Hisarli G
Department of Physical Chemistry, Istanbul University, Faculty of Engineering, 34850 Avcilar, Istanbul, Turkey.
J Colloid Interface Sci. 2005 Jan 1;281(1):18-26. doi: 10.1016/j.jcis.2004.08.089.
The objective of this work was to prepare modified adsorbents from fuller's earth (FE) by acid and alkali treatment for enhancement cationic dye adsorption. Toluidine blue (TB) was selected as adsorbate for evaluating the adsorption performance of fuller's earth samples, which was affected significantly by acid and alkali modification. The adsorption of TB was studied by visible spectra. The absorption band of the monomer at low loading of TB in FE suspension with respect to its maximum in aqueous solution is red-shifted, which is related to accessibility of dye interlamellar space in the presence of positively charged surface sites. Since all surfaces are negatively charged under experimental conditions, this effect has not been observed in acid- and alkali-treated FE suspensions. It was seen that the adsorption capacity of alkali-treated surface (FEAl) for TB was higher than these of acid-treated adsorbent (FEAc) and FE. Scanning electron micrographs (SEM) and X-ray diffraction (XRD) and fluorescence (XRF) spectra were applied to analyze the structure of the raw and modified FE samples. Absence of any identifiable amount of a crystalline compound in the solid reaction products after acid treatment was confirmed by XRD and SEM, whereas the crystalline form of FEAl was preserved. Experimental data for high-concentration regions were well described by Freundlich and Langmuir adsorption equations. The thermodynamic parameters were estimated for FE, FEAc, and FEAl by using temperature dependence of adsorption equilibrium constants.
这项工作的目的是通过酸碱处理从漂白土（FE）制备改性吸附剂，以增强阳离子染料的吸附性能。选择甲苯胺蓝（TB）作为吸附质来评估漂白土样品的吸附性能，酸碱改性对其有显著影响。通过可见光谱研究了TB的吸附情况。在FE悬浮液中低负载量的TB单体吸收带相对于其在水溶液中的最大值发生红移，这与在带正电表面位点存在下染料进入层间空间的可及性有关。由于在实验条件下所有表面均带负电，在酸碱处理的FE悬浮液中未观察到这种效应。可以看出，碱处理表面（FEAl）对TB的吸附容量高于酸处理吸附剂（FEAc）和FE。应用扫描电子显微镜（SEM）、X射线衍射（XRD）和荧光（XRF）光谱分析原始和改性FE样品的结构。XRD和SEM证实酸处理后固体反应产物中不存在任何可识别量的结晶化合物，而FEAl的晶体形式得以保留。通过Freundlich和Langmuir吸附方程很好地描述了高浓度区域的实验数据。利用吸附平衡常数的温度依赖性估算了FE、FEAc和FEAl的热力学参数。
