ASTM_D_6851_-_20.pdf

Designation:D685120Standard Test Method forDetermination of Contact pH with Activated Carbon1This standard is issued under the fixed designation D6851;the number immediately following the designation indicates 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 method is to be used in the determination of the pHof water on initial contact with activated carbon.This testmethod is not meant as a replacement for Test Method D3838and may give a different value.1.2 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 establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.3 This international standard was developed in accor-dance 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 Standards:2D1293 Test Methods for pH of WaterD3838 Test Method for pH of Activated CarbonE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE300 Practice for Sampling Industrial ChemicalsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Summary of Test Method3.1 A sample of carbon is stirred with water and the pH ofthe suspension is measured.4.Significance and Use4.1 The determination of contact pH can be used as a simpleand fast measurement that can allow activated carbon produc-ers and users to have a standard method for assessing the effectvarious carbons will have on the initial pH of the water incontact with the carbon.It has been determined that there is abias between this method and Test Method D3838;they are notequivalent.5.Interferences5.1 pH electrodes used to measure this quantity can even-tually become clogged over time with carbon fines.Suitableelectrodes can be found which have a detachable junctionallowing the user,when necessary,to discard a fouled pHmembrane.5.2 Distilled water can become acidic on standing.Makesure that the water used meets the minimum requirements forASTM Type II water.Determine the pH as indicated in TestMethods D1293.6.Apparatus6.1 A pH meter(ambient temperature of 25 C is assumed;if otherwise,temperature compensation is required for accuratepH measurement).6.2 A combination pH electrode,or glass-calomel elec-trodes used together.6.3 A 100-mL(TD)graduated cylinder.6.4 A 250-mL glass beaker(for each sample).6.5 A polymer-coated magnetic stir bar(for each sample).6.6 Magnetic stir plate.6.7 A balance capable of accurately measuring to 0.1 g.7.Reagents and Materials7.1 Distilled or de-ionized water that meets theASTM TypeII requirements.7.2 Buffers to calibrate the pH meter;typically pH 4.0,pH7.0,pH 10.0,or combinations thereof.8.Hazards8.1 The water in contact with the carbon may have either alow or high pH.Take precautions accordingly and wearnecessary protective equipment to prevent injuries from spillsand splashes.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 Jan.15,2020.Published February 2020.Originallyapproved in 2002.Last previous edition approved in 2011 as D6851 02(2011).DOI:10.1520/D6851-20.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 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 Technical Barriers to Trade(TBT)Committee.9.Sampling,Test Specimens,and Test Units9.1 Follow Practice E300 in the collection and preparationof samples.10.Preparation of Apparatus10.1 Use the procedure of Test Methods D1293 to standard-ize the pH meter before measurement.11.Calibration and Standardization11.1 See above section.12.Conditioning12.1 The sample should be tested as received.13.Procedure13.1 A representative sample should be taken from thequantity to be tested and prepared for testing(as received).13.2 Ten(10)grams of sample(as received)will be used forthe test.Place 10 g of a representative sample into a 250-mLbeaker.13.3 The pH of the water to be used should be determin