Full‐scale demonstration testing of hexavalent chromium reduction via stannous chloride application

Henrie, Tarrah; Plummer, Sarah; Orta, John; Bigley, Steve; Gorman, Craig; Seidel, Chad; Shimabuku, Kyle K.; Liu, Haizhou

doi:10.1002/aws2.1136

Cited by 11 publications

(20 citation statements)

References 12 publications

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“…), to trivalent chromium (Cr(III)), presumably precipitating it as chromium hydroxide (Cr(OH) 3 (s)). On the oxidation side of the reaction, stannous tin (Sn(II)) is converted to stannic tin (Sn(IV)), presumably precipitating as stannic oxide (SnO 2 (s)) (Brandhuber et al, 2004;Henrie et al, 2019;Kennedy et al, 2018). SnCl 2 for Cr(VI) treatment emerged from bench-scale work by Lai and McNeill (2006) and Brandhuber et al (2004), but somewhat unsatisfactory and ambiguous results led to a hiatus in the published literature until recent studies were published by Henrie et al (2019) and Kennedy et al (2018).…”

Section: Introductionmentioning

confidence: 99%

Stannous chloride reduction–filtration for hexavalent and total chromium removal from groundwater

Kennedy

Croft²,

Flint

et al. 2020

AWWA Water Science

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Hexavalent chromium (Cr(VI)) reduction using stannous chloride (SnCl 2 ) has emerged as a possible alternative to chromium treatment technologies such as strong base anion exchange. In an effort to target not only Cr(VI) reduction but, ultimately, total chromium (Cr(T)) removal, SnCl 2 addition followed by rapid sand filtration was tested at the pilot scale on a groundwater with a naturally occurring Cr(VI) concentration of 0.090 mg/L. A SnCl 2 dose of 1.5 mg/L, followed by filtration, was able to consistently remove Cr(T) to less than 0.010 mg/L following an initial ripening period, with limited head loss for 10 sequential 17-to 25-hr filter runs. Total tin and turbidity removal were similar, decreasing to below 0.050 mg/L and raw water levels, respectively. Analysis of filter sand following backwashes and three different material pipe segments that were exposed to unfiltered water dosed with SnCl 2 indicated the accumulation of Cr and Sn on surfaces, which remains a concern.

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Section: Introductionmentioning

confidence: 99%

Stannous chloride reduction–filtration for hexavalent and total chromium removal from groundwater

Kennedy

Croft²,

Flint

et al. 2020

AWWA Water Science

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“…To overcome the disadvantages of over-stoichiometric addition of chemicals and secondary waste generation, a new chemical reductive treatment has recently been developed based on divalent tin Sn(II) addition as the chemical of stannous chloride SnCl 2 . The following redox reaction takes place (Henrie et al, 2019;Kennedy et al, 2020):…”

Section: Sn(ii)-based Reductive Cr(vi) Treatmentmentioning

confidence: 99%

“…A cartridge filtration unit with pore sizes of 0.45 µm has been demonstrated to successfully remove Cr(III) residual solids. In the final treated drinking water coming out the filtration unit, the addition of free chlorine with a contact time of 15 days did not generate Cr(VI), indicating the combination of Sn(II) reductive treatment and subsequent microfiltration or porous media filtration is effective in removing Cr(VI) and total chromium (Henrie et al, 2019).…”

Section: Challenges and Future Outlookmentioning

confidence: 99%

“…3). Recent kinetics model also predicts that Cr(III) oxidation by free chlorine can result in a Cr(VI) concentration at the tap (i.e., the exit of the distribution system) exceeding 10 µg/L, a possible benchmark for future Cr(VI) regulatory standard (Henrie et al, 2019). In addition, the kinetics of Cr(III) oxidation process driven by free chlorine is catalyzed by bromide, a conservative anion typically existing in source water originated from seawater desalination, water reuse or impacted by wastewater discharge from hydraulic fracking.…”

Section: Challenges and Future Outlookmentioning

confidence: 99%

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Hexavalent chromium in drinking water: Chemistry, challenges and future outlook on Sn(II)- and photocatalyst-based treatment

Liu

2020

Front. Environ. Sci. Eng.

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Chromium (Cr) typically exists in either trivalent and hexavalent oxidation states in drinking water, i.e., Cr(III) and Cr(VI), with Cr(VI) of particular concern in recent years due to its high toxicity and new regulatory standards. This Account presented a critical analysis of the sources and occurrence of Cr(VI) in drinking water in the United States, analyzed the equilibrium chemistry of Cr(VI) species, summarized important redox reaction relevant to the fate of Cr(VI) in drinking water, and critically reviewed emerging Cr(VI) treatment technologies. There is a wide occurrence of Cr(VI) in US source drinking water, with a strong dependence on groundwater sources, mainly due to naturally weathering of chromium-containing aquifers. Challenges regarding traditional Cr(VI) treatment include chemical cost, generation of secondary waste and inadvertent re-generation of Cr(VI) after treatment. To overcome these challenges, reductive Cr(VI) treatment technologies based on the application of stannous tin or electron-releasing titanium dioxide photocatalyst hold extreme promise in the future. To moving forward in the right direction, three key questions need further exploration for the technology implementation, including effective management of residual waste, minimizing the risks of Cr(VI) re-occurrence downstream of drinking water treatment plant, and promote the socioeconomic drivers for Cr(VI) control in the future.

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“…Besides ferrous salts, stannous salts (in powder or liquid form) have been extensively employed for the chemical reduction of Cr(VI) to Cr (III) [44], which proceeds according to Eq. ( 1):…”

Section: Introductionmentioning

confidence: 99%

Combination of interfacial reduction of hexavalent chromium and trivalent chromium immobilization on tin-functionalized hydroxyapatite materials

Campisi

Evangelisti

Postole

et al. 2021

Applied Surface Science

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We present an ecofriendly hydroxyapatite (HAP) material functionalized with tin (Sn/HAP) for an efficient interfacial reduction of Cr(VI) to Cr(III).Tin was deposited on HAP at different concentrations (from 0.2 to 1.2 mmol/g) using colloidal or clear acid solutions of SnCl 2 . The morphological and structural properties of fresh and used Sn/HAP samples were determined (N 2 adsorption-desorption, transmission electron microscopy techniques, XRPD, XPS). Tests were performed under various conditions: at different pH 3-7, inert or oxidant atmosphere, sample aging (up to 15 days).Sn/HAP samples prepared using colloidal acid solutions revealed the best performances in the reduction of Cr (VI) to Cr(III), carried out under mild conditions (40 • C in acidified solution) with initial concentration of Cr(VI) in the range from 25 to 50 ppm. Best removal of Cr(VI) (10 mg/g) was obtained by using a Sn-concentration of 0.65 mmol/g with complete adsorption of the formed Cr(III) at HAP surface. This finding was associated with higher Sn-dispersion (surface Sn, 9.4 at.%) compared to samples prepared from clear solutions (surface, Sn 7.7 at. %), as evidenced by HAADF-STEM/EDX and XPS analyses. Remarkably, tin was tightly retained on the HAP surface under reaction conditions (0.7% leaching), confirming the occurrence of Cr(VI) reduction at solid-liquid interphase.

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Full‐scale demonstration testing of hexavalent chromium reduction via stannous chloride application

Cited by 11 publications

References 12 publications

Stannous chloride reduction–filtration for hexavalent and total chromium removal from groundwater

Stannous chloride reduction–filtration for hexavalent and total chromium removal from groundwater

Hexavalent chromium in drinking water: Chemistry, challenges and future outlook on Sn(II)- and photocatalyst-based treatment

Combination of interfacial reduction of hexavalent chromium and trivalent chromium immobilization on tin-functionalized hydroxyapatite materials

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