Chp 5-Colloids and Fine Particles

《Chp 5-Colloids and Fine Particles》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、Week#4MRChapter5ColloidsandFineParticles•Tutorial#4Tutorial#4MARTINMARTINRHODES(2008)RHODES(2008)•MR#5.3,5.5,5.6.IntroductiontoParticleTechnology,2ndEdition.PublisherJohnWiley&Son,•TobediscussedonFeb.8.Chichester,WestSussex,•Byeithervolunteerorclasslist.Englan

2、d.Dragforce~xx26Surfacearea/VolumeSurfacearea/Volume=xx36xistheparticlediameter(1nm–10m)BodyforceOthersurfaceforces:vanderWaals,electricaldouble~x3layer,bridgingandstericforcesBrownianmotionRobertBrown(1827)RobertBrown(1827)Thermalenergyfromenvironmentcaus

3、estheenvironmentcausesthemoleculesoftheliquidtovibrate.Thesevibratingmoleculescollidewitheachotherwitheachotherandwiththesurfaceoftheparticles.IllustrationoftherandomwalkofaBrownianparticle.ThedistancetheparticlehasmovedoveraperiodoftimeisL3kT312Randomthermale

4、nergykTmvIgnoringdrag,collisionandotherfactorsm22((,Einstein,1956))Basedonstatisticalanalysisof1-Drandomwalktodeterminerootmeansquaredistancetraveled.k:Boltzmannconstant=1.381x10-23J/Kf:frictioncoefficient=FD/UxistheparticlediameterExtensionto3Dcase:Lt6Su

5、rfaceforcesdVFdD•VanderWaalsForcesAgroupofelectrohydrodynamicinteractionsthatoccurbetweentheatomsintwodifferentparticles.NotationusedtoindicatethetypeofmaterialforeachparticleandtheinterveningmediumDielectricpropertiesofmedium2isbetweenmaterials1&3.•Electric

6、aldoublelayerforcesNumberdensityperunitareaofneutral(M-OH),positive(M-OH+)2andnegative(M-O-)surfacesitesasafunctionofpHAmeasureofthecounterioncloud(thustherangeoftherepulsion)ithDblthkistheDebyelength,k-1-13.29[](nm)cApproximateEDLpotentialenergy2DVxe

7、EDL00ZetapotentialofaluminaparticlesasafunctionofpHandsaltconcentration•Adsorbingpolymers,bridgingandstericforcesSchematicrepp(resentationof(a))bridgginggflocculationand((b))stericreppulsion•NetinteractionforceDLVOTheory:•Resultofsurfaceforcesonbehaviourinaira

8、ndwater•Influencesofparticlesizeandsurfaceforcesonsolid/liquidseparationbysedimentation2216kT2kTxgPftLtt22531x8gxPf•SuspensionrheologyEinstein(1906),<7%volumesoli