The Use of Pre-Aeration to Reduce the Cost of Neutralizing Acid Mine Drainage

Jageman, T. C.; Yokley, R. A.; Heunisch, George W.

doi:10.21000/jasmr88010131

Cited by 13 publications

(9 citation statements)

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“…The exsolution of CO 2 from the AMD (Eqns. 4 and 5 go to the right) can be accelerated by aggressive aeration (Jageman et al, 1988) or heating of the solution (Langmuir, 1997;American Society for Testing and Materials, 2000). Note that if solids are not dissolved or precipitated as CO 2 exsolves, the acidity due to H 2 CO 3 * will decrease and the pH will increase while the alkalinity is conserved (Cravotta and Hilgar, 2000).…”

Section: Purpose and Scopementioning

confidence: 99%

“…Hence, hot acidity can be measured on fresh or aged samples; however, because it excludes contributions from CO 2 , the hot acidity could underestimate the actual quantity of "caustic" chemicals, such as NaOH or lime, needed to neutralize AMD without preaeration (e.g. Jageman et al, 1988;Means and Hilton, this volume). An evaluation of the difference between the cold acidity on fresh samples and the hot acidity could be useful to indicate the potential benefit of aeration before adding base chemicals to AMD.…”

Section: Comparison Of Measured and Computed Acidity With Ph Of Mine mentioning

confidence: 99%

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Acidity and Alkalinity in Mine Drainage: Practical Considerations

Cravotta¹,

Kirby²

2004

JASMR

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Abstract. In this paper, we emphasize that the Standard Method hot peroxide treatment procedure for acidity determination (hot acidity) directly measures net acidity or net alkalinity, but that more than one water-quality measure can be useful as a measure of the severity of acid mine drainage. We demonstrate that the hot acidity is related to the pH, alkalinity, and dissolved concentrations of Fe, Mn, and Al in fresh mine drainage. We show that the hot acidity accurately indicates the potential for pH to decrease to acidic values after complete oxidation of Fe and Mn, and it indicates the excess alkalinity or that required for neutralization of the sample. We show that the hot acidity method gives consistent, interpretable results on fresh or aged samples.Regional data for mine-drainage quality in Pennsylvania indicated the pH of fresh samples was predominantly acidic (pH 2.5 to 4) or near neutral (pH 6 to 7); approximately 25 percent of the samples had intermediate pH values. This bimodal frequency distribution of pH was distinctive for fully oxidized samples; oxidized samples had acidic or near-neutral pH, only. Samples that had nearneutral pH after oxidation had negative hot acidity; samples that had acidic pH after oxidation had positive hot acidity. Samples with comparable pH values had variable hot acidities owing to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. The hot acidity was comparable to net acidity computed on the basis of initial pH and concentrations of Fe, Mn, and Al minus the initial alkalinity. Acidity computed from the pH and dissolved metals concentrations, assuming equivalents of 2 per mole of Fe and Mn and 3 per mole of Al, was comparable to that computed on the basis of aqueous species and Fe II /Fe III . Despite changes in the pH, alkalinity, and metals concentrations, the hot acidities were comparable for fresh and aged samples. Thus, meaningful "net" acidity can be determined from a measured hot acidity or by calculation from the pH, alkalinity, and dissolved metals concentrations. Together, these water-quality data can be useful for evaluating the potential for toxicity, corrosion, or encrustation and can be helpful for determining the appropriate remediation. By demonstrating the measurements on fresh and aged samples, we hope to encourage (1) consistent use of the hot peroxide treatment procedure for acidity determination and (2) consistent reporting of negative acidity values.

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Section: Purpose and Scopementioning

confidence: 99%

Section: Comparison Of Measured and Computed Acidity With Ph Of Mine mentioning

confidence: 99%

Acidity and Alkalinity in Mine Drainage: Practical Considerations

Cravotta¹,

Kirby²

2004

JASMR

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“…The pH will increase as CO 2 exsolves. Exsolution of CO 2 can be promoted by aeration within a stream or aggressive air sparging in a treatment system (Jageman et al 1988). Unless Mine Water Environ (2007) 26:128-149 129 accompanied by the precipitation of Fe(OH) 3 , CaCO 3 , or other solids, the alkalinity will not be affected by equation 2 because bicarbonate (HCO 3 À ) and hydroxyl (OH À ) ions have equivalent capacity to neutralize acid; that is, they have equivalent alkalinity.…”

Section: Introductionmentioning

confidence: 99%

Passive aerobic treatment of net-alkaline, iron-laden drainage from a flooded underground anthracite mine, Pennsylvania, USA

Cravotta

2007

Mine Water Environ

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“…Thus Acidity due to CO 2 is ephemeral and can be removed from mine drainage by preaeration prior to the addition of caustic chemicals for neutralization of acidity due to H + and metals (e.g. Jageman et al, 1988 concentration is initially high, the measured Acidity due to CO 2 (H 2 CO 3 *) is negligible due to intentional degassing of CO 2 before the titration begins. Similar arguments can be made for Al, Mn, and other metal species, which also contribute to positive acidity.…”

Section: Resultsmentioning

confidence: 99%

Acidity and Alkalinity in Mine Drainage: Theoretical Considerations

Kirby¹,

Cravotta²

2004

JASMR

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Acidity, net acidity, and net alkalinity are widely used parameters for the characterization of mine drainage, but these terms are not well defined and are often misunderstood. Incorrect interpretation of acidity, alkalinity, and derivative terms can lead to inadequate treatment design or poor regulatory decisions. We briefly explain derivations of theoretical expressions of three types of alkalinities (caustic, phenolphthalein, and total) and acidities (mineral, CO 2 , and total). Theoretically defined total alkalinity is closely analogous to measured alkalinity and presents few practical interpretation problems. Theoretically defined "CO 2 -acidity" is closely related to most standard titration methods used for mine drainage with an endpoint pH of 8.3, but it presents numerous interpretation problems, and it is unfortunately named because CO 2 is intentionally driven off during titration of mine-drainage samples. Using the proton condition/massaction approach and employing graphs for visualization, we explore the concept of principal components and how to assign acidity contributions to solution species, including aqueous complexes, commonly found in mine drainage. We define a comprehensive theoretical definition of acidity in mine drainage on the basis of aqueous speciation at the sample pH and the capacity of these species to undergo hydrolysis to pH 8. We demonstrate that "net alkalinity" is a valid mathematical construction based on theoretical definitions of alkalinity and acidity. We demonstrate that, for most mine-drainage solutions, a useful net alkalinity value can be derived from: 1) alkalinity and acidity values based on aqueous speciation, 2) measured alkalinitycomputed acidity, or 3) taking the negative of the value obtained in a standard method "hot peroxide" acidity titration, provided that labs report negative values. We recommend the third approach; i.e., Net alkalinity = -Hot Acidity.Additional Key Words: calculated and measured acidity.

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The Use of Pre-Aeration to Reduce the Cost of Neutralizing Acid Mine Drainage

Cited by 13 publications

References 0 publications

Acidity and Alkalinity in Mine Drainage: Practical Considerations

Acidity and Alkalinity in Mine Drainage: Practical Considerations

Passive aerobic treatment of net-alkaline, iron-laden drainage from a flooded underground anthracite mine, Pennsylvania, USA

Acidity and Alkalinity in Mine Drainage: Theoretical Considerations

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