1、Designation: D5919 96 (Reapproved 2011)Standard Practice forDetermination of Adsorptive Capacity of Activated Carbonby a Micro-Isotherm Technique for Adsorbates at ppbConcentrations1This standard is issued under the fixed designation D5919; the number immediately following the designation indicates
2、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 () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the assessment of activated
3、 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 constituentco
4、ncentrations 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.1.4 T
5、he values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 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
6、. It is the responsibility of the user of this standard toestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD3370
7、 Practices for Sampling Water from Closed ConduitsD2652 Terminology Relating to Activated CarbonD2867 Test Methods for Moisture in Activated Carbon3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this practice relating toactivated carbon, refer to Terminology D2652.3.1.2 For defi
8、nitions of terms used in this practice relating towater, refer to Terminology D1129.4. Summary of Practice4.1 This 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 he
9、ad space container with activated carbon,determining the amount of the constituents removed, andcalculating the adsorptive 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
10、reasonable levels ofremoval of the constituent. The best data is obtained whencarbon dosages are selected that result 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 th
11、e aqueous solution may be used, such as 1000mL.5. Significance and Use5.1 This practice allows the adsorption capacity 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
12、collected usingthis practice can be used to estimate carbon loading capacitiesand usages rates for the constituent present in a water stream atother concentrations.6. Interferences6.1 The water shall not contain any nondissolved compo-nents.6.2 The presence of naturally occurring organic compoundssu
13、ch as humic acids in the water being studied may signifi-cantly affect the ability of the carbon to adsorb the constituent1This practice is under the jurisdiction of ASTM Committee D28 on ActivatedCarbon and is the direct responsibility of Subcommittee D28.02 on Liquid PhaseEvaluation.Current editio
14、n approved March 1, 2011. Published May 2011. Originallyapproved in 1996. Last previous edition approved in 2006 as D5919 96 (2006).DOI: 10.1520/D5919-96R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of AS
15、TMStandards volume 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.of interest. Results obtained when using water other thanreagent grade water may be uniqu
16、e for the particular waterused and it may not be possible to apply these results to otherwater systems.6.3 The adsorption isotherm data 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
17、Equilibrator (or other rotating mixing device), a rotat-ing device operating at 25 rpm which can rotate the isothermbottles end over end 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.
18、S. No. 325-mesh (45 m) sieve.7.3 Isotherm Bottles, narrow neck amber bottles with poly-tetrafluoroethylene (PTFE) coated septum sealed 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
19、 with a PTFE coated floating lid and a 316stainless ball valve to control flow during bottle filling.7.5 Analytical Balance, capable of 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
20、to 1L in size at 2000 rpm.7.8 Magnetic Stirring Bars and Stirrers.8. Reagents8.1 Reagent Water, in accordance with Specification D1193,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 Procedure
21、s9.1 This practice is capable of generating activated carbonadsorption capacity data on aqueous solutions containing ppbw(g/L) levels of adsorbable constituents. It is therefore veryimportant that all equipment and glassware that come incontact with the activated carbon or the water being treated be
22、cleaned thoroughly to remove trace organic compounds.9.2 All equipment and glassware should first be rigorouslycleaned using procedures recommended by the EPAfor prioritypollutant analysis, hot water and detergent wash, reagent gradewater, and solvent (high purity methanol) rinse followed by abake-o
23、ut.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 110C 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
24、 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 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 capp
25、ed and inverted three to fivetimes to mix the contents.10.4 The bottles are then centrifuged at 2000 rpm for 15 minto settle the activated 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 c
26、arbonto settle prior to decanting is also acceptable.10.5 The wet carbon is next dried in an oven at 110C to aconstant weight and placed 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
27、 up to 1 week with reagent grade (TypeII) water.10.7 The dry activated carbon is transferred to clean 1-Lbrown borosilicate bottles with 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 t
28、he carbon to be handled atambient conditions by calculating a correction for wateradsorbed from the air.11.2 The powdered activated carbon sample is allowed tocome to equilibrium in a desiccator containing a saturated saltsolution that will produce a relative humidity comparable toambient laboratory
29、 conditions. During the 24 h conditioningperiod care shall be taken not to expose the carbon to organicvapors.11.3 The moisture picked up by the conditioned activatedcarbon is determined by weighing approximately 500 mg intoa tared (constant weight) bottle, drying for2hat110C,cooling in a desiccator
30、, and re-weighing to determine weightchange (refer to Test Method D2867 for standard procedures).The ratio of change in weight between 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
31、weighed by first taking aweighing boat, adding the desired mass of equilibrated acti-vated carbon, and re-weighing the boat after transferring thecarbon to the bottle. The carbon dosage is the differencebetween the carbon plus the boat weight and the final boatweight. The weighed activated carbon do
32、sage is then correctedfor ambient conditions and the actual dried carbon dosagerecorded.12. Alternative Procedure for Addition of KnownQuantities of Activated Carbon to Isotherm Bottles12.1 This alternate procedure makes use of a clean dryactivated carbon sample prepared according to proceduresdescr
33、ibed in Section 10. Desired concentrations of carbon areadded to each isotherm bottle volumetrically using a carbonslurry of known concentration.12.2 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 i
34、sotherm bottles.12.3 The slurries are pipetted into a pre-weighed baked-outisotherm bottle, baked dry in a 105C oven, cooled, andD5919 96 (2011)2re-weighed to determine the exact quantity of carbon added tothe bottle. This drying technique eliminates any dilution of thewater sample to be tested, all
35、ows the slurry pipet to be rinsedinto the isotherm bottle to ensure complete delivery, and causesthe carbon particles to adhere to 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 i
36、ntroduced.13. Calculation Procedures for Determining CarbonDosages13.1 Preliminary Freudlich constants, K and 1/n, are eithertaken from published literature values or estimated usingPolanyi adsorption potential theory.313.2 The carbon dosages are calculated to give a constituentremoval of from 10 %
37、at the lowest carbon weight to 90 % forthe highest weight. For a target (final) constituent concentra-tion, Ce, the carbon dosage is 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,
38、V = volume of isotherm bottle, L,Co= initial constituent concentration, mg/L, andCe= target (final) constituent concentration, mg/L.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
39、 the laboratory using pure constituents andreagent grade water (refer to Practices D3370 for watersampling). The source water can 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
40、The preparation of a laboratory solution requires theuse of a 10-L, 316 stainless steel delivery container equippedwith a floating 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 buffe
41、r 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 sodium hydroxide solution. Use of aphosphate buffer will change the ionic strength of the solutionand may promote biological activity. Other buffer relationsmay be used p
42、rovided that they do not interfere with theadsorption process.14.4 A stock solution containing the constituent(s) to beadsorbed is 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 am
43、aximum of 40C or the use of a co-solvent such as HPLCgrade methanol may be required. The tightly capped, essen-tially zero headspace 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 bo
44、ttleare analyzed to ensure desired concentrations of the solute(s)were achieved.14.5 The buffered reagent water in the delivery container 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
45、ready to fill the isotherm bottlesby thoroughly mixing the contents of the delivery container bymeans of a PTFE stirring bar and magnetic stirrer. Mixing iscontinued until analysis of water taken through the bottle fillingball valve shows a constant constituent concentration.15. Isotherm Bottle Fill
46、ing and Equilibration15.1 The isotherm bottles are filled by means of a PTFEtube attached to the ball valve on the delivery container. 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
47、with the solution in theisotherm bottles because carbon can cling to the PTFE tube andchange the dosage. To prevent loss of carbon 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 sig
48、nificant solute loss even forvery volatile compounds.15.2 During bottle filling, an empty initial concentrationbottle containing no 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 gradewat
49、er containing no constituents at the beginning and at the endof the filling process.15.4 The isotherm bottles are weighed before and 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 magn
