Abstract Hydrophobic aggregation in cationic surfactant dispersion is an effective method for the dewatering of clay-rich tailing. The effect of head groups type and alkyl chain length on the adsorption of alkylamine cations on montmorillonite (001) surface was investigated by density functional theory (DFT), sedimentation and measurement of contact angle and adsorption quantity. The results showed that the strongest active sites were located above the six-membered oxygen ring (SOR) of montmorillonite layer, around the H atoms on N atom in the head group for alkyl primary amine (CnPA+), secondary amine (CnSA+), tertiary amine (CnTA+) cations and around H atoms in the –CH3 groups for quaternary amine (CnQA+) cation. The alkylamine cations interacted with surfaces by electrostatic attraction and hydrogen bonding where PA+, SA+, and TA+ cations formed three, two and one N Hn ⋯ Os hydrogen bonds with the montmorillonite (001) surface, respectively, while QA+ cations formed non-traditional C Hc ⋯ Os hydrogen bonds. The adsorption energies of Cn alkylamine cations decreased with the increasing substitution degree of –CH3 groups to Hn atoms in the head group. Moreover, the adsorption energies increased with the n increasing from 12 to 16, but changed slightly when beyond 16. The experimental results were consistent with the theoretically calculated results.

中文翻译：

---

烷基胺阳离子在蒙脱石（001）表面的吸附：密度泛函理论研究

摘要 阳离子表面活性剂分散体中的疏水聚集是富粘土尾矿脱水的有效方法。采用密度泛函理论(DFT)、沉降法、接触角和吸附量的测量方法研究了头基类型和烷基链长对烷基胺阳离子在蒙脱石(001)表面吸附的影响。结果表明，最强的活性位点位于蒙脱石层的六元氧环（SOR）之上，烷基伯胺（CnPA+）、仲胺（CnSA+）、叔胺头基中 N 原子上的 H 原子周围。胺 (CnTA+) 阳离子和季胺 (CnQA+) 阳离子的 –CH3 基团中的 H 原子周围。烷基胺阳离子通过静电引力和氢键与表面相互作用，其中 PA+、SA+、和TA+阳离子分别与蒙脱石(001)表面形成三个、两个和一个N Hn ⋯ Os氢键，而QA+阳离子则形成非传统的C Hc ⋯ Os氢键。Cn烷基胺阳离子的吸附能随着-CH3基团对头部Hn原子取代度的增加而降低。此外，吸附能随着n从12增加到16而增加，但超过16时变化很小。实验结果与理论计算结果一致。