1、Designation: D5744 13Standard Test Method forLaboratory Weathering of Solid Materials Using a HumidityCell1This standard is issued under the fixed designation D5744; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、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 theaqueous
3、 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 conductance
4、,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. Application
5、 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 o
6、xidation 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 re
7、sulting 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 Additional
8、ly, 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 eng
9、ineering 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 sample
10、.1.8 This test method is intended to describe the procedurefor performing the laboratory weathering of solid materials. Itdoes not describe all types of sampling and analytical require-ments that may be associated with its application.1.9 The values stated in SI units are to be regarded asstandard.
11、No other units of measurement are included in thisstandard.1.9.1 ExceptionThe values given in parentheses are forinformation only.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 establi
12、sh appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D75 Practice for Sampling AggregatesD276 Test Methods for Identification of Fibers in TextilesD420 Guide to Site Characterization for Enginee
13、ring Designand Construction Purposes (Withdrawn 2011)4D653 Terminology Relating to Soil, Rock, and ContainedFluidsD737 Test Method for Air Permeability of Textile FabricsD1067 Test Methods for Acidity or Alkalinity of Water1This test method is under the jurisdiction of ASTM Committee D34 on WasteMan
14、agement and is the direct responsibility of Subcommittee D34.01.04 on WasteLeaching Techniques.Current edition approved Sept. 1, 2013. Published September 2013. Originallyapproved in 1996. Last previous edition approved in 2012 as D5744-12. DOI:10.1520/D5744-13.2The boldface numbers in parentheses r
15、efer to the list of references at the end ofthis standard.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.4Th
16、e last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D1125 Test Methods for Electrical Conductivity and Resis-tivity of WaterD1193 Specification for Reagent W
17、aterD1293 Test Methods for pH of WaterD1498 Test Method for Oxidation-Reduction Potential ofWaterD2234/D2234M Practice for Collection of a Gross Sampleof CoalD3370 Practices for Sampling Water from Closed ConduitsE276 Test Method for Particle Size or ScreenAnalysis at No.4 (4.75-mm) Sieve and Finer
18、for Metal-Bearing Ores andRelated MaterialsE877 Practice for Sampling and Sample Preparation of IronOres and Related Materials for Determination of Chemi-cal CompositionE1915 Test Methods forAnalysis of Metal Bearing Ores andRelated Materials for Carbon, Sulfur, and Acid-BaseCharacteristicsE2242 Tes
19、t Method for Column Percolation Extraction ofMine Rock by the Meteoric Water Mobility ProcedureD5744 Test Method for Laboratory Weathering of SolidMaterials Using a Humidity CellE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definiti
20、ons:3.1.1 acid-producing potential, AP, nmaximum potentialfor a solid material sample to produce acidic effluent can bedetermined based on the total sulfur present in the sample.3.1.1.1 DiscussionIt is assumed that this sulfur is presentas iron sulfides (for example, pyrite) 4). This assumption lead
21、sto overestimation of the acid-producing potential of samplescontaining non-ferrous sulfide minerals such as galena (PbS) ornon-acid-producing sulfur-bearing minerals such as gypsum(CaSO4). The AP is commonly converted to the amount ofcalcium carbonate required to neutralize the resulting amountof t
22、he acidic effluent produced by the oxidation of containediron sulfide minterals; it is expressed as the equivalent tonnesof calcium carbonate per 1000 tonnes of solid material (3). TheAPis, therefore, calculated by multiplying the percent of sulfurcontained in the material by a stoichiometric factor
23、 of 31.2 (5).3.1.2 interstitial water, nresidual water remaining in thesample pore spaces at the completion of the fixed-volumeweekly leach.3.1.3 leach, nweekly addition of water to solid materialthat is performed either dropwise or by flooding for a specifiedtime period.3.1.4 loading, nmass of a ch
24、emical species, which is theproduct of the species concentration and the mass of theweekly leachate collected.3.1.5 mill tailings, nfinely ground ore processing waste(commonly passing a 150-m 100-mesh screen) resultingfrom the mill processing of ore.3.1.6 neutralizing potential, NP, ncapacity of a s
25、olidmaterial sample to neutralize an acidic effluent while maintain-ing a drainage pH of at least 6.0. NP is expressed in terms oftonnes of calcium carbonate equivalent per 1000 tonnes ofsolid material (3).3.1.6.1 DiscussionNP can be estimated using severaltechniques, including the following (1) det
26、ermining the amountof calcium and magnesium carbonate in the sample; (2)digesting the solid material with an excess of standardized acidand back titrating with a standardized base to measure andconvert the residual acid to calcium carbonate equivalents (2,6); and (3) determining the carbonate carbon
27、 content in thesample (for example Test Method E1915 acid base classifica-tion).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 applicable to any solid material containing
28、iron-sulfide andcarbonate minerals.3.1.6.3 DiscussionCalcium plus magnesium carbonate de-termination generally provides a reasonably accurate NP quan-tification for samples in which carbonate minerals are present.Digestion and back-titration techniques generally overestimatethe capacity of mine wast
29、e samples to neutralize acid whilemaintaining drainage pH 6.0. These techniques can yieldnegative values if there is excess soluble acidity on the sample.Carbonate-carbon determinations will overestimate the capac-ity of mine-waste samples to neutralize acid if they containmetal carbonate minerals t
30、hat are not net neutralizing (forexample, iron carbonates such as siderite FeCO3 (7).3.1.6.4 DiscussionAP and NP comprise most acid-baseclassifications and these two components have historicallybeen determined by several different analytical methods (7).However, only one acid-base classification is
31、currently anASTM standard, Test Method E1915. Test Method E1915 useseither pyrolysis or chemical treatment of the mine-wastesample to speciate and quantify sulfide-sulfur and carbonate-carbon concentrations, which are expressed as acid-generatingpotential (AGP) and acid neutralizing potential (ANP),
32、 respec-tively. Through this speciation, it provides a better estimate ofacid generation than historic AP determinations in whichnon-ferrous and non-acid-generating sulfur minerals are pres-ent (for example, galena PbSO4 and gypsum CaSO4,respectively.3.1.7 run-of-mine, adjusage in this test method r
33、efers 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 excavation fromopen pit or underground mining operations that has an eco-nomic mineral content less than a specified economic cu
34、toffvalue for metallurgical processing.4. Summary of Test Method4.1 This laboratory-weathering procedure is designed toenhance the mass release of acidity/alkalinity, metals, and otherpertinent analytes from a sample of solid material weighing atleast 1000 g. This is done by providing conditions con
35、ducive tosample oxidation and then leaching the sample with a fixed-volume aqueous leach. Ratio of leach volume to sample massD5744 132is0.5:1or1:1depending upon the efficiency of samplewetting and amount of effluent required for chemical analyses.The weekly effluent produced is characterized for di
36、ssolvedweathering products. This test method is performed on eachsample in a cylindrical cell. Multiple cells can be arranged inparallel. This configuration permits the simultaneous testing ofmultiple splits of the same solid material sample, or of solidmaterial samples each characterized by differe
37、nt 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 individual humidity cells.Option A protocol calls for weekly cycles composed of threedays of dry air (less than 10 % relative h
38、umidity) 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 differs from Option Ain that each cell is stored for six days under conditions ofcontrolled and relatively constant temperatur
39、e 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 may be suitable for somesamples, more recent research indicates that a test durationwell beyond 20 weeks may be required depend
40、ing 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 material willproduce an acidic, alkaline, or neutral effluent, (2) identifysolutes in the effluent that represent dissolved wea
41、theringproducts 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 into the effluent)under the closely controlled conditions of the test.5.2 Data generated by the laboratory weathering procedur
42、ecan be used to address the following objectives: (1) determinethe variation of drainage quality as a function of compositionalvariations (for example, iron sulfide and calcium+magnesiumcarbonate contents) within individual mine-rock lithologies,(2) determine the amount of acid that can be neutraliz
43、ed by thesample while maintaining drainage pH 6.0 under the condi-tions of the test, (3) estimate mine-rock weathering rates to aidin predicting the environmental behavior of mine rock, and (4)determine mine-rock weathering rates to aid in experimentaldesign of site-specific kinetic tests.5.3 The la
44、boratory-weathering procedure provides condi-tions conducive to oxidation of solid material constituents andenhances the transport of weathering reaction products con-tained in the resulting weekly effluent. This is accomplished bycontrolling the exposure of the solid material sample to suchenvironm
45、ental parameters as reaction environment temperatureand application rate of water and oxygen.5.4 Because efficient removal of reaction products is vital totrack mineral dissolution rates during the procedure, laboratoryleach volumes are large per unit mass of rock to promote therinsing of weathering
46、-reaction products from the mine-rocksample.Acomparison of laboratory kinetic tests with field testshas shown that more reaction products from mineral dissolu-tion are consistently released per unit weight and unit time inlaboratory weathering tests (9). For example, sulfate releaserates observed in
47、 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 times those forsmall-scale field test piles of Archean greenstone rock (11).Agreater increase is anticipated when laboratory rates are com-par
48、ed with field rates measured from operational waste-rockpiles.5.5 Fundamental assumptions governing OptionsAand B ofthe procedure:5.5.1 Option AAn excess amount of air pumped upthrough the sample during the dry- and wet-air portions of theweekly cycle reduces the potential for oxidation reaction rat
49、esbeing limited by low-oxygen concentrations. Weekly leacheswith low ionic strength water promote the removal of leachablemineral dissolution products produced 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 enhanced. During thedry-air portion of the cycle, the oxygen diffusion rate throughthe sample may increa
