Purification of raw bentonites and organo-bentonite preparations is sometimes required for industrial use. Zeta (electrokinetic) potential (ζ), contact angle (wettability/hydrophobicity), and surface free energy (SFE) are important surface characteristics and vary significantly according to the applied surfactant concentration when preparing organo-bentonite. Changes in these characteristics determine the stability, behavior, and efficiency of organo-bentonites in various applications such as adsorption, composite materials, and drug-delivery systems. Knowing how much surfactant should be used to prepare organo-bentonite is, therefore, critical. The purpose of the present study was to determine the effect of concentration of the cationic surfactant cetyltrimethylammonium bromide (CTAB) adsorbed in organo-bentonite (prepared from two local and commercial raw bentonites with potential for use in adsorbent and composite materials) on the ζ potential, contact angle, and SFE profiles. The raw bentonites were purified using sedimentation and centrifugation techniques prior to preparation of the organo-bentonite. The purification results were evaluated in light of X-ray diffraction (XRD), cation exchange capacity (CEC), free swelling volume (FSV), X-ray fluorescence (XRF), and particle-size analysis data. Most of the gangue minerals (feldspar, calcite, clinoptilolite, opal, quartz, and mica) having particle size >5 μm were removed from the raw bentonites by using a one-stage sedimentation or a Falcon gravity separator (FGS). Higher yields (68.8% and 81.3% for two bentonites) were obtained with the FGS compared to sedimentation while purification levels were almost the same. ζ changed greatly from –35 mV (and –40 mV) toward 38 mV (and 40 mV) with increasing CTAB concentrations. Similar profiles were also obtained for wettability; maximum contact angles for organo-bentonites were measured as ~72–73 o , while they were 12.65 and 14.1 o for two purified and unmodified bentonites. SFEs were calculated using contact-angle data, and decreased to minimum values of 41.5–43.6 mJ/m 2 from 78.6–78.2 mJ/m 2 upon treatment of raw bentonites with CTAB. 100–130% CEC concentration was sufficient to prepare organo-bentonites with maximum hydrophobicity and positively charged surfaces.

中文翻译：

---

土耳其膨润土的纯化和有机膨润土接触角、表面自由能和 ZETA 电位曲线的研究作为 CTAB 浓度的函数

工业用途有时需要对原料膨润土和有机膨润土制剂进行纯化。Zeta（电动）电位 (ζ)、接触角（润湿性/疏水性）和表面自由能 (SFE) 是重要的表面特性，并且在制备有机膨润土时会根据所用表面活性剂浓度而显着变化。这些特性的变化决定了有机膨润土在吸附、复合材料和药物输送系统等各种应用中的稳定性、行为和效率。因此，了解应使用多少表面活性​​剂来制备有机膨润土至关重要。本研究的目的是确定阳离子表面活性剂十六烷基三甲基溴化铵 (CTAB) 的浓度对有机膨润土（由两种当地和商业原始膨润土制备，具有用于吸附剂和复合材料的潜力）吸附的浓度对 ζ 电位的影响、接触角和 SFE 曲线。在制备有机膨润土之前，使用沉降和离心技术纯化粗膨润土。根据 X 射线衍射 (XRD)、阳离子交换容量 (CEC)、自由溶胀体积 (FSV)、X 射线荧光 (XRF) 和粒度分析数据评估纯化结果。大多数脉石矿物（长石、方解石、斜发沸石、蛋白石、石英和云母）的粒径 > 通过使用一级沉降或 Falcon 重力分离器 (FGS) 从原始膨润土中去除 5 μm。与沉降相比，FGS 获得了更高的产量（两种膨润土分别为 68.8% 和 81.3%），而纯化水平几乎相同。随着 CTAB 浓度的增加，ζ 从 –35 mV（和 –40 mV）向 38 mV（和 40 mV）变化很大。润湿性也得到了类似的曲线；有机膨润土的最大接触角测量为~72-73 o ，而两种纯化和未改性膨润土的最大接触角分别为 12.65 和 14.1 o。使用接触角数据计算 SFE，在用 CTAB 处理原始膨润土后，SFE 从 78.6–78.2 mJ/m 2 降至最小值 41.5–43.6 mJ/m 2 。