长链两性修饰土对Cd^(2+)的吸附动力学

Adsorption Kinetics of Cd^(2+) on Soil Modified with Long Chain Amphoteric Modifier

以两性表面修饰剂十八烷基二甲基甜菜碱(BS-18)修饰的塿土土样为研究对象,在Cd2+单一条件和与苯酚共存的复合条件下,通过不同的速度参数研究了修饰土样对Cd2+的吸附动力学特征,并对吸附机制进行探讨。结果显示,在20℃和40℃温度下单一、复合两种处理的条件下,不同修饰比例BS-18修饰土样的各速度参数均大于未修饰土样,且总体上均随着修饰比例的增加而增大,表明修饰可以显著加快塿土土样对Cd2+的吸附速度;吸附反应分为快速反应和慢速反应2个阶段,总反应平均速度Vt由快速吸附反应速度Vf和慢速吸附反应速度Vs共同决定;温度升高,单一处理Cd2+的总反应平均速度基本不变,复合处理则下降;加入苯酚可以加快Cd2+的总反应平均速度,40℃时则表现为抑制效应。Cd2+吸附速度的描述以双常数方程动力学模型为最佳模型,模型参数A、B值可以用来描述吸附速度的大小。

The experiments were carried out to find out the mechanism of adsorption kinetics of Cd2＋ on Lou soil which was modified by amphoteric suface modifying agent-Octadecane-Betaine（BS-18）.The results showed that with the single treatment and complex treatment at 20 ℃ and 40 ℃,all the velocity parameters of modified soil samples were greater than the unmodified soil samples,and the velocity increased as the increase of the modified proportion as a whole.It was showed that the absorption velocity of the soil samples on Cd2＋ could be accelerated significantly by BS-18.Adsorption reaction was divided into two stages：fast adsorption and slow adsorption,total-adsorptionvelocity（V）tof the overall reaction was decided both by reaction rate of the fast-adsorption-velocity（V）fand the slow-adsorption-velocity（V）s jointly.As the temperature rising,the total average speed of the single treatment to Cd2＋ remained basically unchanged,on the contrary,that of the complex treatment decreased.The average rate of the overall reaction could be speed up when phenol was added,but it was slowed down at 40 ℃.As for the description on the experimental data of the adsorption kinetics,the two-constant equation model was the best one,and the model parameters A and B could be used to describe the adsorption rate.