3_physical_chemistry_of_bacterial_leaching.ppt

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1、PhysicalchemistryofbacterialleachingLectureno.3CelladhesionAdhesionofmicroorganismstothemineralsurfaceiseverpresentinthenaturalenvironment.Microbialadhesionoccursandisdetrimentalinwiderangeofareassuchas:BiocorrosionBiofoulingBioleachingBacteriaattach

2、mentTheattachmentofbacteriatothemineralsurfaceisaffectedbyhydrophobicandelectrostaticparameters.Thesurfacechemistryofbacteriaattachment.ThecolonizationofasurfacebybacteriaisoccurringinfourdistinctstepsStepsinthecolonizationofthemineralsurfaceTheoryof

3、adhesionThecontactangleTheadhesionofbacteriatothepolystyrenesurfacewasstronglycorrelatedwiththecontactangleYoungequationThomasYoungproposedtheequationforadropofliquidplacedonasolidsurfaceSurfaceenergy1.FowkespioneeredthesurfacecomponentapproachHedivi

4、dedthetotalsurfaceenergyin2parts.=d+pd–dispersivepart(Londona-vanderWaalsa)p-non-dispersivepart–polarpart2.VanOssandGooddivetedpolarcomponentofsurfaceenergyintoelectronaccepting(+)andelectro-donating(-)parameters.=VdW+ABAB=2√+-Surfaceene

5、rgyandhydrophobicityContactangleHydrophobicitySurfaceenergy00-900hydrophilicHigh(upto100mJ)900-1800hydrophobiclow(10-30mJ)BacteriacellascolloidparticleBacteriainsolutionhavebeenfrequentlydescribedascolloidalsuspension.Thecolloidparticlesinteractionis

6、thecombinationofattractionandrepulsionforces.Attractionforce–vanderWaalsforceRepulsionforce–electrostaticforceVanderWaalsforceVanderWaalsforceisresponsibleforlong-rangeattractiveforcesbetweencolloidparticlesandbetweencolloidparticleandthesurface.Hydr

7、ophobicityariseswhenthemagnitudeofvanderWaalsinteractionbetweenwatermoleculesisgreaterthantheinteractionsofthewatermoleculesandthesurface.AttractionenergyTheattractionenergyVAarisingfromthevanderWaalsforcebetweencolloidalparticlesofradiusrandseparate

8、dbyadistanceH,isgiven:where:A123istheHamakerconstantofthesystem.TheHamakerconstantcanbecalculatedfromcontactanglebyamethodoutlinedbyFowkesInteractionenergycurveElectrostaticforceTheelectrostaticforcesaregenerallyrepulsiveinbacteriasurfaceinteraction.