Humic acids as reducing agents: the involvement of quinoid moieties in arsenate reduction

Palmer, Noel E.; Wandruszka, Ray von

doi:10.1007/s11356-010-0322-2

Cited by 28 publications

(11 citation statements)

References 40 publications

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“…Within the reaction time, a concentration decrease in As 5+ and an increase in As 3+ occurred (Figure 6D). These in situ Raman results are consistent with other reports, 35,36,43 which suggests that HA plays an important role in controlling redox reactions of organic and/or inorganic species throughout natural soil or water environments due to its electron-donating capacity with the reduction potentials ranging from 0.3 to 0.7 V 44,45 and the electron transfer capacity of 0.02−12 mequiv/g. 46,47 After the reduction of As 5+ , a decrease in HAsO 4 2− concentrations may prolong the induction time for nucleation of As 5+ -containing precipitates at the brushite−fluid interface (Figure 2E).…”

Section: ■ Resultssupporting

confidence: 92%

“…The same phenomenon occurred on brushite reacting in 1 mM Na 2 HAsO 4 solutions (pH 8.0) in the presence of 10 mg/L HA (Figure C). The shift to the higher binding energy may result from the decrease of electron cloud density around As 5+ species caused by the electron withdrawing group in HA, such as a phenolic group following As 5+ binding to HA with subsequent As 5+ reduction into As 3+ by HA. − …”

Section: Resultsmentioning

confidence: 99%

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Humic Acids Limit the Precipitation of Cadmium and Arsenate at the Brushite–Fluid Interface

Zhai

Wang

Hövelmann

et al. 2018

Environ. Sci. Technol.

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Bioavailability and mobility of cadmium (Cd 2+ ) and arsenate (As 5+ ) in soils can be effectively lowered through the dissolution of brushite (dicalcium phosphate dihydrate, CaHPO 4 • 2H 2 O) coupled with the precipitation of a more stable mineral phase containing both Cd and As. Due to the ubiquitous presence of humic acid (HA) in soil environments, it is more complex to predict the fate of dissolved Cd and As during such sequestration. Here, we used in situ atomic force microscopy (AFM) to image the kinetics of simultaneous precipitation of Cd and As at the brushite−fluid interface in the presence of HA. Results show that HA inhibits the formation of both amorphous and crystalline Cd (5−x) Ca x (PO 4 ) (3−y) (AsO 4 ) y (OH) on the (010) face of brushite. A combination of X-ray photoelectron spectroscopy (XPS) and real-time surface-enhanced Raman spectroscopy (SERS) reveals that part of As 5+ reduction into As 3+ with HA and [HA-Cd] complexation occurs, modulating the concentrations of free Cd 2+ and As 5+ ions to inhibit subsequent precipitation of a Cd (5−x) Ca x (PO 4 ) (3−y) (AsO 4 ) y (OH) phase on the dissolving brushite surface. A combination of AFM imaging, SERS analyses, and PhreeqC simulations suggests that environmentally relevant humic substances can limit the precipitation of Cd and As at mineral surfaces through a mechanism of oxidation/reduction and aqueous/surface complexation. This may exacerbate the transportation of these contaminants into waters by subsurface fluid flow, and research attempts to weaken the negative effect of HA are needed.

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Section: ■ Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Humic Acids Limit the Precipitation of Cadmium and Arsenate at the Brushite–Fluid Interface

Zhai

Wang

Hövelmann

et al. 2018

Environ. Sci. Technol.

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“…One of the best known examples is natural organic matter. Although its presence may partly explain the controversial findings of Fe(III) reduction-induced As releases between lab model studies and field work in the past (Davranche et al 2013), natural organic matter may also interact with As by (1) serving as an electron donor or carbon source to fuel Fe(III) and As(III) reduction (Lovley et al 1996) and methylation (Zheng et al 2013), (2) as an adsorbant to complete As adsorption to the mineral surface (Weng et al 2009), (3) as a sorbent for As (Thanabalasingam and Pickering 1986) and (4) as an abiotic reductant for As(V) (Palmer and von Wandruszka 2010). This highlights the fact that there are still many unknown factors influencing As fate and mobility in the environment and, at the same time, that the research concerning microbial As is still in its infancy; • Fe(III) treated Baccilus subtulis has 11 times higher As(V) sorption capacity than that of the native bacteria (Yang et al 2012) • The maximum biosorption capacity of living cells of Bacillus cereus for As(III) was found to be 32.42 mg g −1 at pH 7.5, at optimum conditions of contact time of 30 min, biomass dosage of 6 g L −1 , and temperature of 30°C (Giri et al 2013) • Bacillus cereus Strain W2 retained As(III) and As(V) up to 1.87 mg As g −1 of dry cell weight and dry cell removal capacity up to 0.18 mg As g −1 (Miyatake and Hayashi 2011) • The biosorption capacity of the Rhodococcus sp.…”

Section: Discussionmentioning

confidence: 99%

Impact of Microorganisms on Arsenic Biogeochemistry: A Review

Huang

2014

Water Air Soil Pollut

117

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Microorganisms are abundant in many surface and near-surface geochemical environments. They interact with arsenic through a variety of mechanisms, including sorption, mobilisation, precipitation and redox and methylation transformation; sometimes, this is to their benefit, while other times it is to their detriment, substantially affecting the fate and transport of arsenic in the environment. Here, an attempt was made to review the current state of knowledge concerning microbial influences on arsenic transformation and retention processes at the water-solid interface with the goal to elucidate the ability of microorganisms to react with arsenic, and to quantify the role of microorganisms in the biogeochemical arsenic cycle. Such knowledge is indispensable for comprehensive understanding arsenic behaviour in the environment and support accurate assessment of the threat of arsenic contamination to human and environmental health, as well as for the development of novel technologies for arsenic bioremediation.

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“…For example, it has been shown that addition of quinones and riboflavin (both of which can be present in the extracellular matrix) can facilitate the reduction of arsenate by soil microorganisms . Additionally, in vitro assays have demonstrated that reduced quinones and semiquinone free radicals as well as reduced glutathione can reduce arsenate to arsenite. − …”

Section: Introductionmentioning

confidence: 99%

Role of Extracellular Polymeric Substances in Microbial Reduction of Arsenate to Arsenite by Escherichia coli and Bacillus subtilis

Zhou

Kang

et al. 2020

Environ. Sci. Technol.

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We show that arsenate can be readily reduced to arsenite on cell surfaces of common bacteria (E. coli or B. subtilis) or in aqueous dissolved extracellular polymeric substances (EPS) extracted from different microorganisms (E. coli, B. subtilis, P. chrysosporium, D. gigas, and a natural biofilm) in the absence of exogenous electron donors. The efficiency of arsenate reduction by E. coli after a 7-h incubation was only moderately reduced from 51.3% to 32.7% after knocking out the arsenic resistance genes (arsB and arsC). Most (>97%) of the reduced arsenite was present outside the bacterial cells, including for the E. coli blocked mutant lacking arsB and arsC. Thus, extracellular processes dominated arsenate reduction. Arsenate reduction was facilitated by removing EPS attached to E. coli or B. subtilis, which was attributed to enhanced access to reduced extracellular cytochromes. This highlights the role of EPS as a permeability barrier to arsenate reduction. Fourier-transform infrared (FTIR) combined with other chemical analyses implicated some low-molecular weight (<3 kDa) molecules as electron donors (reducing saccharides) and electron transfer mediators (quinones) in arsenate reduction by dissolved EPS alone. These results indicate that EPS act as both reducing agent and permeability barrier for access to reduced biomolecules in bacterial reduction of arsenate.

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Humic acids as reducing agents: the involvement of quinoid moieties in arsenate reduction

Abstract: The existence of different redox pools within the humate was confirmed, with the quinoid-centered redox entities showing the fastest kinetics. The results pertained to all size and polarity fractions.

Cited by 28 publications

References 40 publications

Humic Acids Limit the Precipitation of Cadmium and Arsenate at the Brushite–Fluid Interface

Humic Acids Limit the Precipitation of Cadmium and Arsenate at the Brushite–Fluid Interface

Impact of Microorganisms on Arsenic Biogeochemistry: A Review

Role of Extracellular Polymeric Substances in Microbial Reduction of Arsenate to Arsenite by Escherichia coli and Bacillus subtilis

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