- NERC Open Research Archive
Contents
1. _ VmAN M S where A is Avogadro s number which expresses the number of gas molecules in a mole of gas at standard conditions M is the molar volume of the gas and N is the area of each adsorbed gas molecule By extending the process of gas adsorption so that gas 1s allowed to condense in material pore spaces the fine pore structure of a material may be evaluated As pressure is increased the gas condenses in pores of increasing dimensions until saturation 1s reached when all pores are filled with liquid Incremental reduction in the pressure of the adsorbed gas then evaporates the condensed gas By comparison of the adsorption and desorption isotherms and the hysteresis between them using a range of different models e g BJH method Barrett Joyner and Halenda 1951 reveals information about the material s pore size distribution pore volume pore area and pore shape However since inert gases do not penetrate between layers of expanding clay minerals in general only the external surface area 1s determined using the BET method To measure the total internal and external surface area of clay bearing samples a different technique is employed requiring the adsorption of polar molecules such as for example 2 ethoxyethanol ethylene glycol monoethyl ether EGME Carter et al 1965 IR 08 086 Version 2 Last modified 2009 04 17 16 33 The BGS laboratories are equipped to carry out both the gas and polar molecule adsorption methodol2. Last modified 2009 04 17 16 33 Contents Foreword i Contents ii Summary iv 1 Introduction 1 2 Background 2 2 Gemini VI 2385C System 2 2 2 VacPrep Degasser 4 3 Methods and materials 5 4 Results 7 4 Soil samples 7 4 2 Hydrothermal laboratory experimental materials 4 33 Mudstone core samples 10 5 Conclusions 12 6 Recommendations 12 References 13 Appendix 1 BGS methodology 14 Appendix2 BET sample sheet with example data 21 Appendix3 Example multi point BET report 3 pages 22 Appendix4 Example full isotherm and pore volume distribution report 9 pages 25 FIGURES Figure 1 Micromeritics Gemini VI series physisorption system Micromeritics 2008 3 Figure 2 Schematic for the Gemini VI Micromeritics 2008 3 Figure 3 Micromeritics VacPrep system Micromeritics 2008 5 Figure 4 Cross plot of multi point and single point BET data for the hydrothermal laboratory experimental samples ll 9 IR 08 086 Version 2 Last modified 2009 04 17 16 33 TABLES Table 1 Sample details Table 2 Summary of results for soil samples 7 Table 3 Summary of results for the hydrothermal laboratory experimental samples Table 4 Comparison of multi point and single point BET data hydrothermal laboratory experimental samples 9 Table 5 Summary of results for the mudstone samples associated with containment projects all are 1 2 mm fractions except where indicated 10 111 IR 08 086 Version 2 Last modified 2009 04 17 16 33 summar
3. 610155 2MM t Plot Report Micropore Volume 0 001047 cm g Micropore Area 2 2816 mfg External Surface Area 14 2494 m g Slope 0 041100 0 000351 mmol g Y Intercept 0 030199 0 001511 mmol g Correlation Coefficient 0 999854 Surface Area Correction Factor 1 000 Density Conversion Factor 0 0015468 Total Surface Area BET 16 5310 m g Thickness Range 3 5000 to 5 0000 Thickness Equation Harkins and Jura t 13 99 0 034 log p p 0 5 Relative Statistical Quantity Pressure p p Thickness A X Adsorbed mmol q 0 009993336 2 6224 0 12201 0 042414404 3 1539 0 15546 0 074866061 3 4732 0 17153 0 107341166 3 7343 0 18329 0 139739436 3 9677 0 19343 0 172134854 4 1867 0 20257 0 204584839 4 3985 0 21118 0 2370901 73 4 6072 0 21958 0 269411707 4 8144 0 22776 0 30191 4051 5 0247 0 23578 0 334253087 5 2379 0 24364 0 366698347 5 4576 0 25168 0 39927 4006 5 6859 0 25992 0 431590213 5 9219 0 26852 0 464131579 6 1711 0 27734 0 496344495 6 4315 0 28672 0 528984657 6 7118 0 29675 0 561347636 7 0091 0 30733 0 593696962 7 3292 0 31895 0 626214239 7 6786 0 33167 0 6586947 11 8 0607 0 34554 0 690954938 8 4799 0 36134 0 723472910 8 9519 0 37929 0 756152793 9 4885 0 40031 0 88275789 10 0934 0 42519 0 820517524 10 8013 0 45617 0 853423883 11 6637 0 49651 0 885590866 12 6979 0 55101 0 917905864 14 0173 0 63451 0 950326640 15 7878 0 78270 29 IR 08 086 Version 2 Last modified 2009 04 17 16 33
4. a mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 Serial 144 Page 6 MPL sample MPLN405 Operator Submitter File CAGEMINMDATAY051 SMP Started 04 11 2008 13 46 56PM Analysis Adsorptive N2 Completed 04 11 2008 17 05 45PM Equilibration Time 5 s Report Time 10 11 2008 14 38 11PM Sat Pressure 103 3533 kPa Free Space Diff 1 4809 cm Sample Mass 1 0016 g Free Space Type Measured Sample Density 1 000 g cm Gemini Model 2385 Comments 610155 42MM t Plot Harkins and Jura MPLN405 4 Not Fitted Points 0 8 0 7 0 6 j NI 0 3 Quantity Adsorbed mmol q C 0 1 0 0 ITET TTTT ie O R S O A S S S A ITTI TITT Trig Tried Tred TT T TTTT TTTT ITT TTTT LITT 0 z 3 4 5 B ri 8 g 10 11 12 13 14 15 Thickness 30 IR 08 086 Version 2 Last modified 2009 04 17 16 33 mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 serial 144 Page MPL sample MPLN405 Operator Submitter File C GEMINADATA O51 SMP Started 04 11 2008 13 46 56PM Analysis Adsorptive N2 Completed 04 11 2008 17 05 45PM Equilibration Time 5s Report Time 10 11 2008 14 38 11PM Sat Pressure 103 3533 kPa Free Space Diff 1 4809 cm Sample Mass 1 0016 g Free Space Type Measured Sample Density 1 000 g cm Gemini Model 2385 Comments 610155 2MM BJH Adsorption Pore Distribution Report Faas Correction Halsey t 3 54 5 In p p 0 333 Width Range 17 000
5. surface area and porosity are important parameters when considering the characteristics of rocks and soils particularly with regard to their engineering properties industrial mineral use water hydrocarbon potential gas storage and possible effects on soil quality and human health Two different procedures are employed to determine surface area In Earth Science materials which utilize the adsorption of either gases or polar liquids The most common method is to derive the amount of adsorbed nitrogen or other inert gas on a solid surface at monolayer coverage from either a single point analysis or a multipoint plot of adsorption isotherm data using the nitrogen BET method named after its inventors Brunauer Emmett and Teller Brunauer et al 1938 From a knowledge of the projected cross sectional area per molecule in the monolayer and the quantity of gas adsorbed the surface area of the material may be calculated The method is described by the equation P Pg a diesel Vii P Pe VmC P Pg where V is the volume at standard temperature and pressure STP of gas adsorbed at pressure P P 1s the saturation pressure which is the vapour pressure of liquefied gas at the adsorbing temperature V is the volume of gas STP required to form an adsorbed monomolecular layer and C is a constant related to the energy of adsorption The surface area S of the sample giving the monolayer adsorbed gas volume Vm STP is then calculated from
6. Surface areas are reproducible within the same degree of error Analysis of soils suggests that the technique may be useful in characterising black carbon contents Interestingly the surface area for the ground materials appears lower than that produced for the corresponding lt 2 mm size fraction This 1s the reverse of the expected result and requires further investigation For mudstone samples surface areas appear to correspond to the total concentration of clay minerals present with some influence from the presence of smectite Surprisingly the lowest surface area in this suite of mudstone samples was produced by the Bentonite Sweden sample This may relate to the degassing regime employed 6 Recommendations Users are advised to follow the protocols outlined in this report and the analysis programs setup This report should be quoted when reporting data produced by the physisorption system For low surface area materials 50 m it is recommended that filler rods are used to reduce free space and error Further work beyond the scope of this initial study is required to identify the effects of different degassing routines and the differing surface areas obtained when analysing ground and crushed samples Additional work is also necessary to more fully explore the pore size distribution functions of the physisorption system 12 IR 08 086 Version 2 Last modified 2009 04 17 16 33 References British Geological Surve
7. essentially has the same free space variation as the sample tube and no pressure differential is produced Since free space error 1s the limiting factor in measuring low surfaces with nitrogen common mode rejection of free space variation in the Gemini allows accurate measurements to be performed with nitrogen on low surface area materials Other static volumetric techniques would usually require the use of krypton The sample uptake rate therefore controls the rate at which the gas is delivered through a servo valve therefore the adsorptive 1s delivered as fast as the sample can adsorb it In this manner of dosing there is no under dosing in which the sample waits for more adsorptive nor over dosing in which case the target pressure is exceeded The result is a surface area analyzer that is as fast as the physics of adsorption allows and yet retains accuracy and reproducibility The Windows based software allows the Gemini to be controlled from a PC thus providing more versatility in data archiving networking and printer options In addition the software extends the choices of data reduction methods in each Gemini model to include e Single and Multipoint BET surface area e Langmuir surface area e Pore volume and pore area distributions in the mesopore and macropore ranges by the BJH Barrett Joyner and Halenda method using a variety of thickness equations including a user defined standard isotherm e Pore volume distribution and tot
8. for the lt 2 mm material as the standard deviation value represents only a 1 3 differential but as a result of the low surface area measured in Run 1 for the ground material there appears to be a greater problem with these samples 16 6 differential This is again the reverse of the expected result whereby it would be expected that a more homogeneous sample would be created by grinding to a powder The high surface area sample 610155 corresponds to the sample containing the highest levels of black carbon 6 44 B Rawlins pers comm but the impact of black carbon is more difficult to discern in the remaining samples 611353 2 09 and 611495 0 5 At these lower levels the presence of small quantities of black carbon appear to be obscured by the presence of other 7 IR 08 086 Version 2 Last modified 2009 04 17 16 33 phases such as clay minerals Further samples will be run to explore the link between surface area and black carbon content in soils 4 2 HYDROTHERMAL LABORATORY EXPERIMENTAL MATERIALS The results of surface area analyses on the hydrothermal laboratory experimental samples submitted by Dr Chris Rochelle are summarised in Table 3 Table 3 Summary of results for the hydrothermal laboratory experimental samples BET SA m g Incoming sample name Run3 Mean Std Dev value error value error value error value error value error Quartz 125 250um 00710 00022 00710 0 0022 Albite
9. the Gemini VI Surface and Pore Size Analyzer at the rear of machine The green light on the front of the cabinet should glow green Open the He and N gas supplies by releasing the valve on the top of each cylinder The regulators should be set to read between 1 1 1 2 bar check Wearing gloves eye protection and a lab coat fill the instrument dewar with liquid N to a level 5 cm from the top and place the dewar on the instrument elevator Transfer all the sample tubes from the VacPrep heating stations to their cooling positions Increase the VacPrep temperature to 300 C place the carbon black sample tube in a heating position and leave for 1 hour Ensure that an empty sample tube 1s placed in the instrument balance tube Wearing heat resistant gloves carefully remove the carbon black sample tube HOT from its heating station attach a rubber ear to the tube and place the sealed tube in the cooling station for a few minutes Using a 4 decimal place balance weigh the carbon standard tube ear and foam base Record the weight on the BET sample sheet Start up the instrument PC Double click on the desktop Gemini icon Allow the software initialisation to complete the Initialisation Window will close automatically Using the Gemini software under the Unit dropdown menu select Show Instrument Schematic A window showing an interactive schematic for the instrumental settings will appea
10. to 3000 000 Adsorbate Property Factor 9 53000 Density Conversion Factor 0 0015468 Fraction of Pores Open at Both Ends 0 00 Pore Width Average Width Incremental Cumulative Incremental Cumulative Range A A Pore Volume Pore Volume Pore Area Pore Area cm g cm g mg m g 404 1 247 3 288 4 0 006149 0 006149 0 853 0 853 247 3 178 6 201 5 0 003490 0 009639 0 693 1 545 178 6 140 0 154 3 0 002291 0 011930 0 594 2 139 140 0 114 5 124 5 0 001704 0 013634 0 548 2 687 114 5 97 0 104 2 0 001315 0 014950 0 505 3 192 97 0 84 0 89 5 0 001058 0 016007 0 473 3 665 84 0 73 9 78 2 0 000893 0 016901 0 457 4 122 73 9 65 8 69 3 0 000763 0 017664 0 440 4 562 65 8 59 2 62 1 0 000675 0 018338 0 435 4 997 59 2 53 7 56 1 0 000587 0 018925 0 418 5 415 53 7 48 9 51 1 0 000541 0 019466 0 424 5 839 48 9 44 9 46 7 0 000493 0 019959 0 422 6 261 44 9 41 4 43 0 0 000445 0 020404 0 414 6 675 41 4 38 2 39 6 0 000422 0 020826 0 426 7 101 38 2 35 4 36 0 000394 0 021220 0 430 7 531 35 4 32 9 34 0 0 000364 0 021584 0 428 7 959 32 9 30 6 31 6 0 000359 0 021943 0 454 8 413 30 6 28 4 29 4 0 000338 0 022281 0 459 8 872 28 4 26 5 27 4 0 000329 0 022609 0 480 9 353 26 5 24 7 25 5 0 000318 0 022928 0 499 9 852 24 7 22 9 23 7 0 000329 0 023256 0 554 10 406 22 9 21 3 22 1 0 000340 0 023596 0 616 11 022 21 3 19 7 20 5 0 000347 0 023943 0 678 11 700 19 7 18 2 18 9 0 000345 0 024288 0 730 12 430 18 2 16 7 17 4 0 000362 0 024650 0 83
11. 125 250um 0 6386 0 0112 f 906386 00122 Chemgrade quartz Fluka 150 400 um 0 0427 0 0042 0 0928 0 0028 0 0704 0 0050 0 0686 0 0040 0 0251 0 0011 Chemgrade quartz Fluka 150 400 um 0 0603 0 0041 0 0493 0 0033 0 0527 0 0031 0 0541 0 0035 0 0056 0 0005 Using filler tubes Casablanca cap rock Casablanca reservoir rock 250 500 um 0 8437 0 0080 0 8437 0 0080 In comparison to the soil samples the hydrothermal laboratory experimental samples produced low or very low surface areas ranging from 0 07 2 14 m g The two quartz samples produced particularly low surface areas c 0 07 m g and correlation co efficients of only 0 99 suggesting relatively poor quality data compared to the remaining dataset Such surface areas would appear to be close to the lower limit of accurate surface area detection using the Gemini VI The albite and Casablanca reservoir rock show also show low surface areas c 0 64 and 0 84 m g respectively but these are an order of magnitude higher than the quartz samples Previous X ray diffraction XRD analyses of the Casablanca reservoir rock Rochelle et al 2007 suggest that it is predominantly composed of calcite 95 9 with traces of dolomite 3 and quartz 1 1 Such a mineralogy would be expected to produce a low surface area The Casablanca cap rock produced the highest surface area for the hydrothermal laboratory experimental samples although at
12. 2 14 m g this would still be described as a low value The higher value compared to the reservoir rock is almost certainly due to the presence of phyllosilicates and clay minerals in the cap rock Previous XRD analyses Rochelle et al 2007 confirm that although the cap rock is also carbonate dominated calcite 55 9 dolomite 5 8 ankerite 1 6 with minor quartz 14 3 pyrite 3 8 and albite 0 8 it also contains undifferentiated mica including illite smectite 15 4 and chlorite 2 4 species Three repeat runs for separate sub samples of the very low surface area Chemgrade quartz sample produced a mean surface area of 0 069 m g and standard deviation of 0 025 This relatively large standard deviation value represents a large 36 6 differential and may result from the free space errors or indicate that sample heterogeneity presents a significant problem in low surface area materials IR 08 086 Version 2 Last modified 2009 04 17 16 33 In order to improve the quality of analysis of low surface area materials Micromeritics suggest but did not originally supply BGS the use of filler tubes Solid glass filler tubes with a fine capillary down their lengths are fitted to both the reference and sample tubes to exclude as much free space as possible and therefore ensure optimum precision and accuracy Having obtained the filler tubes at a later date only limited testing was carried out using the filler tubes Three separate subsample
13. 4 13 264 3 IR 08 086 Version 2 Last modified 2009 04 17 16 33 L L a mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 Serial 144 Page 8 MPL sample MPLN405 Operator Submitter File C GEMINIDATA O51 SMP Started 04 11 2008 13 46 56PM Analysis Adsorptive N2 Completed 04 11 2008 17 05 45PM Equilibration Time 5 s Report Time 10 11 2008 14 38 11PM oat Pressure 103 3533 kPa Free Space Diff 1 4809 cm sample Mass 1 0018 g Free Space Type Measured Sample Density 1 000 g cm Gemini Model 2385 Comments 610155 lt 2MM BJH Adsorption dVidlog w Pore Volume Halsey Faas Correction MPLN405 an S BJA Adsorption Cumulative Pore Volume dV dlog w Pore Volume cm g Bwa awnjoA aod 20 40 60 80 100 200 Pore Width A 32 IR 08 086 Version 2 Last modified 2009 04 17 16 33 a a a a mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 Serial 144 Page 9 MPL sample MPLN405 Operator Submitter File CAGEMINIDATA OS1 SMP started 04 11 2008 13 46 56PM Analysis Adsorptive N2 Completed 04 11 2008 17 05 45PM Equilibration Time 5s Report Time 10 11 2008 14 38 11PM Sat Pressure 103 3533 kPa Free Space Diff 1 4809 cm Sample Mass 1 0016 g Free Space Type Measured Sample Density 1 000 g cm Gemini Model 2385 Comments 610155 2MM BJH Adsorption dA dlog w Pore Area Halsey Faas Correction 1 MPLN405 3 BJH Ad
14. Adsorptive N2 Completed 04 11 2008 17 05 45PM Equilibration Time 5s Report Time 10 11 2008 14 38 11PM Sat Pressure 103 3533 kPa Free Space Diff 1 4809 cm sample Mass 1 0016 g Free space Type Measured sample Density 1 000 g cm Gemini Model 2385 Comments 610155 lt 2MM Isotherm Linear Plot 0 8 MPLN405 Adsorption 0 7 x 0 6 Quantity Adsorbed mmel g A o 0 1 T 1 l lI T T T T T f POP I l 0 0 0 1 0 2 0 3 0 4 0 5 0 6 OF 0 8 0 9 Relative Pressure p p CAN O D D S S SS S O S S S S D S S S S E S S 26 IR 08 086 Version 2 Gemini V 2 00 MPL sample Last modified 2009 04 17 16 33 LI 2 mj micromeritics Micromeritics Instrument Corp Unit 1 Serial 144 Page 3 MPLNA05 Operator Submitter File GA GEMINIVWDATA O51 SMP Started Completed Report Time Free Space Diff Free Space Type Gemini Model 04 1 1 2008 13 46 56PM 04 11 2008 17 05 45PM 10 11 2008 14 38 11PM 1 4809 cm Measured 2385 Comments 610155 2MM Analysis Adsorptive N2 Equilibration Time 5s Sat Pressure 103 3533 kPa Sample Mass 1 0016 g Sample Density 1 000 g cm BET Surface Area Report BET Surface Area Slope Y Intercept 16 5310 0 1458 m g 5 879506 0 051200 g mmol 0 022932 0 009420 g mmol C 257 392157 Qm 0 16942 mmol g Correlation Coefficient 0 9998105 Molecular Cross Sectional Area 0 1620 nm Relative Qua
15. British Geological Survey HATURAL ENVIRONMENT RESEARCH COUNCIL Initial testing and a laboratory manual for the Micromeritics Gemini VI physisorption system Laboratory Operations Programme Internal Report IR 08 086 BRITISH GEOLOGICAL SURVEY LABORATORY OPERATIONS PROGRAMME INTERNAL REPORT IR 08 086 Initial testing and a laboratory manual for the Micromeritics Gemini VI physisorption system The National Grid and other Ordnance Survey data are used with the permission of the Controller of Her Majesty s Stationery Office Licence No 100017897 2009 Keywords Surface area nitrogen BET micropore clays black carbon Front cover Micromeritics Gemini VI physisorption system Bibliographical reference KEMP S J TURNER G AND WAGNER D 2009 Initial testing and a laboratory manual for the Micromeritics Gemini VI physisorption system British Geological Survey Internal Report IR 08 086 A1pp Copyright in materials derived from the British Geological Survey s work is owned by the Natural Environment Research Council NERC and or the authority that commissioned the work You may not copy or adapt this publication without first obtaining permission Contact the BGS Intellectual Property Rights Section British Geological Survey Keyworth e mail ipr bgs ac uk You may quote extracts of a reasonable length without prior perm
16. If the value obtained is outside these specifications repeat the procedure with fresh carbon black sample 19 IR 08 086 Version 2 Last modified 2009 04 17 16 33 4 ANALYSIS OF SAMPLES 4 AD 4 3 4 4 4 5 4 6 On the instrument ensure that the top of dewar 1s covered e g with a blank CD to prevent objects from falling into the liquid No Disconnect the sample tube containing the carbon black standard from the instrument by releasing the tube nut Discard the carbon black standard material On the VacPrep unit turn the gas off vac switch to the gas position for 30 seconds Turn the gas off vac switch to the off position Disconnect the sample tube from the instrument by releasing the tube nut Attach ear immediately Using a 4 decimal place balance weigh the sample tube ear and foam base assembly Record the weight on the BET sample sheet Note The weight of sample produced on the BET sample sheet is required when completing the Sample Information tab later Follow the same procedure as that for the carbon black standard steps 3 1 3 18 substituting the appropriate MPL number when completing the Sample Information tab step 3 6 5 TUBE CLEANING AFTER ANALYSIS 5 1 2 2 5 3 Rinse each of the sample tubes with weak detergent Place the tubes In an ultrasonic bath filled with RO water and sonicate for c 5 minutes Rinse the tubes with acetone and leave in an
17. R VOLTOLINI M MAZUREK M VAN LOON L R AND VINSOT A 2008 Preferred orientations and anisotropy in shales Callovo Oxfordian Shale France and Opalinus Clay Switzerland Clay Minerals 56 285 306 13 IR 08 086 Version 2 Last modified 2009 04 17 16 33 Appendix BGS methodology OPERATING INSTRUCTIONS FOR THE MICROMERITICS GEMINI VI SURFACE AREA AND PORE SIZE ANALYZER ROOM P029 IR 08 086 Version 2 Last modified 2009 04 17 16 33 1 SAMPLE PREPARATION DAY BEFORE ANALYSIS 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 Turn on VacPrep 061 on the rear panel Set temperature to desired value to most effectively remove moisture and adsorbed gases without changing the nature of the material e g 300 C for the carbon black standard 60 C for geological samples The carbon black standard must be run before each batch of samples Note that the heating element takes a long time to cool down Label the sample tubes and enter the sample number and description onto the BET sample sheet shown in Appendix 3 Using a 4 decimal place balance weigh the sample into a balance boat c 0 5 g for samples expected to have a high gt 50 m g surface area and c 1 0 g for samples expected to have a low lt 50 m g surface area Set the sample aside Select a labelled sample tube Fit the tube into the foam base and insert a rubber ear into the tube Using a 4 decimal place balance weigh the tube
18. al pore volume in a user defined pore size range e Micropore distribution by the MP method and total micropore volume by the t Plot and as Plot methods e Halsey Harkins Jura Carbon Black STSA Broekhoff de Boer and user entered thickness curves The larger cabinet design of the Gemini VI 2385C model allows extended analysis time greater stability and improved repeatability due to its longer sample tubes and a larger dewar It also allows continuous monitoring of the saturation vapour pressure P of the adsorptive using a dedicated P tube and transducer This feature allows the instrument software to accommodate at each data point any minute change in the saturation vapour pressure that may occur during the course of the analysis resulting in a more meticulously determined relative pressure 22 VACPREP DEGASSER The VacPrep Degasser prepares samples for surface area and pore structure analysis using both the flowing gas method and a vacuum mode which prepares samples by heating and evacuation The VacPrep removes contaminants such as water vapour and adsorbed gases from samples to avoid interference with surface area measurements It features six degassing stations and a choice of vacuum or gas flow preparation on each of the six stations and minimises the chance of 4 IR 08 086 Version 2 Last modified 2009 04 17 16 33 sample contamination during transfer from the degas to analysis The VacPrep allows the operator to select the
19. amples IR 08 086 Version 2 Last modified 2009 04 17 16 33 4 5 MUDSTONE CORE SAMPLES The results of surface area analyses on the mudstone core samples submitted by Dr Jon Harrington are summarised in Table 5 Table 5 Summary of results for the mudstone samples associated with containment projects all are 1 2 mm fractions except where indicated BET SA m2 g Incoming sample name Run3 Mean Std Dev value error value error value error value error value error Bentonite 204925 03077 20492503027 m Bentonite 125m 17 6855 00813 16855 0 0813 lias Clay Liner 240139 02240 24 0139 0 2240_ Nordland Shale 267313 0 1566 267313 0 1566 _ a Ball Clay 342023 0 0895 34 2023 0 0895 German Blue Clay 53 8411 0 4279 53841 04279 0 1272 OpalinsClay 217706 0 1184 f 217706 01184 London Clay 58549 0738 585419 0 7338 BoomClay 269840 012012 26984 0 1212 Opalinus Clay 30 9592 0 2548 30959 0254_ Gault Clay 540795 1 0344 54 0795 1 0344 The surface areas obtained for the mudstone core samples 1 2 mm fractions were the highest for the samples analysed in this project and ranged from c 20 49 Bentonite to 58 54 m e London Clay However as mineralogical data were not available for the same samples discussion of the surface a
20. ct the entry for CARBON BLACK date Click the OK button Check the information in the new window is correct and click the Start button at the bottom of the window A new window will appear which asks you to remove the sample tube from its port On the instrument ensure that the top of dewar is covered e g with a blank CD to prevent objects from falling into the liquid No Disconnect the sample tube from the instrument by releasing the tube nut Note the position of the ferrule and O ring Click the OK button A new window will then appear requesting that you re attach the sample tube 18 IR 08 086 Version 2 Last modified 2009 04 17 16 33 3 13 3 14 3 15 3 16 3 17 3 18 3 19 Place the tube nut ferrule and O rIng in this order onto the sample tube Insert the sample tube into the Instrument housing and tighten the nut to finger tight plus a quarter turn Check that the bases of the sample and reference tubes are level Place the dewar cover over the sample reference and saturation tubes and push to the top Close the protection doors Click the OK button Following completion of the analysis to view the results under the Reports dropdown menu select Start Reports and then select the appropriate file from the CAGEMINDINDATANBGSDAT 1 directory Check that the carbon black standard produces a BET surface area within specifications 30 6 0 75 m 2
21. e areas 0 1 m g these errors can increase to 6 Analysis of soils suggests that the technique may be useful in characterising black carbon contents Interestingly the surface area for the ground materials appears lower than that produced for the corresponding lt 2 mm size fraction This is the reverse of the expected result and requires further investigation For mudstone samples surface areas appear to correspond to the total concentration of clay minerals present with some influence from the presence of smectite Surprisingly the lowest surface area in this suite of mudstone samples was produced by the Bentonite Sweden sample This may relate to the degassing regime employed Users are advised to follow the protocols outlined in this report and the analysis programs setup It is also advised that filler rods are used to reduce free space and error for low surface area materials 50 m g Further work beyond the scope of this initial study 1s required to identify the effects of different degassing routines and the differing surface areas obtained when analysing ground and crushed samples Additional work is also necessary to more fully explore the pore size distribution functions of the physisorption system 1V IR 08 086 Version 2 Last modified 2009 04 17 16 33 Introduction Surface area and porosity are two critical physical properties that determine the nature and reactivity of materials In the Earth Sciences
22. ensity 1 000 g cm Gemini Model 2385 BET Surface Area Plot 1 MPLNAOS VQ 1 0 00 0 05 0 10 0 15 0 20 0 25 0 30 Relative Pressure p p 24 IR 08 086 Version 2 Last modified 2009 04 17 16 33 Appendix 4 Example full isotherm and pore volume distribution report 9 pages a e mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 serial 144 Page 1 MPL sample MPLN405 Operator Submitter File CAGEMINADATA OS1 SMP Started 04 11 2008 13 46 56PM Analysis Adsorptive N2 Completed 04 11 2008 17 05 45PM Equilibration Time 5s Report Time 10 11 2008 14 38 11PM Sat Pressure 103 3533 kPa Free Space Diff 1 4809 cm Sample Mass 1 0016 g Free Space Type Measured Sample Density 1 000 g cm Gemini Model 2385 Comments 610155 2MM Summary Report Surface Area BET Surface Area 16 5310 m2 g t Plot Micropore Area 2 2816 mg t Plot External Surface Area 14 2494 m g Pore Volume Single point adsorption total pore volume of pores less than 406 703 width at p p 0 950326640 0 027136 cm g t Plot micropore volume 0 001047 cm g Pore Size BJH Adsorption average pore width 4V A 74 337 25 IR 08 086 Version 2 Last modified 2009 04 17 16 33 L L a mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 Serial 144 Page 2 MPL sample MPLN405 Operator Submitter File C VGEMINIWDATA O51 SMP Started 04 11 2008 13 46 56PM Analysis
23. foam base and rubber ear and note weight on the BET sample sheet shown in Appendix 3 Remove the tube foam base and rubber ear assembly from the balance Remove the rubber ear from the tube and attach the tube filler funnel Carefully pour the sample from balance boat into the tube Repeat steps 1 3 to 1 6 for up to 6 samples Attach each sample tube to the Vac Prep unit using the stainless steel connectors First slacken the connector nut then insert the sample tube securely and re tighten the nut finger tight Turn on rotary pump at the wall socket 1 10 Ensure all the needle valves at the T pieces above the connectors are closed 1 11 Turn the gas off vac switch to the vac position 1 12 Slowly open each needle valve ensuring that the sample is not drawn up the sample tube 15 IR 08 086 Version 2 Last modified 2009 04 17 16 33 1 13 Place the sample tubes in their heating stations at 60 C or desired temperature and leave overnight 1 14 Repeat steps 1 3 1 6 using between 0 5 0 6 g of carbon black standard Place to one side for the next day 16 IR 08 086 Version 2 Last modified 2009 04 17 16 33 2 PREPARATION FOR ANALYSIS ANALYSIS DAY Z4 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 0 2 10 2 11 2 12 Wearing gloves eye protection and a lab coat obtain a dewar of liquid N gt from the K block supply using established procedures Switch on
24. hern England British Geological Survey Internal Report IR 06 060 Sl pp KEMP S J TURNER G AND WAGNER D 2001 Mineralogical characterisation of the Nordland Shale UK Quadrant 16 northern North Sea British Geological Survey Commissioned Report CR 01 136 52pp KEMP S J PEARCE J M and STEADMAN E J 2002 Mineralogical geochemical and petrographical characterisation of Nordland Shale cores from well 15 9 A 11 Sleipner field northern North Sea British Geological Survey Commissioned Report CR 02 313 40pp KEMP S J MERRIMAN R J and BOUCH J E 2005 Clay mineral reaction progress The maturity and burial history of Lias Group of England and Wales Clay Minerals 40 43 61 KONTA J 1963 Quantitative mineralogical analysis of Blue clay from Vonsov Bohemia a comparative study by nine laboratories Clay Minerals Bulletin 30 5 255 264 MICROMERITICS 2008 Gemini VI Windows Operator s manual v2 00 ROCHELLE C A TURNER G PEARCE J M TAYLOR H KEMP S J SHAW R AND WILLIAMS C 2007 Geochemical interactions between CO and host rocks at the Casablanca field Results of fluid rock interaction experiments British Geological Survey Internal Report CR 07 015 53pp DOGAN A U DOGAN M ONAL M SARIKAYA Y ABURUB A AND WURSTER D E 2006 Baseline studies of The Clay Minerals Society source clays SSA by the Brunauer Emmett Teller BET Method Clays and Clay Minerals 54 62 66 WENK H
25. hison House West Mains Road Edinburgh EH9 3LA Tel 0131 667 1000 Fax 0131 668 2683 email scotsales bgs ac uk Natural History Museum Cromwell Road London SW7 5BD Tel 020 7589 4090 Fax 020 7584 8270 Tel 020 7942 5344 45 email bgslondon bgs ac uk Columbus House Greenmeadow Springs Tongwynlais Cardiff CF15 7NE Tel 029 2052 1962 Fax 029 2052 1963 Forde House Park Five Business Centre Harrier Way Sowton EX2 7HU Tel 01392 445271 Fax 01392 445371 Maclean Building Crowmarsh Gifford Wallingford OX10 8BB Tel 01491 838800 Fax 01491 692345 Geological Survey of Northern Ireland Colby House Stranmillis Court Belfast BT9 5BF Tel 028 9038 8462 Fax 028 9038 8461 www bgs ac uk gsni Parent Body Natural Environment Research Council Polaris House North Star Avenue Swindon SN2 1EU Tel 01793 411500 Fax 01793 411501 www nerc ac uk Website www bgs ac uk Shop online at www geologyshop com IR 08 086 Version 2 Last modified 2009 04 17 16 33 Foreword This report is the published product of a study by the British Geological Survey BGS and was produced under the Laboratory Operations Programme s Maintenance and Development of Capability MaDCap project This report aims to provide a procedural manual for the newly acquired physisorption system and details of initial testing on a range of Earth Science materials including soils mudstones and starting materials from hydrothermal experiments IR 08 086 Version 2
26. ified 2009 04 17 16 33 a mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 Serial 144 Page 2 MPL sample MPLN405 Operator Submitter File CA GEMINIVWDATA OO6 SMP started 29 07 2008 11 58 43PM Analysis Adsorptive N2 Completed 29 07 2008 13 04 07PM Equilibration Time 5s Report Time 10 11 2008 14 14 51PM Sat Pressure 102 4380 kPa Free Space Diff 1 0884 cm Sample Mass 0 9535 g Free Space Type Measured Sample Density 1 000 g cm Gemini Model 2385 BET Surface Area Report BET Surface Area 16 2691 0 2823 me g Slope 5 990563 0 102135 g mmol Y Intercept 0 006884 0 020036 g mmol C 871 226494 Qm 0 16674 mmol g Correlation Coefficient 0 9995643 Molecular Cross Sectional Area 0 1620 nm Relative Quantity 1 Q p 7p 1 Pressure Adsorbed p p mmol g 0 049955999 0 16352 0 32157 0 112538520 0 18720 0 67740 0 175139059 0 20458 1 03788 0 237705656 0 22015 1 41645 0 300132847 0 23489 1 82569 23 IR 08 086 Version 2 Last modified 2009 04 17 16 33 a mj micromeritics Micromeritics Instrument Gorp Gemini V2 00 Unit 1 Serial 144 Page 3 MPL sample MPLN405 Operator Submitter File CAGEMINMDATAXO05 SMP Started 28 07 2008 11 58 43PM Analysis Adsorptive N2 Completed 28 07 2008 13 04 07 PM Equilibration Time 5 s Report Time 10 11 2008 14 14 51PM Sat Pressure 102 4380 kPa Free Space Diff 1 0884 cm Sample Mass 0 9535 g Free Space Type Measured Sample D
27. ission provided a full acknowledgement is given of the source of the extract Maps and diagrams in this book use topography based on Ordnance Survey mapping NERC 2009 All rights reserved Keyworth Nottingham S J Kemp G Turner and D Wagner British Geological Survey 2009 BRITISH GEOLOGICAL SURVEY The full range of our publications is available from BGS shops at Nottingham Edinburgh London and Cardiff Welsh publications only see contact details below or shop online at www geologyshop com The London Information Office also maintains a reference collection of BGS publications including maps for consultation We publish an annual catalogue of our maps and other publications this catalogue is available online or from any of the BGS shops The British Geological Survey carries out the geological survey of Great Britain and Northern Ireland the latter as an agency service for the government of Northern Ireland and of the surrounding continental shelf as well as basic research projects It also undertakes programmes of technical aid in geology in developing countries The British Geological Survey is a component body of the Natural Environment Research Council British Geological Survey offices BGS Central Enquiries Desk Tel 0115 9363143 email enquiries bgs ac uk Fax 0115 936 3276 Kingsley Dunham Centre Keyworth Nottingham NG12 5GG Tel 0115936 3241 Fax 0115 936 3488 email sales bgs ac uk Murc
28. ly nitrogen Gas is dosed into the sample from the reservoirs and balance tubes and a transducer B on the sample side monitors the target pressure Temperature Lenthermal Sensor block Volume Adsarbed Transducer Pressure Balance Traneducer le n Sump Balance Transducer Adjustment Balance Tube Sample Tube Liquid Nitrogen Dewar Elevaior Figure 2 Schematic for the Gemini VI Micromeritics 2008 IR 08 086 Version 2 Last modified 2009 04 17 16 33 As the sample adsorbs gas the pressure would tend to decrease in the sample tube were it not that transducer B causes a fast response servo valve C to hold the pressure constant Transducer D located between the sample and balance tubes detects any pressure difference between the two tubes and causes another servo valve E to balance the pressures in both tubes A third pressure transducer F monitors the pressure between the two reservoirs to determine the amount of gas that is adsorbed on the sample This method of dosing and accounting for the volume of gas uptake enables the Gemini to produce highly accurate highly reproducible results in the minimum time The sample and balance tubes are identical in every way Conditions within one tube exactly reproduce the conditions within the other the only difference being associated with the presence of the sample in the sample tube Free space errors introduced by thermal gradient variations are cancelled because the balance tube
29. nd powders to establish whether sample particle size had any noticeable effect on surface area similarly the bentonite sample was analysed as a 1 2 mm fraction and a 125 um powder e To establish whether sample heterogeneity produced any substantial errors separate sub samples were run for one of the soils both 2 mm and ground materials and one of the quartz samples All samples were prepared using a Micromeritics Gemini VacPrep Degasser and analyses were carried out on the Micromeritics Gemini VI 2385C system All the samples were run on a 5 pressure point program to determine BET surface area One sample was also run on an extended 30 pressure point program to additionally determine pore volume distribution IR 08 086 Version 2 Last modified 2009 04 17 16 33 4 Results A methodology for analysis of Earth Science materials was devised and implemented for all the samples in this study and Is shown in Appendix 1 A sample preparation sheet with example data is shown In Appendix 2 Correlation co efficients for BET analyses provide an indication of the quality and reliability of the data produced The majority of the samples analysed here produced co efficients of better than 0 999 suggesting high quality analyses However the two quartz samples MPLB464 and MPLG 922 characterised by very low surface areas c 0 07 m g produced lower coefficients of 0 99 suggesting poorer quality analyses Reporting of results from the Gemini s
30. ntity 1 Q p 7p 1 Pressure Adsorbed p p mmol g 0 074866061 0 17153 0 47178 0 107341166 0 18329 0 65605 0 139739436 0 19343 0 83976 0 172134854 0 20257 1 02643 0 204584839 0 21118 1 21797 0 2370901 73 0 21958 1 41528 0 269411707 0 22776 1 61905 27 Last modified 2009 04 17 16 33 IR 08 086 Version 2 a mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 Serial 144 Page 4 MPL sample MPLN405 Operator Submitter File CAGEMINIDATA OS1 SMP Started 04 11 2008 13 46 56PM Analysis Adsorptive N2 Completed 04 11 2008 1 7 05 45PM Equilibration Time 5s Report Time 10 11 2008 14 38 11PM Sat Pressure 103 3533 kPa Free Space Diff 1 4809 cm Sample Mass 1 0016 g Free Space Type Measured Sample Density 1 000 g cm Gemini Model 2385 Comments 610155 2MM BET Surface Area Plot L MPLNA405 MIQ p Ip 1 Relative Pressure p p 28 IR 08 086 Version 2 Last modified 2009 04 17 16 33 a mj micromeritics Micromeritics Instrument Corp Gemini V2 00 Unit 1 Serial 144 Page 5 MPL sample MPLN405 Operator Submitter File C GEMINIDATA O51 SMP Started 04 11 2008 13 46 56PM Completed 04 11 2008 17 05 45PM Report Time 10 11 2008 14 38 11PM Free Space Dif 1 4809 cm Free Space Type Measured Gemini Model 2385 Analysis Adsorptive N2 Equilibration Time 5 s Sat Pressure 103 3533 kPa Sample Mass 1 0016 g Sample Density 1 000 g cm Comments
31. oftware can be tailored to the needs of the particular analysis Example output for a typical multi point BET analysis is shown in Appendix 3 and that from a full adsorption isotherm and pore volume distribution in Appendix 4 4 1 SOIL SAMPLES The results of surface area analyses on the soils samples submitted by Dr Barry Rawlins are summarised in Table 2 Table 2 Summary of results for soil samples BET surface area m2 g Incoming sample name Std Dev value error value error value error value error value error 6113532 mm 5 8671 008 ssenjooso 611495 2mm 67906 008 f 66 006 610155 ground 10 0930 0 06 13 8094 0 16 13 5109 0 15 12 4711 0 1233 2 0649 0 0551 611353 ground 5448 001 p 5 5448 6 0050 E 611495 ground 6 0386 0 03 f eoosejooso Mean surface areas for the soil samples range from c 5 86 16 34 m e 2 mm fraction and c 5 54 12 47 m g ground material Soil 610155 shows the greatest surface area for both sample types and soil 611495 shows the lowest surface areas Interestingly in each case the surface area for the ground material is lower than that produced for the corresponding lt 2 mm size fraction This is the reverse of the expected result whereby a greater surface area would be expected to be exposed by grinding material to a powder Sample heterogeneity would not appear to be a significant problem
32. ogies but the capability to perform gas adsorption analyses has been restricted by a relatively old system This report presents the results of a small study carried out during 2008 under the Maintenance and Development of Capability MaDCap project which aimed to e familiarise BGS staff with a newly purchased physisorption system e produce a user manual e advertise the abilities of the new system to BGS project leaders e establish some degree of error for the technique e study the possible effects of sample heterogeneity 2 Background The BGS have provided nitrogen BET surface area analyses since the mid 1980s when a Micromeritics Flowsorb II 2300 system was purchased by the Mineralogy amp Petrology Group and installed at the Grays Inn Road office London The system was subsequently moved to the Keyworth site and ultimately located 1n P Block During this time the system has been sporadically but often intensively used to provide single point BET surface area data to a variety of projects such as e Industrial mineral characterisation and beneficiation projects e Characterisation of lithologies for radioactive waste research e Characterisation of materials before and after hydrothermal laboratory experiments relating to radioactive waste and CO capture and storage e Characterisation of soils e Direct consultancy service to industry and consultancies Despite remaining functional the Flowsorb II 2300 increasingly suffered from i
33. oven set at 50 C until dry 20 Last modified 2009 04 17 16 33 IR 08 086 Version 2 Appendix 2 BET sample sheet with example data ApeuooQ o0 o C j H2 ed n ca nn j o oo o e d8r 7 jjnsai ay pue sejduies umouyun Aue oj lol d uns I ee sana oD s s Barri ms amt 980 L v007 LZ EtL L OZ Kejo snuiledo OCVN IE 69 0 L SvpL2 LC 9 L 02 Kejo woog 6IyN S sd 9v60 GE97 LZ 689L 02 e uopuo INI oo SISAJEUE JO ep uo daJd A di BAOUJ9J veran a mM 6 1u6i9M 3 31dWNVS 3ani qsva uva aanr uonduoseq oN 6 1uBi9M 6 1u BI AA ejdures eAgeujeyv ON Td oN 3g ni 60 10 6 o Ajalewixoidde eq pinoys uuunjoo jeu eui ui poje no eo 1uBI A duies su lqe1 ou o1ur 1uDieM eui pue Buuejue pue sjueuoduuoo je Bury iom seq y oiu 160 ejduies eqni eui Dun Ag 1uBISA ejduies eu euiuuoe1eq Mp sureuleJ ejdues y yey Buiinsu sny ea Joqqns 148suri pue jooo 01 Buiwo e 1942 deJg 9eA eui WO1 pesAjeue eq o ejduues e Buiurejuoo eqni ejduies e sAOWEAI sis A eue oi JOU sisAjeue Jo eq suononulsu Dunejedo ul p uomoes ees 2 09 Je 1uBluj Ao ejenoee pue jun dejg 2eA u seqni jdwes poji eoejd AjeurJ 1uBiuJ8AO UBAO 2 0G UI SACS pu eqni Olu euu 92094991 4oe g uoqieo 69 9 pue 6q o UsamMjeg 1no uBI A Ajjeuy pue sajdwes e 10 sde1s sAoge y y d y 0 O u eoq eoue eq wo ejdures Guunod Ajjnjeueo u u eqni o Je u eqni eui Buiyoeye pue sea saqqn Buia
34. owa zs Aq lduies YlIM eqni l pue s jeos wo sjueuoduJoo eAouJleH MO 9q ejqe1 ur JUBIOM ejou pue 194 960 sjueuoduuoo je uBI AA aqn OU 1ee Jeqgni 146sui pue eseq WO ojui eqni 1I eqni ejdures pej eqe e a299 epise ajdwes 8S Seale eoeyns moj UlIM s jdwes 104 69 pue Sease eoepuns ufiu uw soejduies 10J 66 0 eoq eouejegq e oyu Aojeuirxojdde ajdwes uie A SisAjeue S10 98q APG H3SA IVNV 3ZIS 3dOd ANV V3HV 32V HHVfS IA ININ39 dO4 NOILVEVdsadd AldNVS 21 IR 08 086 Version 2 Last modified 2009 04 17 16 33 Appendix 3 Example multi point BET report 3 pages Quantity Adsorbed mmol g Gemini V 2 00 mj micromeritics Micromeritics Instrument Corp Unit MPL sample MPLN405 Operator Submitter Started Completed Report Time Free Space Diff Free Space Type Gemini Model File CAGEMINIVDATA O06 28 07 2008 11 58 43PM 28 07 2008 13 04 07 PM 10 11 2008 14 14 51PM 1 0884 cm Measured 2305 1 MPLN405 Adsorption 1 Serial 144 SMP Analysis Adsorptive N2 Equilibration Time 5 s Sat Pressure 102 4380 kPa Sample Mass 0 9535 g Sample Density 1 000 g cm Isotherm Linear Plot Page 1 0 05 0 10 I 0 15 0 20 Relative Pressure p p 27 0 30 IR 08 086 Version 2 Last mod
35. r 17 IR 08 086 Version 2 Last modified 2009 04 17 16 33 3 ANALYSIS OF CARBON BLACK STANDARD 3 3 2 2 9 3 4 3 5 3 6 3 7 3 8 3 9 3 10 3 12 Using the Gemini software under the File dropdown menu select Open and then Sample Information Alternatively press F on the keyboard The Open Sample Information File window will appear Select the directory C GEMINI DATA BGSDAT 1 and then Click the OK button A further Open Sample Information File window will appear indicating File C GEMINIDATA BGSDAT I SMP does not exist Do you wish to create it Click the Yes button A multi tabbed window will appear On the Sample Information tab click the Replace All button The Open Sample Information File window will appear Navigate to the C GEMINIDATA METHODS directory and select the 004 SMP BET Surface Area Method Click the OK button On the Sample Information tab in the MPL sample box overtype BET surface area method with CARBON BLACK date and overtype the sample mass shown as 500 0000 g with the value produced on the Excel BET sample sheet Using the buttons at the base of the tab click Save and then click Close Under the Unitl dropdown menu select Start Analysis A Start Analysis window will appear Navigate to the C GEMINI DATA BGSDAT 1 directory and sele
36. rea data is limited to general statements In general terms the surface areas appear to correspond to the total concentration of clay minerals present with some influence from the presence of smectite The higher surface areas therefore appear to correspond to the more clay rich samples where smectite forms a significant proportion of the clay mineral assemblage and the lower surface areas are produced by samples with lower clay contents where smectite 1s largely absent The London Clay and Gault Clay samples present the highest BET surface areas for the sample batch at c 58 54 and 54 08 m e respectively Typically the London Clay shows high clay 20 81 mean 57 Kemp amp Wagner 2006 and smectite contents 5 30 mean 17 Kemp amp Wagner 2006 with moderate 2 ethoxyethanol total surface areas 74 260 m g mean 176 m g Kemp amp Wagner 2008 Similarly the Gault Clay is characterised by high clay contents up to 65 Forster et al 1994 and highly smectitic clay mineral assemblages Jeans 2006 The German Blue Clay c 53 84 m g and the Ball Clay c 34 20 m g samples also present relatively high BET surface areas These clays are most likely to be predominantly composed of disordered kaolinite with minor smectite e g Konta 1963 Typical ball clays contain gt 70 lt 2 um material The majority of the mudstone samples Boom Clay Opalinus Clay Callovo Oxfordian Clay Nordland Shale Lias Clay produce modera
37. reproducibility 11 IR 08 086 Version 2 Last modified 2009 04 17 16 33 5 Conclusions The Micromeritics Gemini VI physisorption system has been successfully installed and a BGS user manual has been written and working methodologies implemented A range of sample types have been analysed for various BGS project leaders with reliable data being generated in all cases Very low surface areas 0 1 m g appear to be slightly less reliable although these results may be improved by employing filler rods Results indicate the lowest detectable surface area is of the order of c 0 05 m g Multi point BET provide more accurate surface areas than those derived from single point measurements Multi point surface areas appear to be slightly larger than those derived from single point values for the same sample On the basis of the samples tested here sample heterogeneity would not appear to be a significant problem for routine samples However analysis of ground material from the same samples revealed a wider spread of results Sample heterogeneity may also be a greater problem when analysing very low surface area materials although this may be accounted for by free space errors For surface areas in the range 0 1 60 m g errors appear to be better than 2 of the value which concurs with data for the supplied carbon black Surface Area Reference Material For lower surface areas 0 1 m g these errors can increase to 6
38. s from the Chemgrade quartz sample were re analysed and results show similar correlation coefficients of c 0 99 a mean surface area of 0 054 m e but a smaller standard deviation of 0 005 suggesting more precise data Comparison of the multi point surface area data produced by the Gemini with previously obtained values from single point analyses performed on the Flowsorb II indicate a strongly positive correlation Table 4 and Figure 4 The albite sample lies farthest from the overall trend It is noticeable that for all the samples with the exception of the Quartz 125 250 um sample the multi point data produces a larger surface area than the previous single point data This concurs with standard data such as that supplied with Surface Area Reference Materials e g carbon black standard multi point surface area 30 6 0 75 m g single point surface area 29 9 0 75 m g Table 4 Comparison of multi point and single point BET data hydrothermal laboratory experimental samples WUIIISI WI ww BET SA m2 g Gemini VI multi point Flowsorb II single point this investigation previous investigations Quartz 125 250 um 0 0710 0 0824 Chemgrade quartz Fluka 150 400 um 1 0 0686 006 y 0 8268x R 0 9317 Flowsorb Il single point BET m2 g 0 0 5 1 1 5 2 2 5 Gemini VI multi point BET m2 g Figure 4 Cross plot of multi point and single point BET data for the hydrothermal laboratory experimental s
39. sorption Cumulative Pore Area 12 10 T o t a o T lt gt D lt 3 6 2 E i TW 4 2 20 40 60 80 100 200 Pore Width A 33
40. te BET surface areas in the range 20 30 m g Literature sources suggest that these lithologies are typically composed of c 50 clay minerals and usually illite or illite smectite dominated clay mineral assemblages e g Wenk et al 2008 10 IR 08 086 Version 2 Last modified 2009 04 17 16 33 Kemp et al 2001 2002 2005 The Boom Clay differs in possessing a smectite dominated clay mineral assemblage Decleer et al 1983 Surprisingly the lowest surface area in this suite of samples was produced by the Bentonite Sweden sample at c 20 49 m2 g However the BET surface area for standard bentonite CMS source clay SWy 2 can produce relatively low 22 7m2 g Umran Dogan et al 2006 As commercial bentonites are usually composed of high proportions of smectite group minerals rarely less than 60 and usually more than 70 such low BET surface areas are puzzling A possible cause of the low surface area may be the inadequate degassing of the sample prior to analysis Further work is necessary to explore the effects of degassing procedures on difficult samples such as bentonites Analytical reproducibility was examined by analysing the same Callovo Oxfordian Clay sub sample three times The three values 28 1373 28 054 and 27 8875 m g indicate a mean surface area of 28 0264 m g with a standard deviation of 0 4896 These values produce a coefficient of variance standard deviation mean of 1 75 suggesting good analytical
41. temperature and preparation technique best suited to the sample type and application 00044 w ahotan Ns Figure 3 Micromeritics VacPrep system Micromeritics 2008 3 Methods and materials Samples for analysis were submitted by BGS colleagues Drs Barry Rawlins Soils Team Chris Rochelle Energy Theme and Jon Harrington Radwaste Team Sample details are shown in Table 1 Table 1 Sample details 610155 lt 2 mm Black carbon bearing soil samples MPLN408 610155 ground Crushed and E dd Starting materials for hydrothermal Chris Rochelle pubs ne i dias da Ball Clay Mudstone core samples associated with Jon Harrington eae London Clay Landfill Liner off cuts Tin X19 13 5 97 Projects Barry Rawlins The samples from Drs Barry Rawlins and Chris Rochelle ground or granular materials were analysed as received but the core samples received from Dr Jon Harrington were first dried at 55 C overnight and then stage crushed to produce a 1 2 mm fraction for analysis 5 IR 08 086 Version 2 Last modified 2009 04 17 16 33 As well as learning how to use the instrument for Earth Science samples the range of sample types submitted allowed the project to explore several lines of investigation e To establish analytical reproducibility the same subsample from one of the mudstone samples was analysed three times e The soil samples were analysed both as 2 mm size fractions and grou
42. ts inability to offer anything other than single point analyses In addition its lack of computer control and manual operation resulted in relatively slow analyses and high unit costs Also despite regular servicing it appeared that most recently the results obtained for low surface area materials had became inconsistent and therefore suspect A capital bid was therefore successfully submitted for a replacement system in the 2007 08 Capital Bid Round and a Micromeritics Gemini VI 2385C instrument was installed in March 2008 This system offered e Both single and the more reliable multi point BET analyses e Total pore volume determinations e Pore volume distribution determinations e Full computer control to enable data collection presentation and interpretation of generated data e A dedicated vacuum preparation system 2 1 GEMINI VI 2385C SYSTEM The Gemini series of surface area analyzers use the Static Volumetric Technique and a twin tube design to generate high speed surface area and porosity data Figure 1 2 IR 08 086 Version 2 Last modified 2009 04 17 16 33 Figure 1 Micromeritics Gemini VI series physisorption system Micromeritics 2008 The Gemini uses an adaptive rate static volumetric technique of operation which adapts the required rate at which gas 1s supplied for equilibration As shown in Figure 2 the instrument has two gas reservoirs A which are filled with equal volumes of the desired adsorptive usual
43. y This report describes initial testing of the newly acquired Micromeritics Gemini VI physisorption system as part of the Laboratory Operations Programme s Maintenance and Development of Capability MaDCap project The report firstly introduces the technique of surface area analysis and BGS s capabilities and then proceeds to present a user manual and suggested working methodologies for the new system The report also presents data produced from a range of sample types including soils mudstones and experimental starting materials to demonstrate the capabilities of the system to various BGS project leaders Reliable data were generated in all cases although very low surface areas close to the system s lowest detection limit c 0 05 m g appear to be sliehtly less reliable Multi point BET analyses provide more accurate but slightly larger surface areas than those derived from single point measurements for the same sample On the basis of the samples tested here sample heterogeneity would not appear to be a significant problem for routine samples However analysis of ground material from the same samples revealed a wider spread of results Sample heterogeneity may also be a greater problem when analysing very low surface area materials For surface areas in the range 0 1 60 m g errors appear to be better than 2 of the value which concurs with data for the supplied carbon black Surface Area Reference Material For lower surfac
44. y holds most of the references listed below and copies may be obtained via the library service subject to copyright legislation contact libuser bgs ac uk for details The library catalogue is available at http geolib bgs ac uk BARRETT E P JOYNER L G AND HALENDA P P 1951 The determination of pore volume and area distributions in porous substances I Computations from nitrogen isotherms Journal of the American Chemical Society 73 373 380 BRUNAUER S EMMET P H AND TELLER E 1938 Adsorption of Gases in Multimolecular Layers Journal of the American Chemical Society 60 309 319 CARTER D L HEILMEN M D AND GONZALEZ F L 1965 Ethylene glycol monoethyl ether for determining surface area of silicate minerals Soil Science 100 356 360 DECLEER J VIAENE W and VANDENBERGHE N 1983 relationships between chemical physical and mineralogical characteristics of the Rupelian Boom Clay Belgium Clay Minerals 18 1 10 FORSTER A HOBBS P R N CRIPPS A C ENTWISLE D C FENWICK S M M RAINES M R HALLAM J R JONES L D SELF S J amp MEAKIN J L 1994 Engineering geology of British rocks and soils Gault Clay British Geological Survey Technical Report WN 94 31 60pp JEANS C V 2006 Clay mineralogy of the Cretaceous strata of the British Isles Clay Minerals 41 47 150 KEMP S J AND WAGNER D 2008 The mineralogy geochemistry and surface area of mudrocks from the London Clay Formation of sout
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