92
A. A. Baba et al.
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
2
3
4
5
R 2
Acid ConcentraƟon (mol/L)
RCCS
PDCS
RCSS
FDSS
PDSS
PHZ
PHF
PHS
AVM
Fig. 3 Relationship of R 2 and acid concentration: RCCS-cylindrical particles reaction control,
PDCS-Cylindrical particles product diffusion, RCSS-chemical reaction control of shrinking core
model, FDSS-film diffusion control of shrinking core model, PDSS-product diffusion control of
shrinking core model, PHZ-zero order pseudo homogeneous model, PHF-first order pseudo homogeneous model, PHS second order pseudo homogeneous model, AVM-Avrami model for Share
kaolinite in hydrochloric acid solutions. (Color figure online)
y = 0.868x - 8.086
R² = 0.999
Ea = 8.314 × 0.868 =
7.22kJ/mol
-5.8
-5.75
-5.7
-5.65
-5.6
-5.55
-5.5
-5.45
2.65
2.7
2.75
2.8
2.85
2.9
2.95
3
3.05
In k
1000/T (K -1 )
Fig. 4 Arrhenius plots for hydrochloric acid leaching process
Conclusion
In summary, mesoporous silica was prepared by the thermal treatment of kaolinite
and subsequent selective acid leaching. The prepared mesoporous silica has specific
surface area of 45.2 m
2 /g with total pore volume of 0.402 cm
3 /g and uniform pore size
at 3.67 nm maximum probability. The prepared porous silica as characterized could
find possible applications as important raw materials in adsorption and industrial
catalytic processes. Also, kinetics investigation suggests the leaching can best be