Study on the thixotropy of aluminum magnesium hydroxide– Na-montmorillonite suspension

 In this paper, the thixotropy of the aqueous suspension consisting of aluminum magnesium hydroxide (AMH) possessing permanent positive charges and Na-montmorillonite possessing permanent negative charges was studied. Besides positive thixotropy and negative thixotropy, a novel thixotropic phenomenon was found, i.e., a given system studied may display, early and late, positive M28.8nthixotropic character and negative thixotropic character, we describe it as “complex thixotropy”. The content of the suspension and electrolyte may influence the forms of thixotropy of the suspension studied. Received: 4 February 1997 Accepted: 15 October 1997     

The Adsorption of Herbicides and Pesticides on Clay Minerals and Soils. Part 2. Atrazine

The adsorption of atrazine and two model compounds,2-chloropyrimidine and 3-chloropyridine on clay minerals(bentonite, montmorillonite and kaolinite), organic matter (humic acid) and soil (with and without organic matter) has beenstudied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressureliquid chromatography (HPLC) and X-ray diffraction (XRD).3-Chloropyridine, 2-chloropyrimidine and atrazine were adsorbedthrough hydrogen bonding on bentonite, montmorillonite, humic acid and soil. In addition tohydrogen bonding, protonation of 3-chloropyridine and atrazine was also observed.In the adsorption of 2-chloropyrimidine on bentonite and montmorillonitean ion exchange mechanism also occurred. No adsorption of 3-chloropyridine or 2-chloropyrimidine wasobserved on the kaolinite clay mineral.Both the clay minerals and organic matter of soil contribute tothe adsorption of organic compounds on soil but the clay minerals bentonite and montmorilloniteplay a major role in their adsorption on soil.     

Gemini表面活性剂改性蒙脱土的制备及其对水中苯酚的吸附

以3种Gemini表面活性剂(n=14,16,18)和常见的表面活性剂十六烷基三甲基溴化铵(CTAB)对钠基蒙脱土进行了有机改性.红外光谱、X射线衍射、热重分析表明,表面活性剂已成功插入蒙脱土片层间.X射线衍射结果显示,Gemini表面活性剂比CTAB表现出更强的插层能力,经CTAB,Gemini 1,Gemini 2,Gemini 3四种表面活性剂改性后,蒙脱土的面间距d001分别为2.18,3.25,3.83,3.84nm,且随着Gemini表面活性剂碳链的增长,蒙脱土的层间距增大.紫外可见光谱分析结果表明,用Gemini表面活性剂改性的蒙脱土明显比CTAB改性的蒙脱土对苯酚的吸附量大,在相同条件下,CTAB改性的蒙脱土对苯酚的吸收率为7.29%,三种Gemini表面活性剂改性的蒙脱土对苯酚的吸收率分别为41.16%,56.28%和65.14%,表明随着Gemini表面活性剂的碳链的增长,对苯酚的吸附量也相应增加.     

双酚A在高岭石和蒙脱石悬浮液中的光降解

选择两种典型的黏土矿物:高岭石和蒙脱石,研究了内分泌干扰物双酚A(BPA)在它们表面的吸附特性及光降解规律.结果表明,BPA在两种黏土矿物表面皆有少量的吸附,符合Langmuir吸附等温式.BPA在两种黏土矿悬浮液中的光降解速度大小顺序为:蒙脱石,高岭石.基于黏土矿物表面形貌的理化分析、颗粒的固体紫外-可见(UV-vis)光谱分析的结果、反应体系中羟基自由基的生成量及铁的形态变化,提出了BPA在两种黏土矿物悬浮液中光降解的可能机制.     

铽配合物——蒙脱土新型复合发光材料的插层组装、表征和发光性能

合成了铽的配合物[TbL] (ClO₄)₃(L: 2, 2, 2', 2'-四[N-苯基-N-苄基(乙酰胺)-2-氧甲基]丁醚), 通过离子交换反应将配离子[TbL]³⁺插层组装到蒙脱土(MMT)层板间, 制备出了新型复合发光材料 [TbL]³⁺-MMT．用元素分析、X射线衍射、傅氏变换红外光谱和紫外-可见光谱对材料进行了表征, 对其荧光性质进行了研究．结果表明, 复合发光材料保持了蒙脱土良好的层柱结构特征和[TbL]³⁺离子的笼状结构特征, [TbL]³⁺离子以单层形式分布于蒙脱土层板间．在紫外光激发下, 复合发光材料发出较强的绿色荧光, 其发射光谱与相应配合物的发射光谱相似．与相应纯配合物比较, 复合发光材料单位质量Tb³⁺的相对荧光强度、荧光单色性和光稳定性有显著改善, 其激发波长向可见光区发生明显位移, 说明插层组装对相应配合物的激发波长有一定的调制作用.     

Adsorption of hexavalent chromium onto montmorillonite modified with hydroxyaluminum and cetyltrimethylammonium bromide

Aluminum hydroxypolycation and cetyltrimethylammonium bromide (CTMAB) were chosen to synthesize inorganic-organic pillared montmorillonite. Three different methods were employed for the intercalation. The characteristics of natural and modified montmorillonite were determined with X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectrum (XPS), and zeta potential. It was found that aluminum hydroxypolycation and CTMAB had either entered the interlayer or sorbed on the external surface of the clay. Different intercalation orders can result in different structures. Batch adsorption of hexavalent chromium (Cr⁶⁺) onto modified montmorillonite was also investigated. The experimental data revealed that if aluminum hydroxypolycation was intercalated before CTMAB, the adsorption capacity was better than that of intercalated simultaneously or CTMAB pre-intercalated. The pH of the solution and environmental temperature had significant influences on the adsorption of Cr⁶⁺. The optimal pH for the removal was about 4, and the temperature of 298 K was best suitable. All adsorption processes were rapid during the first 5 min and reached equilibrium in 20 min. The adsorption kinetics can be described quite well by pseudo-second-order model. The adsorption rates of ACM, CAM and ACCOM were 3.814, 0.915, and 3.143 mg/g/min, respectively. The adsorption capacities of Cr⁶⁺ at 298 K on ACM, CAM, and ACCOM inferred from the Langmuir model were 11.970, 6.541, and 9.090 mg/g, respectively. The adsorption of Cr⁶⁺ on modified montmorillonite was mainly induced by the surface charge and the complexation reaction between CTMA⁺ and hexavalent chromium species at the edge of the clay particle.     

Montmorillonite K10 catalyzed highly regioselective azidolysis of epoxides: A short and efficient synthesis of phenylglycine

A series of β‐hydroxyazides were effectively synthesized from the regioselective ring opening of epoxides by sodium azide using montmorillonite K10 as a novel heterogeneous catalyst in aqueous acetonitrile in good to excellent yields. The utility of this method has been demonstrated by achieving a short synthesis of phenylglycine in 33.5% overall yield.