1、Designation: D6647 18Standard Test Method forDetermination of Acid Soluble Iron via Atomic Absorption1This standard is issued under the fixed designation D6647; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. 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 test method covers the determination of the acidsoluble iron content of granular and powdered activatedcarbons, using an at
3、omic absorption spectroscopy method bydirect aspiration. Hydrochloric acid is used to extract the iron.This test method is not directly usable to determine the totaliron concentration of a sample.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use
4、. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.For a specific hazard statement, see Section 8.1.3 This international standard was developed in accor-d
5、ance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM S
6、tandards:2D1193 Specification for Reagent WaterD2652 Terminology Relating to Activated CarbonE11 Specification for Woven Wire Test Sieve Cloth and TestSievesE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE287 Specification for Laboratory Glass Graduated BuretsE288 Specifica
7、tion for Laboratory Glass Volumetric FlasksE300 Practice for Sampling Industrial ChemicalsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 NIST Publication:3Circular 602 Testing of Glass Volumetric Apparatus3. Terminology3.1 DefinitionsTerms relatin
8、g to this standard are definedin Terminology D2652.3.1.1 atomic absorptionin flame atomic absorptionspectrometry, a sample is aspirated into a flame and atomized.A light beam is directed through the flame, into amonochromator, and onto a detector that measures the amountof light absorbed by the atom
9、ized element in the flame.Because each metal has its own characteristic absorptionwavelength, a source lamp of that element is used. The amountof energy at the characteristic wavelength absorbed in theflame is proportional to the concentration of the element in thesample over a limited concentration
10、 range.4. Summary of Test Method4.1 Arepresentative sample of the material to be analyzed iscollected according to Practice E300. A known weight of thesample is ground until 95 % or more of the sample passes 325mesh. The ground sample is oven dried, and then mixed witha dilute hydrochloric acid. The
11、 solution is boiled for 5 min toconvert the iron into a soluble chloride, and then cooled andfiltered. The filter cake is washed with water. Then the filtrateis transferred quantitatively to a beaker. The concentration ofiron in the filtrate is measured by atomic absorption against aset of standards
12、. The acid soluble iron concentration is thencalculated against the weight of the original sample.5. Significance and Use5.1 In certain applications, such as acid purification, acidicfood or chemical purification or decolorization, or otherapplications wherein iron may be leached out of the carbon,
13、theuse of acid-washed carbons will reduce or eliminate colorpickup in the effluent or in the product. The acid soluble ironcontent is usually specified by the carbon supplier to preventunacceptable levels of iron leach occurring.5.2 Detection limits, sensitivity, and optimum ranges willvary with the
14、 models of atomic absorption spectrophotometers.General instrumental parameters are as follows:1This test method is under the jurisdiction of ASTM Committee D28 onActivated Carbon and is the direct responsibility of Subcommittee D28.02 on LiquidPhase Evaluation.Current edition approved May 1, 2018.
15、Published June 2018 Originally approvedin 2001. Last previous edition approved in 2011 as D6647 01 (2011). DOI:10.1520/D6647-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume informatio
16、n, refer to the standards Document Summary page onthe ASTM website.3Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA
17、19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Te
18、chnical Barriers to Trade (TBT) Committee.15.2.1 Iron hollow cathode lamp.5.2.2 Wavelength: 248.3 nm.5.2.3 Fuel: acetylene (high purity).5.2.4 Oxidant: air (from compressed air line, laboratorycompressor, or a cylinder of compressed airall need to beclean and dry).5.2.5 Type of flame: oxidizing.5.2.
19、6 The following lines may also be used:248.8 nm Relative Sensitivity 2271.9 nm Relative Sensitivity 4302.1 nm Relative Sensitivity 5252.7 nm Relative Sensitivity 6372.0 nm Relative Sensitivity 105.3 The method, as written, is intended for carbons havingan acid soluble iron content of 0.0030 to 0.050
20、 %. For carbonshaving higher iron contents, larger dilutions or smaller aliquotsmay be used.5.4 The user should validate that there are no interferencesfrom other metals in the sample matrix.5.5 To prevent erroneous results, the user should ensure thatno iron instruments contact any of the sample or
21、 the solutionsused in this procedure. Only glass, ceramics, or plastic shouldbe allowed to contact the sample or solutions.6. Apparatus6.1 Atomic Absorption Spectrometer, consisting of a lightsource emitting the line spectrum of an element (see 5.2.1), adevice for vaporizing the sample (usually a fl
22、ame), a means forisolating an absorption line (monochromator or filter andadjustable slitsee 5.2.2 and 5.2.6), and a photoelectricdetector with its associated electronic amplifying and measur-ing equipment.6.2 BeakersGriffen, low form, 400 mL, Pyrex or equiva-lent.6.3 CylinderASTM, graduated, 100 mL
23、.6.4 FlaskFiltering, with side tube, 250 mL.6.5 Buchner FunnelSize D, 71-mm ID.6.6 Filter PaperWhatman No. 3, 7.0 cm or equivalent.6.7 FlasksVolumetric, 50, 100, 250, 500, and 1000 mL.6.8 PipettesVolumetric, 1, 2, 5, 10, 25, and 100 mL.6.9 325-Mesh Screen (U.S. Sieve series).6.10 Analytical Balance,
24、 accuracy 60.0001 g.6.11 Hotplate.NOTE 1All volumetric measuring equipment should meet or exceedthe requirements of NIST Circular 602. Volumetric glassware meetingthose specifications is normally designated as “Class A.” See alsoSpecifications E287 and E288.7. Reagents7.1 Purity of ReagentsReagent-g
25、rade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available. Other grades may beused, provided it is first a
26、scertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterReferences to water shall be under-stood to mean reagent water conforming to SpecificationD1193 for Type II reagent water.7.3 Standard Iron Solution IComp
27、letely dissolve 0.1000 gof iron wire, C.P., in 20 mL of hydrochloric acid, concentratedACS hydrochloric acid grade, and 50 mL of water. Allow tostand overnight. Quantitatively transfer the solution into a 1-Lvolumetric flask and dilute to the mark with water. Mixthoroughly. This solution contains 0.
28、1 mg of iron per mL.7.4 Standard Iron Solution IIPipette 100.0 mL of standardiron solution I into a 1-L volumetric flask. Dilute to the markwith water. Mix thoroughly. This solution contains 0.01 mg ofiron/mL.NOTE 2Commercially available iron solutions obtained from chemi-cal supply houses have been
29、 found to be acceptable, provided the accuracyof the solution meets specified requirements.8. Hazards8.1 Several potential hazards are associated with conductingthis test procedure. It is not the purpose of this standard toaddress all potential health and safety hazards associated withits use. The u
30、ser is responsible for establishing appropriatehealth and safety practices and determining the applicability ofany federal and state regulations before attempting to use thistest method.8.1.1 Since this procedure involves the use of hydrochloricacid, all necessary personal protective equipment for h
31、andlingacids should be used, including rubber gloves, lab apron, andgoggles. Careful handling and good laboratory techniqueshould always be used when working with chemicals. Avoidcontact with hydrochloric acid or acid vapor. Care should betaken to prevent burns during handling of various solutionsdu
32、ring this test procedure.8.1.2 The atomic absorption spectrometer should be ventedappropriately, as recommended by the instrumentmanufacturer, to dissipate fumes and vapors generated by thecombustion the flame. This precaution protects laboratorypersonnel from toxic vapors, protects the instrument f
33、romcorrosive vapors, and prevents flame stability from beingaffected by room drafts.8.1.3 The user of this test should comply with all federal,state, and local regulations for safe disposal of all samples andreagents used.9. Sampling9.1 Collect a representative sample of the carbon to betested using
34、 Practice E300. Approximately 10 g of the repre-sentative sample will be needed for this test.10. Procedure10.1 Calibration Standards:10.1.1 For those instruments which do not read out directlyin concentration, a calibration curve is prepared to cover theappropriate concentration range. Usually, thi
35、s means the prepa-ration of standards which produce an absorbance of 0.0 to 0.7.D6647 182Calibration standards are prepared by diluting the stock metalsolutions at the time of analysis. For best results, calibrationstandards should be prepared fresh each time a batch ofsamples is analyzed.10.1.2 Pre
36、pare a blank and several calibration standards asfollows: For the blank, pipette 25.0 mL of concentratedhydrochloric acid into a 250-mL volumetric flask, and dilute tothe mark with water. Follow steps 10.12 10.16 to determinethe absorbance relative to 0 % acid soluble iron. For thestandards, pipette
37、 1.0, 3.0, 5.0, and 10.0 mL of standard ironsolution II, from Section 7, into separate 50-mL volumetricflasks. Repeat steps 10.12 10.16 to determine the absorbancerelative to each level of acid soluble iron measured. Plot theabsorbance versus milligrams of iron per mL on linear graphpaper. This will
38、 give you four points on the curve, representing0.0002 mg/mL, 0.0006 mg/mL, 0.001 mg/mL, and0.002 mg mL. Retain the calibration curve for use in the finalreport.10.2 This procedure is applicable to either powdered orgranular activated carbon. When granular carbon is to betested, grind approximately
39、10 g of the sample until 95 % ormore of the sample will pass through a 325-mesh screen (U.S.Sieve series, see Specification E11). Carbon received in thepowder form may need additional grinding to meet the particlesize requirement given above.10.3 Oven dry the sample at 150 C for 3 h and cool to room
40、temperature in a desiccator.10.4 Weigh 5.0 g of the dried sample to the nearest 0.1 mgand record the weight. This weight represents the sampleweight (SW) used in Section 11.10.5 Quantitatively transfer the sample to a clean 400-mLbeaker.10.6 Carefully add 100.0 mL of water and 25.0 mL ofconcentrated
41、 hydrochloric acid to the beaker and swirl thecontents until the carbon is wetted.10.7 Place the beaker on the hotplate and allow to boil for5 min. A watch glass placed on top of the beaker will reducewater loss during the 5-min boil.10.8 Remove the beaker from the hotplate and allow to coolto room
42、temperature.10.9 Filter the sample by vacuum through a Buchner funnel,using Whatman No. 3 filter paper, or equivalent. The filtershould be prepared in advance by wetting the paper with water,and having the vacuum on before the sample is added to thefilter.10.10 Wash the carbon retained on the filter
43、 paper withseveral 5-mL portions of water.10.11 Quantitatively transfer the filtrate into a 250-mLvolumetric flask, and dilute to the mark with water. Mixthoroughly. If the carbon is suspected of having an acid solubleiron content above 0.03 %, the filtrate may be diluted to500 mL. This volume repre
44、sents the initial volume (IV) used inthe calculation below, and should be recorded.10.12 Pipette a 25.0-mL aliquot of the solution into a50.0-mL volumetric flask. Dilute to the mark with water andmix thoroughly. This aliquot is the aliquot value (AT) used inthe calculation below, and the volume here
45、 represents the finalvolume value (FV) used in the calculation below. These valuesshould be recorded.10.13 Differences between the various makes and models ofsatisfactory atomic absorption spectrophotometers prevent theformulation of detailed instructions applicable to every instru-ment. The analyst
46、 should follow the manufacturers operatinginstructions for a particular instrument. In general, after choos-ing the proper lamp for the analysis per 5.2, allow the lamp towarm up for a minimum of 15 min, unless operated in a doublebeam mode. During this period, align the instrument, positionthe mono
47、chromator at the correct wavelength per 5.2, select theproper monochromator slit width, and adjust the currentaccording to the manufacturers recommendation.10.14 Light the flame and regulate the flow of fuel andoxidant. Adjust the burner and nebulizer flow rate for maxi-mum percent absorption and st
48、ability. Balance the photometer.10.15 Aspirate the sample and determine the absorbance.Compare to the calibration curve to determine the concentra-tion of iron in mg/mL of the diluted sample.10.16 Calculate the concentration of the acid soluble iron in% for the sample by the procedure in Section 11
49、below.11. Calculation11.1% Acid Soluble Iron 5C 3 IV 3 FV 3100SW 3 AT 31000(1)where:C = concentration of iron, mg/mL (10.15),IV = initial volume, mL (10.11),FV = final volume, mL (10.12),SW = sample weight, g (10.4),AT = aliquot taken, mL (10.12),1000 = conversion from g to mg, and100 = conversion from decimal to percentage.12. Report12.1 In the report of this test, include the values for initialvolume, final volume, aliquot taken, the conditions used for thespectrophotometer, and the calculated result for % acid solubleiron.13. Precision and Bias13.1 Preci
