Introduction:
In industrial production, a small amount of saffron T emissions will cause increase of water color
and increase of chemical oxygen consumption, so study of the decolorization of saffron T wastewater has an important
practical significance.
Methods:
MCM (Mobil Composition of Matter)-41 molecular sieve was synthesized by hydrothermal method. Power Xray diffraction and scanning electron microscopy were used to characterize the sample. Safranine T dye was adsorbed
from water by the MCM-41 prepared. Kinetics and thermodynamics of the adsorption were studied.
Results:
The MCM-41 sample presented spherical particles and regular. The BET (Brunner-Emmett-Teller) specific
surface area of the sample determined by 77 K low temperature nitrogen adsorption-desorption isotherm was 932 m2
/g. Its
average particle diameter was 110 nm. TEM (transmission electron microscopy) results showed that the sample structure
presented a honeycomb pore structure and the average pore diameter was 3.0 nm. The results showed that when room
temperature was 20 ± 1 ℃, adsorbate safranine T: adsorbent MCM-41 = 20 : 1，the optimum pH value of adsorption was
4.0 and contact time was 20 min, the adsorption rate reached 98.29% and the adsorption capacity was 19.66 mg/g. The
entropy change and enthalpy change of the adsorption system are respectively ΔS0 = 157.5 J/(mol·K); ΔH0 = 21.544
kJ/mol. When temperature was 277.15, 293.15, 303.15 K，the free energy change was respectively △G1 0 = -22.107
kJ/mol, △G2
0 = -24.627 kJ/mol, △G3
0 = -26.202 kJ/mol.
Conclusion:
The adsorption of safranine T by MCM-41 belongs to a pseudo-second-order adsorption. This adsorption
accords with the Freundlich equation and belongs to a heterogeneous adsorption. The adsorption is an endothermic
reaction of entropy increase, being spontaneous.
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