Abstract Because it is difficult to hydrophobically agglomerate fine kaolinite particles to obtain stronger, larger flocs using only dodecylamine (DDA) as a flocculant, octanoic acid (OA) was used as a synergistic flocculant to improve DDA-induced fine-kaolinite particle agglomeration. Particle settlement tests were conducted to study flocculation and synergistic flocculation behaviours of fine kaolinite particles for different DDA and/or OA concentrations. Results showed that OA strengthened DDA-induced particle agglomeration. Aggregate sedimentation rates and Stokes’ equivalent diameters exceeded 21.7 m/h and 84.4 µm, respectively. A clearer kaolinite suspension was obtained and a more compact aggregate layer accumulated within 3 min. Contact angles and Fourier-transform infrared (FTIR) spectroscopy were used to investigate kaolinite hydrophobicity before and after hydrophobisation and mechanisms of DDA and/or OA interactions with the kaolinite surface. Results suggested that faster sedimentation and larger equivalent-diameter aggregates were both related to significantly increased kaolinite-surface hydrophobicity. FTIR data confirmed that enhanced kaolinite surface hydrophobicity was owed to DDA and OA physisorption. The kaolinite micro-particle aggregation mechanism was analysed by SEM images. Kaolinite particle self-aggregation changed after OA was adsorbed on the kaolinite Si–O basal plane. Owing to DDA/OA synergistic effects, kaolinite particles hydrophobically agglomerated by actions of Al–O/Al–O and Al–O/Si–O faces, thereby promoting fine-kaolinite particle agglomeration and sedimentation. Study findings could lead to development of enhanced water-purification methods.

中文翻译：

---

十二胺与辛酸结合协同增强细高岭石颗粒疏水团聚

摘要 由于仅使用十二胺（DDA）作为絮凝剂难以疏水团聚细高岭石颗粒以获得更强、更大的絮凝物，因此使用辛酸（OA）作为协同絮凝剂来改善DDA诱导的细高岭石颗粒团聚。进行颗粒沉降试验以研究不同 DDA 和/或 OA 浓度下细高岭石颗粒的絮凝和协同絮凝行为。结果表明OA加强了DDA诱导的颗粒团聚。骨料沉降率和斯托克斯等效直径分别超过 21.7 m/h 和 84.4 µm。在 3 分钟内获得更清晰的高岭石悬浮液和更致密的骨料层。接触角和傅里叶变换红外 (FTIR) 光谱用于研究疏水化前后高岭石的疏水性以及 DDA 和/或 OA 与高岭石表面相互作用的机制。结果表明，更快的沉降和更大的等效直径聚集体都与显着增加的高岭石表面疏水性有关。FTIR 数据证实，高岭石表面疏水性的增强归因于 DDA 和 OA 物理吸附。通过SEM图像分析了高岭石微粒聚集机制。OA 吸附在高岭石 Si-O 基面上后，高岭石颗粒的自聚集发生了变化。由于 DDA/OA 的协同作用，高岭石颗粒在 Al-O/Al-O 和 Al-O/Si-O 面的作用下疏水团聚，从而促进细高岭石颗粒团聚和沉降。研究结果可能会导致开发增强的水净化方法。