1、Designation: D 5744 07Standard Test Method forLaboratory Weathering of Solid Materials Using a HumidityCell1This standard is issued under the fixed designation D 5744; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of las
2、t revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This kinetic test method covers a laboratory weatheringprocedure that (1) enhances reaction-product transport in theaqueo
3、us leach of a solid material sample of specified mass, and(2) measures rates of weathering-product mass release. Solubleweathering products are mobilized by a fixed-volume aqueousleach that is performed and collected weekly. Leachate samplesare analyzed for pH, alkalinity/acidity, specific conductan
4、ce,sulfate, and other selected analytes.1.1.1 This test method is intended for use to meet kinetictesting regulatory requirements for mining waste rock and oressized to pass a 6.3-mm (0.25-in.) Tyler screen.1.1.2 Interlaboratory testing of this method has been con-fined to mine waste rock. Applicati
5、on of this test method tometallurgical-processing waste (for example, mill tailings) isoutside the scope of the test method.1.2 This test method is a modification of a laboratoryweathering procedure developed originally for miningwastes(1-3).2However, it may have useful application wher-ever gaseous
6、 oxidation coupled with aqueous leaching areimportant mechanisms for contaminant mobility.1.3 This test method calls for the weekly leaching of awell-characterized solid material sample (weighing at least1000-g), with water of specified purity, and the collection andchemical characterization of the
7、resulting leachate. Test dura-tion is determined by the users objectives of the test.1.4 As described, this test method may not be suitable forsome materials containing plastics, polymers, or refined met-als. These materials may be resistant to traditional particle sizereduction methods.1.5 Addition
8、ally, this test method has not been tested forapplicability to organic substances and volatile matter.1.6 This test method is not intended to provide leachatesthat are identical to the actual leachate produced from a solidmaterial in the field or to produce leachates to be used as thesole basis of e
9、ngineering design.1.7 This test method is not intended to simulate site-specificleaching conditions. It has not been demonstrated to simulateactual disposal site leaching conditions. Furthermore, the test isnot designed to produce effluents that are in chemical equilib-rium with the solid phase samp
10、le.1.8 This test method is intended to describe the procedurefor performing the laboratory weathering of solid materials togenerate leachates. It does not describe all types of samplingand analytical requirements that may be associated with itsapplication.1.9 The values stated in SI units are to be
11、regarded as thestandard. The values given in parentheses are for informationonly.1.10 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and d
12、etermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D75 Practice for Sampling AggregatesD 276 Test Methods for Identification of Fibers in TextilesD 420 Guide to Site Characterization for Engineering De-sign and Construction PurposesD 653 Ter
13、minology Relating to Soil, Rock, and ContainedFluidsD 737 Test Method for Air Permeability of Textile FabricsD 1067 Test Methods for Acidity or Alkalinity of WaterD 1125 Test Methods for Electrical Conductivity and Re-sistivity of WaterD 1193 Specification for Reagent WaterD 1293 Test Methods for pH
14、 of WaterD 1498 Test Method for Oxidation-Reduction Potential ofWaterD 2234/D 2234M Practice for Collection of a Gross Sampleof CoalD 3370 Practices for Sampling Water from Closed Conduits1This test method is under the jurisdiction of ASTM Committee D34 on WasteManagement and is the direct responsib
15、ility of Subcommittee D34.01.04 on WasteLeaching Techniques.Current edition approved Oct. 1, 2007. Published November 2007. Originallyapproved in 1996. Last previous edition approved in 2001 as D 5744-96(2001).2The boldface numbers in parentheses refer to the list of references at the end ofthis sta
16、ndard.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, P
17、O Box C700, West Conshohocken, PA 19428-2959, United States.E 276 Test Method for Particle Size or Screen Analysis atNo. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Oresand Related MaterialsE 877 Practice for Sampling and Sample Preparation of IronOres and Related MaterialsE 1915 Test Methods for
18、Analysis of Metal Bearing Oresand Related Materials by Combustion Infrared-AbsorptionSpectrometryE 2242 Test Method for Column Percolation Extraction ofMine Rock by the Meteoric Water Mobility Procedure3. Terminology3.1 Definitions:3.1.1 acid producing potential (AP), nthe maximum po-tential for a s
19、olid material sample to produce acidic effluent canbe determined based on the total sulfur present in the sample.It is assumed that this sulfur is present as iron sulfides (forexample, pyrite) (4). This assumption leads to overestimationof the acid producing potential of samples containing non-ferro
20、us sulfide minerals such as galena (PbS) or non-acidproducing sulfur-bearing minerals such as gypsum (CaSO4).The AP is commonly converted to the amount of calciumcarbonate required to neutralize the resulting amount of acidiceffluent produced by the oxidation of contained iron sulfideminerals; it is
21、 expressed as the equivalent tonnes of calciumcarbonate per 1000 tonnes of solid material (3). The AP istherefore calculated by multiplying the percent of sulfurcontained in the material by a stoichiometric factor of 31.2 (5).3.1.2 interstitial water, nthe residual water remaining inthe sample pore
22、spaces at the completion of the fixed-volumeweekly leach.3.1.3 leach, na weekly addition of water to solid materialthat is performed either dropwise or by flooding for a specifiedtime period.3.1.4 loading, nthe mass of a chemical species, which isthe product of the species concentration and the mass
23、 of theweekly leachate collected.3.1.5 mill tailings, nfinely ground mine waste (commonlypassing a 150-m (100 mesh screen) resulting from the millprocessing of ore.3.1.6 neutralizing potential (NP), nthe potential for asolid material sample to neutralize an acidic effluent based onthe amount of carb
24、onate present in the sample. The NP is alsoexpressed in terms of tonnes of calcium carbonate equivalentper 1000 tonnes of solid material (3). It is calculated bydigesting the solid material with an excess of standardized acidand back titrating with a standardized base to measure andconvert the resid
25、ual acid to calcium carbonate equivalents(2,6). The residual acid is subtracted from the acid added todetermine the acid consumption or acidity present.3.1.6.1 DiscussionIt should be noted that NP tests gener-ally overestimate the capacity of mine waste samples toneutralize acid while maintaining dr
26、ainage pH $ 6.0; thecalcium plus magnesium carbonate content of the sampleprovides a more accurate NP quantification (7).3.1.6.2 DiscussionThe AP and NP are specifically appli-cable to the determination of AP from mining wastes com-prised of iron-sulfide and carbonate minerals. These terms maybe app
27、licable to any solid material containing iron-sulfide andcarbonate minerals.3.1.7 run-of-mine, adjusage in this test method refers toore and waste rock produced by excavation (with attendantvariable particle sizes) from open pit or underground miningoperations.3.1.8 waste rock, nrock produced by exc
28、avation fromopen pit or underground mining operations that has an eco-nomic mineral content less than a specified economic cutoffvalue for metallurgical processing.4. Summary of Test Method4.1 This laboratory-weathering procedure is designed toenhance the mass release of acidity/alkalinity, metals,
29、and otherpertinent analytes from a sample of solid material weighing atleast 1000 g. This is done by providing conditions conducive tosample oxidation and then leaching the sample with a fixed-volume aqueous leach. Ratio of leach volume to sample massranges from 0.5:1to1:1depending upon the efficien
30、cy ofsample wetting and amount of effluent required for chemicalanalyses. The weekly effluent produced is characterized fordissolved weathering products. This test method is performedon each sample in a cylindrical cell. Multiple cells can bearranged in parallel. This configuration permits the simul
31、ta-neous testing of multiple splits of the same solid materialsample, or of solid material samples each characterized bydifferent compositions.4.2 Two protocol options (Options A and B) comprise thetest procedure, and these options differ only in the way that theoxygen is supplied to samples in the
32、individual humidity cells.Option A protocol calls for weekly cycles composed of threedays of dry air (less than 10 % relative humidity) and threedays of water-saturated air (approximately 95 % relative hu-midity) pumped up through the sample, followed by a leachwith water on Day 7. Option B protocol
33、 differs from Option Ain that each cell is stored for six days under conditions ofcontrolled and relatively constant temperature and humidity,and oxygen is supplied to the sample by diffusion (and possiblyadvection) of ambient air rather than by pumping. Although atest duration as short as 20 weeks
34、may be suitable for somesamples, more recent research indicates that a test durationwell beyond 20 weeks may be required depending upon theobjectives of the test (8,9).5. Significance and Use5.1 The laboratory weathering procedure will generate datathat can be used to: (1) determine whether a solid
35、material willproduce an acidic, alkaline, or neutral effluent, (2) identifysolutes in the effluent that represent dissolved weatheringproducts formed during a specified period of time, (3) deter-mine the mass of solute release, and (4) determine the rate atwhich solutes are released (from the solids
36、 into the effluent)under the closely controlled conditions of the test.5.2 Data generated by the laboratory weathering procedurecan be used to address the following objectives: (1) determinethe variation of drainage quality as a function of compositionalvariations (for example, iron sulfide and calc
37、ium+magnesiumcarbonate contents) within individual mine-rock lithologies,D5744072(2) determine the amount of NP accessible in a mine-rocksample to neutralize acid and maintain drainage pH$6.0 underthe conditions of the test, (3) estimate mine-rock weatheringrates to aid in predicting the environment
38、al behavior of minerock, and (4) determine mine-rock weathering rates to aid inexperimental design of site-specific kinetic tests.5.3 The laboratory-weathering procedure provides condi-tions conducive to oxidation of solid material constituents andenhances the transport of weathering reaction produc
39、ts con-tained in the resulting weekly effluent. This is accomplished bycontrolling the exposure of the solid material sample to suchenvironmental parameters as reaction environment temperatureand application rate of water and oxygen.5.4 Because efficient removal of reaction products is vital totrack
40、 mineral dissolution rates during the procedure, laboratoryleach volumes are large per unit mass of rock to promote therinsing of weathering-reaction products from the mine-rocksample.Acomparison of laboratory kinetic tests with field testshas shown that more reaction products from mineral dissolu-t
41、ion are consistently released per unit weight and unit time inlaboratory weathering tests (9). For example, sulfate releaserates observed in laboratory tests of metal-mine rock have beenreported to be 3 to 8 times those for small-scale field test pilesof Duluth Complex rock (10), and from 2 to 20 ti
42、mes those forsmall-scale field test piles of Archean greenstone rock (11).Agreater increase is anticipated when laboratory rates are com-pared with field rates measured from operational waste-rockpiles.5.5 Fundamental assumptions governing OptionsAand B ofthe procedure:5.5.1 Option AAn excess amount
43、 of air pumped upthrough the sample during the dry- and wet-air portions of theweekly cycle reduces the potential for oxidation reaction ratesbeing limited by low-oxygen concentrations. Weekly leacheswith low ionic strength water promote the removal of leachablemineral dissolution products produced
44、from the previousweeks weathering cycle. The purpose of the three-day dry-airportion of the weekly cycle is to evaporate some of the waterthat remains in the pores of the sample after the weekly leachwithout totally drying out the sample. Consequently, samplesaturation is reduced and air flow is enh
45、anced. During thedry-air portion of the cycle, the oxygen diffusion rate throughthe sample may increase several orders of magnitude ascompared to its diffusion rate under more saturated conditionsof the leach. This increase in the diffusion rate under near-dryness conditions helps promote the oxidat
46、ion of such con-stituents as iron sulfide. Additionally, evaporation from thethree days of dry air increases pore water cation/anion concen-trations and may also cause increased acidity (for example, byincreasing the concentration of hydrogen ion generated frompreviously oxidized iron sulfide). Incr
47、eased acid generationwill enhance the dissolution of additional sample constituents.As evaporation continues, the remaining water may becomeover-saturated with respect to some mineral phases, conse-quently causing them to precipitate. Some precipitated miner-als are potential sources of acidity when
48、 re-dissolved (forexample, melanterite, FeSO47H2O; and jarosite,K2Fe6(OH)12(SO4)4). Compared to the three days of dry airwhere the pore-water mass decreases over time, the wet(saturated)-air portion of the weekly cycle helps maintain arelatively constant mass of pore water in the sample (12). Thisma
49、y help promote some diffusion of weathering products (forexample, re-dissolved precipitation products) in the remainingpore water without totally saturating the sample and adverselyaffecting oxygen diffusion.NOTE 1Under idealized conditions (that is, infinite dilution in air andwater), published oxygen diffusion rates in air are five orders of magnitudegreater than in water (0.178 cm2s-1versus 2.5 3 10-5cm2s-1at 0 and25C, respectively) (13).5.5.2 Option BIn contrast to OptionA, Option B protocoldoes not include dry air or wet air introduction to the humiditycells du
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