蒙脱土表面键合配位体固相萃取填料的制备及其对重金属离子的吸附性能

通过酸洗、硅烷偶联剂表面活化、键合苯甲酰异硫氰酸酯对蒙脱土进行改性,制得新型固相萃取(SPE)材料。 采用红外光谱、扫描电子显微镜、X射线光电子能谱表征了改性蒙脱土的结构和形貌。 考察了制备的SPE填料对水中As³⁺、Bi³⁺、Cu²⁺、Sb³⁺、Sn²⁺和Pb²⁺的吸附性能,确定了最佳固相萃取条件,对6种金属离子吸附容量分别为10.83、11.92、12.67、10.43、10.01及10.54 mg/g。 通过SPE与电感耦合等离子体质谱联用测定了样品中As³⁺、Bi³⁺、Cu²⁺、Sb³⁺、Sn²⁺和Pb²⁺ 6种重金属离子的含量,检出限分别为0.024、0.013、0.075、0.037、0.011和0.064 μg/L。     

LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES MODIFIED BY ETHYLENE COPOLYMERS： EFFECTS OF FUNCTIONALIZED SEGMENTS ON MORPHOLOGY

Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene （LDPE）, ethylene copolymer and organoclay. X-ray diffraction （XRD） and transmission electron microscopy （TEM） were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer.     

Polyvinyl pyridines as flocculating agents

Summary High molecular weight poly 2- and 4-vinyl pyridines were synthesized by ionic polymerisation and their flocculation efficiency tested against kaolin and silica dispersions at pH 3. Low additions of the polymers, around 3 parts per 10₃ parts solid, destabilize the dispersions and clarify silica dispersions to a remarkable extent; however, over-addition of polymer leads to partial restabilization. The flocculation efficiency improves with increase of solids content, especially with clay dispersions. Flocculation efficiency increases with polymer molecular weight, especially over the lower part of the range covered, but is relatively independent of pH in the range 2–4. Quaternization of poly(4-vinyl pyridine) with bromobutane produces a good flocculant for aqueous silica dispersions in which the degree of restabilization on over-dosing depends on the KCI content. TheN-oxide derivatives of the vinyl pyridine polymers do not affect the colloidal stability of silica dispersions. The observations are interpreted in terms of bridging flocculation by the cationic polymer molecules between anionic surface sites on the solid particles.     

On the electrophoretic mobility and zeta potential of montmorillonite in non-aqueous media

Experimental results on the electrophoretic velocity and mobility of Ca-montmorillonite in 2-propanol are reported. The variation of the electrophoretic velocity with the externally applied electric field and the particle size range, at constant volume fraction and temperature, is considered. Given the difficulties for determining the types and concentrations of ions present in these liquid media, two methods are discussed for the estimation of the double layer thickness and hence the product, necessary for the determination of the zeta potential () of the interface. Although both methods of calculation yield different values of, the results for the zeta potential are very similar in the regions of and characteristic of our systems. The application to the experimental data of three theoretical relations between electrophoretic mobility and zeta potential is also discussed.     

Cure behavior of epoxy resin/MMT/DETA nanocomposite

The Flory's gelation theory, non-equilibrium thermodynamic fluctuation theory and Avrami equation have been used to predict the gel time t _g and the cure behavior of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposites at various temperatures and organo-montmorillonite loadings. The theoretical prediction is in good agreement with the experimental results obtained by dynamic torsional vibration method, and the results show that the addition of organo-montmorillonite reduces the gelation time t _gand increases the rate of curing reaction, the value of k, and half-time of cure after gelation point t_1/2 decreases with the increasing of cure temperature, and the value of n is ~2 at the lower temperatures (<60°C) and decreases to ~1.5 as the temperature increases, and the addition of organo-montmorillonite decreases the apparent activation energy of the cure reaction before gelation point, but has no apparent effect on the apparent activation energy of the cure reaction after gelation point. There is no special curing process required for the formation of epoxy resin/organo-montmorillonite/diethylenetriamine intercalated nanocomposite. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electrodeposition of mercury film on electrodes modified with clay minerals

A new type of carbon paste electrode modified with clay mineral and covered with a mercury film is presented in this work. Electrodeposition of the mercury film was performed on the carbon paste electrode modified with montmorillonite. The mercury film was deposited by both electrodeposition in situ and a preliminary electrodeposition. The pre-deposited film of mercury showed to be suitable for anodic stripping voltammetry. An open-circuit sorption of Cd, Pb, and Cu with subsequent anodic stripping voltammetry exhibited higher current responses of metals. Besides the enhanced sensitivity superior separation of the current responses during a simultaneous stripping of metals is expected to be achieved by means of the newly prepared electrode. Presented at the 57th Congress of Chemical Societies, Tatranské Matliare, 4–8 September 2005.     

改性凹凸棒的制备及对砷离子的吸附研究

针对日益严重的砷离子污染问题，本文采用灵敏简便的原子荧光分析法，探究了凹凸棒石粘土吸附剂对砷离子的吸附性能，测定了pH、吸附时间、砷离子的初始浓度等因素对凹凸棒石粘土负载铁氧化物对砷离子吸附能力的影响，并通过SEM、EDX、FTIR对所制得的吸附剂进行了表征研究，同时进行了吸附动力学和吸附等温模型的分析。研究结果表明，改性后的凹凸棒对砷离子的吸附性能有了显著提升，在较低浓度时吸附效率可达98%，该吸附符合Langmuir等温吸附模型和准二级动力学方程。     

Intercalation and exchange reactions of clay minerals and non-clay layer compounds

Presently, a large variety of layered materials are synthesized that are able to intercalate neutral guest molecules or to exchange inorganic and organic ions for interlayer ions. Several of these materials are also found as minerals.The intracrystalline reactivity of a few selected compounds will be described and compared to clay minerals:

累托石/聚丙烯插层纳米复合材料的制备与性能

采用熔融共混法制备了有机改性累托石 (OREC)粘土 均聚聚丙烯 (PP)纳米复合材料 ,以X 射线衍射分析 (XRD)及透射电子显微镜分析 (TEM)观察了复合材料的相貌结构 ,研究了复合材料的力学性能及热性能 .结果表明 ,OREC在添加份数较少时可与均聚聚丙烯熔融插层形成插层型聚丙烯纳米复合材料 ,该复合材料与纯PP相比 ,具有较高的拉伸强度、断裂伸长率及冲击强度 .在有机粘土添加 2 %时 ,复合材料的拉伸强度、断裂伸长率、冲击强度最高 ,与纯PP相比 ,2 %添加量的聚丙烯纳米复合材料拉伸强度提高 6 5 7% ,断裂伸长率提高 2 89 3% ,冲击强度提高 14 1% ,10 %失重率时对应的热分解温度提高 50K .     

Comparison of solution-blending and melt-intercalation for the preparation of poly(ethylene-co-acrylic acid)/organoclay nanocomposites

Ethylene-acrylic acid copolymers (EAAs) and commercial montmorillonite clays organically modified with dimethyldihydrogenatedtallowammonium ions (Cloisite^® 15A and 20A) were used for the synthesis of nanocomposites by melt-compounding, static melting of polymer/clay mixtures and solution-intercalation in order to compare the effectiveness of these procedures and to shed light on the thermodynamics and the kinetics of the intercalation process. The preparation from solution was made by the use of several solvents, such as toluene, xylene, chloroform, etc., which were then removed from the hybrids by precipitation in different non-solvents or by evaporation. Particular attention was paid to the effect of the thermal treatments which are often used when processing the composites prepared from solution. X-ray diffraction (XRD) of the solution-blended composites showed that no intercalation of the EAAs inside the clay galleries can be achieved if solvent removal is made by precipitation in non-solvents or by room-temperature evaporation. On the contrary, intercalation was found to occur very rapidly (in less than 1 min) when both the hybrids prepared from solution and the mechanical blends of powdered components were melted in the absence of shear. Polymer intercalation was also found to occur, though with a lower rate, upon annealing the powder mixtures at temperatures lower than the EAA melting point. Microscopic observations made by polarized optical microscopy, scanning electron microscopy and transmission electron microscopy showed that the clay particles dispersion is appreciably lower for the composites prepared from solution, compared to those produced in the melt under shear flow conditions. The hybrids obtained by static melting of powder mixtures, on the other side, were expectedly found to comprise micron sized clay agglomerates, although intercalation was demonstrated also for these materials by XRD. The structure of the intercalated silicate layers stacks, characterized by an interlayer spacing of 4.0 nm, was shown to be independent of the preparation procedure and to correspond to thermodynamic equilibrium.