Rates of manganese oxidation in aqueous systems

Hem, John David

doi:10.1016/0016-7037(81)90229-5

Cited by 165 publications

(70 citation statements)

References 5 publications

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“…For hausmannite, the value of pK,, is 21.33 (Sadiq & Lindsay 1978). This equation, and the work of Hem (1981), shows that a rise in the pH of 1 unit will give a 100-fold increase in the rate of precipitation. On the other hand an increase in dissolved oxygen has only a marginal effect on Q.…”

Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 88%

“…According to Hem (1981) the rate of precipitation (pptn) of hausmannite can b e represented by the relation:…”

Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 99%

“…In the experiments performed by Hem (1981). The value of kppt, which we calculated from the work of Hem (1981) has a high temperature dependency:…”

Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 99%

“…(1) inside the algal colonies. Finally, combining these results with the k,,,, from the work of Hem (1981) will give a n estimate of the surface area of the precipitating manganese inside the algae, which will be an essential parameter when the effect of this precipitation process on the scavenging of other metals and phosphate from the seawater by adsorption is estimated. This however will need further detailed investigation.…”

Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 99%

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Manganese accumulation in the high pH microenvironment of Phaeocystis sp. (Haptophyceae) colonies from the North Sea

Lubbers

Gieskes²,

Castilho³

et al. 1990

Mar. Ecol. Prog. Ser.

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ABSTRACT. Colonies of Pharocjstis sp. (Ilaptophyceae] isolated from the North Sea accumulated manganese during ~ncubati.on of 15 d in a culture med~um w~t h near-natural (0 45 ~rmol l ' 1:ln) conccntratlon When maximum cell density was reached, u p to 75'1L of the manganese originally prcsrnt in the medium was found in the colonies; the amount of manganese in the single cells remained at a constant level of about 7 '%B.

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Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 88%

“…According to Hem (1981) the rate of precipitation (pptn) of hausmannite can b e represented by the relation:…”

Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 99%

“…In the experiments performed by Hem (1981). The value of kppt, which we calculated from the work of Hem (1981) has a high temperature dependency:…”

Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 99%

Section: Geochemistry Of Manganese As It Affects Manganese Uptake Of mentioning

confidence: 99%

See 2 more Smart Citations

Manganese accumulation in the high pH microenvironment of Phaeocystis sp. (Haptophyceae) colonies from the North Sea

Lubbers

Gieskes²,

Castilho³

et al. 1990

Mar. Ecol. Prog. Ser.

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show abstract

“…The first stage of the reaction increased with increasing temperature, but not the second stage. Increased available energy at elevated temperatures would have inceased the rate of initial reaction with interlayer Mn(III,IV) and the precipitation of arsenic manganese compounds (Hem, 1981). To reach Mn(IV) in the octahedral sheets, during the second stage, however, reaction Would require diffusion, a process which was apparently not as dependent on temperature, because later rates were similar at different temperatures.…”

Section: Reaction Schemementioning

confidence: 99%

Reaction Scheme for the Oxidation of as(III) to as(V) by Birnessite

Moore

Walker

Hayes

1990

Clays and clay miner.

100

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Abstract--The oxidation of As(III) to As(V) by K-birnessite was examined at different temperatures, pHs, and birnessite/As(III) ratios. Experiments ranged in duration from 5 to 64 hr, and solution and solid products were determined at several intervals. All experiments showed that the reaction produced large amounts of K + to solution and very little Mn 2+. As(V) was released to solution and incorporated into the K-birnessite. The oxidation was initially rapid and then slowed. The oxidation of As(III) was probably facilitated initially by autocatalytic Mn-As(V) reactions occurring mostly in the interlayer, in which large amounts of As(V) and K + could be easily released to solution. The reaction also slowed when interlayer Mn was exhausted by forming Mn-As(V) complexes. Mn(IV) could only be acquired from the octahedral sheets of the birnessite. The two-stage reaction process proposed here depended on the layered structure of birnessite, the specific surface, and presence of exchangeable cations in K-birnessite.

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Green‐Chemical Synthesis of Ultrathin β‐MnOOH Nanofibers for Separation Membranes

Peng

Ichinose

2011

Adv Funct Materials

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Ultrathin β -MnOOH nanofi bers can be produced on a large scale via a greenchemical method using an aqueous solution of very dilute Mn(NO 3 ) 2 and aminoethanol at room temperature. High-magnifi cation electron microscopy demonstrates that the β -MnOOH nanofi bers are 3-5 nm thin and up to 1 micrometer long and the nanofi bers are parallel assembled into bundles with an average diameter of 25 nm. By a fi ltration process, ultrathin mesoporous membranes with strong mechanical, thermal, and chemical stabilities are prepared from the β -MnOOH nanofi ber bundles. The membranes can separate 10-nm nanoparticles from water at a fl ux of 15120 L m − 2 · h − 1 · bar − 1 , which was 2-3 times higher than that of commercial membranes with similar rejection properties. Based on the Young-Laplace equation, β -MnOOH nanofi ber/ polydimethylsiloxane composite membranes are developed through a novel downstream-side evaporation process. From nanoporous to dense separation membranes can be achieved by optimizing the experimental conditions. The membranes show desirable separation performance for proteins, ethanol/ water mixtures, and gases. The synthesis method of β -MnOOH nanofi bers is simple and environmentally friendly, and it is easily scalable for industry and applicable to other metal oxide systems. These composite membranes constitute a signifi cant contribution to advanced separation technology.

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Rates of manganese oxidation in aqueous systems

Cited by 165 publications

References 5 publications

Manganese accumulation in the high pH microenvironment of Phaeocystis sp. (Haptophyceae) colonies from the North Sea

Manganese accumulation in the high pH microenvironment of Phaeocystis sp. (Haptophyceae) colonies from the North Sea

Reaction Scheme for the Oxidation of as(III) to as(V) by Birnessite

Green‐Chemical Synthesis of Ultrathin β‐MnOOH Nanofibers for Separation Membranes

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