsion between the negatively charged oxoanion and the more negatively charged iron oxide as the pD increased. From competitive adsorption experiments it was found that arsenate species were more strongly bonded to the iron oxide than phosphate species. Furthermore, it was found that two different phosphate complexes formed on the iron surface at pD 4, one deuterated and the other one de-deuterated. The complexes showed very different stability. The deuterated phosphate complex was desorbed easily from the iron oxide film as arsenate was added to the system whereas the de-deuterated phosphate complex only desorbed slightly from the film upon adding arsenate.This work has increased the fundamental knowledge of the iron oxide/arsenate/phosphate system, which will be of importance for the development of more effective soil remediation techniques.
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| 10. |
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| 11. |
- Garcia, Gustavo, et al.
(author)
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Preparation of zeolite A with excellent optical properties from clay
- 2015
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In: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 619, s. 771-777
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Journal article (peer-reviewed)abstract
- Discoloration of zeolite A powder is a common problem when natural raw materials such as kaolin clay are used because of the formation of colored iron compounds. In this study, we report on a novel method to produce zeolite A with excellent optical properties, from clays. The brightness is as high as 94.5 and the yellowness is as low as 3.0. The product is comprised of intergrown zeolite A crystals with cubic habit and a length ranging between 0.5 and 2 μm. Good optical properties are obtained when the raw material contains magnesium, as some natural raw materials do, or alternatively, when a magnesium compound is added to the raw material. Magnesium probably forces iron inside colorless extraneous magnesium aluminosilicate compounds. This simple process appears very promising for the preparation of zeolite A with good optical properties from inexpensive natural raw materials.
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| 12. |
- Gusiatin, Zygmunt Mariusz, et al.
(author)
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Remediation of smelter contaminated soil by sequential washing using biosurfactants
- 2021
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In: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 18:24
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Journal article (peer-reviewed)abstract
- This paper presents experimental results from the use of biosurfactants in the remediation of a soil from a smelter in Poland. In the soil, concentrations of Cu (1659.1 mg/kg) and Pb (290.8 mg/kg) exceeded the limit values. Triple batch washing was tested as a soil treatment. Three main variants were used, each starting with a different plant-derived (saponin, S; tannic acid, T) or microbial (rhamnolipids, R) biosurfactant solution in the first washing, followed by 9 different sequences using combinations of the tested biosurfactants (27 in total). The efficiency of the washing was determined based on the concentration of metal removed after each washing (CR), the cumulative removal efficiency (Ecumulative) and metal stability (calculated as the reduced partition index, Ir, based on the metal fractions from BCR sequential extraction). The type of biosurfactant sequence influenced the CR values. The variants that began with S and R had the highest average Ecumulative for Cu and Pb, respectively. The Ecumulative value correlated very strongly (r > 0.8) with the stability of the residual metals in the soil. The average Ecumulative and stability of Cu were the highest, 87.4% and 0.40, respectively, with the S-S-S, S-S-T, S-S-R and S-R-T sequences. Lead removal and stability were the highest, 64–73% and 0.36–0.41, respectively, with the R-R-R, R-R-S, R-S-R and R-S-S sequences. Although the loss of biosurfactants was below 10% after each washing, sequential washing with biosurfactants enriched the soil with external organic carbon by an average of 27-fold (S-first variant), 24-fold (R first) or 19-fold (T first). With regard to environmental limit values, metal stability and organic carbon resources, sequential washing with different biosurfactants is a beneficial strategy for the remediation of smelter-contaminated soil with given properties.
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| 13. |
- Johansson, Kim, et al.
(author)
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Immobilisation of arsenic in contaminated soil by electrokinetics in an outdoor experiment
- 2024
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In: Science of the Total Environment. - : Elsevier B.V.. - 0048-9697 .- 1879-1026. ; 918
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Journal article (peer-reviewed)abstract
- Although landfilling is environmentally and economically unsustainable, it is the dominant soil remediation method in EU member states. This paper describes part of a study on mixed contaminants that investigated the stabilisation of arsenic (As) in contaminated soil in an outdoor box experiment with electrokinetic treatment (EK). The experiment was conducted in two 1 m3 boxes, each containing a 20 cm bottom layer of sand, overlaid with 20 cm of peat. In EK, a pulsating, low-voltage current was applied with the intention of corroding the zerovalent iron (Fe) electrodes, migrating ionic Fe species, and forming secondary iron minerals, thereby immobilizing As. Porewater samples were collected over two seasons to determine whether the treatment decreased the concentration of dissolved As. Sequential extraction was performed on the soil samples to determine whether the fraction of Fe-bound As increased. Reed canary grass was planted in one of the boxes during the second season and analysed for As uptake. The results showed that the treatment decreased the porewater As concentration in sand by 50–54 %, while the concentration of Fe increased. The sequential extraction of sand showed that the fraction of As bound to poorly crystalline Fe oxides increased during this time. This treatment effect was less visible in the peat. Moreover, the exchangeable As fraction increased in both peat and sand, most likely because of the decrease in redox potential at the end of the experiment. The plants grown in treated soil accumulated less As than those grown in untreated soil, indicating that the phytoavailable As fraction decreased. This study showed that EK remediation can be a suitable in situ remediation technique, mostly in sand. Future research should focus on redox control to further optimise EK remediation and ensure long-term As stability in treated soils.
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| 14. |
- Kasiuliene, Alfreda, et al.
(author)
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Hydrothermal carbonisation of peat-based spent sorbents loaded with metal(loid)s
- 2019
-
In: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 26:23, s. 23730-23738
-
Journal article (peer-reviewed)abstract
- Hydrothermal carbonisation (HTC) is a wet and relatively low-temperature process where, under autogenous pressures, biomass undergoes a chain of reactions leading to the defragmentation of organic matter. As well as its other uses (e.g. for producing low-cost carbon-based nano-compounds), HTC is utilised for the treatment of wet wastes, such as manure and biosludge. This study aimed to determine if hydrothermal carbonisation is a feasible treatment method for spent sorbents that are highly enriched with arsenic, chromium, copper, and zinc. The chemical properties of hydrochar and process liquid were evaluated after HTC treatment, where peat-based spent sorbents were carbonised at 230 °C for 3 h. Analysis of Fourier transform-infrared spectra revealed that during HTC, the oxygenated bonds of ethers, esters, and carboxylic groups were cleaved, and low-molecular-weight organic fragments were dissolved in the process liquid. A large fraction of arsenic (up to 62%), copper (up to 25%), and zinc (up to 36%) were transferred from the solids into the process water. Leaching of these elements from the hydrochars increased significantly in comparison with the spent sorbents.
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| 15. |
- Kasiuliene, Alfreda, et al.
(author)
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Iron coated peat as a sorbent for the simultaneous removal of arsenic and metals from contaminated water
- 2018
-
In: Environmental Arsenic in a ChangingWorld - 7th International Congress and Exhibition Arsenic in the Environment, 2018. - London : CRC Press/Balkema. - 9781138486096 ; , s. 439-440, s. 439-440
-
Conference paper (peer-reviewed)abstract
- This study aimed at combining peat, an industrial residue, with Fe(II)-Fe(III) compound to produce a sorbent suitable for a simultaneous removal of arsenic (As) and metals (cadmium, copper, nickel, lead, zinc) from a contaminated water. Using a newly produced sorbent – iron-peat – the removal of As from contaminated water was almost 17 times higher than using an uncoated peat. On the other hand, the removal of metals by the iron-peat was slightly less efficient in comparison to the uncoated peat. Simultaneous removal of As and metals could be seen as an advantage over multiple-step treatment of contaminated groundwater.
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| 16. |
- Kasiuliene, Alfreda, et al.
(author)
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Leaching of metal(loid)s from ashes of spent sorbent and stabilisation effect of calcium-rich additives
- 2020
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In: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 27:23, s. 29248-29256
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Journal article (peer-reviewed)abstract
- Contaminated water with multiple contaminants, including As, Cr, Cu and Zn, was treated with a sorbent prepared by coating peat with Fe oxides. Because As has a relatively little explored market, the regeneration of the spent sorbent was not feasible. Meanwhile, the disposal of As wastes in landfills can cause landfill leachate treatment problems. Under the reducing conditions prevailing at landfills, As(V) is reduced to As(III), which is a toxic and more mobile form. In this study, incineration was explored as a management option to treat the spent sorbent that was loaded with As, Cr, Cu and Zn. The first objective of this study was to evaluate the leaching of these metal(loid)s from the ashes and compare it with the leaching from the spent sorbents before incineration. The second objective was to evaluate the leaching behaviour when the spent sorbent was co-incinerated with a Ca-rich additive (lime). To achieve these objectives, the obtained ashes were subjected to leaching tests, sequential extraction, and X-ray diffraction analyses. After the incineration, the ash content ranged from 9 to 19% of the initial mass of the spent sorbents. The leaching of As, Cu and Zn decreased compared with that from the spent sorbents before the thermal treatment because of the high incineration temperatures and/or co-incineration with lime. However, the leaching of Cr increased, which would hinder the disposal of the obtained ashes in a landfill because the limit value for disposal at a landfill for hazardous wastes was exceeded by 50 times. However, co-incineration with 10 wt% lime significantly decreased the leaching of Cr as a result of the formation of water-insoluble Ca-Cr compounds.
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| 17. |
- Kasiuliene, Alfreda
(author)
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Peat Coated with Iron Oxides : Purification of Metal(loid)-Contaminated Water and Treatment of the Spent Adsorbent
- 2019
-
Doctoral thesis (other academic/artistic)abstract
- In Sweden due to the industrial activities, such as wood impregnation, multiple point sources of arsenic (As) contamination in soil and water bodies are scattered over the country. Metals, such as chromium (Cr), copper (Cu), lead (Pb), nickel (Ni), cadmium (Cd) or zinc (Zn) at varying concentrations are usually present as well. Since adsorption is a common method to purify contaminated water, research and development of adsorbents have been actively carried out in the last few decades. However, seldom spent sorbent is safely handled afterwards and often end up in landfill, thus creating new problems and posing new risks to humans and environment.The aim of this study was to develop a waste-based adsorbent for simultaneous removal of As and associated metals: Cr, Cu and Zn, and to analyse sustainable ways how to manage the spent adsorbent without creating secondary pollution.In the model system two well-establish adsorbents: Fe oxides (deriving from FeCl3) and peat (waste-based), were combined and the concept of simultaneous removal of cationic and anionic contaminants was tested in a batch adsorption experiment. Due to Fe coating, removal of As and Cr increased by 80% and 30%, respectively, as compared to non-coated peat. Removal of Cu and Zn was higher (up to 15%) on non-coated peat than on Fe-coated peat. Similar results were obtained in the up-scaled column adsorption experiment, where Fe salt was substituted with a waste-based Fe hydrosol. Within the same pH environment (pH=5), Fe-coated peat effectively adsorbed all four investigated contaminants (As, Cr, Cu and Zn). Non-coated peat was effective for Cr, Cu and Zn. While, Fe oxides (coated on sand) adsorbed only As.Three management strategies for spent adsorbents, obtained after column adsorption experiment, were investigated in this study. i) Long-term deposit in a landfill was simulated by exposing spent adsorbents to a reducing environment and evaluating metal(loid) leaching. Leaching of As increased manifold (up to 60% in a 200-day experiment) as compared to the standardized batch leaching experiment under oxidizing conditions. It was determined that about one third of As(V) was reduced to As(III), which is more mobile and toxic. ii) Valorisation of the spent adsorbent was attempted through hydrothermal carbonisation. It was expected that obtained hydrochar could be used as a beneficial soil amendment. However, treatment resulted in the process liquid and the hydrochar both having high loads of As, Cu and Zn. Additional treatment of process water and hydrochar imply higher management costs for spent adsorbents. iii) Possibility of thermal destruction was investigated by combusting spent adsorbents. After the treatment volume of the waste (ash) was by 80-85% smaller as compared to spent adsorbents. Combustion at higher temperature (1100 °C vs 850 °C) resulted into a weaker metal(loid) leaching from ashes. Furthermore, co-combustion with calcium (Ca)-rich lime (waste-based) decreased leaching of all four investigated elements, Cr in particular, below the limit values for waste being accepted at landfills for hazardous waste. Therefore, combustion enabled possibility of safe and long-term deposit of As-bearing ashes. At the same time, less As would be circulating in society. For the future work, studies that could broaden the spectrum of contaminants targeted by Fe-coated peat would be beneficial. At the same time it is important not only to find alternative utilisation methods for Fe-coated peat, but also investigate other management options for the spent adsorbents.
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| 18. |
- Kasiuliene, Alfroda, et al.
(author)
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Removal of metal(oid)s from contaminated water using iron-coated peat sorbent
- 2018
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 198, s. 290-296
-
Journal article (peer-reviewed)abstract
- This study aimed at combining iron and peat to produce a sorbent suitable for a simultaneous removal of cations and anions from a solution. Peat powder, an industrial residue, was coated with iron by immersing peat into iron salt solutions. The adsorption efficiency of the newly produced sorbent towards As, Cr, Cu and Zn was tested by means of batch adsorption experiments at a constant pH value of 5. Coating of Fe on peat significantly increased the adsorption of As (from <5% to 80%) and Cr (from <3% to 25%) in comparison to uncoated peat. Removal of cations on coated peat slightly decreased (by 10–15%), yet remained within acceptable range. Electron Microscopy combined with X-Ray Energy Dispersive Spectroscopy revealed that iron coating on the peat was rather homogenous and As and Cr were abundantly adsorbed on the surface. By contrast, Cu and Zn displayed a sparing distribution on the surface of the iron coated peat. These results indicate that iron-peat simultaneously target sufficient amounts of both cations and anions and can be used for a one-step treatment of contaminated groundwater.
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| 19. |
- Kasiuliene, Alfreda, et al.
(author)
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Treatment of metal (loid) contaminated solutions using iron-peat as sorbent : is landfilling a suitable management option for the spent sorbent?
- 2019
-
In: Environmental Science and Pollution Research. - : Springer. - 0944-1344 .- 1614-7499. ; 26:21, s. 21425-21436
-
Journal article (peer-reviewed)abstract
- This study firstly aimed to investigate the potential of simultaneous metal (loid) removal from metal (oid) solution through adsorption on iron-peat, where the sorbent was made from peat and Fe by-products. Up-flow columns filled with the prepared sorbent were used to treat water contaminated with As, Cu, Cr, and Zn. Peat effectively adsorbed Cr, Cu, and Zn, whereas approximately 50% of inlet As was detected in the eluent. Iron-sand was effective only for adsorbing As, but Cr, Cu, and Zn were poorly adsorbed. Only iron-peat showed the simultaneous removal of all tested metal (loid)s. Metal (loid) leaching from the spent sorbent at reducing conditions as means to assess the behaviour of the spent sorbent if landfilled was also evaluated. For this purpose, a standardised batch leaching test and leaching experiment at reducing conditions were conducted using the spent sorbent. It was found that oxidising conditions, which prevailed during the standardised batch leaching test, could have led to an underestimation of redox-sensitive As leaching. Substantially higher amounts of As were leached out from the spent sorbents at reducing atmosphere compared with oxidising one. Furthermore, reducing environment caused As(V) to be reduced into the more-toxic As (III).
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| 20. |
- Kumpiene, Jurate, et al.
(author)
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Arsenic immobilisation in soil using electricity-induced spreading of iron in situ
- 2023
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In: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 325:Part A
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Journal article (peer-reviewed)abstract
- An in situ method for spreading iron amendments to arsenic (As)-contaminated soil has been investigated in the laboratory and field. This study tested the distribution of Fe from corroding electrodes through soil using a low-voltage direct current in a laboratory setting and validated the method in the field for As immobilisation in contaminated soil. Laboratory tests revealed that the corrosion of Fe electrodes in soil occurred in a way similar to that during the Fe electrocoagulation in water, which decreased the As concentrations in flow-through water from 150 μg L−1 to undetectable levels. Method validation over one year in the field using electric current pulses with reversing polarity revealed a decrease in As concentration in groundwater by 72–97% in five of the six groundwater wells within the experimental area. This method of introducing Fe amendments to soil can reduce the need for soil excavation upon chemical immobilisation of contaminants in soil.
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| 21. |
- Kumpiene, Jurate, et al.
(author)
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In situ chemical stabilization of trace element-contaminated soil : Field demonstrations and barriers to transition from laboratory to the field : A review
- 2019
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In: Applied Geochemistry. - : Elsevier. - 0883-2927 .- 1872-9134. ; 100, s. 335-351
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Journal article (peer-reviewed)abstract
- The chemical stabilization, or immobilization, of trace elements (metals and metalloids; TE) in contaminated soil has been studied for decades. A vast number of scientific publications are available on the method performance in laboratory settings, reporting that the application of various soil amendments to contaminated soil reduces TE mobility, bioavailability and toxicity. The most commonly used soil amendments include organic matter, iron oxides, phosphates, ashes, and lately biochar, alone or in combination with each other and/or lime. Most of the implemented field studies show a certain degree of improvement in soil and/or vegetation status following amendment. Regardless the positive performance of the technique in the laboratory, field validations and demonstrations remain scarce. The establishment of a field experiment often involves permits from authorities and agreements with site owners, both of which are considerably more time-consuming than laboratory tests. Due to conservative institutional structures, public authorities have been slow to adopt alternative remediation technologies, especially when the total TE concentration in soil remains the same and all of the associated risks are not yet convincingly described. For this reason, researchers should also focus on enhancing public knowledge of alternative remediation techniques so that future projects which aim to demonstrate the effectiveness of in situ immobilization techniques under natural conditions will be supported.
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| 22. |
- Kumpiene, Jurate, et al.
(author)
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Leaching of arsenic, copper and chromium from thermally treated soil
- 2016
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In: Journal of Environmental Management. - : Elsevier BV. - 0301-4797 .- 1095-8630. ; 183:3, s. 460-466
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Journal article (peer-reviewed)abstract
- Thermal treatment, if properly performed, is an effective way of destroying organic compounds in contaminated soil, while impact on co-present inorganic contaminants varies depending on the element. Leaching of trace elements in thermally treated soil can be altered by co-combusting different types of materials. This study aimed at assessing changes in mobility of As, Cr and Cu in thermally treated soil as affected by addition of industrial by-products prior to soil combustion. Contaminated soil was mixed with either waste of gypsum boards, a steel processing residue (Fe3O4), fly ash from wood and coal combustion or a steel abrasive (96.5% Fe0). The mixes and unamended soil were thermally treated at 800 °C and divided into a fine fraction <0.125 mm and a coarse fraction >0.125 mm to simulate particle separation occurring in thermal treatment plants. The impact of the treatment on element behaviour was assessed by a batch leaching test, X-ray absorption spectroscopy and dispersive X-ray spectrometry. The results suggest that thermal treatment is highly unfavourable for As contaminated soils as it increased both the As leaching in the fine particle size fraction and the mass of the fines (up to 92%). Soil amendment with Fe-containing compounds prior to the thermal treatment reduced As leaching to the levels acceptable for hazardous waste landfills, but only in the coarse fraction, which does not justify the usefulness of such treatment. Among the amendments used, gypsum most effectively reduced leaching of Cr and Cu in thermally treated soil and could be recommended for soils that do not contain As. Fly ash was the least effective amendment as it increased leaching of both Cr and As in majority of samples.
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| 23. |
- Kumpiene, Jurate, et al.
(author)
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LONG-TERM stability of arsenic in iron amended contaminated soil
- 2021
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In: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 269
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Journal article (peer-reviewed)abstract
- This study aimed at elucidating the long-term efficiency of soil remediation where chemical stabilization of arsenic (As) contaminated soil using zerovalent iron (Fe) amendments was applied. A combination of chemical extraction and extended X-Ray absorption fine structure (EXAFS) spectroscopy technique was applied on soils collected from five laboratory and field experiments in Sweden and France. All soils were treated with 1 wt% of zerovalent Fe grit 2–15 years prior to the sampling. The results indicate that all studied soils, despite the elapsed time since their amendment with Fe grit, had substantial amounts of ferrihydrite and/or lepidocrocite. These metastable and the most reactive Fe (oxyhydr)oxides (mainly ferrihydrite) were still present in substantial amounts even in the soil that was treated 15 years prior to the sampling and contributed most to the As immobilisation in the amended soils. This increases confidence in the long-term efficiency of As immobilisation using zerovalent Fe amendments. Both applied methods, sequential extraction and EXAFS, were in line for most of the samples in terms of their ability to highlight As immobilisation by poorly crystalline Fe phases.
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| 24. |
- Kumpiene, Jurate, et al.
(author)
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Remediation of soil contaminated with organic and inorganic wood impregnation chemicals by soil washing
- 2017
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In: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 184, s. 13-19
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Journal article (peer-reviewed)abstract
- The aim of this study was to evaluate the efficiency of a large scale washing/wet sieving technique for a soil contaminated with wood impregnation chemicals by 1) defining the final distribution of trace elements (As, Cu, Cr, Zn) and polycyclic aromatic hydrocarbons (PAH) in separated soil particle size fractions; and 2) defining the leaching behavior of the contaminants in these soil fractions. A soil washing experiment was implemented at waste management facility in Sweden using a full scale soil sorting and washing equipment. Five tons of soil was loaded to the equipment and wet-sieved into the following fractions: >16 mm, 8–16 mm, 2–8 mm, 0.2–2 mm, <0.2 mm and a fraction that floated on top of the slurry before the final separation phase, composed of organic matter (OM). Analysis of total concentrations of contaminants in all soil fractions indicated that wet sieving/soil washing was not efficient to reduce the total volume of soil that needs further treatment. Even the coarsest soil fractions (>8 mm) contained elevated concentrations of total As and PAH. Leaching of As from all washed soil fractions was so high, that none of the particle size fractions could be disposed of without additional treatment.
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| 25. |
- Kumpiene, Jurate, et al.
(author)
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Roads with underlying tar asphalt - spreading, bioavailability and toxicity of their polycyclic aromatic hydrocarbons
- 2021
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In: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 289
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Journal article (peer-reviewed)abstract
- Some of the older Swedish roads contain road tar underneath a surface layer of bituminous asphalt. This road tar, also known as tar asphalt, contains large amounts of polycyclic aromatic hydrocarbons (PAHs). There is concern about PAHs spreading from the bottom layers of these older roads to the surrounding environment, and that because of this spreading road tar asphalt should not be recycled but rather placed in landfills. However, a risk assessment of PAH spreading below roads has not yet been conducted. The first aim of this study was to assess this potential spreading of PAHs from underlying tar asphalt to the sand beneath, the soil next to the roads, as well as nearby groundwater. The second aim was to measure the bioavailability and estimate the toxicity of PAHs in all relevant media using polyoxymethylene (POM) passive samplers. Four road sections and nearby groundwater in northern Sweden were investigated, including a control road without tar asphalt. PAHs were detected in all analysed solid media at varying concentrations: in asphalt from 2.3 to 4800 mg kg−1, in underlying sand from <1.5 to 460 mg kg−1 and in slope soil from <1.5 to 36 mg kg−1. However, the spread of PAHs from the asphalt to roadside soil and groundwater was very limited. Groundwater at most of the road sections contained very low or non-detectable levels of PAHs (<0.08–0.53 μg L−1, excluding one site where fuel contamination is hypothesized). The PAHs generally showed low bioavailability. Only asphalt with PAH content >1200 mg kg−1 exhibited bioavailable concentrations that exceeded threshold concentrations for serious risk. The most PAH contaminated sand and soil samples exhibited low toxicity when considering bioavailability, only in some cases exceeding chronic toxicity threshold concentrations. These results were compared with the Swedish EPA's guideline values for PAH in contaminated soil, which is shown to overpredict toxicity for these sites. Further research on the leaching and transportation processes of PAHs from subsurface tar asphalt is recommended for developing risk analysis approaches.
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| 26. |
- Lázaro, Carlos, et al.
(author)
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Thermal Transformation of Natural Schwertmannite in the Presence of Chromium
- 2022
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In: Minerals. - : MDPI. - 2075-163X. ; 12:6
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Journal article (peer-reviewed)abstract
- Schwertmannite is a metastable mineral playing a crucial role in the immobilization of metal(oid)s in acid mine drainage (AMD) systems. High temperatures associated with wildfires could lead to a sudden schwertmannite transformation, changing the mobility of metal(oid)s. The objective of the present study was to examine the thermal transformation from schwertmannite to hematite, and the subsequent effect on the chromium partitioning. The immobilization of arsenate after thermal transformation and its implications on chromium mobility was also evaluated. Natural schwertmannite, with increasing contents of chromium, was thermally treated between 200 to 800 °C. Transformation products were characterized by solid-phase techniques and selective chemical extractions. Results indicated a transformation to hematite at temperatures above 400 °C. The presence of chromium barely affected the temperature at which the transformation occurred, although partitioning of chromium in the mineral changed with temperature. As the temperature increased from 25 °C to 400 °C, chromium was less mobile and less outcompeted by arsenic adsorption, suggesting a larger contribution of inner-sphere complexes with increasing temperature. At temperatures above 600 °C, non-mobile forms strongly associated with neo-formed hematite were found. Finally, neo-formation of hematite led to a decrease in arsenic adsorption, implying a potentially enhanced arsenic mobility in AMD systems upon wildfires.
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| 27. |
- Lidelöw, Sofia, et al.
(author)
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Leaching behaviour of copper slag, construction and demolition waste and crushed rock used in a full-scale road construction
- 2017
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In: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 204:1, s. 695-703
-
Journal article (peer-reviewed)abstract
- The leaching behaviour of a road construction with fayalitic copper slag, recycled concrete and crushed rock as sub-base materials was monitored over ten years. All studied materials used in the road construction, including crushed rock, contained concentrations of several elements exceeding the guideline values recommended by the Swedish EPA for total element concentrations for waste materials used in constructions. Despite that, leaching from the road construction under field conditions in general was relatively low. The leachates from the recycled materials contained higher concentrations of several constituents than the leachates from the reference section with crushed rock. The leaching of the elements of interest (Cr, Mo, Ni, Zn) reached peak concentrations during the second and fourth (Cu) years and decreased over the observation period to levels below the Swedish recommended values. Carbonation of the concrete aggregates caused a substantial but short-term increase in the leaching of oxyanions such as chromate. The environmental risks related to element leaching are highest at the beginning of the road life. Ageing of materials or pre-treatment through leaching is needed prior to their use in construction to avoid peak concentrations. Also, the design of road constructions should be adjusted so that recycled materials are covered with low-permeability covers, which would minimize the exposure to atmospheric precipitation and weathering.
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| 28. |
- Potapova, Elisaveta, et al.
(author)
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Studies of collector adsorption on iron oxides by in-situ ATR-FTIR spectroscopy
- 2010
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 49:4, s. 1493-1502
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Journal article (peer-reviewed)abstract
- In this work, the adsorption of three model collectors, viz., poly(ethylene glycol) monooleate (PEGMO), ethyl oleate, and maleic acid, as well as the commercial fatty-acid-type collector Atrac 1563, was studied in situ on synthetic hematite using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The adsorption behavior of the studied compounds on hematite was determined to a large extent by the polar headgroup. Adsorption of Atrac and PEGMO as a function of concentration showed good agreement with the Freundlich adsorption model, suggesting energetically heterogeneous adsorption. In situ desorption experiments revealed that a large fraction of the Atrac was weakly attached to the hematite surface, as it was partially removed by flushing with water at pH 8.5 and 10. These results suggest that a separate washing unit after the flotation step could be beneficial in reducing the contamination of iron ore by flotation chemicals.
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| 29. |
- Ren, Zhongfei, et al.
(author)
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Combination of adsorption/desorption and photocatalytic reduction processes for PFOA removal from water by using an aminated biosorbent and a UV/sulfite system
- 2023
-
In: Environmental Research. - : Elsevier. - 0013-9351 .- 1096-0953. ; 228
-
Journal article (peer-reviewed)abstract
- Per- and polyfluoroalkyl substances (PFAS) are stable organic chemicals, which have been used globally since the 1940s and have caused PFAS contamination around the world. This study explores perfluorooctanoic acid (PFOA) enrichment and destruction by a combined method of sorption/desorption and photocatalytic reduction. A novel biosorbent (PG-PB) was developed from raw pine bark by grafting amine groups and quaternary ammonium groups onto the surface of bark particles. The results of PFOA adsorption at low concentration suggest that PG-PB has excellent removal efficiency (94.8%–99.1%, PG-PB dosage: 0.4 g/L) to PFOA in the concentration range of 10 μg/L to 2 mg/L. The PG-PB exhibited high adsorption efficiency regarding PFOA, being 456.0 mg/g at pH 3.3 and 258.0 mg/g at pH 7 with an initial concentration of 200 mg/L. The groundwater treatment reduced the total concentration of 28 PFAS from 18 000 ng/L to 9900 ng/L with 0.8 g/L of PG-PB. Desorption experiments examined 18 types of desorption solutions, and the results showed that 0.05% NaOH and a mixture of 0.05% NaOH + 20% methanol were efficient for PFOA desorption from the spent PG-PB. More than 70% (>70 mg/L in 50 mL) and 85% (>85 mg/L in 50 mL) of PFOA were recovered from the first and second desorption processes, respectively. Since high pH promotes PFOA degradation, the desorption eluents with NaOH were directly treated with a UV/sulfite system without further adjustment. The final PFOA degradation and defluorination efficiency in the desorption eluents with 0.05% NaOH + 20% methanol reached 100% and 83.1% after 24 h reaction. This study proved that the combination of adsorption/desorption and a UV/sulfite system for PFAS removal is a feasible solution for environmental remediation.
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| 30. |
- Trublet, Mylene, et al.
(author)
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Competitive Sorption of Metal Ions on Titanium Phosphate Sorbent(TiP1) in Fixed-Bed Columns : A Closed-Mine Waters Study
- 2019
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In: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 7:9, s. 8145-8154
-
Journal article (peer-reviewed)abstract
- Sorptionfixed-bed column experiments were performed using atitanium phosphate ion-exchanger composed of−H2PO4units [TiO(OH)(H2PO4)·H2O]. Model mine water containingfive divalent metal ions (Cu2+,Zn2+,Mn2+,Ni2+,and Co2+) and a few closed-mine water samples were treated to evaluate the sorptionpreference of the material. For thefirst time, dynamic ion-exchange capacities(estimated to be between 3.2 and 4.2 mequiv g−1) and static ion-exchange uptakes(calculated to be between 3.1 and 3.5 mequiv g−1) were obtained for the same TiP1sorbent and data were discussed in terms of sorption behavior. It was found thatsorption processes on TiP1 in model and closed-mine waters during a columnexperiment could be accurately predicted from the corresponding batch experiment(including the sorbent’s capacities in different types of waters). A competitivesorption phenomenon in favor of Cu2+on TiP1 was established for all cases, pointingtoward the possibility of isolating pure copper concentrate from closed-mine waters.The relatively high amounts of calcium and magnesium ions present in mine waters did not appear to considerably affect theselectivity of TiP1 material. Exploratory experiments for sorbent regeneration and desorption using a low concentration of nitricacid were demonstrated.
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| 31. |
- Uwayezu, Jean Noel, et al.
(author)
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Combination of separation and degradation methods after PFAS soil washing
- 2023
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In: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 907
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Journal article (peer-reviewed)abstract
- The current study evaluated a three-stage treatment to remediate PFAS-contaminated soil. The treatment consisted of soil washing, foam fractionation (FF), and electrochemical oxidation (EO). The possibility of replacing the third stage, i.e., EO, with an adsorption process was also assessed. The contamination in the studied soils was dominated by perfluorooctane sulfonate (PFOS), with a concentration of 760 and 19 μg kg−1 in soil I and in soil II, accounting for 97 % and 70 % of all detected per-and polyfluoroalkyl substances (PFAS). Before applying a pilot treatment of soil, soil washing was performed on a laboratory scale, to evaluate the effect of soil particle size, initial pH and a liquid-to-soil ratio (L/S) on the leachability of PFAS. A pilot washing system generated soil leachate that was subsequently treated using FF and EO (or adsorption) and then reused for soil washing. The results indicated that the leaching of PFAS occurred easier in 0.063–1 mm particles than in the soil particles having a size below 0.063 mm. Both alkaline conditions and a continual replacement of the leaching solution increased the leachability of PFAS. The analysis using one-way ANOVA showed no statistical difference in means of PFOS washed out in laboratory and pilot scales. This allowed estimating twenty washing cycles using 120 L water to reach 95 % PFOS removal in 60 kg soil. The aeration process removed 95–99 % PFOS in every washing cycle. The EO and adsorption processes achieved similar results removing up to 97 % PFOS in concentrated soil leachate. The current study demonstrated a multi-stage treatment as an effective and cost-efficient method to permanently clean up PFAS-contaminated soil.
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| 32. |
- Uwayezu, Jean Noel, et al.
(author)
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Combining electrochemistry and ultraviolet radiation for the degradation of per- and poly-fluoroalkyl substances in contaminated groundwater and wastewater
- 2023
-
In: Journal of Water Process Engineering. - : Elsevier. - 2214-7144. ; 54
-
Journal article (peer-reviewed)abstract
- Electrochemical and ultraviolet-based methods are advanced oxidation processes emerging as viable water and wastewater treatment options. In this study, a combination of these two methods (EO-UV) using boron-doped diamond (BDD) electrodes and ultraviolet radiation at both 185 and 254 nm was assessed for the degradation of poly-fluoroalkyl substances (PFAS). Sodium persulfate (Na2S2O8) and sodium sulfate (Na2SO4) were used as electrolytes. The method was investigated on model solutions containing perfluorooctanoic acid (PFOA) and perfluorosulfonic acid (PFOS). The method's effectiveness was assessed by comparing PFAS removal efficiencies and energy demands associated with the use of separate and combined treatments. The results showed that the highest removal of PFOA and PFOS was 96 % and 85 % respectively, which was achieved using EO-UV and persulfate electrolytes. Average removal efficiencies were 1.5–2 times higher in EO-UV than in EO and 4–6 times higher than in UV treatment. The degradation of PFAS under EO-UV and persulfate applied to PFAS-contaminated groundwater and wastewater reached 94 % PFOA and 88 % PFOS in groundwater and 51 % and 63 % in wastewater. The removal of the sum of eleven PFAS was 86 % and 66 % in groundwater and wastewater, respectively. The combination of EO, UV and persulfate was the most effective option for PFAS treatment at lower energy consumption.
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| 33. |
- Uwayezu, Jean Noel, et al.
(author)
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Electrochemical degradation of per- and poly-fluoroalkyl substances using boron-doped diamond electrodes
- 2021
-
In: Journal of Environmental Management. - : Elsevier. - 0301-4797 .- 1095-8630. ; 290
-
Journal article (peer-reviewed)abstract
- Electrochemical degradation using boron-doped diamond (BDD) electrodes has been proven to be a promising technique for the treatment of water contaminated with per- and poly-fluoroalkyl substances (PFAS). Various studies have demonstrated that the extent of PFAS degradation is influenced by the composition of samples and electrochemical conditions. This study evaluated the significance of several factors, such as the current density, initial concentration of PFAS, concentration of electrolyte, treatment time, and their interactions on the degradation of PFAS. A 24 factorial design was applied to determine the effects of the investigated factors on the degradation of perfluorooctanoic acid (PFOA) and generation of fluoride in spiked water. The best-performing conditions were then applied to the degradation of PFAS in wastewater samples. The results revealed that current density and time were the most important factors for PFOA degradation. In contrast, a high initial concentration of electrolyte had no significant impact on the degradation of PFOA, whereas it decreased the generation of F−. The experimental design model indicated that the treatment of spiked water under a current density higher than 14 mA cm−2 for 3–4 h could degrade PFOA with an efficiency of up to 100% and generate an F− fraction of approximately 40–50%. The observed high PFOA degradation and a low concentration of PFAS degradation products indicated that the mineralization of PFOA was effective. Under the obtained best conditions, the degradation of PFOA in wastewater samples was 44–70%. The degradation efficiency for other PFAS in these samples was 65–80% for perfluorooctane sulfonic acid (PFOS) and 42–52% for 6–2 fluorotelomer sulfonate (6-2 FTSA). The presence of high total organic carbon (TOC) and chloride contents was found to be an important factor affecting the efficiency of PFAS electrochemical degradation in wastewater samples. The current study indicates that the tested method can effectively degrade PFAS in both water and wastewater and suggests that increasing the treatment time is needed to account for the presence of other oxidizable matrices.
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| 34. |
- Uwayezu, Jean Noel
(author)
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Remediation of PFAS-contaminated soil and wastewater : Feasibility of chain treatment applying destructive techniques
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals ubiquitously distributed in soil and aquatic media, resulting from their wide range of industrial applications. Today, PFAS is a global concern due to their persistence in the environment and their adverse effects on humans and the ecosystem. Despite the considerable efforts to develop PFAS treatment methods, a viable solution has not yet been established.This Ph.D. thesis investigated the potential of applying electrochemical oxidation (EO) and UV radiation assisted with persulfate (PS/UV), both individually and in combination(EO-UV), for PFAS degradation in solutions. Furthermore, integrating destructive technique showing the most promising results, i.e., EO, within a treatment chain comprising soil washing (SW) and foam fractionation (FF) was assessed to eliminate PFAS from contaminated soil. Perfluorooctanesulfonic acid (PFOS) accounted for 97% of the PFAS contamination in the soil. The EO and PS/UV showed the potential to break down PFAS in spiked solutions. Removal of 99 % perfluorooctanoic acid (PFOA) was found at a current density of 23.4 mA cm-2 and 4 h whereas 80% PFOA, 60% PFOS, and 57% perfluorobutanoic acid (PFBA) were removed in 4 h and in the presence of 5 g L-1 Na2S2O8. By transferring the best experimental conditions for the treatment of PFAS-contaminated wastewater, the removal of 56% ∑11PFAS was reached using EO whereas PS/UV led to an increase in the concentration of PFAS. It was highlighted that optimizing EO would lead to higher removal and reduce energy consumption. Nevertheless, PFAS removal from groundwater using PS/UV treatment was almost as effective as in synthetic solutions, highlighting its potential for treating PFAS in matrix-free water. Combining EO and UV led to substantial removal improvements due to degradation processes in both systems, probably due to synergistic effects. Adding FF to soil SW led to an average removal of 82% and 92% ∑11PFAS in soil and leachate respectively, at the L/S of 5 (five washing cycles) and pH 11.5. As per estimations, employing 20 treatment cycles could result in 94% and 91% of PFAS removal in soil and leachate. The EO at 60 mA cm-2 and 2 h removed 88.3% of ∑11PFAS, which was contained in wastewater resulting from the FF process. Overall, the SW-FF-EO three-stage treatment led to the removal of 67% ∑11PFAS, estimated to be 88% if the SW-FF consecutive treatments are repeated 20 times. Incorporating FF in the treatment chain enabled leachate recycling and reduced water volume needs in the soil treatment process, but also concentrated PFAS in a smaller water volume, thereby allowing the EO step to be more cost-effective.
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| 35. |
- Uwayezu, Jean Noel, et al.
(author)
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Validation of UV/persulfate as a PFAS treatment of industrial wastewater and environmental samples
- 2023
-
In: Journal of Water Process Engineering. - : Elsevier. - 2214-7144. ; 53
-
Journal article (peer-reviewed)abstract
- The contamination of natural water and industrial wastewater with per- and polyfluoroalkyl substances (PFAS) occurs globally. Thus, proper technologies are required to reduce PFAS in the environment and mitigate the adverse effects of these pollutants on human health and the environment. This study used a 23 full factorial design to evaluate the importance of operating factors including the level of persulfate (PS), the initial concentration of PFAS, and the time to the photochemical degradation of PFAS via ultraviolet irradiation at 185/254 nm assisted with persulfate (PS/UV method) in spiked solution. The method was then applied to break down PFAS in industrial wastewater, landfill leachate and groundwater samples using the highest factor levels applied in the 23 full factorial design. The results showed that the three investigated factors played an important role in the degradation of PFAS. The highest PFAS degradation was 57 % perfluorobutanoic acid (PFBA), 80 % perfluorooctanoic acid (PFOA) and 60 % perfluorooctane sulfonate (PFOS) using 10 mg L−1 PFAS, 5 g L−1 PS for 4 h. The defluorination also increased in the presence of PS but decreased in the presence of potassium hydrogen phthalate, nitrates, and chlorides. The PS/UV method decreased the concentration of PFAS in wastewater samples by 20–25 % PFOS and 13–15 % perfluorohexane sulfonate (PFHxS). PFAS degradation in wastewater improved with increasing treatment time. Under the PS/UV treatment, the degradation of major PFAS in groundwater was 94 % 6–2 FTS, 75 % PFOA, 62 % PFOS and 61 % PFHxS. The removal of major compounds in landfill leachate reached up to 12 % PFHxA, 32 % PFPeA, 56 % PFOA and 43 % PFOS. Our study indicated matrix effects leading to decreased PFAS degradation in different contaminated waters. The level of PS should also be controlled to an optimal value because higher levels led to a decrease in treatment efficiency.
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