.
\\C Fen Bilinıleri Enstitli�Cı Den�_isi I().Cilt. 1 .sn, ı 1006
. ...
-• 1on- lsothermal Kinetic Stulh On l'lıc DchYdralinn ()f
�
NON-ISOTHERMA.L KINETI C STUDY ON
THE DEHYDRA TION
OF MECHANICALLY
ACTIVATED
ALUNITE
.. .. ı 2
Furkan KUÇUK
,Kenan
YILDIZ
1 Kortek Ltd.Şti., İ stanbul
1 •.
-Sakarya Univ., Mlih. Fak., Metal u�ji ve M aiz. Müh., Adapazarı. Tel:264 2955770, k�nyi 1:-.({! S�Ü ... arya.ed�ı.tr
ABSTRACT
ln this sttıd), a l u n i tc ore \\'as activated nıcc h a n ically in an attritor for 15 nı i n and thcn therınal a nalysis vvas carried out on
both non-activat ed and activatcd aluııitc i n diffcrent hcating rates. Usiııg oftherıııograviınetry data, the de hydration kinetics
of al un it e \Vas studying ,,·j th 1\. AS (K i s se n ger-Akahi ra-S uno se) eq u at i on. l'he effect of nı ec han i ca 1 acti vation on the
deh� dratİOn 1-...inctic Of' alunite and its thernıal behaVİOllf \Yere İnvestigatcd.
hc�·words- alu n i te. dehy dration. ınechani cal activation, non-isothern1al k i netic
• • • • • • • •• •
MEKANIK AKTIVE EDILMIŞ ALUNITIN DEHIDRATASYONU UZERINE
• • •
IZOTERMAL OLMAYAN KINETIK ÇALIŞMASI
••
OZET
Bu çalışnıada, a l u n it ccvheri bir atritörde 15 dakika süreyle aktive edil nıiş, daha sonra farklı ısıt nıa hızlarında henı aktive
cdilnıcnıiş heııı de aktive edil nıiş a l u nitin ternıaJ analizleri alınnııştır. Tcrınogravin1etrik data kull anılarak. a
l
tınitindehidratasyon k i nctiği K.AS (Kissenger-Ak ahira-Sunose) denklenıiyle incelennıiştir. A l u nitin dehidratasyon kinetiği ve terınal davranışı üzerine nıekan ik aktivasyon u n etkisi araştırılnııştır.
Anahtar 1\.elimcler- Al un it, dehidratasyon, nıekanik aktivasyoıı, izeterınal al nıayan k i netik
1. INTRODliCTION
ı\lunitc is one o f the nı inerals of the jarosite group. l t is a
pot cı s s i u nı-a 1 u nı o c c ur i n g ge n er a l l y i n r h o ın b o h e dr a 1 an d
hexcıgona 1 c rys ta ls. l t s che nı i cal fo rnıul a is
KAl
1
(S
O
.
ı)
�
(OH
)tı, and as a source of a l u ın, potass i u nı andaluıııinuııı, it i s a conınıercial raw nıaterial for the cheınİcal
industry. In Turkey, alun ite reserves are Iocated in
Şebinkarahisar-Gi resun ( 15-20 m i l l ion tons ),
Şaphane-1\.Litahya (7 nıi l l ion ton s ) and Foça-Jzın ir (5 nıi l l ion tons)
regions ll -3].
The stnıcturc o f alunite contai ns alunıi n i unı sulphate and potassiunı sulphate, both ofthenı dissolve in water.
37
However, alunite does not d i s solve i n water, acid s and bases u n less calci ned. Alunite calci ned at temperatures over 500°C d issolves due to the decompos i tion of the struct u re.
lt i s \1\1 i d e 1 y u s e d i n the nı a n u fa ct ur i n g of a 1 u nı i n i u nı
su lphate, potassiunı alunı, a l u n1İna a nd potassi unı sulphate.
The ore calci ned at 600-650°C i s converted to the a bove nıe n t io ned products by acidic and basic extractions. A t one
of t he production method of a l u nı i n a fronı a l unite, the ore i s
calci ned at 600-650°C and extracted with sulphuric acid. After Ieaching the sol id part i s caicined. This calc i n e is
cxtracted w ith h ot water to renıove the soluble potass i u nı
S '\C· Fen Bilimleri �:nstitüsli Dergi� i 1 ().( 'ilt. I.Sayı 2006
The nıcchaııical activation or nıincrals ıııakc� it possiblc to r�ducc their dccnnıpnsition tcınpcr,ıturc nr ct'uıses such <:1
d c�rcc uf d i�t1rdcri ng. The nı i ne ra ı acti' at inn ı cad s tu n
� �
pt) s i.t i ' e i n fl u e n c c o n t lı e 1 ca c lı i n g re a c t i o n k i n ct i c s a n d to
�n incrcasc in the ıncasurcd surf'ace area ı(>
j.
\ lcclıanicalacti\'atinn of ıııincraıs b' iııtcnsive t!.riııdiıı0. is a non-� � .._
t ra d it i o n a ı '' a) o r i ııtlu c n c i n g t h c p ro c e s� c s i n c x t ra ct i v c
ıııetallurg). Creation or finc particle ' inereeL c in spccific surface area and forıııatinn nf defccti\ c structurcs are aıııonQ the ıııain t'actors '' hich acccıeratc lc.:achiıı� in - ._
h) droıııetallurg:. Soıııc spccial rcginıc� of grinciing ca use
not on ı: the ph: �ico-clıcıııicrll traıısforıııatioııs but nl�o the changes in tlıe clıenıical COillpO::,iti�)flS of the acti\ ated ııı i n c r�ı b
171.
lıı thi� stu(l\ . ıll1n-i��Hherın,ll kinctic stud\ t)J1 the r �
dclı\ dration l)r hnth noıı-{ıt:ti\ atcd and acti\ atcd �ılunite "a"
iıı' c�ti�atcd. �
2. 1 '1 ah.' ri a 1
\ıuııite t1re ll"ıcd in the �tud) \\ as providcd fronı l)ostcl \ıuııııı1uııı \ulphatc I td. in Şaphaııc-KCıtah)a. Turkey. lt
"�t'\ crtı'\lıcd and gn)uııd and sic\ cd tn -100 pııı size. ·rııc
chcn1İL�ıl"' u"cd in the e'\tractioıı �tud\ and in the aııal\�i� r
-'' ere �)htained l'n)ııı f\.lcrcl-. Clıcınical Co. The che nı i cal
a n a h "' i "' o r l ıl un i t c t H c i .., 1 " . 9 R 0 o \ ı : CJ , . ...ı . 6 6 o o K .:-C) .
-l:' .:'ü0 o SiC)". 18.0�0 o SO�. O.ô 1° o Fe�() i.
O.
t 6° oc·.ıc>· \Jg() and S.00°o li::C)
181.
2.2 E\pcrinırntal Procedurc
\Jcclı�1111Cal llCtİ\ atiun ur �lltıııite orc \\3S perlt)J'J11Cd İn �\ll aıtritor (')tirrin� hall ıııil\) undcr h.1llo"ing cnndition"ı: �
'--\\Cight ni' the �aıııpk: ı 0 g. \\ Cight of balls: .200 g of
�t�lıı1lc"'"' �tccl hall.., '' ith 5.5 nını in dianıctcr. �riııdin!! t1nıc: �
-O nııd
1 �
ın in. stırrıng rtHc: X.50 rpnı.\:-ra) dillr�1ctioıı aııalysis ,,·en.� pcrforıııed usiııg a Rigaku l ltıııı<l '\-rıt\ di ITılıctonıcter and Cu Ku racliatioıı \\J"ı usccl ( �() k\'. i O ııı:\ ). l'lıcrnıal analysis studies ( TC1 and r)Tr\) '' a.., pcrf<.>rıned us i ııg � ctzsc lı R T-1 500C TG 1\/I)T:\ a p p arat u � at d i IT c r c n t
(
S' ' , 1 O c , 1 5 c an d1
O
' 'C/ ı n i n ) lı ca t i n Q._
rat es.
2.3. l�inctir Stu(h bv .. - Ther·n1oaraYimetrv � "'
De h� dration of �ol i ds is the �ubjcct of nı an; k inetic studies. lt lıclp.., lt) uııder�tand the follo\\ ing deconıpo�itil)Jl nıcchaııi�nı: .\(�) •B(s) ·C( ... u_) .
1'\c'�n- ı�nth�rmal K inetic Sıud] On l'hc Dch\dratı 1
\lcclwnicall� /\cti\ilkU .\lunıı
�
. f'. "-uThis i� a nıodcl-frec nıcthud. \\ hich iınoh.cs nıca�urin� tcıııpcratures currcspuncting to ri\cd vaıues or u
i·r
c\pcrinıcnts <H dirtcrcııt hcatiııg ratcs
(f3).
The acti\,cııeruies (1·:) can be cnlculated accordiııo � b to
i�oconvertion::1l ıncthocls of KAS (Kissenger-Akal ...
S u n o s c ). F ri c d n ı a n a n d O/ a \Va ı 9 J . In k i n ct i c st u d\' 0 f ı
noıı-acti\·atcd and acti\ atecl alunite, K;\S cquation was � to detcrıııine the actiYation cncrgy of the dehydraı rcactıons.
The kinctic nındel or dclıydratioıı that occurs ın n
i"ılHhcrınal cnndıtıon� i� dc�cribcd b) KA cq. (ı),
1'
\ ı . -ı In R�.du)l .. • \ R r(
1· ı ( ı )\\ here (J. İ'-1 lhL' �.k·.�11'L'e ur�nııver�ioıı,
f1
is the lıcatinQ rat � k.ınin . \ ı� the pı c-c'\poıı�ntial factor in min-. 1tL· nı pc rat u r L' i n k , R ı s t lı c g a � c o n st ant, E i a ct i\ a
cner!..!\ in k.l.nıtlı and ... .. "--!!.(<ı.) i� the iııtce.ral fnrnı """"' of the
\ v h i c lı i s t h c ı c� lL'1 i u n ıı H) d c 1.
\ccordin� ll) the <.ıbovc ıncııtioncd equatıon, the plo
In (
r)
ı)
\ L'l' s ll� ı o o o rr c or re sp o d i 11 g to d i ff ecorner�ion� ıı c�ın he obt<1iııcd bv a linear regrcss .. '-- of 1
�quare ıııctllod. l lıc acti\'atioıı cnergy (E) can be calcul
l'r o 111 t ll c s
1
o p L' n 1 L' \ c r: ı i ll c \\ i t h b ct te r l i n e ar c o r re l acnefticicnt (r)
lt>.!Oj.
llıi� lllL'tlıud i"' u�cd to calcuıatc the activation energ� c
procc�"' \\ ıtlıl)llt it\ kiııetic ıııechanisnı.
3. RESl·ı:rs .\�D J)IS('liSSIO�
3. 1 . :X- Ra' D i IT ra r t i o n :\ na 1 y s i s
I he "\-ra\ dil'lractinn anal\ sis of noıı-acti,ated -
-acti\'�ltcd alunite nrc i� !.!.ivcıı in Figure ._ � 1. Considerin2
-pc ak .., o r n n ll-d ct i ' at c d an d a ct i va te d a ı u n it e. it c .. 11
clcarly �ccıı th<.ıt all diffraction peaks of aluııite get sh
<ı n cr ı n c c ll an i ca ı a ct i va t i o ıı . T h i s i s d u e to t h c start ı n
�ıınorplıisatioıı in alunitc structure. In literaturcl6.7.11
\\as re pu rt cd that the ın ec han i ca ı acti vation res u ı te d ir
anıorphi�ation or nıincral particles. The peak� of Si'
not ancctcd \\ ith ıncehanical activation because o
_·\C' Fen Biliınlcri Enstitüsü Dcr�i ·i l O.Cilt. l.Savı ?006 .• •. ,i ... • ı;l) :: - ---!J. � ; ,r,,. �./ı 1 W) ı ı ll� ı n Hı ı .. ıt llı1 ·H.ı S· 1.\ı·:..�l lllı i(ıfj} 1---+· ---·-· ·---� i
ı
� i]
.
'"'.· '.
: -.....
......
.....
...
....
. .....
....
....
� ..
.. ...
�...
......
...
..
...
...
..
... . . ..
...
...
...
..
.....
. .ı
O \ : �' -jÔI' -:::· k • ·-·--. .. .. --· .. "" .:ı :. ' ' .H V� • • A 1 l �� � ; · S " ... .� � l: ' • .. ' ... .; ı '=: · ... : ,.._ l C' .. (' ,.. ... , �J- #o w -... •• 1 • • '""' •• ... • • - • -.
... . • • ,{;, i )� .v ';; . "; ,: ::> ::> .:4 ; l l ' ; ı � ..J '- ' .... ,:lt t , ' -" " l > "'ı., � � ..., � "-'!,,_.
... � ._..
"'-.,..__,-' ... .... __ """"'_��"" "-''-"·_;�·-�· '-.. 1 ,; .--.. � : . .. i ··ll.· ·.tl. ..
: . ,,. t·. �..: : (a) 2 TIIETA i ı ı ı ... -··· ... ... ·-··· ... ,, • .. . ""' . ·"":'· .� .
. .-
1
... .. ... . ... .....
....
. . . � ... .... ... .... ... ... . � . . . �-...
... _ ... ... -... _ ... ....
.... ... .. -... -... � ... .. . ı:ı.c . '·' ! . . . .. . - . . .. .. ..
t ,. ., • l - .. .,.,.. � O •• O ,..,.,,,,,, ,,.,..,, ''''"''''''_..,.,, H"'-'''' ••••••o•••u••·"••••••••oo. �- •. , ... ı, ! . 1 .;1 , ı ı§
.
':
·•· --
...
""j"'"
...-...
ı
o . t . . .... i G . Jll
. . ... ! (b) ı 1 . · l J ' ! • ı __,• ,..,___ ... < . ... ! ...ı. • " .L 1 .... ... ! . ... '" ... �...ry �... •.. .....
. !��,�. ··f:lt"�.-...---'.ı..ty"-l: �.� .. � �� ... _.... ... "" . . . -. •. .� 1 . ...
'": ·-.· 2 TIIEIA -.. _ ·-···· ... --···-···"'"-'-... ·----·--·---··...J !Fi!!ııı'l' ı. \-ı,ı\ dıl'ı'r-tcıı�ııı p.ıttcrn .... lır (�1) ıwn-actı\atcJ alunıte and (h)
.ıc!l\:ıll'd ,llunııc
3.2. Therınal l)cconıpo ition of Non-activated and
..\ctivattı.d Alunite
The tlıcrınal analysis (TC) and DT A) of non-activated and
meclıanically activatcd aluııite ore is given in Figure 2 . The
DT:\ cun·cs f()r both al u ni te o res show two endotherınic
pcak aııd t)ne sıııalı cxothernıic peak. The fırst endothernıic
pc<th\ at �1bout 560°C for non-activated and 545°C for lll'tİ\�ıtcd alunitc ores are strong and sharp. This is due to the dehyclration of the structural \Vater and the
transi(H·ınation of alunitc into KAI(S04h and an1orphous
.\ 1�0 ,. a� giveıı in Eq. (').
K \ 1
d
S ( > 1)
"'
(C)
H)
c) � KA ı(S
O 4)
.., + A ı , O 3 + 3 H 2 O-
-l'lıc cxothcrn1ic peaks at about 787°C for both alunite ore
appcar inııned iate Iy beforc the second endotherınic peak at
ahout 820 C· for non-activated aıunite o re and 8 1 0°C for
activated alunitc orc.
....
39
Non- lsothern1a\ K i net i c Study On The Dehydration ()f
Mechanically Acti atcd Alunite. F. Küçük
TC (%ı) N.ı..-\-A.hınite (fG) !\ıL-\.-Al:unite (DTA) DTA
O Ql:ı' � • -...,.":"'""'' • ••••-.•••u•-•••"• ,,.-• ••� T�""' o o ... ... _ ... ... . ' "-� -_ .. _.,.. ... " ... 1 ...
.
... ' ...
, ... , - ' 1 • ' '·*"' _.,.. ... .._ ··---.. /.-;.--�- '.
, ı ı' ·-, '"'-. .. /.� / ... ----- _ .... ··--._ l/"\\,
··.' 1"\:
·
ı
.
ı' ... ... ıt.lA ·' 1 •t (T;�-:)-· -··=�·� - ·. l ·t ,. ,� '/. u· -.ı.."'l..l.unı e v ;/ ·-. ' 1 . · ı l l . r' . .. .... ... '. • . ;, .... ' ,�:; ·�'l .1 ··.1 ı1
� . .1/y
r . • • • • � .. (· , ·· ... ı.... .. .. . . .._. -.\
1
1
.
, ... .. ... .... • • • •.• 1• V J •• •. \/
'
ı�
·
···.. ,Lr
ı
. -. 1 i . \·,ıJ / ) .. t:) ( • � . . :·.1
ı ! ··: ı,\ ,,� ı 1 N ·' ·' 1 • · .•'ı\ l 1 1 .LA-.&.-u. unı te · · .
. •ıt ,. ı · , •. ıı.: ' ··,\ ,.-/ ' J (DT.ı.." .} · ... "> ••• . � ,•; � ·.· . . /) . . ... \\ f( ""'-'-.. �:.:;.. .. ·· -."' .... .. .... ··. ıx• ··:·· . .. ......... ... ..... . , ... . >J."'ı'ı Oôl. .. � '·'·' "' $, .... . ·,' . ... ... . . � ,.,.. Tfn.IPER.ı..-\.UTRE (C) ..
.
. .. " . .. ' "'* ... �..
-. . .. '�-# ""'�··Figurc 2. Therınal analysis ( TG and OTA) or non-acti\ ated (NA-al u n ıle)
and acti\'uted alunite (MA-Alunite)
lt was stated [ 4] that this s nı all exothern1ic pea k at about
787oc was probably caused by the recrystallization of
l(Al(S0-+)2 into K3Al(S0-ıh and AI2(SO.ıh, as given in Eq .
(3 )�
'>KAI(S04 ) , � 7j' K 3Al(S0.1 )3 + 7j' Al, (S04 ) , (3)
The second endotherınic peak at 820°C for non-activated
alunite ore is due to the desulphation by \vhich K,Al(S0_ı)3
and Al2(SO-+), decoınposc into K2S0.1 and Al203, as given
in Eq. (4) and Eq. (5) .
7j'K3Al(S04)3 � K2S04 + /j' Al,(S04)3
_%
A12(S04)3 � 7j Al203 +2S02 +02(-+)
(5)
The TG curve for non-activated alunite ore shovvs two steps of weight losses correspond ing to the two endotherınic peaks. The weight losses are about 8°/o for the fırst
endotherın ( dehydration) and about 22% as the total weight
lo ss after the second endothernı ( desulphation ). On the comı'trary, the dehydration of ınechanical Iy activated al un i te ore is started fronı 1 00°C. This is result of anıorphisation
and structural d isordering, provid ing w ith ın ec han i cal activation. l�he \Veight loss up to 650°C is about
8�/o
foractivated aıunite ore. The nıechanical activation affected
inıpoıtantly on dehydration behaviour of alunite ore.
The dehydration temperature decreases about 15°C in
n1echanicaıty activated alunite ore. The most İnıportant
point about the dehydration of mechanicaiJy activated
alunite is i ts starting fronı 1 00°C, due to amorphisation and
structural di sordering in alunite. In a previous study[ l l] it
vvas investigated the effect of tiıne of mechanical activation .._
on the thernıal decoınposition of alunite ore and it was �
observed that J 5 nı in of nıechanical activation is enough to
Si\ Cl Fen Bilimleri Enstitüsü Dergisi ı O.Cilt. ı .Sayı 7()()()
3.3. Non-isotherınal l�inctic Study
For the dehydration kinctic study of non-activated and activated alunite, their TG datas \verc uscd in non isothernıal conditions. The dehydration part of non activated aluııite is given in Figurc 3 and that or activated aıunite in Figure 4. According to rf('J data. u (deQrec of
canv ersion or rat i o of de h: drcHion) and rclated tcnıı;erature ' a ı u e s ( K ) '' c re ı i st c cl i n Ta b 1 c 1 . , -- -bl · --· 100 ı==-:.:;::-:=-;--: _::-_ _--- ---, -- ._ • ı•) • )t,.
L---. - ... -... ... ' . ' " \. \.\ \ \ \ \ \ \ :=, f /ıı ll ll 1 Ll ı /rııırı 11ı l /111111 -_· _ -__ :: _o-��
\ . \\ \ \ \ . \ \ \ \ \\ \. , , " ... ... ... -... _ -- --- -. ��+---.---,.---,---=::::::::::...---l
'\IJO 650 'I ftnp t·ranu·<·. 0 (_'1· i ı,! un· J. 1 <i L'lır \ L' �,r ıhııı-�ıL·tı\ ;.ıtcJ ;.ı lunıle
� '/ --· ı t 12 ııııı <)(. :;, ı irnırı 1111 lrnııı --- ıı_.Liırıırı - - ·- .:!0 (!ının 9(1
+----.,---,.----.,.----r---.---�
o 100 ,:\00 -ı o o �o o 600Figurc .t. I'G c un e ol' uctıyateJ ulunite
According to the equation( 1 )� the plots of ln(�/T�) versus
l 000/T corrcspoding to different conversions a are given in
Figure 5 for non-activated alunite and in Figure 6 for
activated alunite. The activation energies (E) were
calculated fronı the slope of every line and regression
coeffıcients were listed in Tab le 1.
�
Non- Isothcrmal K inetic Study Oıı 1 he Deh�dratıoı
tvlechanicnll) Acti,atcd Alunite. f Ku
As see n fronı Tab le 2, the activation eneroy \ alue
deydration reaction of non-activated al un i te� are van ır
betwcen 173.5 and 303.9 kJ/nıol, corresponding to
diff�r
conversions. These values for activated alunite are \af\r
bet\veen 41.16 and 778.29 kJ/nıol. In literature,
su�h
rclationship between activation energy and
d
egreeconversıon \Vas stated [ 12, 131. It can be said that 1
activation energy of dehydration reaction of non-actıva
alunitc is about 780-300 kJ/ıııol.
On the contrary, the activation encrgy values are var) in!!
,,·ide ranges. The canıparison of the acti ation en
;
r\ a 1 u e s for n o n-a ct i va te d a n d a ct i va tc d alu n i te i s u. i, e ıı
F i� ur c 7. �
�
Ta h le 1. ıı and T( K) 'alu es lör d ı rrc re nt lıeatıng rat � c ·
T�ınperaturc (K)
Noıı-acti\'ated aluıııte Actı\ ated alunıte
1 lcatıııg rateW. Klıııiıı) ı kating ratecr�. K ının)
(J, 5 lO 15 20 5 lll 15 (). 1 7 6..J. 6 785.7 796.ı 80 1.6 393.6 -ı 13 6 -l24 2 () 2 792.6 806.8 8 1 .'1.2 8ı9.J ..J42.0 456.1 46Cı.O xo..ı .5 8 ı 7. ı 824.1 82R.7 ,ı8R.6 5 1 ı . 1 5 18.7 O-t X 1 1 <) 82-t j R31.7 8] (ı . ..t �'i6.9 587.8 '\ 9-t :; () " X ıR 1 831.1 838.() 84 3 5 (ı '\2. ı 69ı ı 694 3 -- -() (ı X23 9 817 1 84 _- '\ X5ı ı ı 7Jı ı 7 54 -ı 760 ı () 7 x-w 1 X-t ·t 'i R'\3 8 R(ıO 2 7Mı.3 7X3 7 788.2 r-ll X X -12 () 853 l) R(ı..J <) 872 6 78..J. 7 8 ()() 1 803 <) ,o -!35 � 4 77 lJ -... ı ' ) .. 1 61 o .. 713 . 771 ı 79-t 9 �WlJ.9 L_ __ 40 -10.! ---�-.... -10 .ı -10 () -,� 11.0 = -11.� � -1 L 4 -J J () -J l,S 0.8 0.7 c),
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\ ' \ \ \ \ \ \ \ • -12 .O t--..,----.--.--.--..----,----r--ı--,.---1 ıooo·T ıl K)Figurc 5. The plots of ln(f3/T2) ,·ersus 1 000/T correspodıng to dı n
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S,\C Fen Bilinıleri Enstitüsü Der�isi l(LCilt. l.SaYı '006
'! -. c::. -,.. � � -')_(1 �---, -·1.:' -10.0 -10 � . J t.O -ll� 1],6 n :=ı - . - . o ı '( \ ı çı ··';. 1
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L'Ctll\ersıcJilS u rl)r acti\�Hed aluıııtc
Tahir 2. :'\cı ı' atH)Il encrgıcs (E) and r ,·alues lt"'lr non-aclİYated and
.h.:tl\ .ILL'd .ııunıle
. nıı-nc tı \'at ed al un i tc ActiYated alunite
ı! l: (ld/nıol) r ı:: (k.l/ml11) r --nı ı73.5 0.99 ı 6 4ı.l6 0.997 ı (l 2 1 67.8 () 9982 6ı.09 0.9781 (ı ) 302. ı (). 9988 63. ı 7 0.9845 0.-t 303.9 0.999' 64.-+ ı 0.9648 () 5 297.6 0.999] 76. ı o 0.930 ı .. ( ı (' '�'.6 0.9999 ı )_ --, '-+ 0.9755 --- -·--· -- .. _ +-·- -· -() 7 -1-8 .) . ( 8 0.9997 233.06 0.9769 tl X ")64.3 0.9828 278.29 0.975X . ��o oy---, -o �(J() ,.. -LOO • no n· acÜ; al ed alu rı ı te --::::- aı::t ıva te d alu n ıtf!
u +---�-�--�-...,...---.---�-�-�-�
0.0 0.1 0.2 0.3 0.� 0.5 0,6 o -' 0,8 0,9
a.
Figurr 7. Coınrarison of activation energies calculated by KAS equation
ı·ur 11L)I1<ıctı\·ated and activcıted alunite
41
Non-lsotherınal Kinctic Stud\ Un lhc lkh\drc.lti�H1 - ()!'
Mechanicc.1ll) ;\eti\ c.1tcd ;\\unitc. F. KL·ıçük
As seen in Figure 7, the activatiön energy values are in the range of 41 and 76 kJ/nıol, up to 0.5 of o.. A fter a=0.5, this value was increased sharply to a bout 278 kJ/nıol. The lo\ver activation energy values of dehydration of activated alunite, up to a=0.5, than that of non-activated alunite is due to arnorphization and structural defornıation in alunite during the nıechanical activation process. lt \Vas observed with x ray diffraction ana lysis that the re was no 1 00°/o of anıorphization in structure, therefore the activation energy value increased to about 278 kJ/mol.
4. CONC'LUSIONS
It \vas deternıined with x-ray difTraction analvsis that the
alunite structure was partially anıorphized by nıechanical
activation.
M ec han i cal activation affected on teınperature ran ge of dehydration reaction of alunite. l�his reaction occured after 1 00°C for activated alunite� while it \vas occured after 450°C for non-activated alunitc. This behaviour was supported with TG and DT A .
The dehydration kinetics of non-activated and activated alunite was investigated by non-isothernıal nıethod, \Vİthout kinetic nıechanism. The activation energy values of dehydration of non-activated a lunite were calculated betvveen 173 and 264 kJ/ınol by using of KAS (Kissenger Akahira-Sunose) kinetic equation. The mechanical activation pronıoted soıne aınorphization, but not coınpletely, and structural disorders in alunite. This pretreatnıent decreased the activation energy val u es to the range or 41-76 kJ/ınoL due to aınorphization, up to u
(degree of conversion)=0.5 and then activation energy vvas İncreased tO actual values SO that there \V3S 110
1
ÜÜ01o aınorphization in alunite stnıcture.REFEI{ENCES
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