Kinetics of adsorption of cationic surfactants at silica-water interface

被引:96
作者
Biswas, SC [1 ]
Chattoraj, DK [1 ]
机构
[1] Jadavpur Univ, Dept Food Technol & Biochem Engn, Calcutta 700032, W Bengal, India
关键词
adsorption kinetics; silica-water interface; cationic surfactants; rate constants; acivation parameters; diffusion coefficient;
D O I
10.1006/jcis.1998.5574
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The kinetics of adsorption of cationic surfactants (CTAB, MTAB and DTAB) at silica surface has been studied at various values of bulk surfactant concentration (C-2(t)), pH, ionic strength, and temperature and in presence of different electrolytes and urea. The adsorption process has been found to follow a two-step first-order kinetic rate equation with two different rate constants k(1) and k(2). From the variation of k(1) and k(2) with temperature, values of energies of activation E-a1 and E-a2 for both the kinetic steps have been evaluated. The corresponding values of enthalpies of activation (Delta H-1# and Delta H-2#), entropies of activation (Delta S-1# and Delta S-2#) have been evaluated using Eyring's equation for absolute reaction rate. It has been found that for both the kinetic steps, Delta H-1# < T(av)Delta S-1# and Delta H-2# < T(av)Delta S-2# which means that activation reaction is largely entropy controlled. Again, for both kinetic steps, Delta H# varies linearly with T(av)Delta S#, and Delta G(1)# and Delta G(2)# vary between 70 and 88 kJ/mole of surfactant, respectively. Thus there is a entropy-enthalpy compensation effect in the adsorption process. (C) 1998 Academic Press.
引用
收藏
页码:12 / 20
页数:9
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