A comparison and estimation of usefulness of a quantitative analysis of montmorillonite in foundry bentonites, was the aim of this research. The investigations were made by means of three different techniques: methylene blue (MB) adsorption method, Cu(II)-triethylenetetramine complex (Cu(II)-TET) adsorption method, and infrared spectroscopy (FTIR) method. Tests were performed for 9 kinds of bentonites originated from various producers. The achieved results indicated that, the results obtained by the FTIR method were, in general, even 10% lower than the ones obtained by other methods. The best correlation with the data given by the producers were obtained for the Cu(II)-TET method. In addition, this method was characterised by the smallest value of standard deviations. A very essential advantage of the Cu(II)-TET method is a much shorter time needed for the analysis and its easier execution, which is important under production conditions.Cilj ovog istraživanja je bila procjena upotrebljivosti kvantitativne analize montmorilonita u ljevaoničkim bentonitima. Istraživanja su provedena pomoću tri različite tehnike: adsorpcija metilenskog modrila (MB), adsorpcija Cu(II)-trietilentetramin kompleksa (CU(II)-TET), i infracrvena spektroskopija (FTIR). Ispitivanja su provedena na 9 vrsta bentonita koji potječu od različitih proizvođača. Rezultati dobiveni FTIR metodom u prosjeku su za čak 10,0% niži od rezultata dobivenih ostalim metodama. Najbolja korelacija s podatcima od proizvođača dobivena je primjenom Cu(II)-TET metode. Osim toga, kod te metode najmanje su vrijednosti standardnih devijacija. Vrlo važna prednost Cu(II)-TET metode je znatno kraće vrijeme potrebno za anaalizu i lakše provođenje, što je značajno u proizvodnim uvjetima

A. Bobrowski

B. Grabowska

M. Holtzer

English

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M. HOLTZER, A. BOBROWSKI, B. GRABOWSKAMONTMORILLONITE: A COMPARISON OF METHODSFOR ITS DETERMINATION IN FOUNDRY BENTONITESReceived – Prispjelo: 2010-04-10Accepted – Prihva}eno: 2010-10-20Preliminary Note – Prethodno priop}enjeINTRODUCTIONCurrently, approximately 70-80 % of casting produ-ction of ferrous alloys is done with sands containingbentonite (green sands). Information on an amount ofactive bentonite in moulding sands, after shakeout ofcasting, is necessary in the rebounding process of ben-tonite sands – under real casting house conditions. It de-cides how much of fresh bentonite should be added tomoulding sands, thereby influencing their technologicalproperties and cost of the rebounding process 1. Astandard method of an active bentonite estimation inmoulding sands normalised in the Polish foundry plantsand in the majority of European ones is based on themethylene blue adsorption 2. This is a time-consumingmethod and therefore the results are available for a tech-nologists some hours after the introduction of reboundsands into the circulation. This is specially important inthe case of a variable casting production (it mainly con-cerns casting sands), which causes different sand over-heating degree, thus causing various amounts of inac-tive bentonite in a whole sand volume. Therefore sev-eral companies which are dealing with a bentonite ormixtures bentonite – lustrous carbon carrier productionfor the foundry industry, perform intensive investiga-tions in order to develop a reliable and simultaneouslyfast method of the active bentonite (montmorillonite)estimation in moulding sands. In order to do that, thespectrophotometric determination method, which is ap-plying triethylenetetramine complex (Cu(II)-TET) usedin geology for checking clays activity, was also intro-duced. This method is much faster and much simplerfrom the analytical point of view, than the methyleneblue adsorption method. Tests of applying the infraredspectroscopic method (FTIR) are also undertaken. Thismethod allows for a very fast determination of activebentonite, which is essential under production condi-tions. However, it has certain limitations related to someadmixtures present in bentonite, causing distortions ofthe final result 3–6.Investigations in this field aimed at the developmentof the proper analytical method as well as the correct in-METALURGIJA 50 (2011) 2, 119-122 119A comparison and estimation of usefulness of a quantitative analysis of montmorillonite in foundry bentonites,was the aim of this research. The investigations were made by means of three different techniques: methyleneblue (MB) adsorption method, Cu(II)-triethylenetetramine complex (Cu(II)-TET) adsorption method, and infra-red spectroscopy (FTIR) method. Tests were performed for 9 kinds of bentonites originated from various produ-cers. The achieved results indicated that, the results obtained by the FTIR method were, in general, even 10 %lower than the ones obtained by other methods. The best correlation with the data given by the producerswere obtained for the Cu(II)-TET method. In addition, this method was characterised by the smallest value ofstandard deviations. A very essential advantage of the Cu(II)-TET method is a much shorter time needed for theanalysis and its easier execution, which is important under production conditionsKey words: foundry, green sands, bentonite, montmorillonite, FTIRMontmorilonit – usporedba metoda za njegovo odre|ivanje u ljevaoni~kim bentonitima. Cilj ovogistra`ivanja je bila procjena upotrebljivosti kvantitativne analize montmorilonita u ljevaoni~kim bentonitima.Istra`ivanja su provedena pomo}u tri razli~ite tehnike: adsorpcija metilenskog modrila (MB), adsorpcijaCu(II)-trietilentetramin kompleksa (CU(II)-TET), i infracrvena spektroskopija (FTIR). Ispitivanja su provedena na 9vrsta bentonita koji potje~u od razli~itih proizvo|a~a. Rezultati dobiveni FTIR metodom u prosjeku su za ~ak10,0 % ni`i od rezultata dobivenih ostalim metodama. Najbolja korelacija s podatcima od proizvo|a~a dobive-na je primjenom Cu(II)-TET metode. Osim toga, kod te metode najmanje su vrijednosti standardnih devijacija.Vrlo va`na prednost Cu(II)-TET metode je znatno kra}e vrijeme potrebno za anaalizu i lak{e provo|enje, {to jezna~ajno u proizvodnim uvjetima.Klju~ne rije~i: ljevaonica, svje`a kalupna mje{avina, bentonit, montmorilonit, FTIRISSN 0543-5846METABK 50(2) 119-122 (2011)UDC – UDK 621.746:621.742=111M. Holtzer, A. Bobrowski, B. Grabowska, AGH – University of Scienceand Technology, Faculty of Foundry Engineering, Krakow, Polandterpretation of the obtained results have been performed,for a couple of years already, in the Department of Engi-neering of Foundry Processes, Faculty of Foundry Engi-neering, AGH - University of Science and Technology.DETERMINATION METHODSOF THE MONTMORILLONITE CONTENTSpectrophotometric method of the methyleneblue adsorption. This method is based on measuringmethylene blue adsorption on montmorillonite particlescontained in bentonite 7, 8.The methylene blue cation is easily adsorbed byclays, including also montmorillonite. The adsorptionprocess has three stages 8. The absorption was mea-sured by the VIS ODYSSEY DR/2 500 spectropho-tometer of the HACH Company, with an automaticwave length calibration, at a wave length of 470 nm. Theresult is given as a number of mg of methylene blue ad-sorbed by 1 gram of the tested sample. The following re-agents were used: tetrasodium pyrophosphate (pro-duced by SIGMA), methylene blue (produced byCHEM), demineralized water.Cu(II) – triethylenetetramine complex (Cu-TET)adsorption method. This method is based on measur-ing the copper complex adsorption on montmorilloniteparticles contained in bentonite 9.Absorption measurements were carried out by thesame equipment as in the case of the methylene bluemethod but at a wave length of 620 nm. The result wasgiven as a consumption of Cu(II)-TET complex inmmol/l, and than recalculated into the cation exchangecapacity, CEC, (mmol/100 g). The following reagentswere used: copper sulphate (VI), anhydrous, analyti-cally pure (produced by MERCK Company), triethyle-notetramine pure >97 % (produced by FLUCKA), de-mineralised water.Infrared Spectroscopy method (FTIR). Infraredspectrometry belongs to analytical methods enabling toinvestigate samples in all three states of matter. The se-lection of the proper measuring technique for the givensample depends on the purpose, which we would like toachieve: quantitative or qualitative analysis, as well as onthe sample size, its state of aggregation and the possibilityof the components interaction in the analysed sample.For minerals containing montmorillonite the charac-teristic SiO band occurs at the wave number of app. 1040 cm-1. Vibrations of OH groups have the maximumat the wave number of app. 3 630 cm-1. In order to deter-mine the montmorillonite content the mutual relationsof the band intensity (peak heights) and surface areas be-low the band related to stretching vibrations of Si-O inthe ratio to the band corresponding to stretching vibra-tions of OH group - were analysed 10.Investigations of samples performed by the FTIRmethod was done by means of the Excalibur FTS 3 000spectrometer of the BIO-RAD Company with the DTGSdetector. Samples for testing were prepared by the pellettechnique with potassium bromide (KBr). Investiga-tions were performed by the transmission technique.Bands were recorded as the absorbance function, withinthe wave number range 4 000–400 cm-1 at a resolution of4 cm-1. The montmorillonite content was calculated onthe basis of the medium spectrum.The typical bentonite spectrum obtained by the FTIRtechnique is presented in Figure 1.Two methods were applied for the quantitative anal-ysis of the obtained spectra:1) Determination of the relation in between the in-tensity of Si-O and O-H bands Si-O band at awave number app. 1 040 cm-1 and O-H band at awave number app. 3 630 cm-1 is obtained for thestandard of the known montmorillonite content(German VDG Ref. Bentonite is treated as thereference). The relations of the height of analyti-cal bands for the reference and investigated sam-ple is calculated according to equation (1):SiOOHASiOOHreferencereferenceinvestigatedinvestigatedB (1)2) Determination of the relation between surface ar-eas below Si-O and O-H bands.The procedure is analogical as in the case 1, with theonly difference, that this time the surface areas under therespective bands are taken into account (in the estab-lished wave number range). The values obtained for thestandard bentonite are considered the reference values.The mutual relations of surface areas obtained for ana-lytical bands for the reference and investigated sampleare calculated according to equation (1).MATERIALS USED IN EXPERIMENTSBentonites from various producers, applied in themajority in the Polish foundry plants: S&B IndustrialMinerals: Bentonite S, Bentonite E, Süd-Chemie: GekoB, Geko S, Geko Optimum, CETCO Szczytno: benton-120 METALURGIJA 50 (2011) 2, 119-122M. HOLTZER et al.: MONTMORILLONITE: A COMPARISON OF METHODS FOR ITS DETERMINATION IN FOUNDRY...Figure 1 Typical bentonite spectrum obtained by the in-frared spectroscopy methodite A, bentonite B, bentonite C, ZGH Zêbiec: bentoniteSpecjal, Standard: German VDG Ref. Bentonite (Bavar-ian) – methylene blue adsorption 360 mg/g; CEC 70,04mmol/l, 75 % montmorillonite.THE OBTAINED RESULTSAND THEIR DISCUSSIONIn the sets of results of the montmorillonite content(for each sample 6-10 measurements were performed bythe given method), obtained by each of the method,arithmetic means “x”, standard deviations “s” and rela-tive standard deviations “v” – were calculated. Investi-gations of mutual dependencies of the average results ofthe montmorillonite content carried out by variousmethods, was performed by means of the linear regres-sion analysis.The obtained results are shown in Table 1.The comparison of the accuracy of the montmorillo-nite determination by various methods indicated evenlarger differences than the comparison of average val-ues. The relative standard deviation of the results fromthe IR spectroscopy was in the range: 1,4 to 12,7 %,from the MB method usually did not exceed 2 %, (onlyfor Bentonite E it was above 4 %), from the Cu (II)-TETmethod to 1,5 % (exceptionally above 2 %) at a smallmontmorillonite content.Regression equations indicate that the montmorillo-nite content obtained by spectrophotometric methods(MB and Cu(II)-TET) are comparable to the producers’data (within limits of error). The best correlation wasobtained for the Cu(II)-TET method (Figure 2). Quitegood correlation was also obtained for the FTIR methodbased on measuring the intensity and the surface areabelow peaks. However, the correlation between resultsobtained by the spectrophotometric methods MB andCu(II)-TET (Figure 3) was quite poor. The reason of thepoor correlation of the results obtained by the FTIRmethod and the results obtained by other methods can bethe dependence of this methods on particle sizes in ana-lysed samples as well as the presence of contaminations(e.g. feldspars, kaolinite, mullite), which can disturb theFTIR method analysis.CONCLUSIONOn the basis of broad studies concerning the determi-nation of the montmorillonite content in foundryMETALURGIJA 50 (2011) 2, 119-122 121M. HOLTZER et al.: MONTMORILLONITE: A COMPARISON OF METHODS FOR ITS DETERMINATION IN FOUNDRY...Figure 2 Comparison of the results of the montmorillo-nite content (%) obtained by spectrophotome-tric methods with the results supplied by thebentonite producersFigure 3 Comparison of the results of the montmorillo-nite content (%) obtained by the spectrophoto-metric methods (MB and Cu(II)-TET)Table 1 The obtained results and the data supplied by the bentonite producersSampleProducer’sdataMethylene bluemethod MBComplex methodCu(II)-TETFTIR method(peak height)FTIR method(surface area)X/ % X/ % s í X/ % s í X/ % s í X/ % s íBentonite S 91 94 0,80 0,79 91 0,72 0,80 84 1,40 1,67 80 4,89 6,10Bentonite E 74 76 3,35 4,36 71 1,79 2,48 72 4,15 5,91 69 3,30 4,80Geko B 71 71 1,15 1,62 69 1,05 1,50 77 1,15 1,50 73 1,22 1,68Geko S 88 84 1,02 1,19 88 0,86 0,98 83 1,17 1,36 84 4,67 5,50Geko Optimum 96 91 0,77 0,85 92 0,41 0,45 87 1,74 2,01 84 1,63 1,95Bentonite A 88 92 1,92 2,10 87 0,95 1,09 75 3,95 5,27 83 2,19 3,03Bentonite B 84 81 0,91 1,14 83 1,26 1,55 75 3,99 5,32 66 5,36 8,16Bentonite C 66 71 1,44 2,03 65 1,77 2,71 70 6,83 9,80 64 8,03 12,70Special 80 78 1,70 2,20 83 1,09 1,30 60 0,90 1,50 54 1,75 3,22Standard 75 - - - - - - - - - - - -X – arithmetic mean, s – standard deviation;  – relative standard deviation / %bentonites performed by various methods, it can bestated that:– The adsorption method of the Cu(II)-TET com-plex can be fully utilised for the determination ofthe montmorillonite content in foundry bento-nites. This method is much faster (2–3 times) thanthe currently applied method based on measuringthe methylene blue adsorption.Simultaneously it provides the results, which corre-late well with the data supplied by the bentonite produc-ers. Therefore it seems appropriate to implement thismethod in the foundry plants.– The infrared spectroscopy (FTIR) method, basedboth on measuring the peaks intensity and surfaceareas, can eventually be applied for the determina-tion of the smaller montmorillonite content(70–75 %), due to the fact that bentonites containsubstances, which disturb the obtained spectrum.This method should rather be used for compara-tive analyses of the same kind of bentonite.REFERENCES1 Lafay V.S., Neltner S.L., Grefhorst C., AFS Transactions2009, 117 (2009) 807–823.2 Polska Norma Bran¿owa, BN-77, 4024–16.3 Bobrowski A., Materia³y Konferencyjne III KKMU (2008)61–65.4 Paluszkiewicz C., Holtzer M., Bobrowski A., Journal ofMolecular Structure, 880 (2008) 1–3, 109–114.5 Madejová J., Vibrational Spectroscopy 31 (2003) 1–10.6 Tyagi B., ChudasamaC. D., Jasra, R.V., SpectrochimicaActa, Part A 64 (2006) 273–278.7 Bindernagel I., Granitzki K.-E., Orths K., Giesserei, 50(1963) 15, 457– 460.8 Worrall W. E., Origin and General Properties, London1968, Maclaren and Sons.9 Meier L. P., Kahr G., Clays and Clay Minerals, 47 (1999) 3,386 – 388.10 Holtzer M., Grabowska B., Bobrowski A., ¯ymankowska -Kumon S., Archives of Foundry Engineering, 9 (2009) 4, 69–72.This study was financed within the research project ofthe MNiSW No. N N507 370835 realised in years2008-2010.Note: The responsible for English language is “ANGOS” Translate Of-fice, Krakow, Poland122 METALURGIJA 50 (2011) 2, 119-122M. HOLTZER et al.: MONTMORILLONITE: A COMPARISON OF METHODS FOR ITS DETERMINATION IN FOUNDRY...

Montmorilonit – usporedba metoda za njegovo određivanje u ljevaoničkim bentonitima

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