CTMAB对BS-12修饰膨润土的复配修饰模式

研究了十六烷基三甲基溴化铵(CTMA)在十二烷基二甲基甜菜碱(BS-12)修饰膨润土表面的复配模式,通过BS-12膨润土表面Ca2+/2和CTMA总浓度(SCC)变化及20℃和40℃条件下CTMA吸附量的变化可知:存在离子交换和疏水键合模式。CTMA在25%、50%、100%BS-12修饰(25BS、50BS和100BS)膨润土表面出现疏水键的临界比例(RC)分别为20.30%、11.56%和2.00%,且疏水比例随CTMA复配比例(R)及其摩尔分数的增大而增大,疏水键合模式占绝对优势的临界比例(RC′)分别为200%、150%和100%。对于BS-12单一修饰及BS-12+CTMA复配修饰比例之和,50%及200%分别是膨润土表面出现疏水键合及其占绝对优势的转折点。RRC,离子交换模式;RC≤R≤RC′,离子交换与疏水键合共存;RRC′,疏水键合占绝对优势。RC、RC′及CTMA最大吸附量(qm)呈现25BS50BS100BS特点,升温使qm减小。

Mechanism of CTMAB Modifying BS-12 Modified Bentonite

Mechanism of hexadecyl trimethyl ammonium bromide(CTMA)modifying the surface of dodecyl dimethyl betaine(BS-12)modified bentonite was studied. Judging by changes in the Sum of CTMA and Calcium ion(SCC)on the surface of BS-12 modified bentonite and CTMA adsorption as affected by temperature,20℃or 40℃,it was found that there were two modes of CTMA adsorption on BS-12 modified bentonite:ion exchanging and hydrophobic bonding. On the surface of BS-12 modified bentonites(25BS, 50BS and 100BS)varying in modification degree,25%,50% and 100%,the adsorption of CTMA in the mode of hydrophobic bonding reached its critical level in proportion(RC),that is,20.30%,11.56%and 2.00%,respectively,and the percentage of hydrophobic bonding increased with increasing CTMA modification ratio(R)and mole fraction. The critical ratio(RC′)reached 200%,150% and 100%, respectively,when hydrophobic bonding assumed its absolute dominancy. On the surface of bentonites modified with BS-12 only or with BS-12 and CTMA,50% and 200% was the turning point for hydrophobic bonding to appear and to assume absolute dominancy,Separately. When R < RC,CTMA adsorption was mainly in the ion exchanging mode;when RC ≤ R ≤ RC′,it was in both modes,ion exchanging and hydrophobic bonding;and when R > RC′,it was overwhelmingly dominated with hydrophobic bonding mode. RC、RC′ and the maximum adsorption of CTMA(qm)displayed an order of 25BS>50BS>100BS. With rising temperature,qm declined.