Effects of pH and dissolved oxygen on the reduction of hexavalent chromium by dissolved ferrous iron in poorly buffered aqueous systems

Schlautman, Mark A.; Han, Inwoo

doi:10.1016/s0043-1354(00)00408-5

Cited by 115 publications

(68 citation statements)

References 27 publications

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“…These results are similar to those found in many other studies (Zhilin et al 2004;Deiana et al 2007), indicating that reductions of Cr(VI) by organic materials can be accelerated at low pH. As the pH of Pinchen soils increased to 5.0 and 6.2 from 4.5 by the adding of CaCO 3 , this probably took them out of the most favorable pH range for Cr(VI) reduction (Wittbrodt and Palmer 1996;Schlautman and Han 2001). However, for the Neipu soils, there was no dependence of pH on the extent of Cr(VI) reduction.…”

supporting

confidence: 90%

Effects of liming on Cr(VI) reduction and Cr phytotoxicity in Cr(VI)-contaminated soils

Chen

Juang

Lee

2012

Soil Science and Plant Nutrition

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Liming is the most common approach for the amelioration of soil acidity in agriculture, and is widely used to reduce the mobility and bioavailability of heavy metals in soil. The purpose of this study was to investigate the hexavalent chromium [Cr(VI)] reduction and chromium (Cr) phytotoxicity in Cr(VI)-contaminated soils at different pH levels as a result of liming. Calcium carbonate (CaCO 3 ) was added to two acid agricultural soils of Taiwan (Neipu and Pinchen) at their natural pH of about 4, to adjust soil pH to approximately 5 and 6, respectively. The soils were then spiked with six levels of Cr(VI) (0, 150, 300, 500, 1000 and 1500 mg kg À1). X-ray absorption near edge structure spectroscopy (XANES) of Cr was used to determine the extent of the reduction of Cr(VI) at different pH levels. At the same time, extractions of Cr by Dowex M4195 and Chelex 100 resins were carried out to determine the availability of Cr(VI) and trivalent chromium [Cr(III)] in the Cr(VI)-spiked soils, respectively. Also, a pot experiment with wheat (Triticum vulgare) seedlings was carried out to test the phytotoxicity of the Cr(VI)-spiked soils. The results showed that for Cr(VI)-contaminated soils which contain a high amount of organic matter, such as the Neipu soil, the effect of liming on Cr(VI) reduction and Cr phytotoxicity is insignificant. However, for Cr(VI)-contaminated soils which have a low amount of organic matter, such as the Pinchen soils, liming could decrease the extent of Cr(VI) reduction and increase the availability of Cr(VI), thereby enhancing the phytotoxicity of Cr.

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supporting

confidence: 90%

Effects of liming on Cr(VI) reduction and Cr phytotoxicity in Cr(VI)-contaminated soils

Chen

Juang

Lee

2012

Soil Science and Plant Nutrition

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“…It is known that the relative rates of Cr(VI) reduction and Fe(II) aerobic oxidation are dependent both on the pH and on the concentration of the species: Fe(II) aerobic oxidation becomes faster at pH higher than 8 or very low Cr(VI) concentrations (<<10 mM) Han 2001 andreferences therein, Sung andMorgan 1980).…”

Section: Resultsmentioning

confidence: 99%

“…Once reduced to Cr(III), the reoxidation to Cr(VI) is disfavoured in natural groundwater environments and is thought to be limited to the action of oxygen and manganese oxide as oxidants (Eary and Rai 1987, Hwang et al 2002, Schlautman and Han 2001, Sung and Morgan 1980. The most commonly used reductants are iron metal, ferrous iron or sulfur compounds for chemically engineered processes (Ludwig et al 2007, Martin and Kempton 2000, Patterson et al 1997, Qin et al 2005, Yang et al 2007, and organic materials for biological remediation (Rama Krishna andPhilip 2005, Tokunaga et al 2003).…”

mentioning

confidence: 99%

Iron(II) modified natural zeolites for hexavalent chromium removal from contaminated water

Lofù¹,

Mastrorilli²,

Dell’Anna³

et al. 2016

Archives of Environmental Protection

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Three different types of Fe(II)-modified natural zeolites were tested as supports in continuous-flow columns for the treatment of Cr(VI) contaminated water. The natural zeolites chosen as support were commercially available Zeosand (80% clinoptilolite), ATZ (79% phillipsite/chabazite), and ZS-55RW (90% Chabazite). All the examined modified zeolites turned out active for hexavalent chromium abatement, lowering its concentration below the European regulation level, even at relatively high flow rates (40 mL/h, linear velocity 15 cm/h). Zeosand, having a broader pH range of stability, was found to be the best one in terms of both Fe(II) uptake (0.54 wt%) and Cr removal (90 mg Cr/Kg zeolite).

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“…However, this molar ratio may vary in a relatively broad range, considering the findings of different researchers. A molar ratio [Cr(VI)]:[Fe(II)] = 1:3 was found by several researchers in batch tests at pH range 6.0-8.0 [16] and 3.5-6.0 [17], as well as in full scale application at pH range 3.7-4.7 [18]. In contrast, higher molar ratios up to 1:10 were also found at pH range 6.5-8.2 [19].…”

Section: Introductionmentioning

confidence: 83%

Effect of Organic Matter on Cr(VI) Removal from Groundwaters by Fe(II) Reductive Precipitation for Groundwater Treatment

Gröhlich

Langer

Mitrakas

et al. 2017

Water

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Due to its toxicity, Cr(VI) is undesirable in groundwater. Its chemical reduction to Cr(III) species, followed by precipitation is the most widely practiced treatment technique for the removal of Cr(VI) from polluted waters. The resulting Cr(III) species present low solubility, is much less toxic, and can be subsequently removed either by precipitation, or by adsorption onto iron oxy-hydroxides and co-precipitation. The effects of several parameters, such as the pH value of water to be treated, the applied Fe(II) dose, and the presence of appropriate mineral surfaces, are well investigated and understood. However, the impact of the presence of humic acids (HAs) in this process has only been considered by rather few studies. The main aim of this study was to determine the effect of humic substances on Fe(II) reductive precipitation of Cr(VI) within a pH range relevant for drinking water treatment. Jar test experiments were performed, using artificial groundwater of defined composition and initial Cr(VI) concentration 100 µg/L, ferrous sulphate dosages 0.25-2 mg Fe(II)/L, and pH values 6.5-8. It was found that Cr(VI) and total chromium (Cr(total)) can be reliably removed in the absence of HAs in the tested pH range with the addition of Fe(II) dosage of 1 mg Fe(II)/L. Further on, the results indicated that the reduction of Cr(VI) is only slightly affected by the presence of HAs. However, increased residual total Cr concentrations were found at lower Fe(II) dosages and/or higher pH values. Additionally, the removal of the Cr(III) species formed during Cr(VI) reduction was strongly inhibited by the presence of HAs under the examined experimental conditions, since residual concentrations higher than 60 µg/L were determined. The results of this study will have implications to the ongoing discussion of a new, stricter, European Union regulation limit, regarding the presence of total chromium in drinking water.

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Effects of pH and dissolved oxygen on the reduction of hexavalent chromium by dissolved ferrous iron in poorly buffered aqueous systems

Cited by 115 publications

References 27 publications

Effects of liming on Cr(VI) reduction and Cr phytotoxicity in Cr(VI)-contaminated soils

Effects of liming on Cr(VI) reduction and Cr phytotoxicity in Cr(VI)-contaminated soils

Iron(II) modified natural zeolites for hexavalent chromium removal from contaminated water

Effect of Organic Matter on Cr(VI) Removal from Groundwaters by Fe(II) Reductive Precipitation for Groundwater Treatment

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