Fate of Cr(III) during Ozonation of Secondary Municipal Wastewater Effluent

Katsoyiannis, Ioannis A.; Gachet, Caroline; Gunten, Urs von

doi:10.1080/01919512.2018.1481362

Cited by 6 publications

(3 citation statements)

References 24 publications

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“…In water, chromium is present in its two most stable oxidation states, namely, Cr(III), and Cr(VI). In chromium-containing natural water, the prevailing form is Cr(VI), because it is very soluble, whereas Cr(III) is quite insoluble, easily forming complexes with iron oxides or other minerals and, therefore, precipitating out of water [4].…”

Section: Introductionmentioning

confidence: 99%

Cr(VI) Femoval from Ground Waters by Ferrous Iron Redox-Assisted Coagulation in a Continuous Treatment Unit Comprising a Plug Flow Pipe Reactor and Downflow Sand Filtration

2020

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Chromium(VI) (Cr(VI)) is the main chromium species found in groundwater and is considered as a highly toxic and carcinogenic element to humans. In the present study, removal of Cr(VI) by coagulation with ferrous iron is studied in a continuous flow treatment unit comprising pipe flocculation reactors followed by a sand filter. The studied parameters, regarding their effect on the removal of hexavalent chromium, were the ferrous iron dose, the effect of linear velocity, and the effect of the starting Cr(VI) concentration. The experiments have shown that the Cr(VI) removal achieved was very efficient and residual Cr(VI) and total Cr concentration in the treated water was lower than 10 μg/L, provided that the required dose of ferrous iron is provided. In particular, the study demonstrated that the removal of hexavalent chromium, from initial concentration of 50 μg/L and 100 μg/L, was more than 90% with ferrous doses of 1 mg/L and 2 mg/L respectively, applying linear velocity of 8 m/h, at an initial pH value of 7.3. Iron concentration in treated water was very low, far below 200 μg/L, which is the limit for iron in drinking water. This unit comprises a simple treatment option, for applications at the household level, with minimum maintenance requirements capable of removing Cr(VI) to concentrations below 10 μg/L, which might be the future limit for chromium in drinking water.

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Section: Introductionmentioning

confidence: 99%

Cr(VI) Femoval from Ground Waters by Ferrous Iron Redox-Assisted Coagulation in a Continuous Treatment Unit Comprising a Plug Flow Pipe Reactor and Downflow Sand Filtration

2020

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“…The higher Cr(VI) reduction by Fe(II) at acidic pH values, is due to the lower competition caused by O 2 for Fe(II) oxidation and thus more Cr(VI) reacts with Fe(II), at constant Fe(II) dosage. The formed Cr(III) however remains in big parts in the solution, firstly because the solubility is higher at lower pH values [40] than it is at pH 7 and also that the Fe(III) formation caused by the Fe(II) oxidation is not so efficient at acidic pH values, while Fe(III) precipitation is also not so effective at acidic pH values.…”

Section: Effect Of Initial Ph On As(v) and Cr(vi) Removal By Fe(ii)mentioning

confidence: 99%

Simultaneous Removal of Arsenate and Chromate from Ground- and Surface- Waters by Iron-Based Redox Assisted Coagulation

et al. 2020

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Arsenic (As) and chromate (Cr(VI)) contamination of ground and surface waters is a major problem worldwide. Given that a new drinking water limit is anticipated for Cr(VI) and that the limit of arsenic in drinking water is quite low (10 μg/L), there is an urgent need for evaluating technologies that could be efficient for removal of both contaminants simultaneously. In this work, the use of Fe(II) redox assisted coagulation was investigated to simultaneously remove the contaminants of interest. The basic principle of this technology is that Fe(II) could react with Cr(VI) and form Fe(III)-hydroxides and insoluble Cr(III) species, while the freshly formed Fe(III) hydroxides are very efficient adsorbents for As(V). The effect of pH, the water matrix composition, Fe(II) dose, initial contaminant concentrations, NOM presence and phosphate concentration were the examined parameters. The results revealed that with a dose of 2 mg/L Fe(II), residual As(V) and Cr(VI) concentrations were both below 10 μg/L, from initial concentrations of 50 μg/L. Though, this is effective only at circumneutral pH values. This is however not a big obstacle, since most natural waters, especially groundwaters, have near neutral pH values. At these pH values, residual iron concentration was far below 200 μg/L. The presence of phosphate anions inhibited As(V) removal but had no effect on Cr(VI) removal. Increasing Fe(II) concentrations eliminated the effect of phosphate and provided simultaneous phosphate removal. Therefore, Fe(II) coagulation can be applied, with secured results, for simultaneous As(V), Cr(VI) and phosphate removal from waters.

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“…Trivalent chromium is a microelement, and both its deficiency and excess may have an adverse effect on the human body and on living organisms. However, there is a real risk of the oxidation of Cr(III) into the very toxic Cr(VI), for example, during water treatment using oxidants, such as sodium hypochlorite [10,11], chlorine [12] or ozone [11,13].…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Chromium and Nickel Ions on Commercial Activated Carbon—An Analysis of Adsorption Kinetics and Statics

Lach,

Okoniewska

2023

Molecules

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The adsorption of nickel Ni(II) and chromium Cr(III) ions on the commercial activated carbons WG-12, F-300 and ROW 08, which differ in their pore structure and the chemical nature of their surfaces, were analyzed. The nickel ions Ni2+ were best adsorbed on the WG-12 activated carbon, which had the largest number of carboxyl and lactone groups on the surface of the activated carbons, and the largest specific surface area. Chromium, occurring in solutions with pH = 6 in the form of Cr(OH)2+ and Cr(OH)2+ cations, was best adsorbed on the ROW 08 Supra activated carbon, which is characterized by the highest values of water extract. The precipitation of chromium hydroxide in the pores of the activated carbon was the mechanism responsible for the high adsorption of Cr(III) on this carbon. For the other sorbents, the amount of carboxyl and lactone groups determined the amount of Cr(III) and Ni(II) adsorption. The adsorption kinetics results were described with PFO, PSO, Elovich and intraparticle diffusion models. The highest correlation coefficients for both the Cr(III) and Ni(II) ions were obtained using the PSO model. Among the seven adsorption isotherm models, very high R2 values were obtained for the Toth, Temkin, Langmuir and Jovanovic models. The Cr(III) ions were removed in slightly larger quantities than the Ni(II) ions. The capacities of the monolayer qm (calculated from the Langmuir isotherm) ranged from 55.85 to 63.48 mg/g for the Cr(III), and from 40.29 to 51.70 mg/g for the Ni(II) ions (pH = 6). The adsorption efficiency of Cr(III) and Ni(II) cations from natural waters with different degrees of mineralization (spring, weakly and moderately mineralized) was only a few percent lower than that from deionized water.

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Fate of Cr(III) during Ozonation of Secondary Municipal Wastewater Effluent

Cited by 6 publications

References 24 publications

Cr(VI) Femoval from Ground Waters by Ferrous Iron Redox-Assisted Coagulation in a Continuous Treatment Unit Comprising a Plug Flow Pipe Reactor and Downflow Sand Filtration

Cr(VI) Femoval from Ground Waters by Ferrous Iron Redox-Assisted Coagulation in a Continuous Treatment Unit Comprising a Plug Flow Pipe Reactor and Downflow Sand Filtration

Simultaneous Removal of Arsenate and Chromate from Ground- and Surface- Waters by Iron-Based Redox Assisted Coagulation

Adsorption of Chromium and Nickel Ions on Commercial Activated Carbon—An Analysis of Adsorption Kinetics and Statics

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