MÖSSBAUER EFFECT STUDY OF SOME YUGOSLAV BAUXITES

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MÖSSBAUER EFFECT STUDY OF SOME YUGOSLAV BAUXITES

S. Musik, Z. Dragčevik, O. Lahodny-Sarc, I. Nagy-Czakó, A. Vértes

To cite this version:

S. Musik, Z. Dragčevik, O. Lahodny-Sarc, I. Nagy-Czakó, A. Vértes. MÖSSBAUER EFFECT STUDY

OF SOME YUGOSLAV BAUXITES. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-305-C1-

306. �10.1051/jphyscol:19801110�. �jpa-00219592�

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JOURNAL DE PHYSIQUE Colloque C1, suppltrment au n ^O1, Tome 41, janvier 1980, page C1-305

~SSBAUER EFFECT STUDY OF S W YUGOSLAV BAUXITES

,tilt

S . Musi6, 2 . ~ra~Ge'evi6+, 0. ~ahodn~- arc*, I . Nagy-Czako and A. ~ g r t e s *at Rudher ~ o g k o v i c I n s t i t u t e , Zagreb, Yugos Zavia.

+

TechnoZogicaZ Department, University of Zagreb, YugosZavia.

x Mining, GeoZogy and PetroZewn Engineering Department, University of Zagreb, YugosZavia.

W + I n s t i t u t e of PhysicaZ Chemistry and Radiozogy, L. E8tv8s University, Budapest, Hungary.

In t h i s work some Yugoslav b a u x i t e minerals of d i f f e r e n t o r i g i n have been s t u d i e d by Mijssbauer spectroscopy t o a s c e r t a i n t h e chemical and c r y s t a l form of t h e i r o n oxide c o n s t i t u e n t s .

Experimental.- On t h e b a s i s o f X-ray d i f f r a c t - i o n , DTA and TGA i n v e s t i g a t i o n s samples with c h a r a c t e r i s t i c mineralogical composition were s e l e c t e d . The Mossbauer s p e c t r a were recorded by a conventional constant a c c e l e r a t i o n spectrometer a t room and l i q u i d n i t r o g e n temperature. A 1 0 m C i Co 57 ( P t ) source was used. The e v a l u a t i o n o f t h e

s p e c t r a was performed by a l e a s t square f i t t i n g computer program ("SIRIUS", KFKI

,

Budapest).

R e s u l t s and Discussion.- The mineral composition o f t h e b a u x i t e s examined is summarized i n Table I. From t h e X-ray d i f f r a c t i o n , DTA and TGA r e s u l t s it can be concluded t h a t t h e i r o n components contained i n t h e s e samples a r e hematite ( 6 - F e 0 )

2 3 and g o e t h i t e ( A-F~OOH) .

Figure 1 shows t h e Massbauer s p e c t r a o f sample B-1 a t room ( a ) and l i q u i d n i t r o g e n temperature ( b ) and f i g u r e 2 t h e s p e c t a o f sample B-4 measured

.

under t h e same conditions. The c h a r a c t e r i s t i c MiSssbauer parameters f o r each component o f samples B-1, B-2, B-3 and B-4 a r e summarized i n Table 11.

I n t h e a n a l y s i s of our r e s u l t s t h e known Mossbauer parameters f o r bulk and f i n e g r a i n e d $-Fe203 and

$-FeOOH 11, 2 , 3 , 4, 51 and f o r /3-FeOOH,

~'F~OOH

/ 2 / and t h e ~ e a t t h e o c t a h e d r a l ~ + site i n k a o l i n i t e o r c l a y minerals /5, 61 have been ,used. Comparing t h e Mossbauer parameters o f t h e b a u x i t e samples and t h o s e o f d i f f e r e n t i r o n oxides and oxy-hydroxides it can be e a s i l y seen t h a t t h e i r o n i s predominantly p r e s e n t a s $-!?e 0 and &-FeOOH, which i s i n accord

2 3

w i t h t h e X-ray d i f f r a c t i o n , DTA and TGA r e s u l t s . The Mossbauer s p e c t r a o f samples B-1 and B-2 a t l i q u i d n i t r o g e n temperature a r e a s u p e r p o s i t i o n o f two magnetic s p l i t t i n g components (MI and M2). A t room temperature t h e y c o n s i s t o f one magnetically s p l i t component (MI) and a quadrupole doublet ( Q ) . The e f f e c t i v e magnetic f i e l d of t h e M1 component can be a t t r i b u t e d t o f-F'e2o3 and t o t h e superparamag- n e t i c $-Fe 0 (2/. Since 6/-Fe 0 could not be

2 3 2 3

recognized by t h e o t h e r methods we b e l i e v e i n t h e second supposition. The parameters of M1 a g r e e , w i t h i n t h e limits o f experimental e r r o r , w i t h t h o s e o f $-Fe203 w i t h an average p a r t i c l e s i z e of 180

W,

a s found by Kiindig and co-workers / I / . Parameters M2 and Q o f t h e same samples a r e i n accord w i t h

t h o s e of f i - F e 0 0 ~ o r superparamagnetic

k-F~OOH

/ 7 / . G o e t h i t e shows superparamagnetism when t h e average p a r t i c l e s i z e is s m a l l e r than 1 7 0

8

/8/.

S i n c e t h e presence o f f i - F e 0 0 ~ i s not confirmed by X-ray d i f f r a c t i o n , DTA and TGA, t h e second explana- t i o n seems t o have a high p r o b a b i l i t y . The s u p e r - paramagnetic behaviour o f B-1 and B-2 samples

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19801110

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C1-306 JOURNAL DE PHYSIQUE

i n d i c a t e s t h a t i r o n oxides a r e p r e s e n t i n t h e form of f i n e p a r t i c l e s . The Miissbauer spectrum o f sample B-3 a t l i q u i d n i t r o g e n temperature c o n s i s t s o f a m&petically s p l i t component M2 and a c e n t r a l quad&

eupble l i n e p a i r Q. A t room temper t u r e

B

it h a s only i quadrupohe d o u b l e t , which can be considered a s u p e r p b s i t i o n o f two doublets. The Mossbauer p a r a h & t e r s of t h e f i r s t doublet correspond t o t h e supePparamagnetic f i n e p a r t i c l e s o f $-F~OOH, add t h e second doublet seems t o belong t o t h e i r o l i ( ~ ~ 1 ) p r e s e h t i n t h e o c t a h e d r a l p o s i t i o n s o f t h e c l a y component / 5 , 6/ i n t h e bauxite mineral. W p b e B-4 s e e k t o be homogeneous. Parameters M1 and Q dorPespond t o hematite with an average p a r t i c l e s t P e o f 180

8.

Table I : Mineralogical composition (%) o f SOIT&

Yugoslav bauxites.

VELOalY Imm 1 s I

Fig. 1 : Mijssbauer spectrum o f b a u x i t e mineral (sample B-1)

.

P i g . 2 : Mossbauer spectrum o f bauxite mineral

(sample B-4 )

.

Table I1 : Mossbauer parameters of some Yugoslav b a u x i t e s (1,s. v a l u e s a r e r e l a t i v e t o m e t a l l i c i r o n ; A i s t h e a r e a o f a l i n e expressed a s a percentage o f t h e whole a r e a c a l c u l a t e d on t h e b a s i s o f t h e l i q u i d n i t r o g e n temperature s p e c t r a ) .

References

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/ 3 / Anagnostopoulou-Konsta, A., Anagnostopoulos, T., Proc. 4 t h I n t . Congress f o r t h e Study o f Bauxites, Alumina and Aluminium, Athens, Greece, 1978, p. 1 / 4 / horeira, J.E.

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Knudsen, J.M., DC, Lima, C.G.,

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1

(1973) 151.

/7/ _' Goavert, A., Dauwe, C., De Grave, E., De S i t t e r , J., Proc. I n t . Conf. on Mijssbauer Spectroscopy, Cracow, Poland, 1975, p.' 521.

18/ Suzdalev, I.P., Proc. o f t h e Conf. on t h e Application o f t h e Mossbauer E f f e c t , Tihany, Hungary, 1969, P. 193.