5
Interaationa! Coiference of tlrc lndon*ian Chemical Sociey'
HK
Thermodinamic Parameters on the sorption of Phosphate
Ions by Montmorillonite
Jaslin lkhsan', Endang Wi-djajanti LFX, and Sunado
and
The Department of chemistry Educatiorg The Faculty of Mathematics
Sciences,
The State University of Yogyakarta
Email : j ikhsan@Ymail-com
ABSTRACT
inv.estiSated
SOiC
The sorption of phosphate by montmorillonite at 10, 30t an!
1as
of surface
il mainly d*rmine thermodinamic parameters for the formation
collected
were
Daa
"i*irg
mon'norilloniteUy
loni
phosphate
*rnpi"*", in OJaasorptlon of
bv adsomtion edge experiments investigating the effea of pH' adsorption iso$erms
.ff"c-t oI sorb"te concentraion, and acid-base titration calculating Protons
out using surhce
"i"UG'O"taken up by adsorption process. Data analysis
releaseior
"!o "T""d
shrdy
""*pr"-".i'"moaettofitt}redatacollectedin&isstudyusingthe.par.aletelobtained
study, as welt as to calculate the values of aH and AS. Previous
;;;;;;;
complexes with active
;;;;J*rrt ptogpt"t" loos fo.m"o two outer-sphereInsurface
the first comqtel . t(X$ohydrogeo bontiing'
sites of montnorillonit* tt
HrLT,
f"""r,
-ogf,
the phosphate was held-to
pi*"tt*t*tt"tg" X- sites on the tetrahedral
siloxane
through the
ocglet
t'he siond
titsolsoHtf lurt'1-1-2was -forryd
"na between the"o*pt"*'
phosphate'and variablJcharge strface l,yeogl groups at the
interaction
alumina faces. The values of aH
Jg"r.f r"ontn"rillonitecryslls and on the
kJ mol-r respectively' Since
3.765x10-7
and
are
39.?56
,".*on,
second
and
for the first
that the reactions are
concluded
can
be
it
botlre""tior,s have positive entalphy values,
sites (permanent
by
is
needed
reaction
the'first
for
energy
Large
endothermic.
on wtrich K* or
desolvate4
partially
negatively charge sites oi-montmorillonitQ to be
and are
protonated
the
Surface
ions
in
Process,
H*
by
replaced
are
other surface cations
the second
if,* ,"ray to interact phosphate iorts in the solution. Small values ofAH forsites
in the
reactions indicates *rit nyA.ogen bonds formed by phosphate 19 lOH.
easl,tV-!19rt{ from the
secorrd reaction are easity Urofen ou! and the phosphate can
X-
surface.ThevaluesofAdforthefirstandsecondreictions atel22-523dan2'393x10-2
; K. *o1:i, which are greater than -10 U mol-l and indicates that the surface reactions
occurs through dissociative mechanisms'
Keywords: temPerature, adsorption, extended constant capacitance
complexation nodet
surface
(ECCM), entalpn1\, reaction me'chanisms'
135