| 1. |
- Suresh, Prashanth, et al.
(författare)
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Arsenic adsorption by iron-aluminium hydroxide coated onto macroporous supports : Insights from X-ray absorption spectroscopy and comparison with granular ferric hydroxides
- 2016
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Ingår i: Journal of Hazardous Materials. - : Elsevier. - 0304-3894 .- 1873-3336. ; 302, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates the arsenic adsorption characteristics of a macroporous polymer coated with coprecipitated iron-aluminium hydroxides (MHCMP). The MHCMP adsorbent-composite fits best with a pseudo-second order model for As(III) and a pseudo-first order kinetic model for As(V). The MHCMP shows a maximum adsorption capacity of 82.3 and 49.6 mgAs/g adsorbent for As(III) and As(V) ions respectively, and adsorption followed the Langmuir model. Extended X-ray absorption fine structure showed that binding of As(III) ions were confirmed to take place on the iron hydroxides coated on the MHCMP, whereas for As(V) ions the binding specificity could not be attributed to one particular metal hydroxide. As(III) formed a bidentate mononuclear complex with Fe sites, whereas As(V) indicated on a bidentate binuclear complex with Al sites or monodentate with Fe sites on the adsorbent. The column experiments were run in a well water spiked with a low concentration of As(III) (100 mu g/L) and a commercially available adsorbent (GEH (R) 102) based on granular iron-hydroxide was used for comparison. It was found that the MHCMP was able to treat 7 times more volume of well water as compared to GEH (R) 102, maintaining the threshold concentration of less than 10 mu gAs/L, indicating that the MHCMP is a superior adsorbent.
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| 2. |
- Suresh, Prashanth, et al.
(författare)
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Arsenite adsorption on cryogels embedded with iron-aluminium double hydrous oxides: Possible polishing step for smelting wastewater?
- 2013
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Ingår i: Journal of Hazardous Materials. - : Elsevier BV. - 1873-3336 .- 0304-3894. ; 250, s. 469-476
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Tidskriftsartikel (refereegranskat)abstract
- Arsenic is among the most toxic elements and it commonly exists in water as arsenite (As(III)) and arsenate (As(V)) ions. As(III) removal often requires a pre-oxidation or pH adjustment step and it is a challenge to adsorb As(III) at circumneutral pH. In this study, iron-aluminium double hydrous oxides were synthesized and incorporated into cryogels. The resulting composite cryogels were evaluated for As(III) adsorption. Initial experiments indicated that the adsorbent showed similar adsorption kinetics for both As(V) and As(III) ions. The adsorption of As(III) best fit the Langmuir isotherm and the maximum adsorption capacity was 24.6mg/g. Kinetic modeling indicated that the mechanism of adsorption was chemisorption, making the adsorbent-adsorbate interactions independent of charge and hence allowing the adsorbent to function equally efficient across pH 4-11. A Swedish smelting wastewater was used to evaluate the adsorption performance in continuous mode. The studies showed that the adsorbent was successful in reducing the arsenic concentrations below the European Union emission limit (0.15mg/l) in a smelting wastewater collected after two precipitation processes. The arsenic removal was obtained without requiring a pH adjustment or a pre-oxidation step, making it a potential choice as an adsorbent for As(III) removal from industrial wastewaters.
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| 3. |
- Önnby, Linda, et al.
(författare)
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Improved arsenic(III) adsorption by Al2O3 nanoparticles and H2O2: Evidence of oxidation to arsenic(V) from X-ray absorption spectroscopy.
- 2014
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Ingår i: Chemosphere. - : Elsevier BV. - 1879-1298 .- 0045-6535. ; 113, s. 151-157
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the oxidation of inorganic As(III) with H2O2 catalysed by Al2O3, using X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy. The effects of different reaction conditions (pH, time and initial H2O2 concentration) were also studied as were the kinetics of the oxidation reaction. We demonstrated that As(III) was oxidized to As(V) in the presence of H2O2 and Al2O3. Furthermore, all arsenic species found on the Al2O3 surface were in the As(V) state. The presence of both Al2O3 and H2O2 was necessary for oxidation of As(III) to take place within the period of time studied. The oxidation kinetics indicate a mechanism where reversible As(III) binding to the alumina surface is followed by irreversible oxidation by H2O2 leading to strongly bound As(V). Results from this study indicate that there is a surface-catalysed oxidation of As(III) on Al2O3 by H2O2, a reaction that can take place in nature and can be of help in the development of novel treatment systems for As(III) removal.
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