蒙脱土对聚羧酸减水剂的吸附特性及其影响因素研究

采用凝胶渗透色谱法研究了蒙脱土对聚羧酸减水剂( PCE)的吸附平衡及其影响因素。结果表明,蒙脱土对PCE具有很强的吸附作用,PCE浓度越大,其吸附量也越大。当PCE浓度为2.00 g·L-1(混凝土中PCE标准掺量)时,其吸附量为7.03 mg·g-1；当PCE为4.00 g·L-1时,其吸附量为14.61 mg·g-1；蒙脱土对PCE的最大吸附量(饱和吸附)约为21.18 mg·g-1。当PCE浓度≤2.50 g·L-1,体系pH值的变化对吸附量影响不大,但Ca2+、Mg2+金属离子的存在会增大PCE吸附量,其中Mg2+离子的影响尤为明显。蒙脱土吸附PCE是一吸热过程反应,过程符合准二级动力学方程,平衡仅需5~10 min。

Absorption Characteristics and Influencing Factors of Montmorillonite to Polycarboxylate Superplasticizer

The absorption equilibrium of polycarboxylate-type superplasticizer ( PCE ) on montmorillonite ( MMT ) and its influencing factors were investigated by the gel permeation chromatography ( GPC ) method. The results show that montmorillonite had strong adsorption for PCE and its adsorption amount increased with concentration. The adsorption amount was 7. 03 mg·g-1 as the concentration of PCE was 2. 00 g·L-1(PCE standard dosage in the concrete),While the concentration of PCE was double of the above, the adsorption amount was 14. 61 mg · g-1;The maximum adsorption capacity of PCE on montmorillonite (saturated adsorption amount) was about 21. 18 mg·g-1. The change of the pH value has little impact on adsorption quantity when the concentration of PCE was lower than 2. 50 g·L-1 . But the presence of Ca2+, Mg2+metal ions could increase the adsorptionamount of PCE among which Mg2+ion was particularly evident. Further studies had shown that adsorption of PCE on montmorillonite was an endothermic process and adsorption process conforms to the secondary dynamics equation. The adsorption could reach equilibriumjust in 5-10 min.