THE BEHAVIOUR OF KAOLINITE- CALCIUM CARBONATE MINERAL MIXTURES. Angelica M. Palomino November 23, 2005

Transcription

1 THE BEHAVIOUR OF KAOLINITE- CALCIUM CARBONATE MINERAL MIXTURES Angelica M. Palomino November 23, 2005

2 Outline Introduction Fabric Formation Microscale Phenomena Materials and Methods Experimental Results Conclusions

3 Introduction Coating Paper Fibers Walter, 1993

4 Microscale Phenomena in Fabric Formation

5 Mineralogy Microscale Phenomena Kaolinite Al 2 Si 2 O 5 (OH) 4 1:1 phyllosilicate Aluminum Octahedral Sheet Silica Tetrahedral Sheet OH - O 2-3 layers/6 sheets MDL Chime web browser plug-in (Barak and Nater, 2003).

6 Mineralogy Microscale Phenomena Calcium Carbonate CaCO 3 O C Ca MDL Chime web browser plug-in (Barak and Nater, 2003).

7 Diffuse Double Layer Microscale Phenomena bulk electrolyte Potential Stern layer Gouy diffuse layer ψ St mineral surface ζ ψ St / e shear plane ψ e -x O = OH - ~ t ddl x ph ionic concentration & valence

8 Particle-Fluid Interactions Microscale Phenomena r / ϑ ( RTc ) e ε ' RT R DL = 64 A 0 ϑ = Att vdw = h c0 z F 6πr DLVO (Derjaguin, Landau, Verwey, Overbeek) low c o force repulsion intermediate c o high c o attraction interparticle distance

9 Kaolinite Dissolution-Stability Microscale Phenomena K4 Al(aq) = K [H ] + K [H ] + K [H ] [H4SiO4] [H ] Total Al Concentration in Solution (mol/l) Initial Concentration H 4 SiO mol/l ph K n = Stability Constants

10 Kaolinite Fabric Map Microscale Phenomena ph 11 Convergence 9 Edge IEP 7 5 Face or Particle IEP 3 Particle dissolution FF aggregation 1 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 c th NaCl Concentration (mol/l)

11 Particle Size Microscale Phenomena Weight W = ( πg s γ w / 6) d 3 Capillary F cap = πt s d Skeletal 2 N = σ'd Electrical Att. Ah Att = 2 24t d 1.E-01 1.E-03 Skeletal for σ'=1 MPa 10 kpa 1 Capillary Force [N] 1.E-05 1.E Weight van der Waals 1.E E-11 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 Diameter [m] (Santamarina, 2002)

12 Relative Size and Shape Microscale Phenomena Relative Particle Size Shape

13 Particle Configurations Microscale Phenomena Electrical Mechanical Single Minerals Dispersed Flocculated Stacked EF Flocculated FF Aggregated Loose Dense Mineral Mixtures Electrically-Controlled Fabric Mechanical Ordering Mechanical Bridging

14 Materials and Methods Height Ti me

15 Materials Materials and Methods Kaolinite RP2, =0.36µm SA1, =1.1µm Calcium Carbonate GCC #12 White, =12µm PCC Rhombic, =1µm

16 Relative Sizes d Materials and Methods Kaolinite SA1 =1.1µm t 70nm S a = 13 m 2 /g t Kaolinite RP2 =0.36µm t 45nm S a = 22 m 2 /g Precipitated Calcium Carbonate PCC =1µm t 0.50µm S a = 10 m 2 /g Ground Calcium Carbonate GCC =12µm t 12µm S a = 2 m 2 /g X 12

17 Inherent ph Effects Surface Charge [C/m 2 ] Kaolinite Calcium Carbonate ph After Stumm (1992)

18 Experimental Methodology Materials and Methods Sedimentation Low Solids Content, Observed settling behavior Settlement velocity Final sedimentation height φ = solids volume total volume Rheology Moderate Solids Viscosity profile at various shear rates Viscosity at single shear rate condition Fall Cone Liquid Limit High Solids Liquid Limit Slope of liquid limit vs. water content line

19 Devices and Methods Materials and Methods Sedimentation Viscometer Freeze Dry System Specific Surface Analyzer Fall Cone Scanning Electron Microscope MC-H-800/emc-h-800.html

20 Sedimentation Materials and Methods Interface movement Clear Clear Flocculated Voluminous Sediment Cloudy Cloudy Dispersed Interface movement Compact Sediment (Pierre et al., 1995)

21 Rheology Materials and Methods Viscosity Profiles Flow Unit Response Low Shear High Shear Viscosity Shear Thinning Shear Thickening Flocculated Newtonian Clay Suspensions Shear Rate Dispersed

22 Liquid Limit Materials and Methods Cone Penetration Depth 20mm Particle Associations movement hindered LL Water Content Decreases with: Particle Alignment Dispersion FF Aggregation Dispersed high repulsive forces FF Aggregation less fluid in pores

23 Experimental Results Height Ti me

24 Sedimentation Induction Period Experimental Results Suspension Height Initial Settlement Velocity α Sediment Height H log (Time) Kaolinite RP2 =0.36 µm GCC =12µm Suspension Height [cm] RP2:GCC 100:0% 90:10 80:20 70:30 60:40 50:50 40:60 30:70 20:80 10:90 0: Time [min]

25 Sedimentation Experimental Results Kaolinite RP2 =0.36 µm GCC =12µm Initial Settling Velocity α [cm/min] RP2:GCC % Clay

26 Sedimentation Experimental Results Kaolinite RP2, SA1 =0.36, 1.1 µm GCC =12µm Sediment Height at 24 hours [cm] RP2:GCC SA1:GCC % Clay

27 Sedimentation Experimental Results Kaolinite RP2 =0.36 µm GCC =12µm Measured ph RP2:GCC % Clay

28 Rheology Spindle #1 Experimental Results Kaolinite SA1 =1.1 µm PCC =1 µm Viscosity [mpa s] Increasing Flocculation 100:0 SA1:PCC 25:75 0:100 50:50 75:25 Viscosity at 100 RPM [mpa sec] Spindle Rotational Speed [rpm] SA1:PCC Spindle #

29 Liquid Limit Experimental Results Kaolinite SA1 =1.1 µm GCC =12µm Cone Penetration [mm] SA1:GCC 20:80 0:100 40:60 60:40 80:20 100:0 LL Line Moisture Content [%]

30 Liquid Limit Experimental Results Kaolinite SA1 =1.1 µm S a = 13 m 2 /g GCC =12µm S a =2 m 2 /g Liquid Limit LL Slope SA1:GCC Slope of LL Line [mm/w%] % Clay 0

31 Conclusions

32 Conclusions Kaolinite-carbonate associations take place irrespective of carbonate-induced fluid ph (above kaolinite iep) Fabric is most relevant at low to moderate solids content. Kaolinite-carbonate inter-mineral associations produce: Larger flow units Slower initial settlement velocities More voluminous structure Higher viscosity Specific surface dominates at high solids content Shear strength with carbonate content

33 Thank You