Low level detection and quantification of carbonate species using
Contents
1. NERC 2010 All rights reserved BRITISH GEOLOGICAL SURVEY MINERALOGY PETROLOGY AND BIOSTRATIGRAPHY FACILITY INTERNAL REPORT IR 09 074 Low level detection and quantification of carbonate species using thermogravimetric and differential thermal analysis S J Kemp D Wagner and I Mounteney Keyworth Nottingham British Geological Survey 2010 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 shop online www geologyshop com The London Information Office also maintains 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 936 3143 email enquiries bgs ac uk Fax 0115 936 3276 Kingsley Dunham Centre Keyworth Nottingham NG12 5GG2. 27
3. Tel 0115 936 3241 Fax 0115 936 3488 email sales bgs ac uk Murchison 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 0207589 4090 Fax 020 7584 8270 Tel 020 7942 5344 45 email bgslondonGbgs 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 09 074 Version 2 Last modified 2010 03 25 09 11 Foreword This report is the published product of a study by the British Geological Survey BGS and was produced under the Science Facilities Maintenance and Development of Capability MaDCap project This report aims to provide a procedural manual for the newly acquired simultaneous thermogravimetric and differential thermal analysis system and details of initial testing to determine the low level dete
4. iv IR 09 074 Version 2 Last modified 2010 03 25 09 11 Introduction The International Confederation for Thermal Analysis and Calorimetry ICTAC defines thermal analysis TA as a group of techniques in which a physical or chemical property of a sample is monitored against time or temperature while the temperature of the sample in a specified atmosphere is programmed Hill 1991 The more frequently used thermal analysis techniques and their uses are summarised in Table 1 modified from Haines 2002 Table 1 Thermal methods Thermogravimetry Differential thermal analysis Differential thermal analysis DTA Temperature difference Phase changes reactions Differential scanning Power difference of heat flow Heat capacity phase calorimetry changes reactions Thermomechanical analysis Mechanical changes Evolved gas analysis E Gases evolved or reacted Ma netic changes Curie As with many areas of analytical science it is unlikely that any single TA technique can provide all the information required to understand the behaviour of a sample Instruments that provide two or more types of TA measurement at the same time Simultaneous Thermal Analysis STA are therefore commonly employed e g TG DTA TG DSC TG DTA EGA TA techniques are widely employed across a range of disciplines including chemistry materials science foods and pharmaceuticals but are more rarely employed in geological environmental laborat
5. 1989 Thermal analysis studies of the dolomite ferroan dolomite ankerite series 2 Decomposition mechanism in flowing CO atmosphere Thermochimica Acta 152 2 279 297 MORGAN DJ 1977 Simultaneous DTA EGA of minerals and natural mineral mixtures Journal of Thermal Analysis 12 2 245 263 MORGAN D J WARNE S ST J WARRINGTON S B AND NANCARROW P H A 1986 Thermal decomposition reactions of caledonite and their products Mineralogical Magazine 50 357 521 526 MORGAN D J WARRINGTON S B AND WARNE S ST J 1988a Earth sciences applications of evolved gas analysis a review Thermochimica Acta 135 207 212 MORGAN D J MILODOWSKI A E WARNE S ST J WARRINGTON S B 1988b Atmosphere dependence of the thermal decomposition of manganite gamma MnO OH Thermochimica Acta 135 273 277 15 IR 09 074 Version 2 Last modified 2010 03 25 09 11 PARSONS A J INGLETHORPE S D J MORGAN D J AND DUNHAM A C 1997 Evolved gas analysis EGA of brick clays Journal of Thermal Analysis 48 1 49 62 SNYDER R L AND BISH D L 1989 Quantitative analysis In Bish D L Post J E Eds Modern Powder Diffraction Reviews in Mineralogy Volume 20 Mineralogical Society of America USA pp 101 144 Chapter 5 WARNE S ST J BLOODWORTH A J AND MORGAN D J 1985 Thermomagnetometry and evolved gas analysis in the identification of organic and pyritic sulfur in coal and oil shale Thermochimica Acta 93 745 748 WARNE S S
6. 650 700 750 800 850 900 950 1000 1050 RC194 1 Calcite Canada MPLM703 amp MPLM703 MPLM703 66 3100 mg 00 t Y 95 90 854 7 Onset 948 70 T Endset 986 73 1 Step 43 9397 96 7 29 1364 mg 80 4 0 005 4 VT 754 705 65 60 552 a a ee Sa a T ELIO CIT 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 25 IR 09 074 Version 2 Last modified 2010 03 25 09 11 RC769 1 Siderite Greenland MPLM704 102 amp MPLM704 4 MPLM704 45 4400 mg Onset 474 27 1 Endset 537 00 Step 27 7040 Ms 12 5887 mg 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 Quartz MPLM705 4 8 705 quartz MPLM705 quartz 8 3400 mg Co et hh het th hot et ee i to i tt i it ot it 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 26 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Low detection limit mixture 99 991 quartz 0 009 calcite j amp IMPLM702mix13 MPLM702mix13 159 5850 mg 100 00 99 99 Step 6 72916 03 10 7387 03 mg 99 98 99 95 99 98 99 9 99 9 99 89 99 87 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050
7. C HAINES P J 2002 Principles of Thermal Analysis and Calorimetry In HAINES P J editor The Royal Society of Chemistry 320p HARRISON D J INGLETHORPE S D J Mitchell C J KEMP S J CHAODUMRONG P and CHARUSRIBANDHU M 1998 Procedures for the rapid assessment of limestone resources British Geological Survey Technical Report WC 98 1 HILL J O 1991 For Better Thermal Analysis and Calorimetry Ed International Confederation for Thermal Analysis ICTA Newcastle Australia HILLIER S SUZUKI K AND COTTER HOWELLS J 2001 Quantitative determination of Cerussite lead carbonate by X ray powder diffraction and inferences for lead speciation and transport in stream sediments from a former lead mining area of Scotland Applied Geochemistry 16 597 608 INGLETHORPE S D J AND MORGAN 1993 Detection of ammonium in geological materials by evolved gas analysis Journal of Thermal Analysis 40 29 40 KEMP S J INGLETHORPE S D J and WASPE 1991 Bulk mineralogical data for samples from the Devonian of Dounreay UK Core Characterisation Series Report CC91D 030 IF A C MILODOWSKI A E AND MORGAN D J 1980 Identification and estimation of carbonate minerals at low levels by evolved CO analysis Nature 286 248 249 MILODOWSKI A E AND MORGAN D J 1984 Thermal reactions of Leadhillite Clay Minerals 19 5 825 841 MILODOWSKI A E MORGAN D J WARNE S ST J
8. T 933 962 23 6167 dolomite decomposition 3 RC769 1 Siderite MPLM704 c 474 537 27 7040 siderite decomposition 11 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Table 7 Summary of thermal analysis of dolomite GSR 12 mixtures Weight loss i Mixture vane dolom 2 temperature attributed to ee range content 601 628 47 7829e dolomite decomposition 1 2 000 738 6 758 04136 dolomite decomposition 2 937 945 0 5042 dolomite decomposition 3 641 657 12 3291e dolomite decomposition 1 1 000 c 133 753 0 1424 dolomite decomposition 2 937 944 0 1820 dolomite decomposition 3 737 c 159 94 2459 2 dolomite decomposition 1 0 500 Ea 934 946 0 1477 dolomite decomposition 2 c 738 747 45 6772e dolomite decomposition 1 0 200 c 937 c 940 61 3174 3 dolomite decomposition 2 EX 732 15 8691e dolomite decomposition 1 0 100 ES 935 942 29 0146 3 dolomite decomposition 2 735 750 6 3248e dolomite decomposition 1 0 050 939 941 17 1661e dolomite decomposition 2 730 750 1 4801e dolomite decomposition 1 0 020 937 948 9 2926e dolomite decomposition 2 Table 8 Summary of thermal analysis of calcite RC191 1 Eire mixtures as Weight loss Equivalent calcite content Mixture quartz
9. the TG DTA technique additional experiments were carried out using a Sartorius MES 6 decimal figure balance Sample MPLM702 Calcite RC191 1 was chosen as it showed the highest purity The smallest transferable quantities of calcite were weighed into a platinum crucible before adding between c 120 and c 160 mg quartz to produce calcite concentrations of 0 01 100 ppm The sample mixtures were then analysed as those previously Sample details and results are shown in Table 9 lower entries An example TG curve for a low detection limit mixture is shown in Appendix 2 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Using such a technique TG DTA analyses successfully recorded a weight loss of 6 7291e which equates to an initial calcite weight of 0 015 150 ppm Considering the size of the weight loss measured Appendix 2 it would appear that the technique is capable of detecting lower calcite concentrations of perhaps 100 mg However proving this to be the case is precluded by handling weighing difficulties 10 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Table 6 Summary of thermal analyses of mineral standards Weight loss Equivalent Equivalent Equivalent Incoming sample name BGS Code temperature attributed to calcite content dolomite content siderite content c 611 c 642 2 1278 dolomite decomposition 1 BEEN 7 GSR 12 Dolomite MPLM701 c 744 c 169 21 1893 dolomite decomposition 2
10. the new system to BGS project leaders IR 09 074 Version 2 Last modified 2010 03 25 09 11 2 Materials and methods 2 MATERIALS The following pure mineral standards were sourced from the BGS reference collection RC769 1 Siderite Ivigtut Greenland RC193 1 Dolomite Larangwe Blantyre District Malawi e RC194 1 Calcite Canada 191 1 Calcite Eire together with e GSR 12 Dolomite mineral standard from BGS XRFS laboratories e Quartz BGS XRD lab locality unknown 2 2 SAMPLE PREPARATION A representative sub sample of each sample was removed and then hand crushed in a pestle and mortar The crushed material was then ball milled to lt 0 125 mm 2 3 CHARACTERISATION OF MINERAL STANDARDS To identify whether the selected materials were suitable for this study each was firstly mineralogically examined using XRD analysis followed by major element geochemical analysis by X ray fluorescence spectroscopy XRFS 2 3 1 X ray diffraction analysis In order to provide a finer and uniform particle size for whole rock XRD analysis a c 3 5 portion of the ball milled material was wet micronised under acetone for 10 minutes dried disaggregated and back loaded into standard stainless steel sample holders for analysis XRD analysis was carried out using a PANalytical X Pert Pro series diffractometer equipped with cobalt target tube X Celerator detector and operated at 45kV and 40mA The samples were scanned from 4 5 8
11. to accept these new values 1 6 Perform another check Section 3 to see if the values are now within limits 23 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Appendix 2 Thermal analysis traces for the carbonate mineral standards and low detection limit mixture TG traces are shown in red DTG traces are shown in black except for low detection limit sample where only the TG trace isshown GSR 12 Dolomite MPLM701 7 amp MPLM701 pibe ides 1 MPLM701 65 8400 mg et E 3 Step 2 1278 96 1 4009 00 Et Gh 95 90 Onset 744 17 Endset 769 00 Step 21 1893 18 9510 mg 80 0 005 754 Onset 933 66 C Endset 962 36 Step 23 6167 704 15 5492 mg 651 605 554 505 DTTTTTEITTOTELDTETRTRDTRTACSCLTOCSLTO C CT3 ULITTTOEI DITTTET T TT T 50 100 150 200 250 300 350 400 450 500 600 650 800 850 950 1000 1050 24 IR 09 074 Version 2 Last modified 2010 03 25 09 11 RC191 1 Calcite Eire MPLM702 p 4 amp MPLM702 MPLM702 75 8800 mg 00 Bi 95 90 J Onset 949 97 J Endset 986 91 1 _ Step 43 8504 33 2737 mg 85 80 3l 0 005 E 754 704 65 604 4 55 5 oC SP a a ae SP SU CIO 50 100 150 200 250 300 350 400 450 500 550 600
12. 1 6 Select Ingres intelligent database from the list 1 7 Within the new window select the on tab 1 8 Fill in the log in name Vngres and password weiqingl and click the Apply button 1 10 A window The account Nngres has been granted the Log On As A Service right will appear Click OK button 1 11 On the General tab click Start button A window will appear advising that Windows is attempting to start the Ingres Intelligent Database Click OR 1 12 Close all windows and log off 1 13 log on AD domain as per usual 22 IR 09 074 Version 2 Last modified 2010 03 25 09 11 APPENDIX M2 Total adjustment This procedure is necessary if the results of the In AI calibration check are outside specification 11 From within the software click on the Routine editor and select Total adjustment 1 2 Prepare the sample for the experiment by following the instructions in text box An alumina crucible with In AI total is already placed on the carousel on position 131 which can be re used The weight for this pre prepared standard is shown on the sheet on the notice board in P029 1 3 Fill in sample name n AI total the sample weight from details on the notice board and sample position 3 1 4 Click Send Experiment 1 5 After completion of the experiment an information box will appear with the new calibration values Click OK button
13. 5 26 at 2 76 20 minute Diffraction data were initially analysed using PANalytical X Pert HighScore Plus Version 2 2a software coupled to the latest version of the International Centre for Diffraction Data ICDD database Following identification of the mineral species present in the samples mineral quantification was achieved using the Rietveld refinement technique e g Snyder amp Bish 1989 using PANalytical HighScore Plus software This method avoids the need to produce synthetic mixtures and involves the least squares fitting of measured to calculated XRD profiles using a crystal structure databank Errors for the quoted mineral concentrations are typically 2 5 for concentrations gt 60 wt 5 for concentrations between 60 and 30 wt 10 for concentrations between 30 and 10 wt 20 for concentrations between 10 and 3 wt and 40 for concentrations 3 wt Hillier et al 2001 Where a phase was detected but its concentration was indicated to be below 0 5 it is assigned a value of 0 546 since the error associated with quantification at such low levels becomes too large IR 09 074 Version 2 Last modified 2010 03 25 09 11 2 3 2 X ray fluorescence spectroscopy For geochemical analysis the ground samples were dried at 105 C before fusion and determination of loss on ignition LOI To determine the LOI samples were heated in a muffle furnace for 1 hour at 1050 C Approximately 1 2 of sample was weighed accurately into a
14. British Geological Survey NATURAL ENVIRONMENT RESEARCH COUNCIL Low level detection and quantification of carbonate species using thermogravimetric and differential thermal analysis Mineralogy Petrology and Biostratigraphy Facility Internal Report IR 09 074 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 2010 Keywords calcite dolomite siderite low level detection thermogravimetry differential thermal analysis Front cover TGA SDTA sample robot Bibliographical reference KEMP S J WAGNER D AND MOUNTENEY I 2010 Low level detection and quantification of carbonate species using thermogravimetric and differential thermal analysis British Geological Survey Internal Report 1 09 074 35pp 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 permission 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
15. T J 1986 Applications of variable atmosphere DTA in CO2 to improved detection and content evaluation of anhydrous carbonates in mixtures Thermochimica Acta 109 243 252 16 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Appendix 1 BGS methodology OPERATING INSTRUCTIONS FOR THE METTLER TOLEDO SDTA851 THERMAL ANALYSIS SYSTEM ROOM P029 IR 09 074 Version 2 Last modified 2010 03 25 09 11 1 RESTING CONDITIONS The TGA SDTA851 should be permanently left on and the balance constantly purged with as a protective gas c 10cm min on flowmeter may also be used as a protective gas for short time period where is to be used as reactive gas to avoid an unexpected low temperature weight gain Check the recirculating cooling agent 22 C on a regular basis for water level and contamination If the water level has dropped top up as necessary If the coolant shows any cloudiness drain the fluid and replace using the correct dilution ratio Also check that the water flow is maintained using the red flow wheel indicator 2 PREPARATION DAY BEFORE ANALYSIS 21 Ensure TGA SDTA851 is switched on The mains switch red is located towards the top of the rear panel of the module 2 2 Switch on the PC and log on to the AD domain 2 3 Double click on the STAR software program icon on the desktop Note If an error message appears refer to Appendix MI for guidance 24 Enter username METTLER and pa
16. and faster more vigorous reactions over a smaller temperature range A summary of common carbonate mineral decomposition characteristics is shown in Table 2 Table 2 Carbonate mineral decomposition in flowing CO atmosphere Carbonate species CaCO CO 900 1000 43 97 gt CaCO 550 765 23 86 the siderite decomposition mechanism is strongly linked to oxygen fugacity The data shown relates to low oxygen fugacity as would be expected to be produced by a flowing CO atmosphere The rapid low level detection and quantification of carbonate species afforded by TA techniques is capable of providing useful data to a wide range of BGS projects but is particularly important in studies related to storage from analogue and demonstration sites to supporting laboratory studies Reactions between CO rich porewaters and carbonate cements in reservoirs and or cap rocks are relatively fast Therefore the detection of low levels of carbonate minerals is fundamental to understanding long term storage processes This report therefore presents the results of a small study carried out during 2008 09 under the Maintenance and Development of Capability MaDCap project which aimed to e familiarise BGS staff with the newly purchased thermal analysis system e produce a user manual e determine the lower limits of detection for carbonate species by TG DTA e advertise the abilities of
17. been successfully installed and a BGS user manual has been written and working methodologies implemented For the detection and quantification of low levels of carbonate species combined TGA DTA analysis offers significantly lower levels of detection than other mineralogical techniques such as X ray diffraction analysis e TGA DTA studies have measured concentration levels as low as 200 ppm dolomite siderite and 150 ppm calcite in synthetic mixtures Even lower detection limits are possible using this method but proving these is precluded by the difficulty of handling weighing such small quantities 5 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 thermal analysis system 14 IR 09 074 Version 2 Last modified 2010 03 25 09 11 References British Geological Survey 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 BLOODWORTH A J KEMP S J INGLETHORPE S D J and MORGAN D J 1987 Mineralogy and lithochemistry of strata beneath proposed low level radioactive waste site at Bradwell Essex Report to Sir William Halcrow and Partners Site Investigation Consultants British Geological Survey Technical Report 87 13
18. calcite no temperature attributed to range 12 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Table 9 Summary of thermal analysis of calcite RC194 1 Canada mixtures ae loss Equivalent quartz calcite lcit tent 96 temperature attributed to range 99 500 0 500 947 961 0 2140 calcite decomposition 0 49 99 800 0 200 c 949 961 88 1119 1 calcite decomposition 0 20 99 900 0 100 948 964 55 9616 calcite decomposition 0 13 HX 99 950 0 050 c 949 c 963 32 0740 1 calcite decomposition 0 07 99 980 0 020 945 954 12 6495e calcite decomposition 0 03 EN 99 0000 0 0090 c 940 970 6 8588e calcite decomposition 0 016 m 99 0000 0 0160 c 940 970 8 9111e calcite decomposition 0 020 99 5000 0 0090 c 940 970 6 7291e calcite decomposition 0 015 99 8000 0 0120 940 970 7 2632e calcite decomposition 0 017 99 9000 0 0120 c 940 970 6 7902e calcite decomposition 0 015 Table 10 Summary of thermal analysis of siderite RC769 1 Ivigtut Greenland mixtures Weight loss quartz siderite 8 ptis temperature attributed to siderite conten range C So ERR ope e ee ee R9 13 IR 09 074 Version 2 Last modified 2010 03 25 09 11 4 Conclusions The Mettler Toledo SDTA851e thermal analysis system has
19. ck on the Routine editor From the Method drop down menu select Select Check TGA851 Place an alumina crucible containing the prepared In Al mixture in position 34 on the carousel Note The In Al standard can be re used for future calibrations Fill in the weight of pre prepared In AI taking details from the sheet pinned to notice board in P029 add the sample name In Al check and sample position 134 Click Send Experiment To evaluate whether the In Al check is within specification open the Evaluation Window by minimising the Module Control Window From the Functions drop down menu select Evaluation Window From the File drop down menu select Open and then Evaluation Select the relevant In Al check and follow the instructions that appear in the window The In Al check is evaluated automatically If the values are within specification the following text appears The Module is within specifications If the values are not within specification the following text appears Please adjust the TGA SDTA851 If the results of the check are not within specification repeat the experiment with new standard materials If the results are still not within specification carry out a total adjustment see Appendix M2 19 IR 09 074 Version 2 Last modified 2010 03 25 09 11 4 4 1 4 2 4 3 4 4 4 5 4 6 SAMPLE ANALYSIS Fro
20. ction and quantification of carbonate species IR 09 074 Version 2 Last modified 2010 03 25 09 11 Contents Foreword i Contents ii Summary iv 1 Introduction 1 1 1 Thermal analysis in the BGS 1 12 Mettler Toledo SDTA851 System 2 1 3 Thermal analysis of carbonates 4 2 Materials and methods 5 2 Materials 3 2 2 Sample preparation 5 2 3 Characterisation of mineral standards 5 2 4 Thermal analysis 6 3 Results of thermal analyses 9 3 1 Mineral standards 9 3 2 Detection limits 9 4 Conclusions 14 5 Recommendations 14 References 15 Appendix 1 BGS methodology 17 Appendix 2 Thermal analysis traces for the carbonate mineral standards and low detection limit mixture 24 FIGURES Figure 1 Mettler Toledo SDTA851 system installation at BGS Keyworth 2 Figure 2 Detail of sample robot loading a platinum crucible 3 Figure 3 Crucible sitting in its measurement position on the balance arm Note that the sample changer has been removed and furnace retracted for clarity The reactive gas supply capillary is arrowed ii 3 IR 09 074 Version 2 Last modified 2010 03 25 09 11 TABLES Table 1 Thermal methods Table 2 Carbonate mineral decomposition in flowing CO atmosphere Table 3 Summary of quantitative XRD analyses for the mineral standards Table 4 Summary of XRFS geochemical analysis for the mineral standards Table 5 Summary mixtures of quartz and carbonate oOo nN N A Table 6 Summary of thermal analyses of mineral s
21. d XRFS analyses indicated that the remaining samples were of sufficient purity for their inclusion in the study 2 4 THERMAL ANALYSIS Prior to commencing analyses the TG DTA system was calibrated using the specified Indium Aluminium In Al melting test As the measured values were outside the specified limits a total adjustment was performed and the In Al check repeated to check compliance Zero runs were then completed for empty 150 ul platinum crucibles from 30 to 1100 C in a gas flow of 80 ml minute at a heating rate of 10 C minute However when employing as the purge gas and gas as the reactive gas the TG curve showed an unaccountable weight loss at approximately 100 C Having excluded all the possible causes for this new platinum crucibles exchange of gas cylinder and replacement gas lines in the laboratory advice was sought from the manufacturer Mettler Toledo suggested that baseline runs should be performed without any crucibles under following conditions N protective gas and no reactive gas N protective gas and reactive gas N protective gas and reactive gas e CO protective and reactive gas The results of these runs showed that the mysterious weight loss at c 100 C was only produced with a combination of as the protective gas and CO as reactive gas Mettler Toledo could not provide an adequate explanation for this phenomenon but believed it to be the result of gas m
22. e of the art thermal analysis system which would offer simultaneous thermogravimetric and differential thermal analysis TG DTA and efficiency gains through a sample changer facility 12 METTLER TOLEDO SDTA851 SYSTEM The purchased Mettler Toledo SDTAS851 system Figure 1 provides the following High resolution 1 ug internally calibrated thermobalance e Large temperature range ambient to 1600 C furnace e High temperature accuracy 0 5 C calibrated by pure metal melting points e Sample robot with 34 position sample changer allowing automatic processing and different crucible program options Figure 2 e Parallel guided balance ensures accurate position independent weight measurements Figure 3 Sample sizes up to 1000 mg in up to 900 ul crucibles e Data collection and interpretation using STARe software suite running on dedicated PC e Programmable gas controller enabling two channel gas flow measurement switching and monitoring e Standalone re circulating water cooling to provide constant measuring conditions and faster cooling between samples e Ability to add coupled devices e g FTIR spectrometer mass spectrometer Figure 1 Mettler Toledo SDTA851 system installation at BGS Keyworth 2 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Figure 3 Crucible sitting in its measurement position on the balance arm Note that the sample changer has been removed and furnace retracted for clarity Th
23. e reactive gas supply capillary is arrowed Following installation the system has provided useful data to a variety of projects e g storage limestone and industrial mineral assessment contract analyses for external clients such as BPB Plc but its potential has not been fully exploited due to a lack of R amp D funding IR 09 074 Version 2 Last modified 2010 03 25 09 11 13 THERMAL ANALYSIS OF CARBONATES The presence of carbonate species particularly calcite dolomite ankerite and siderite in geological materials can routinely be determined and quantified by powder X ray diffraction XRD analyses However the lower detection limits afforded by XRD for such species is of the order of 0 lwt Thermal analysis techniques such as coupled TG DTA have the ability to quantify lower levels of carbonate species and so complement XRD analysis particularly where lower levels of detection are required An important development in the detection and quantification of carbonate species was the use of variable atmosphere thermal analysis Warne 1986 It was discovered that running carbonate species TA experiments in flowing CO rather than N or air provided improved individual peak and reaction definition By adopting the same purge gas as that released during sample decomposition the carbonate species has to overcome the increased partial pressure before decarboxylation This results in increased decomposition temperatures
24. ep Tang Values for weight loss in and g will appear adjacent to the curve When calculations graphical manipulation complete click the File drop down menu and select Save evaluation Fill in appropriate file name using MPL code 20 IR 09 074 Version 2 Last modified 2010 03 25 09 11 5 6 To export an evaluation for reporting purposes click the File drop down menu and select Import Export and Export other format e g emf tif txt 6 TERMINATING THE STAR SOFTWARE AND SHUT DOWN 6 1 In Evaluation window click the drop down menu and select Exir 6 2 From the main STAR software window click System drop down menu and select the Exit Shut down PC as usual 6 3 Turn back gas flow of Nitrogen until c 10cm min is shown on the flow meter In case of usage turn off gas at the gas tap in P029 and via the regulator and cylinder in DP407 21 IR 09 074 Version 2 Last modified 2010 03 25 09 11 APPENDIX M1 Error message while logging into the STARe software This procedure is necessary if an error message is received when attempting to start the STARe software system This procedure restarts the INGRES database 11 Log off AD domain 12 Login as KWP19767 this computer 1 3 Enter username INGRES and password weiqingl 1 4 From the Start Menu select Control Panel 1 5 Select Administrative Tools and then Services
25. he siderite bearing sample RC769 1 produced a lower temperature weight loss between c 474 and 537 of c 27 7 equivalent to c 97 4 siderite 3 2 DETECTION LIMITS Seven mixtures of each carbonate standard were run in 150 ul platinum crucibles from 30 to 1100 C in a gas flow of 80 ml minute CO at a heating rate of 10 C minute The results are summarised in Tables 7 to 10 As shown by the tabulated data TA confirms the presence of carbonate in the mineral mixtures and quantification suggests concentrations very close to those that were planned Variation from the planned concentrations generally lt 5 is almost certainly due to errors inherent in the weighing and preparation of the mixtures Larger errors were encountered for the siderite mixtures which may be due to the greater difficulty in separating and accurately weighing the iron rich siderite particles which exhibit a mild magnetism and tend to form aggregates The larger siderite errors may also possibly relate to the incomplete or dual reactions suggested in section 2 4 In all cases the lowest carbonate concentration 0 020 96 200 ppm was detected and quantified However the detection of lower carbonate concentrations was precluded by the inability to accurately weigh samples of 0 01 mg using the 5 decimal place Sartorius R200D balance due to static effects between the mineral grains In order to determine the lowest detection limit for calcite in a composite sample using
26. ixing and possible back pressure s Despite the possible corrosive effect of CO on the 6 IR 09 074 Version 2 Last modified 2010 03 25 09 11 Table 3 Summary of quantitative XRD analyses for the mineral standards Mineralogy Incoming sample name pe 5 GSR 12 Dolomite RC191 1 Calcite Eire MPLM702 cm cate Can __ ve oa w w RC769 1 Siderite Greenland MPLM704 m MPLM705 100 KEY nd not detected o om om un 5 ad S Table 4 Summary of XRFS geochemical analysis for mineral standards Eo EE IS Ee Eco SSS SS ee ee 0j code aan ne om 0 owe n Fa 9 kc nor star nas sis nos fenor fox non ons om non enor ar s om om is 022 nos oor om nor vos oz ur o nor lt or oo as euros nas 422 va nos oos nas caa nas nns oz nas om noz fos som tas nos nos nm fr no som oz oos om oon eom oom KEY n a not available IR 09 074 Version 2 Last modified 2010 03 25 09 11 delicate microthermobalance Mettler s suggesti
27. m within the STAR software click on the Routine editor From the Method drop down menu select Select and choose the relevant method from the options displayed in the window On the Sartorius 5 figure balance weigh a clean crucible of correct material for analysis platinum aluminium ceramic etc zero the balance and weigh sample material usually c 50mg into the crucible Record the sample weight In the software window fill in the sample name sample weight and sample position in the carousel The first sample position on the sample carousel is 101 Note When carrying out experiments involving temperatures above 1100 C and platinum crucibles make sure that a sapphire disk is placed on the sample holder arm before analysis Click Send Experiment 5 EVALUATION 5 1 9 2 5 3 5 4 9 5 From the main STAR software window click Functions drop down menu and select the Evaluation window In the new window from the File drop down menu select Open curve Select the required sample curve and click Open To additionally display the DTG curve select Math and 1 derivative To additionally display the DTA curve select and SDTA To calculate weight losses click on the original curve always remember to click on the curve you want to work on and draw a window over the area of the weight loss Select TA and Step Horiz or St
28. ncomplete reaction or the combination of two separate reactions The standard siderite weight loss of 27 70 was used throughout this study IR 09 074 Version 2 Last modified 2010 03 25 09 11 3 Results of thermal analyses 3 1 MINERAL STANDARDS The results of thermal analysis of the selected carbonate mineral standards are summarised in Table 6 and the labelled thermal analysis traces in Appendix 2 The dolomite bearing sample GSR 12 shows two major weight losses between c 730 and c 770 C and between c 930 and c 960 C which can both be ascribed to dolomite decomposition Assuming that the dolomite has a close to end member non ferroan composition CaMg CQ3 2 the dolomite concentration was calculated by comparison with the weight loss of a standard non ferroan dolomite 47 73 Table 2 The slight difference in weight loss between the two endothermic reactions suggests that the Mg Ca ratio is not exactly 1 1 possibly caused by the substitution of Mn Zn or Ni in the dolomite structure A weak third endothermic effect between 600 and c 650 C presents further evidence of some in the dolomite structure which is also confirmed by geochemistry data Table 4 The two calcite bearing samples RC191 1 and 194 1 show similar thermogravimetric profiles with a major c 44 weight loss between c 950 987 The weight loss suggests close to pure calcite contents of 99 73 RC191 1 and 99 93 RC194 1 respectively T
29. on to run measurements with as both the protective and reactive gas was used throughout this study Subsequent discussions with other users of the same instrument at Saint Gobain Gypsum East Leake revealed that they had encountered similar problems when running with an protective gas and CO reactive gas The cause is still unknown For thermal analysis c 50 65 mg portions of each powdered sample were heated in 150 ul platinum crucibles from 30 to 1100 C in a gas flow of 80 ml minute at a heating rate of 10 C minute In order to establish the lower detection limit of the different carbonate species a series of mixtures of quartz with each carbonate species was prepared for TG DTA analysis Table 5 A total of 50 mg of each standard mixture was then accurately weighted into 150 ul platinum crucibles using a 5 decimal place Sartorius R200D balance Table 5 Summary mixtures of quartz and carbonate carbonate Mixture no The presence and quantification of the different carbonate species was determined by comparison with empirically derived standard weight losses and temperatures Table 2 However in the case of the siderite standard RC769 1 TGA produced a weight loss of 27 70 not 37 99 as shown by the equation in Table 2 Despite intensive research no single stoichiometric equation could be derived to explain this weight loss and it is therefore presumed to represent either i
30. ories However as demonstrated by the BGS laboratories see next section thermal methods frequently provide very useful complimentary data on the mineralogy and behaviour of geological materials 1 1 THERMAL ANALYSIS IN THE BGS The BGS Mineralogy amp Petrology laboratories have a history of carrying out geoscience related TA research since the 1960s In fact the facility is certainly the premier UK institution for TA in the geosciences with a prominent international reputation established by the frequent journal publications produced during the 1970s 80s and 90s e g Morgan 1977 Milodowski amp Morgan 1980 1984 Warne et al 1985 Morgan et al 1986 1988ab Milodowski et al 1989 Inglethorpe amp Morgan 1993 Parsons et al 1997 The equipment also proved invaluable for industrial mineral development projects e g Harrison et al 1998 and the characterisation of materials from UK NIREX s low level Sellafield and Dounreay investigations e g Bloodworth et al 1987 Kemp et al 1991 IR 09 074 Version 2 Last modified 2010 03 25 09 11 However during the late 1990s and early 2000s BGS TA activity declined due to a combination of a downturn in demand from both radwaste characterisation and industrial mineral projects a loss of specialist staff and the restrictive nature of the 1970 80s purchased equipment In order to help re stimulate TA activity in BGS a successful proposal was made in April 2005 to purchase a stat
31. porcelain crucible The crucible was weighed before and after heating and the two weights compared The resulting relative loss in sample weight was reported as the LOI Fused beads were prepared by fusing 0 9000 g sample plus 9 000 g flux 66 34 11 4 and LiBO at 1200 C All samples were analysed using these conditions for internal consistency within the batch After fusion the melt was cast into a 40 mm fused glass bead which was then analysed by XRFS The XRFS spectrometer used was a Philips MagiX Pro fitted with a 60 kV generator and 4 kW rhodium Super Sharp end window X ray tube controlled via PC running PANalytical SuperQ application package The PANalytical calibration algorithm is used to fit calibration curves and inter element effects are corrected by theoretical alpha coefficients calculated by the PANalytical method spectral backgrounds and peaks are corrected for instrument drift using two external ratio monitors 2 3 3 Results The results of initial characterisation of the project materials by XRD and XRFS are summarised in Tables 3 and 4 XRD analysis of sample 193 1 Dolomite Larangwe Blantyre District Malawi showed that although dolomite formed the major component of this material significant quantities of quartz calcite and undifferentiated mica species were also identified No further analyses were therefore carried out on this sample and it was removed from the investigation XRD an
32. ssword 2 5 Check that adequate supplies of N and or CO gases are available in the cylinder store DP407 in P U block quadrangle and open relevant regulators 2 6 In P029 gradually turn on the gas supply at the relevant gas tap or making sure that the gas pressure indicated on the inline pressure gauge does not exceed 0 8 bar 2 7 On TGA SDTA851 control panel depress the Rotate button until 1 and Gas appear on LCD display Then also on the TGA SDTA851 control panel depress the gas button 2 gas cylinder symbols labelled 1 and 2 to indicate the reactive gas flow rate Note that by default Gas 1 indicates and Gas indicates CO 2 8 the gas flow control unit TSO800GC1 beside the TGA SDTA851 turn the knob 1 or 2 respectively to adjust the reactive gas flow to 80ml min shown on 85 1 control panel Make sure that the protective gas CO flows at 10cm min on the flowmeter adjusting using the knob on the flowmeter itself 2 9 Leave the gas es switched on overnight to settle and purge the TGA SDTA851 18 IR 09 074 Version 2 Last modified 2010 03 25 09 11 3 CALIBRATION AND ADJUSTMENT 3 1 32 3 3 3 4 3 5 3 6 3 7 3 8 3 9 3 10 3 11 Before each batch of samples perform a calibration check using the supplied In Al metal standards From within the STAR software cli
33. tandards Table 7 Summary of thermal analysis of dolomite GSR 12 mixtures 12 Table 8 Summary of thermal analysis of calcite RC191 1 Eire mixtures 12 Table 9 Summary of thermal analysis of calcite RC194 1 Canada mixtures 13 Table 10 Summary of thermal analysis of siderite RC769 1 Ivigtut Greenland mixtures 13 iii IR 09 074 Version 2 Last modified 2010 03 25 09 11 Summary This report describes a procedural manual for the newly acquired simultaneous thermogravimetric and differential thermal analysis system and details of initial testing to determine the low level detection and quantification of carbonate species This work was carried out as part of the Science Facilities Maintenance and Development of Capability MaDCap project The report firstly introduces the techniques of thermal analysis and BGS s capabilities in this area The report then details a series of experiments designed to determine the low level detection and quantification of carbonate species calcite dolomite and siderite Results indicate that combined TGA DTA analysis offers significantly lower levels of detection than other mineralogical techniques such as X ray diffraction analysis Measured carbonate species concentration levels as low as 200 ppm dolomite and siderite and 150 ppm calcite in synthetic mixtures are proved Lower detection limits are possible but proving these is precluded by the difficulty of handling weighing such small quantities
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