ASTM_E_1357_-_90_2001.pdf

Designation:E 1357 90(Reapproved 2001)Standard Test Method forDetermining the Rate of Bioleaching of Iron From Pyrite byThiobacillus Ferrooxidans1This standard is issued under the fixed designation E 1357;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(e)indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers procedures for determining therate of bioleaching of iron from pyrite(FeS2)by the bacteriumThiobacillus ferrooxidans.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 and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:D 516 Test Methods for Sulfate Ion in Water2D 1068 Test Methods for Iron in Water2D 1193 Specification for Reagent Water2D 4455 Test Method for Enumeration of Aquatic Bacteriaby Epifluorescence Microscopy Counting Procedure33.Terminology3.1 Definition:3.1.1 soluble ironthe complexed and dissolved iron asdetermined by Vuorinen et al.4in their study of the species ofiron released from pyrite oxidation by T.ferrooxidans.Theyfound that values of complexed and dissolved iron corre-sponded closely with“total iron”as determined after hotsulfuric acid digestion of samples,particularly at 1 to 2%pulpdensity.4.Summary of Test Method4.1 Cells of T.ferrooxidans grown on ferrous iron are addedto conical flasks containing finely ground iron pyrite in aninorganic salts medium(2%pulp density).The culture isincubated with agitation and samples are periodically with-drawn for determination of soluble iron.The rate of pyriteleaching is determined from the linear portion of a curve-plotting soluble iron produced versus time.4.2 The average rate of soluble iron production in mg ofiron/L/h is reported along with values for uninoculated con-trols.The standard deviation for triplicate flasks is alsoreported.Also to be reported is the particle size range of thepyrite and the initial and final pH values of the test solutions.5.Significance and Use5.1 The development and refinement of processes for bi-oleaching of metal ores and coal desulfurization requireintercomparison of bioleaching data both to better understandmetal ore bioleaching mechanisms and to develop moreeffective strains.For uncertain reasons,different strains of T.ferrooxidans exhibit different pyrite leaching rates and differentsources of pyrite vary widely in susceptibility to microbialattack.5.2 This test method has been developed to provide astandard procedure for evaluating the rate of bioleaching ofiron from iron pyrite(FeS2),a commonly used growth sub-strate for T.ferrooxidans and an important mineral that isbiologically degraded in commercial bioleaching operationsand in many exposed coal deposits.Ahigh leaching rate in thistest is evidence for potential degradability of the mineral inmining operations.A low rate of bioleaching suggests that themineral is inherently not a good substrate or that it containstoxicants toward thiobacilli,and might not be readily bioleach-ing in a mining operation.6.Apparatus6.1 An Gyratory Incubator-Shaker,for maintaining culturesat constant temperature(28 6 2C)and agitation rate(200r/min)during both inoculum preparation and the leaching test.6.2 An Ultraviolet-Visible Light Spectrophotometer,Colo-rimeter or Atomic Absorption Spectrophotometer,for deter-mining concentration of soluble iron.6.3 A Centrifuge,for harvesting cells of T.ferrooxidansprior to inoculation of the pyrite suspension and for removingparticles of iron from solution prior to analysis for soluble iron.A filtration apparatus may also be used for particle removalprior to analysis for soluble iron.6.4 Conical Flasks,500,250 ml or 125 mL(non-baffled).7.Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended that1This test method is under the jurisdiction of ASTM Committee E48 onBiotechnology and is the direct responsibility of Subcommittee E48.03 on UnitProcesses and Their Control.Current edition approved May 25,1990.Published July 1990.2Annual Book of ASTM Standards,Vol 11.01.3Annual Book of ASTM Standards,Vol 11.02.4Vuorinen,A.,Hiltunen,P.,Hsu,J.C.,and Tuovinen,O.H.,“Solubilization andSpeciation of Iron During Pyrite Oxidation by Thiobacillus ferrooxidans,”Geomi-crobiology Journal,Vol 3,1983,pp.95120.1Copyright ASTM,100 Barr Harbor Drive,West Conshohocken,PA 19428-2959,United States.all reagents conform to the specifications of the Committee onAnalytical Reagents of the American ChemicalSociety wheresuch specifications are available.5Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh p