1、Designation:D5744071Designation: D5744 12Standard 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 revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEEditorial corrections made in April 2010.1. Scope1.1 This kinetic test method covers a laboratory weathering p
3、rocedure that (1) enhances reaction-product transport in theaqueous 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 aqueous leach that is performed and collected weekly. Leachate
4、 samples areanalyzed for pH, alkalinity/acidity, specific conductance, sulfate, and other selected analytes.1.1.1 This test method is intended for use to meet kinetic testing regulatory requirements for mining waste rock and ores sizedto pass a 6.3-mm (0.25-in.) Tyler screen.1.1.2 Interlaboratory te
5、sting of this method has been confined to mine waste rock. Application of this test method tometallurgical-processing waste (for example, mill tailings) is outside the scope of the test method.1.2 This test method is a modification of a laboratory weathering procedure developed originally for mining
6、 wastes (1-3).2However, it may have useful application wherever gaseous oxidation coupled with aqueous leaching are important mechanismsfor contaminant mobility.1.3 This test method calls for the weekly leaching of a well-characterized solid material sample (weighing at least 1000-g), withwater of s
7、pecified purity, and the collection and chemical characterization of the resulting leachate. Test duration is determined bythe users objectives of the test.1.4 As described, this test method may not be suitable for some materials containing plastics, polymers, or refined metals. Thesematerials may b
8、e resistant to traditional particle size reduction methods.1.5 Additionally, this test method has not been tested for applicability to organic substances and volatile matter.1.6 This test method is not intended to provide leachates that are identical to the actual leachate produced from a solid mate
9、rialin the field or to produce leachates to be used as the sole basis of engineering design.1.7 This test method is not intended to simulate site-specific leaching conditions. It has not been demonstrated to simulate actualdisposal site leaching conditions. Furthermore, the test is not designed to p
10、roduce effluents that are in chemical equilibrium withthe solid phase sample.1.8 This test method is intended to describe the procedure for performing the laboratory weathering of solid materials togenerate leachates. materials. It does not describe all types of sampling and analytical requirements
11、that may be associated withits application.1.9 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.9.1 ExceptionThe values given in parentheses are for information only.1.10 This standard does not purport to address all of the s
12、afety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D75 Practice for Sampling Aggreg
13、ates1This test method is under the jurisdiction ofASTM Committee D34 on Waste Management and is the direct responsibility of Subcommittee D34.01.04 on Waste LeachingTechniques.Current edition approved Oct. 1, 2007. Published November 2007. Originally approved in 1996. Last previous edition approved
14、in 2001 as D5744-96(2001). DOI:10.1520/D5744-07.Current edition approved Feb. 15, 2012. Published July 2012. Originally approved in 1996. Last previous edition approved in 2007 as D5744-07. DOI: 10.1520/D5744-12.2The boldface numbers in parentheses refer to the list of references at the end of this
15、standard.3For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intende
16、d only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current
17、versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D276 Test Methods for Identification of Fibers in TextilesD420 Guide to Site Characterization for En
18、gineering Design and Construction PurposesD653 Terminology Relating to Soil, Rock, and Contained FluidsD737 Test Method for Air Permeability of Textile FabricsD1067 Test Methods for Acidity or Alkalinity of WaterD1125 Test Methods for Electrical Conductivity and Resistivity of WaterD1193 Specificati
19、on for Reagent WaterD1293 Test Methods for pH of WaterD1498 Test Method for Oxidation-Reduction Potential of WaterD2234/D2234M Practice for Collection of a Gross Sample of CoalD3370 Practices for Sampling Water from Closed ConduitsE276 Test Method for Particle Size or ScreenAnalysis at No. 4 (4.75-m
20、m) Sieve and Finer for Metal-Bearing Ores and RelatedMaterialsE877 Practice for Sampling and Sample Preparation of Iron Ores and Related Materials for Determination of ChemicalCompositionE1915 Test Methods for Analysis of Metal Bearing Ores and Related Materials for Carbon, Sulfur, and Acid-BaseChar
21、acteristicsE2242 Test Method for Column Percolation Extraction of Mine Rock by the Meteoric Water Mobility Procedure3. Terminology3.1 Definitions:3.1.1 acid producing potential (AP), nthe maximum potential for a solid material sample to produce acidic effluent can bedetermined based on the total sul
22、fur present in the sample. It is assumed that this sulfur is present as iron sulfides (for example,pyrite) (4). This assumption leads to overestimation of the acid producing potential of samples containing non-ferrous sulfideminerals such as galena (PbS) or non-acid producing sulfur-bearing minerals
23、 such as gypsum (CaSO4). The AP is commonlyconverted to the amount of calcium carbonate required to neutralize the resulting amount of acidic effluent produced by theoxidation of contained iron sulfide minerals; it is expressed as the equivalent tonnes of calcium carbonate per 1000 tonnes of solidma
24、terial (3). TheAPis therefore calculated by multiplying the percent of sulfur contained in the material by a stoichiometric factorof 31.2 (5).3.1.2 interstitial water, nthe residual water remaining in the sample pore spaces at the completion of the fixed-volume weeklyleach.3.1.3 leach, na weekly add
25、ition of water to solid material that is performed either dropwise or by flooding for a specified timeperiod.3.1.4 loading, nthe mass of a chemical species, which is the product of the species concentration and the mass of the weeklyleachate collected.3.1.5 mill tailings, nfinely ground mine waste (
26、commonly passing a 150-m (100 mesh screen) resulting from the millprocessing of ore.3.1.6 neutralizing potential (NP), nthe potential for a solid material sample to neutralize an acidic effluent based on theamount of carbonate present in the sample. The NP is also expressed in terms of tonnes of cal
27、cium carbonate equivalent per 1000tonnes of solid material (3) . It is calculated by digesting the solid material with an excess of standardized acid and back titratingwith a standardized base to measure and convert the residual acid to calcium carbonate equivalents (2,6) . The residual acid issubtr
28、acted from the acid added to determine the acid consumption or acidity present.3.1.6.1 DiscussionIt should be noted that NP tests generally overestimate the capacity of mine waste samples to neutralizeacid while maintaining drainage pH$6.0; the calcium plus magnesium carbonate content of the sample
29、provides a more accurateNP quantification (7).3.1.6.2 DiscussionThe AP and NP are specifically applicable to the determination of AP from mining wastes comprised ofiron-sulfide and carbonate minerals. These terms may be applicable to any solid material containing iron-sulfide and carbonateminerals.3
30、.1.7 run-of-mine, adjusage in this test method refers to ore and waste rock produced by excavation (with attendant variableparticle sizes) from open pit or underground mining operations.3.1.8 waste rock, nrock produced by excavation from open pit or underground mining operations that has an economic
31、mineral content less than a specified economic cutoff value for metallurgical processing.4. Summary of Test Method4.1 This laboratory-weathering procedure is designed to enhance the mass release of acidity/alkalinity, metals, and otherpertinent analytes from a sample of solid material weighing at le
32、ast 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 mass rangesfrom is 0.5:1toor1:1depending upon the efficiency of sample wetting and amount of effluent required for chemical an
33、alyses.The weekly effluent produced is characterized for dissolved weathering products. This test method is performed on each sampleD5744 122in a cylindrical cell. Multiple cells can be arranged in parallel. This configuration permits the simultaneous testing of multiple splitsof the same solid mate
34、rial sample, or of solid material samples each characterized by different compositions.4.2 Two protocol options (OptionsAand B) comprise the test procedure, and these options differ only in the way that the oxygenis supplied to samples in the individual humidity cells. Option A protocol calls for we
35、ekly cycles composed of three days of dryair (less than 10 % relative humidity) and three days of water-saturated air (approximately 95 % relative humidity) pumped upthrough the sample, followed by a leach with water on Day 7. Option B protocol differs from Option A in that each cell is storedfor si
36、x days under conditions of controlled and relatively constant temperature and humidity, and oxygen is supplied to the sampleby diffusion (and possibly advection) of ambient air rather than by pumping. Although a test duration as short as 20 weeks maybe suitable for some samples, more recent research
37、 indicates that a test duration well beyond 20 weeks may be required dependingupon the objectives of the test (8,9).5. Significance and Use5.1 The laboratory weathering procedure will generate data that can be used to: (1) determine whether a solid material willproduce an acidic, alkaline, or neutra
38、l effluent, (2) identify solutes in the effluent that represent dissolved weathering productsformed during a specified period of time, (3) determine the mass of solute release, and (4) determine the rate at which solutes arereleased (from the solids into the effluent) under the closely controlled co
39、nditions of the test.5.2 Data generated by the laboratory weathering procedure can be used to address the following objectives: (1) determine thevariation of drainage quality as a function of compositional variations (for example, iron sulfide and calcium+magnesiumcarbonate contents) within individu
40、al mine-rock lithologies, (2) determine the amount of NP accessible in a mine-rock sample toneutralize acid and maintain drainage pH$6.0 under the conditions of the test, (3) estimate mine-rock weathering rates to aid inpredicting the environmental behavior of mine rock, and (4) determine mine-rock
41、weathering rates to aid in experimental designof site-specific kinetic tests.5.3 The laboratory-weathering procedure provides conditions conducive to oxidation of solid material constituents andenhances the transport of weathering reaction products contained in the resulting weekly effluent. This is
42、 accomplished bycontrolling the exposure of the solid material sample to such environmental parameters as reaction environment temperature andapplication rate of water and oxygen.5.4 Because efficient removal of reaction products is vital to track mineral dissolution rates during the procedure, labo
43、ratoryleach volumes are large per unit mass of rock to promote the rinsing of weathering-reaction products from the mine-rock sample.A comparison of laboratory kinetic tests with field tests has shown that more reaction products from mineral dissolution areconsistently released per unit weight and u
44、nit time in laboratory weathering tests (9). For example, sulfate release rates observedin laboratory tests of metal-mine rock have been reported to be 3 to 8 times those for small-scale field test piles of Duluth Complexrock (10), and from 2 to 20 times those for small-scale field test piles of Arc
45、hean greenstone rock (11). A greater increase isanticipated when laboratory rates are compared with field rates measured from operational waste-rock piles.5.5 Fundamental assumptions governing Options A and B of the procedure:5.5.1 Option AAn excess amount of air pumped up through the sample during
46、the dry- and wet-air portions of the weeklycycle reduces the potential for oxidation reaction rates being limited by low-oxygen concentrations. Weekly leaches with low ionicstrength water promote the removal of leachable mineral dissolution products produced from the previous weeks weatheringcycle.
47、The purpose of the three-day dry-air portion of the weekly cycle is to evaporate some of the water that remains in the poresof the sample after the weekly leach without totally drying out the sample. Consequently, sample saturation is reduced and air flowis enhanced. During the dry-air portion of th
48、e cycle, the oxygen diffusion rate through the sample may increase several orders ofmagnitude as compared to its diffusion rate under more saturated conditions of the leach. This increase in the diffusion rate undernear-dryness conditions helps promote the oxidation of such constituents as iron sulf
49、ide. Additionally, evaporation from the threedays of dry air increases pore water cation/anion concentrations and may also cause increased acidity (for example, by increasingthe concentration of hydrogen ion generated from previously oxidized iron sulfide). Increased acid generation will enhance thedissolution of additional sample constituents. As evaporation continues, the remaining water may become over-saturated withrespect to some mineral phases, consequently causing them to precipitate. Some precipitated minerals are potential sources ofacidity when re-dissolve
