有机阳离子[C18mim]＋在蒙脱土层间的物理化学吸附与聚集状态*

咪唑基离子液体(N鄄十八烷基鄄N忆鄄甲基溴化咪唑盐[C18mim]Br)中的[C18mim]+可以通过离子交换反应进入蒙脱土层间.本文用TGA、FTIR和XRD 研究了[C18mim]+在蒙脱土层间的物理和化学吸附及其聚集状态. 研究结果表明, 蒙脱土存在着饱和的化学吸附量, 其总吸附量随物理吸附量的增加而增加；随着[C18mim]+在蒙脱土层间吸附量的增加, 其聚集态结构的有序性增加, 并伴有分子链的构象变化,导致层间距的增加.     

改性蒙脱土吸附2,4-二氯-5-硝基苯酚的研究

分别采用新型双子阳离子表面活性剂Y-16和十六烷基三甲基溴化铵(CTAB)改性钠基蒙脱土,通过IR、TGA、XRD对其进行表征,研究了表面活性剂的浓度、改性蒙脱土的用量以及接触时间对2,4-二氯-5-硝基苯酚(DCNP)吸附的影响。结果表明:上述两种表面活性剂成功插入钠基蒙脱土层间结构且扩大了其层间距。随着表面活性剂的浓度、改性蒙脱土的用量、接触时间的增加,改性蒙脱土对DCNP的吸附量也随之增加,并达到最大值。当采用0.1g 1.8CEC改性蒙脱土且接触时间为180min时,CTAB-MMT和Y-16-MMT对DCNP达到最大吸附量分别为184.84mg·g~(-1)、164.47mg·g~(-1)。改性蒙脱土对DCNP的吸附行为符合二级动力学方程和Langmuir等温吸附方程。     

酯化淀粉乳化剂制备的高效氯氟氰菊酯O/W乳液的稳定机制

通过测定辛烯基琥珀酸淀粉钠的用量、盐离子、pH值和温度等因素对油滴Zeta电位及表面吸附量的影响,分析了以酯化淀粉辛烯基琥珀酸淀粉钠为乳化剂制备的5％高效氯氟氰菊酯水乳剂的稳定机制.结果表明,辛烯基琥珀酸淀粉钠质量分数为7％时,Zeta电位达到最大值,油滴表面吸附量接近饱和;Na+、Mg2+和Al3+压缩油滴表面的双电层,降低Zeta电位,削弱静电排斥作用,增加辛烯基琥珀酸淀粉钠分子柔性,提高辛烯基琥珀酸淀粉钠表面吸附量,且随着Na+、Mg2、Al3+离子强度依次增大,压缩双电层能力依次增强,Zeta 电位降低和表面吸附量增加程度依次增大;pH值影响辛烯基琥珀酸淀粉钠在水中的解离,在碱性范围内解离出较多羧酸根,静电排斥力较大,Zeta电位较高,但表面吸附量有所降低;温度升高,辛烯基琥珀酸淀粉钠在水溶液中溶解度增大,呈舒展状态,且辛烯基琥珀酸淀粉钠从油滴表面逃逸的趋势增加,油滴表面Zeta电位和表面吸附量均随着温度升高而降低,在低温区差别不大,温度越高二者变化越明显.辛烯基琥珀酸淀粉钠通过吸附于油滴表面为其提供较强的静电斥力和空间位阻作用而维持O/W乳液稳定.     

双单体原位接枝插层法制备聚丙烯纳米复合材料的研究Ⅰ.制备、表征及力学性能的研究

用有机插层剂处理蒙脱土原土 ,制得有机蒙脱土 (O MMT) .采用双单体 (马来酸酐和苯乙烯 )原位接枝插层法 ,制备了聚丙烯 蒙脱土纳米复合材料母料 .将母料与聚丙烯基体在双螺杆上共混挤出 ,制得聚丙烯 蒙脱土纳米复合材料 (PP Montmorillonetenanocomposites,PMNC) .这是制备聚合物纳米复合材料的一种新方法 .通过X 射线衍射测试 (XRD)表明 ,有机蒙脱土片层 0 0 1面间距从原土的 1 4 9nm扩大到 2 96nm ,复合材料中蒙脱土片层 0 0 1面间距由有机蒙脱土的 2 96nm扩大到 4 0nm .力学性能测试表明 ,复合材料的力学性能明显优于PP基体 ,在提高材料拉伸强度的同时 ,缺口冲击强度也得到很大的提高 .用扫描电镜 (SEM)对材料的冲击断面形貌进行了研究 ,并从理论上分析了断裂机理 .随着蒙脱土含量的增加 ,冲击断裂形式逐渐从脆性断裂变成韧性断裂     

蒙脱土和高岭土对Pb2+的吸附

选择带结构负电荷的蒙脱土和带微量结构负电荷的高岭土,研究了其对Pb2+的吸附性能,并探讨了吸附机理。 研究表明,蒙脱土和高岭土吸附Pb2+的动力学曲线符合准二级动力学方程,吸附等温线符合Langmuir方程。 Pb2+同时以内层络合和外层配合形式吸附,其相对量与pH值有关。 在pH值小于4和大于8的范围内,以内层配合物为主;而pH值在4～8范围内外层配合物比例增大。 Pb2+能进入蒙脱土的层间,而不能进入高岭土的层间;部分Pb2+可进入黏土颗粒的微孔中被固定。 蒙脱土对Pb2+的吸附能力和饱和吸附量明显高于高岭土。     

阳离子改性蒙脱土及对活性翠蓝K-GL染料的吸附性能研究

以十六烷基三甲基溴化铵(CTMAB)作为有机改性剂对钠基蒙脱土(MMT)进行改性得到阳离子化有机改性蒙脱土(CTMAB-MMT)。X-Ray衍射结果表明,随CTMAB用量的增加,MMT的层间距增加。以CTMABMMT为吸附剂,研究了其对活性翠蓝K-GL染料的吸附性能,结果表明,CTMAB-MMT对染料的吸附容量随CTMAB用量的增加或吸附温度的提高而增大;在弱酸性条件下CTMAB-MMT的吸附容量明显优于碱性条件;随着吸附时间的延长,CTMAB-MMT对染料的吸附容增加,一定时间后趋向于平衡。     

部份层无序锆交联蒙脱土结构的研究

通过锆交联蒙脱土的X射线衍射、阳离子交换量及孔径分布等实验测定,利用部分无序层状结构的衍射公式,建立了相应的三维统计结构模型.交联剂中Zr(Ⅳ)主要以四聚及三聚的方式存在,在与Na-Mt交联过程中,四聚及三聚Zr(Ⅳ)离子先吸附一定量的水,与水共同支撑开蒙脱土层,使层间距分别达到2.55nm和2.10nm,如此层间距的层在整体结构中分别占35％和27％.水分子进入了其余层间域,层间距为1.26nm.     

不同分子量壳聚糖对蒙脱土插层复合物的影响

于醋酸溶液中通过溶液插层技术将不同分子量的壳聚糖与钠基蒙脱土进行插层复合,制备了系列壳聚糖/蒙脱土插层复合物. 通过XRD、TEM、FTIR测试技术对插层复合物的结构进行了表征. 结果表明,仅通过醋酸溶液处理,残留的HAc就可使MMT层间距由原来的1.3 nm增加至1.55 nm,并使结构规整性提高;降低壳聚糖分子量有利于MMT层间距增大,并出现更多剥离形态的蒙脱土;当壳聚糖分子量为4.1×104时,最大层间距可达2.48 nm,但进一步降低壳聚糖分子量层间距反而略微减小;红外光谱分析表明,插层复合物中壳聚糖与蒙脱土间存在明显的静电作用. TGA分析结果表明,插层复合物中壳聚糖的含量随分子量的降低而增加,残留的醋酸使插层复合物中壳聚糖的热稳定性能下降.     

丁二烯/苯乙烯/4-乙烯基吡啶共聚物蒙脱土嵌入混杂材料的研究

用聚合物乳液与蒙脱土的水分散体共混共凝的方法制备混杂材料.在混合过程中乳胶粒与蒙脱土晶层相互穿插,用盐酸絮凝,带正电的共聚物能够嵌入带负电的蒙脱土层间.萃取实验发现在混杂材料中蒙脱土吸附了大量的共聚物,说明蒙脱土晶层与共聚物之间存在静电吸附作用.XRD实验发现在混杂材料中蒙脱土的晶层结构发生了膨胀,并且变得混乱,而在共混物中蒙脱土晶层结构几乎不变.用TEM观察在混杂材料中蒙脱土晶层均匀分散于共聚物基体中,蒙脱土的层间距大于6nm.共聚物嵌入蒙脱土的层间,受到蒙脱土晶层的限制作用,共聚物的T_g发生了变化.交联以后的混杂材料的性能比共聚物有了较大的提高,蒙脱土晶层在共聚物基体中起到很好的补强作用.     

Al_2O_3-交联蒙脱土的合成及其对甲苯丙烯烷基化的催化性能

本文研究了蒙脱土在交联前后的面间距、比表面及酸性的变化,并与甲苯丙烯烷基化制伞花烃(Cymene,IPT)的催化活性和关联。当原土经Al_2O_3处理成Al_2O_3交联蒙脱土后,其层间距扩大到0.89nm,比表面增加七倍,酸量增加四倍,成为甲苯丙烯烷基化反应较好的催化剂。在连续进料及常压、低温(50～70℃)的温和条件下,甲苯转化率为～46％,IPT选择率为～68％。     

Interaction between cationic surfactants and montmorillonites under nonequilibrium condition

Surfactant adsorption by two different montmorillonites was characterized by examining the time dependence of surfactant behavior on clay surfaces. Surfactants with different micelle concentrations were conducted in our experiment to observe a nonequilibrium activity of cationic surfactant on the clay over reaction periods ranging from 0.1 min to 11 days. Compared with Ca-montmorillonite (SAz), a more active intrusion of surfactant molecules into the interlayers was found in Na-montmorillonite (SWy). During a short "initiation" stage, the basal spacing of SWy montmorillonite increased rapidly with logarithmic time. For SAz montmorillonite, however, the abrupt basal spacing increase occurred at a later stage of the reaction. From the results, it is assumed that the difference in the adsorption behavior exhibited by the two montmorillonite types partly arises from their intrinsic nature; that is, inorganic cations originally existed on the clay surfaces. Additionally, the micelle concentration of the surfactants affects the development of organomontmorillonite, especially in the intercalant formation and stabilization under nonequilibrium.     

钙蒙脱土吸附镧的影响因素及其应用

以钙基蒙脱土(Ca-MMT)为载体,研究其对镧(La)的吸附。 采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和元素mapping分析、傅里叶红外光谱(FT-IR)、BET、X射线荧光光谱分析(XRF)对其晶型结构、表面形态、比表面积、化学结构进行表征,考察了La的初始浓度、pH值、温度对Ca-MMT吸附镧性能的影响,考察了载镧钙基蒙脱土(Ca-MMT@La)的除磷效果。 结果表明:Ca-MMT投入量为10 g/L时,Ca-MMT的平衡吸附量随镧的初始浓度增加而增大,最大吸附量为49.62 mg/g;随着pH值增大,吸附能力增强,pH=6时为最佳pH吸附镧条件,吸附量为38.36 mg/g;随温度的升高,其吸附量先下降再上升,20 ℃吸附能力最大,吸附量为41.23 mg/g。 Langmuir等温吸附方程推断其吸附属于单分子层吸附。 Ca-MMT不具有吸附磷效果,而Ca-MMT@La对磷酸根有很强的吸附能力,吸附量为7.24 mg/g,除磷率为72.41%,其除磷率随含镧量增大而增大。     

Apparent and partial specific adsorption of 1,10-phenanthroline on mixtures of Ca-montmorillonite, activated carbon, and silica gel

The process of 1,10-phenanthroline adsorption at pH 5 on Ca-montmorillonite, activated carbon, and silica gel mixtures was studied as a function of the equilibrium concentration and the composition of the mixture. A model is presented for determining adsorption of the main component (the variable in the system) of the mixture, based on the thermodynamic concept of apparent and partial quantities, in combination with an equation representing total adsorption of the other two adsorbents as a function of the weight fraction of one of them and introducing the concept of mean total adsorption. The partial specific adsorption of orthophenanthroline (OP) on Ca-montmorillonite is strongly influenced by the presence of activated carbon and silica gel. Owing to a phenomenon of cationic exchange, adsorption on the clay is higher at low proportions in the mixture, but the strong effect of carbon and silica gel becomes apparent at increasing amounts of clay in the mixture. The partial specific adsorption of orthophenanthroline on activated carbon and silica gel was determined using a total adsorption equation for the two adsorbents as a function of the weight fraction of one of them and shows behavior inverse to that of adsorption on clay.     

Removal of diphenhydramine from water by swelling clay minerals

Frequent detection of pharmaceuticals in surface water and wastewater attracted renewed attention on studying interactions between pharmaceuticals and sludge or biosolids generated from wastewater treatment. Less attention was focused on studying interactions between pharmaceuticals and clay minerals, important soil and sediment components. This research targeted on investigating interactions between diphenhydramine (DPH), an important antihistamine drug, and a montmorillonite, a swelling clay, in aqueous solution. Stoichiometric desorption of exchangeable cations accompanying DPH adsorption confirmed that cation exchange was the most important mechanism of DPH uptake by the swelling clay. When the solution pH was below the pK(a) of DPH, its adsorption on the swelling clay was less affected by pH. Increasing solution pH above the pK(a) value resulted in a decrease in DPH adsorption by the clay. An increase in d(001) spacing at a high DPH loading level suggested interlayer adsorption, thus, intercalation of DPH. The results from this study showed that swelling clays are a good environmental sink for weak acidic drugs like DPH. In addition, the large cation exchange capacity and surface area make the clay a good candidate to remove cationic pharmaceuticals from the effluent of wastewater treatment facilities.     

Adsorption of Triarylmethane Dye on Ca-Montmorillonite: Equilibrium,Kinetics, and Thermodynamics

The equilibrium, kinetics, and thermodynamics of adsorption of triarylmethane dye, crystalline violet, from aqueous solutions on Ca-montmorillonite have been studied. The regularities of the influence of the physicochemical parameters (suspension pH, clay and dye concentrations, temperature, and contact time) on the specific adsorption value of the dye have been found. It has been shown that Ca-montmorillonite is capable of removing the dye from aqueous solutions in a wide range of concentrations with an efficiency of up to 99.8%. The adsorption of crystalline violet obeys the Langmuir model (the correlation coefficient is 0.999), which corresponds to monolayer adsorption on a homogeneous surface. The kinetics of dye adsorption is described by a pseudo-second-order equation, which is characteristic of chemisorption. The thermodynamic parameters of adsorption, ΔH = 40.42 kJ/mol, ΔS = 139.6 J/mol, and ΔG =–4.68 kJ/mol (323 K), have been determined and lead to the conclusion that the dye adsorption is a spontaneous endothermic process.     

Adsorptive removal of methylene blue from colored effluents on fuller's earth

The adsorption behavior of methylene blue (MB) on four fuller's earth (FE) samples of varying compositions was investigated using a spectrophotometric technique to obtain information on the color removal. The distribution coefficient (K(D)) increased with an increase in the initial concentration (C(0)) of the dye, attained a maximum value, and decreased again at higher initial concentrations. Dye solutions became colorless for a C(0) value corresponding to maximum K(D). A progressively increased flocculation behavior in the clay suspensions was observed and the maximum value of K(D) corresponds to optimum flocculation of the clay. The K(D) values were found to decrease exponentially after of the solution again became colored while the amount adsorbed increased with an increase in the initial concentration of MB. Only adsorption data obtained for this region could be defined by adsorption isotherm equations. The shifts of the C(0) values corresponding to K(D)(max) toward higher concentrations were correlated with the composition of FE samples by using XRF, XRD patterns, and SEM images. The influence of temperature on MB adsorption was also studied and thermodynamic parameters were calculated.     

聚(丙烯酸-co-丙烯酰胺)/蒙脱土/腐殖酸钠复合物对Pb2+的吸附性能

用制备的聚(丙烯酸-co-丙烯酰胺)/蒙脱土/腐殖酸钠复合吸附剂,研究了溶液pH值、吸附时间和Pb2+溶液初始浓度等因素对重金属Pb2+的吸附性能,探讨了复合吸附剂对Pb2+的吸附机理。结果表明,在pH值为6.0、吸附时间2 h、Pb2+溶液初始浓度0.01 mol/L和吸附剂用量0.10 g的条件下,复合吸附剂对Pb2+的吸附量达到364.05 mg/g,平衡所需的时间为15 min。与蒙脱土相比,复合吸附剂具有更高的吸附容量和更快的吸附速率。     

Adsorptive removal of tannin from aqueous solutions by cationic surfactant-modified bentonite clay

The removal of tannin from aqueous media by cationic surfactant-modified bentonite clay was studied in a batch system. The surfactant used was hexadecyltrimethylammonium chloride. Adsorbent characterizations were investigated using X-ray diffraction, infrared spectroscopy, surface area analysis, and potentiometric titration. The effects of pH, contact time, initial solute concentration, adsorbent dose, ionic strength, and temperature on the adsorption of tannin onto modified clay were investigated. The adsorbent exhibited higher tannin removal efficiency (>99.0%) from an initial concentration of 10.0 micromol/L at pH 3.0. Adsorption capacity decreased from 90.1 to 51.8% with an increase in temperature from 10 to 40 degrees C at an initial concentration of 25.0 micromol/L. The adsorption process was found to follow pseudo-first-order kinetics. Film diffusion was found to be the rate-limiting step. Tannin adsorption was found to decrease with increase in ionic strength. The tannin equilibrium adsorption data were fitted to Langmuir and Freundlich isotherm models, the former being found to provide the best fit of the experimental data. The maximum monolayer adsorption capacity for tannin was 69.80 micromol/g at 30 degrees C. Comparison of adsorption capacity of the modified clay with reported adsorbents in the literature was also presented. Adsorbed tannin on modified clay can be recovered by treatment with 0.1 M NaOH solution. Regeneration experiments were tried for four cycles and results indicate a capacity loss of <10.0%. From the results it can be concluded that the surfactant-modified clay could be a good adsorbent for treating tannin-contaminated waters.     

Preparation and characterization of organoclays based on an amphoteric surfactant

The uptake of the amphoteric surfactant, cocamidopropyl betaine (CAB) by a sodium montmorillonite clay was studied with respect to concentration and pH. A series of organoclays was prepared in which the basal spacings were found to depend on both parameters. Adjusting the solution pH during preparation influenced the adoption of either 1.8 or 2.0 nm spacing, whereas the 3.9 nm spacing in the same sample was unaffected. The presence of the carboxyl group in the CAB molecule enabled dispersion of the clay at higher pH by which means pure organoclays of high spacing could be obtained, whereas, without dispersing the clay, mixed populations were obtained. The results indicate the optimum parameters for preparing organoclays of desired spacings for use in clay-reinforced nanocomposites.     

Preparation and Barrier Properties of Chitosan-Layered Silicate Nanocomposite Films

Summary: In this study, chitosan nanocomposite films were prepared using a solvent-casting method by incorporation of an organically modified montmorillonite (Cloisite 10A). The effect of filler concentration on the water vapor permeability, oxygen permeability, mechanical and thermal properties of the composite films was evaluated. The structure of nanocomposites and the state of intercalation of the clay were characterized by XRD. The water vapor permeability of pure chitosan films was measured as a function of relative humidity (RH). It was found that the permeability value increased with an increase in RH. The water vapor and gas permeability values of the composite films decreased significantly with increasing filler concentration. Permeation data was fitted to various phenomenological models predicting the permeability of polymer systems filled with nanoclays as a function of clay concentration and aspect ratio of nanoplatelets. According to the XRD results, an increase in basal spacing was obtained with respect to pure clay for chitosan/clay nanocomposites. This demonstrated the formation of intercalated structure of clay in the polymer matrix. Tensile strength and elongation at break of the composites increased significantly with the addition of clay, however the thermal and color properties of the films were not much affected by the intercalation of clay into polymer matrix.