Refinement of ADTI-WP2 Standard Weathering ProcEdures, and Evaluation of Particle Size and Surface Area Effects upon Leaching Rates: PART 2: PRACTICAL AND THEORETICAL ASPECTS OF LEACHING KINETICS

Brady, Keith B.C.; White, William Β.; Hornberger, Roger J.; Scheetz, Barry E.; Loop, Caroline M.

doi:10.21000/jasmr04010174

Cited by 4 publications

(5 citation statements)

References 8 publications

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“…Regarding operational consistency of the method, large amounts of fine particles within specific zones of the leaching columns were found to impede uniform fluid flow and/or gas flow in this study, and similar problems with fines are described in Caruccio (1990, 1995) and Hornberger and Brady (1998). Regarding the determination of reaction kinetics, the importance of surface area to volume ratios is described in Part II of this paper (Brady et al, 2004), and significant differences in crushed particle size distributions and effective surface areas were found among the lithologic units tested in this study. Standardizing the particle size distribution in each leaching column promotes control of that variable at the start of the weathering test, and facilitates the evaluation of surface area and related kinetic variables after weathering.…”

Section: Second Year (2003) Weathering Test Resultsmentioning

confidence: 86%

“…Whereas, the major factors controlling sulfate (and acidity) production from a rock sample with appreciable total sulfur content include particle size and surface area. These relationships are discussed in more detail in Brady et al (2004), Geidel (1979) and Hornberger and Brady (1998). column sizes upon analyte concentrations showed that mean and maximum alkalinity concentrations produced from the shale sample in the 6 inch column were not greater than those corresponding to the smaller column diameters.…”

Section: Second Year (2003) Weathering Test Resultsmentioning

confidence: 99%

“…(2) improving test methods by (a) maintaining a carbon dioxide-enriched environment to optimize carbonate mineral dissolution and (b) quantifying particle size variables to evaluate reaction kinetics; and (3) providing flexibility in test method implementation consistent with EPA guidelines for Performance-Based Measurement Systems (PBMS). The companion paper by Brady et al (2004) addresses practical and theoretical aspects of leaching kinetics, including surface area to volume ratios.…”

Section: Introductionmentioning

confidence: 99%

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Refinement of Adti-Wp2 Standard Weathering Procedures, and Evaluation of Particle Size and Surface Area Effects Upon Leaching Rates: Part 1: Laboratory Evaluation of Method Performance

Hornberger¹,

Brady²,

Cuddeback³

et al. 2004

JASMR

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The second year of method development work was conducted on the ADTI-WP1 (Humidity Cell) and the ADTI-WP2 (Leaching Column) standard test methods. The performance of the leaching column method was superior to the humidity cell method. In making improvements to the leaching column method, variations in column diameter and water-handling/gas-handling procedures were evaluated. Two commercial laboratories and a university research lab participated in the study. Relative percent differences between duplicate samples and relative standard deviations between laboratories were evaluated. Surface area measurements, using BET methods, were conducted on each of 8 particle size classes, before and after weathering tests on 4 different lithologic samples. Observed alkalinity concentrations were consistent with the elevated PCO 2 and approached saturation with respect to calcite for calcareous rocks. The maximum concentrations of acidity (33,700 mg/L), sulfates (37,404 mg/L) and iron (9,120 mg/L) for the high-sulfur coal refuse sample were consistent with the maximum concentrations observed in the field. The measured surface areas of the shale samples were significantly higher than the sandstone, limestone and coalrefuse samples. However, the surface area measurements post-weathering were not significantly different from the pre-weathering measurements for most rock samples and most particle size classes.

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Section: Second Year (2003) Weathering Test Resultsmentioning

confidence: 86%

Section: Second Year (2003) Weathering Test Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Refinement of Adti-Wp2 Standard Weathering Procedures, and Evaluation of Particle Size and Surface Area Effects Upon Leaching Rates: Part 1: Laboratory Evaluation of Method Performance

Hornberger¹,

Brady²,

Cuddeback³

et al. 2004

JASMR

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“…Initial development in phases I and II included evaluation of different test apparatus, effects of particle size, gas composition, leaching frequency and other variables. Phases I and II results are reported by Brady et al (2004) and Hornberger et al (2004). In Phase III, a standard column leaching protocol was used by eight commercial, government and university labs to test five rocks of different lithology, pyrite and carbonate content.…”

Section: Introductionmentioning

confidence: 99%

Standard Weathering Procedure for Coal Overburden, Inter-Laboratory Study of Leachate Composition

Perry¹,

Cuddeback²,

Brady³

et al. 2008

ASMR

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Abstract. Simulated weathering tests are used to estimate leachate quality from rocks containing varying concentrations of pyrite and carbonates at mines. Five rock samples of coal overburden materials were subjected to a standardized column leaching test at eight commercial, university and government laboratories. Splits from sized, homogenized bulk samples were loaded in duplicate columns, incubated under humid air containing 10% CO 2 , and leached every 7 days for a 14 week period. Leachates were analyzed for mine drainage parameters including acidity, alkalinity, metals, sulfate and selected trace elements.Relative percent difference (RPD) and relative standard deviation (RSD) statistics show the variation within individual labs and among the group of labs. Fe, Al, Se, Zn and Acidity exhibited the greatest variability in results across all rock samples and labs. RPD's usually exceeded 30% for these parameters. The variation in Fe and Acidity increased with weathering duration. Ca, Mg, Na, SO 4, and specific conductance were the most consistent parameters. Mass weighting the chemical concentrations to account for differences in sample mass and leachate volumes did not noticeably improve the RPD and RSD statistics. Cumulative quantities leached were, however, consistent among labs for most parameters.About 2 to 6 % of the total sulfur present in the rocks was leached during the test. One rock sample was near saturation for gypsum, and some sulfate may have been retained in the column. Acid neutralizing capacity was depleted at a faster rate than acid producing potential. Carbonate dissolution varied, with 3 of 5 rocks producing solutions that were saturated for calcite, while two rocks produced under-saturated solutions. Four of five rocks had less than 5 % of total Ca and Mg leached, with similar or smaller leaching fractions for other elements. More than 90% of the iron mobilized by pyrite weathering was retained in the column for all samples. One acid forming sample leached elements more aggressively than the rocks producing neutral leachates.The inter-lab results show that the standard column test can yield consistent estimates of mine water composition, and differentiate the behavior of various rock and mineral assemblages. __________________

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“…al., (2003Hornberger et. al., ( , 2005 and Brady et al, (2004). The final step to completing the development of the final draft of the ADTI-WP2 Leaching Column Method and publishing it in the Federal Register as a standard EPA method is a full inter-laboratory validation study in accordance with the ASTM D -2777 protocol.…”

mentioning

confidence: 99%

Acid Drainage Technology Initiative: Ten Years of Mining Industry, Government Agencies and Academia Collaboration in the Metal and Coal Mining Sectors in the Usa

Zyl¹,

Parsons²,

McLemore³

et al. 2006

JASMR

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The Acid Drainage Technology Initiative (ADTI) was initiated in 1995 by federal agencies, the National Mining Association and the Interstate Mining Compact Commission to identify, evaluate and develop cost-effective and practical acid drainage technologies. In 1999, ADTI was expanded through the addition of the metal mining sector, which is focused on drainage quality issues related to metal mines. ADTI addresses drainage quality issues from abandoned, active, and future coal and metal mines. The guiding principle of ADTI is to build consensus among industry, federal and state regulatory agencies on acid drainage technology development and technology transfer issues. ADTI is focusing its efforts on mine drainage prediction, sampling/monitoring, modeling and avoidance/remediation. ADTI is not a regulatory or policy development program. ADTI includes the Coal Mining Sector and the Metal Mining Sector under the overall guidance of the ADTI Operations Committee. The Operations Committee consists of representatives from industry, state and federal government and academia. The Coal Mining Sector recently formed a number of groups to address a wide range of topics. The following groups have been formed: Water Quality, Coal Combustion By-Products (CCBs), Underground Mining, Passive Treatment, Technology Transfer. White papers have been prepared on 18 topics that are currently being studied. The Metal Mining Sector includes a steering committee and work groups on prediction, sampling and monitoring, modeling, mitigation, and pit lakes. The Metal Mining Sector has a committee that works with the Questa mine of Molycorp in the review of the waste rock pile study.

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Refinement of ADTI-WP2 Standard Weathering ProcEdures, and Evaluation of Particle Size and Surface Area Effects upon Leaching Rates: PART 2: PRACTICAL AND THEORETICAL ASPECTS OF LEACHING KINETICS

Cited by 4 publications

References 8 publications

Refinement of Adti-Wp2 Standard Weathering Procedures, and Evaluation of Particle Size and Surface Area Effects Upon Leaching Rates: Part 1: Laboratory Evaluation of Method Performance

Refinement of Adti-Wp2 Standard Weathering Procedures, and Evaluation of Particle Size and Surface Area Effects Upon Leaching Rates: Part 1: Laboratory Evaluation of Method Performance

Standard Weathering Procedure for Coal Overburden, Inter-Laboratory Study of Leachate Composition

Acid Drainage Technology Initiative: Ten Years of Mining Industry, Government Agencies and Academia Collaboration in the Metal and Coal Mining Sectors in the Usa

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