阳离子膨润土对分散染料的吸附动力学研究

Kinetics of Adsorption of Disperse Dyes at Cationic Bentonites

研究了阳离子膨润土(EPI-DMA/B t,PD/B t,CTMAB/B t)对分散染料(分散黄棕S-2RFL,分散大红S-R,分散蓝SBL,分散黄SE-6GFL)的吸附动力学行为.结果表明,阳离子膨润土对分散染料的吸附过程符合二阶段吸附速率方程,各阶段具有不同的吸附动力学常数(k1,k2)以及吸附活化能(Ea1,Ea2)、活化焓(ΔH1*,ΔH2*)和活化熵(ΔS1*,ΔS2*);在阳离子膨润土对分散染料的吸附过程中,k1随着阳离子插层剂烷烃链的增加而增大,表明较大的晶片层间距,疏水的层间域和表面正电荷增加均有利于吸附速率增大;对于两个吸附动力学阶段,ΔH1★<-TavΔS1★,△H2★<-TavΔS2★和ΔG★>0表明整个吸附过程活化熵的影响大于活化焓.

Kinetics of adsorption of each of disperse dyes, namely, Disperse Yellow Brown S-2RFL（ DYB S2RFL） , Disperse Red S-R（ DR S-R） , Disperse Blue SBL（ DB SBL） and Disperse Yellow SE-6GFL（ DY SE6GFL） onto cationic bentonites（EPI-DMA/Bt, PD/Bt, CTMAB/Bt） were studied. The results show that the adsorption processes follow a two-step first-order kinetic rate equation with two different rate constants （ k1 , k2 ）, energies of activation（ Ea1, Ea2 ）, enthalpies of activation（ △H^＊ , △H2^＊ ） and entropies of activation （ △S1^＊ , △S2^＊ ）. With the increasing of the alkyl of cationic intercalary reagents, the kinetic rate constants also increase, which indicate that the large space between layers, more hydrophobic interlayer environment and more positive charges of cationic bentonites are important influence factors to accelerate adsorption. It has been found that for both the adsorption kinetic steps, △H1^＊ 〈 -Tav△S1^＊,△H2^＊ 〈 -Tav△S2^＊ and △G^＊ 〉0 which means that the influence of the entropy is more remarkable than the enthalpy in the activation reaction.