1、Designation: D 5919 96 (Reapproved 2006)Standard Practice forDetermination of Adsorptive Capacity of Activated Carbonby a Micro-Isotherm Technique for Adsorbates at ppbConcentrations1This standard is issued under the fixed designation D 5919; the number immediately following the designation indicate
2、s the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the assessment of activa
3、ted carbonfor the removal of low concentrations of adsorbable constitu-ents from water and wastewater using the bottle point isothermtechnique. It can be used to characterize the adsorptiveproperties of virgin and reactivated activated carbons.1.2 This practice can be used in systems with constituen
4、tconcentrations in the low milligrams per litre or microgramsper litre concentration ranges.1.3 This practice can be used to determine the adsorptivecapacity of and Freundlich constants for volatile organiccompounds provided the handling procedures described in thispractice are followed carefully.1.
5、4 The following safety caveat applies to the proceduresection of this practice: This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-min
6、e the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 3370 Practices for Sampling Water from Closed ConduitsD 2652 Terminology Relating to Activated CarbonD 2867 Test Methods f
7、or Moisture in Activated Carbon3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this practice relating toactivated carbon, refer to Terminology D 2652.3.1.2 For definitions of terms used in this practice relating towater, refer to Terminology D 1129.4. Summary of Practice4.1 This
8、 practice consists of the determination of the ad-sorptive capacity of activated carbon for adsorbable constitu-ents by contacting the aqueous solution contained in anessentially zero head space container with activated carbon,determining the amount of the constituents removed, andcalculating the ad
9、sorptive capacity and the Freundlich con-stants, K and 1/n, from a Freundlich isotherm plot.4.1.1 The weights of activated carbon used in this practicemay have to be adjusted to achieve reasonable levels ofremoval of the constituent. The best data is obtained whencarbon dosages are selected that res
10、ult in no more than 90 % orno less than 10 % of the adsorbable constituents being removedfrom the water by the carbon.4.1.2 If carbon dosages used are less than 1 mg, largervolumes of the aqueous solution may be used, such as 1000mL.5. Significance and Use5.1 This practice allows the adsorption capa
11、city at equilib-rium of an activated carbon for adsorbable constituents presentin water to be determined. The Freundlich K and 1/n constantsthat can be calculated based upon information collected usingthis practice can be used to estimate carbon loading capacitiesand usages rates for the constituent
12、 present in a water stream atother concentrations.6. Interferences6.1 The water shall not contain any nondissolved compo-nents.1This practice is under the jurisdiction of ASTM Committee D28 on ActivatedCarbon and is the direct responsibility of Subcommittee D28.02 on Liquid PhaseEvaluation.Current e
13、dition approved Oct. 1, 2006. Published November 2006. Originallyapproved in 1996. Last previous edition approved in 2001 as D 5919 96 (2001).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vol
14、ume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 The presence of naturally occurring organic compoundssuch as humic acids in the water being studied
15、may signifi-cantly affect the ability of the carbon to adsorb the constituentof interest. Results obtained when using water other thanreagent grade water may be unique for the particular waterused and it may not be possible to apply these results to otherwater systems.6.3 The adsorption isotherm dat
16、a collected using this prac-tice can be affected by the ionic strength, pH and temperatureof the water, and the presence and growth of microorganisms.7. Apparatus7.1 Equilibrator (or other rotating mixing device), a rotat-ing device operating at 25 rpm which can rotate the isothermbottles end over e
17、nd ensuring good dispersion of the powderedactivated carbon in the water being treated.7.2 Grinding Mill, capable of grinding material so that 90 %passes through a U.S. No. 325-mesh (45 m) sieve.7.3 Isotherm Bottles, narrow neck amber bottles with poly-tetrafluoroethylene (PTFE) coated septum sealed
18、 caps of 250,500, and 1000 mL capacity suitable for use in a centrifugeoperating at 2000 rpm.7.4 Solution Delivery Tank, a 10-L, 316 stainless steelcontainer equipped with a PTFE coated floating lid and a 316stainless ball valve to control flow during bottle filling.7.5 Analytical Balance, capable o
19、f weighing to the nearest0.1 mg.7.6 Oven, forced-air circulation, capable of temperatureregulation up to 250C.7.7 Centrifuge, capable of handling isotherm bottles up to 1L in size at 2000 rpm.7.8 Magnetic Stirring Bars and Stirrers.8. Reagents8.1 Reagent Water, in accordance with SpecificationD 1193
20、, Type II.8.2 Methanol, high purity HPLC grade.8.3 Potassium Monobasic Phosphate (KHPO4), 1 M solu-tion.8.4 Sodium Hydroxide (NaOH), 1 M solution.9. Cleaning Procedures9.1 This practice is capable of generating activated carbonadsorption capacity data on aqueous solutions containing ppbw(g/L) levels
21、 of adsorbable constituents. It is therefore veryimportant that all equipment and glassware that come incontact with the activated carbon or the water being treated becleaned thoroughly to remove trace organic compounds.9.2 All equipment and glassware should first be rigorouslycleaned using procedur
22、es recommended by the EPAfor prioritypollutant analysis, hot water and detergent wash, reagent gradewater, and solvent (high purity methanol) rinse followed by abake-out.9.3 The glassware is baked out in an oven at 250C for aminimum of one hour. All PTFE and stainless steel apparatusare dried at 110
23、C for one hour.10. Preparation of the Activated Carbon10.1 This practice requires the use of well washed activatedcarbon that has been reduced in particle size so that 90 % orgreater passes through a U.S. No. 325-mesh (45 m) sieve bywet screening or equivalent.10.2 Approximately 25 g of the powdered
24、 activated carbonsample is placed into each of four clean 250-mL bottles. Theremainder of the bottle is filled with reagent grade water.10.3 The bottle is tightly capped and inverted three to fivetimes to mix the contents.10.4 The bottles are then centrifuged at 2000 rpm for 15 minto settle the acti
25、vated carbon. The supernate is poured off andthe procedure is repeated until the supernatant is clear. Allow-ing the mixture to sit for a period of time to allow the carbonto settle prior to decanting is also acceptable.10.5 The wet carbon is next dried in an oven at 110C to aconstant weight and pla
26、ced in a desiccator to cool.10.6 As an alternate technique to drying the carbon sample,carbon may be placed in a soxhlet extraction device andextracted for a period of up to 1 week with reagent grade (TypeII) water.10.7 The dry activated carbon is transferred to clean 1-Lbrown borosilicate bottles w
27、ith PTFE liners in the caps andstored in an inert atmosphere such as nitrogen for future use.11. Activated Carbon Sample Weighing Procedure11.1 This procedure allows the carbon to be handled atambient conditions by calculating a correction for wateradsorbed from the air.11.2 The powdered activated c
28、arbon sample is allowed tocome to equilibrium in a desiccator containing a saturated saltsolution that will produce a relative humidity comparable toambient laboratory conditions. During the 24 h conditioningperiod care shall be taken not to expose the carbon to organicvapors.11.3 The moisture picke
29、d up by the conditioned activatedcarbon is determined by weighing approximately 500 mg intoa tared (constant weight) bottle, drying for2hat110C,cooling in a desiccator, and re-weighing to determine weightchange (refer to Test Method D 2867 for standard procedures).The ratio of change in weight betwe
30、en the activated carbon atequilibrium with air and after drying is calculated and used asa correction factor for the weighed carbon dosages.11.4 The carbon dosages are weighed by first taking aweighing boat, adding the desired mass of equilibrated acti-vated carbon, and re-weighing the boat after tr
31、ansferring thecarbon to the bottle. The carbon dosage is the differencebetween the carbon plus the boat weight and the final boatweight. The weighed activated carbon dosage is then correctedfor ambient conditions and the actual dried carbon dosagerecorded.12. Alternative Procedure for Addition of Kn
32、ownQuantities of Activated Carbon to Isotherm Bottles12.1 This alternate procedure makes use of a clean dryactivated carbon sample prepared according to proceduresdescribed in Section 10. Desired concentrations of carbon areadded to each isotherm bottle volumetrically using a carbonslurry of known c
33、oncentration.D 5919 96 (2006)212.2 The concentrations of the slurries are chosen so that 5,10, and 20 mL volumes of each slurry would contain appro-priate amounts of carbon for 250 mL isotherm bottles.12.3 The slurries are pipetted into a pre-weighed baked-outisotherm bottle, baked dry in a 105C ove
34、n, cooled, andre-weighed to determine the exact quantity of carbon added tothe bottle. This drying technique eliminates any dilution of thewater sample to be tested, allows the slurry pipet to be rinsedinto the isotherm bottle to ensure complete delivery, and causesthe carbon particles to adhere to
35、the container walls which willminimize carbon loss during bottle filling.12.4 The isotherm bottles containing the carbon are kepttightly capped until a sample is to be introduced.13. Calculation Procedures for Determining CarbonDosages13.1 Preliminary Freudlich constants, K and 1/n, are eithertaken
36、from published literature values or estimated usingPolanyi adsorption potential theory.313.2 The carbon dosages are calculated to give a constituentremoval of from 10 % at the lowest carbon weight to 90 % forthe highest weight. For a target (final) constituent concentra-tion, Ce, the carbon dosage i
37、s calculated based on the followingmass balance within the isotherm bottle:M 5 V Co2 Ce#/KCe1/n#(1)where:K and 1/n = as determined in 13.1,M = required carbon dosage, g,V = volume of isotherm bottle, L,Co= initial constituent concentration, mg/L, andCe= target (final) constituent concentration, mg/L
38、.14. Solution Preparation and Handling14.1 The source of the water used in this practice canoriginate from a contaminated water or wastewater source orcan be prepared in the laboratory using pure constituents andreagent grade water (refer to Practices D 3370 for watersampling). The source water can
39、be used directly in thispractice provided it is essentially free of particulate matter. ThepH of the water should be checked and adjusted or corrected asappropriate.14.2 The preparation of a laboratory solution requires theuse of a 10-L, 316 stainless steel delivery container equippedwith a floating
40、 cover and flow control ball valve.14.3 If reagent grade water is to be used, it may be bufferedto avoid pH effects on the adsorption of the organic constituent.The buffer is prepared by adding 1 mL of a 1 M potassiummonobasic phosphate solution to 1 Lof water and adjusting thepH to 6.0 using a 1 M
41、sodium hydroxide solution. Use of aphosphate buffer will change the ionic strength of the solutionand may promote biological activity. Other buffer relationsmay be used provided that they do not interfere with theadsorption process.14.4 A stock solution containing the constituent(s) to beadsorbed is
42、 prepared by injecting the pure component(s) intoreagent grade water contained in a 250 mL bottle. For poorlysoluble compounds, heating the tightly closed container to amaximum of 40C or the use of a co-solvent such as HPLCgrade methanol may be required. The tightly capped, essen-tially zero headspa
43、ce bottle is tumbled using the equilibratorfor a sufficient time (usually 1 to 3 days) to ensure the solute iscompletely dissolved. The contents of this stock solution bottleare analyzed to ensure desired concentrations of the solute(s)were achieved.14.5 The buffered reagent water in the delivery co
44、ntainer isspiked with the stock solution prepared in 14.4 and the floatingcover is put in place on top of the solution to preventvolatilization.14.6 The solution is made ready to fill the isotherm bottlesby thoroughly mixing the contents of the delivery container bymeans of a PTFE stirring bar and m
45、agnetic stirrer. Mixing iscontinued until analysis of water taken through the bottle fillingball valve shows a constant constituent concentration.15. Isotherm Bottle Filling and Equilibration15.1 The isotherm bottles are filled by means of a PTFEtube attached to the ball valve on the delivery contai
46、ner. Thebottles are filled as quickly as possible but in a way that causesthe least amount of agitation of the solution. The PTFE tube isnot allowed to come into contact with the solution in theisotherm bottles because carbon can cling to the PTFE tube andchange the dosage. To prevent loss of carbon
47、 from the isothermbottle when they are capped, approximately 1 mLof headspaceis left in the bottle. This small amount of headspace aidsmixing and does not result in a significant solute loss even forvery volatile compounds.15.2 During bottle filling, an empty initial concentrationbottle containing n
48、o activated carbon is filled at the beginning,in the middle, and at the end of the bottle filling process.15.3 Two blank bottles are filled with buffered reagent gradewater containing no constituents at the beginning and at the endof the filling process.15.4 The isotherm bottles are weighed before a
49、nd aftercarbon addition and after filling with the solution being treated.Based on these weights the exact weight of water added to eachbottle is determined.15.5 The isotherm bottles are placed in an equilibratorlocated in a constant temperature room (typically 20 6 1C)and allowed to rotate at 25 rpm for five days. This length oftime under most circumstances ensures that full equilibrium isachieved. If an equilibrator is not available, a magnetic stirringbar can be placed in each bottle prior to filling, and mixing canbe achieved through the use of a magnetic stirrer.15.
