Selectivity Coefficients for Divalent Oxyanions from the Continuous Foam Fractionation of a Quaternary Ammonium Surfactant

Abstract

An experimental investigation is presented of the continuous, single equilibrium stage foam fractionation of chromate (CrO₄ ^2-) and of thiosulfate (S₂O₃ ^2-) from 0.4 to 3.0 × 10–⁴ M aqueous solutions. The cationic surfactant, ethyl-hexadecyldimethylammonium bromide (EHDA-Br), is modeled as a soluble ion exchanger, considering the exchange of CrO₄ ^2- and S₂O₃ ^2- or EHDA-CrO₄ ^? and EHDA-S₂O₂ ^? for Br^?. The data indicate that EHDA-CrO₄ ^? or EHDA- S₂O₃ ^? is exchanged with Br^?. The selectivity coefficient for chromate is 3.90 and that for thiosulfate is 16.8.     

Experimental Foam Fractionation Selectivity Coefficients for the Alkali (Group IA) Metals

Abstract

An experimental investigation is presented of the continuous-flow foam fractionation of each of the colligends Li⁺, K⁺, Rb⁺, and Cs⁺ versus Na⁺, the counterion of the dodecylsulfate anion over the aqueous solution concentration range of 1.0 × 10^?4 to 6.0 × 10^?4 M. Initial experiments with K⁺ confirm the achievement of a single-equilibrium-stage separation. Surfactant selectivity coefficients, defined in terms of a colligend-surfactant counterion exchange model at the interfaces of the rising gas bubbles, are established. They represent the ratio of colligend to sodium in the interfacial “stream” to that in the residual steam and are Li⁺, 0.92; K⁺, 1.10; Rb⁺, 1.51; Cs⁺, 1.65. The selectivity sequence is compared to the sequence of absolute partial molal entropies of the cations in aqueous solution.     

季铵盐体系金的萃取与反萃

在碱性条件下研究了十六烷基三甲基溴化铵(CTAB)微乳液体系萃取KAu(CN)2. 实验考察了水相金浓度、反萃液中卤素离子、NH4SCN及羟乙基硫醚浓度对金萃取和反萃的影响及有机相中水含量与金萃取的关系. 结果表明：CTAB/己醇/庚烷微乳液体系可将绝大部分金从水相萃取到有机相;随着萃入金的增加,有机相水含量减少. 卤素离子的反萃能力顺序为：KI>KBr>KCl;高KI浓度(>2.0 mol/L)可将有机相中绝大部分(94%)的金反萃出来. 羟乙基硫醚及NH4SCN也是金的良好反萃剂,两者混合可以降低反萃液粘度,又可以减小NH4SCN浓度,而保持较高的金反萃率.     

Synthesis,Characterization and Surface-Activity of a Polyoxyethylene Ether Trimeric Quaternary Ammonium Surfactant

A trimeric quaternary ammonium salt surfactant containing polyoxyethylene chains was synthesized from fatty alcohol polyoxyethylene ether, pentamethyldiethylenetriamine and thionyl chloride by a two-step process. Its chemical structure was characterized, and the surface activity in aqueous solution was studied at different temperatures. The results showed that when the concentration attains the CMC (1.0 mmol/L), the surface tension is 38.9 mN m⁻¹ and the conductivity is 105.3μS cm⁻¹ at 25 °C. These show that the trimeric quaternary ammonium salt surfactant containing polyoxyethylene chains exhibits high surface activity and effectively reduces the surface tension of water.     

Trace elements (Mn,Cr, Pb,Se, Zn,Cd and Hg) in emissions from a pulverized coal boiler

The concentrations of seven trace elements (Mn, Cr, Pb, Se, Zn, Cd, Hg) in raw coal, bottom ash and fly ash were measured quantitatively in a 220 tons/h pulverized coal boiler. Factors affecting distribution of trace elements were investigated, including fly ash diameter, furnace temperature, oxygen concentration and trace elements' characteristics. Modified enrichment factors show more directly element enrichment in combustion products. The studied elements may be classified into three groups according to their emission features: Group 1: Hg, which is very volatile. Group 2: Pb, Zn, Cd, which are partially volatile. Group 3: Mn, which is hardly volatile. Se may be located between groups 1 and 2. Cr has properties of both Groups 1 and 3. The smaller the diameter of fly ash, the higher is the relative enrichment of trace elements (except Mn). Fly ash shows different adsorption mechanisms of trace elements and the volatilization of trace elements rises with furnace temperature. Relative enrichments of trace elements (except Mn and Cr) in fly ash are larger than that in bottom ash. Low oxygen concentration will not always improve the volatilization of trace elements. Pb forms chloride more easily than Cd during coal combustion.     

4-(N'-甲基-1-哌嗪基)-N-甲基-1,8-萘二甲酰烯丙基氯季铵盐的合成与光学性质

以4-Br-1,8-萘酐和甲胺为原料,经过酰胺化、胺化、烷基化、季铵化四步反应,得到一种水溶性荧光单体4-(N'-甲基-1-哌嗪基)-N-甲基-1,8-綦二甲酰烯丙基氯季铵盐.采用红外光谱、质谱、核磁共振氢谱及元素分析等测试技术对产物进行了结构表征,并对其紫外光谱、荧光光谱等光学性质进行了初步的研究.     

Priority pollutants (Hg and Cd) removal from water by ETS-4 titanosilicate

The synthetic microporous titanosilicate material ETS-4 has been used for the removal of Hg²⁺ and Cd²⁺ from water. Batch stirred experiments were carried out to study the equilibrium and the kinetics of the removal of Hg²⁺ and Cd²⁺ from water. It has been demonstrated that ETS-4 has a great affinity for both these metal cations even when their initial concentrations are low. The uptake rates for both Hg²⁺ and Cd²⁺ were well described by the pseudo-second order model which constants confirmed that the kinetics of the removal of Cd²⁺ is faster than that of Hg²⁺. However, at the equilibrium, ETS-4 has a higher capacity to remove Hg²⁺ than Cd²⁺. Adsorption isotherms for both Hg²⁺ and Cd²⁺ were well fitted to Langmuir isotherm and the corresponding monolayer capacities of ETS-4 are 0.43 and 0.24 µmol mg^- 1, respectively, which are quite consistent with those predicted by the pseudo-second order kinetic equation. Hence, the contribution of this work is to support the use of this material for the removal of Hg²⁺ and Cd²⁺ from water.     

Electroflotation Studies on Cu,Ni, Zn,and Cd with Ammonium Dodecyl Dithiocarbamate

Abstract

The concentration of Cu, Ni, Zn, and Cd ions by electroflotation using the ammonium salt of dodecyl dithiocarbamic acid as an anionic collector is examined. Quantitative studies reveal better separation efficiency by this method as compared to column flotation using dodecyl dithiocarbamic acid ligand as a chelating surfactant.     

羟基季胺盐清洁压裂液的制备及流变性行为研究

通过酰化和季铵化两步反应制得两种酰胺型季胺盐类阳离子表面活性剂C22-3N和C18-3N。通过室内评价,当C22-3N和C18-3N质量浓度为2∶1,异丙醇做溶剂时,复配形成清洁压裂液稠化剂后效果最佳,同时考察了浓度、温度等对其粘度的影响。在高温下,发现加入2%~3%乙二醇后能有效抵御体系的粘度变小,并从微观结构上分析表面活性剂的结构与性能的关系,探索稠化原理。     

Synthesis,crystal structure and properties of Zn(II) and Cd(II) complexes with 2-(4-isopropyl-4-methyl-5-oxo-4,5-dihydro-1H-imidazol-2-yl)nicotinic acid ligand

Two novel complexes, namely [Cd(L)₂] (1) and [Zn(L)₂(H₂O)₂] (2) have been synthesized (HL = 2-(4-isopropyl-4-methyl-5-oxo-4,5-dihydro-1H-imidazol-2-yl)nicotinic acid), which are characterized by elemental analysis, infrared spectrum and X-ray crystal diffraction. While strong hydrogen bonds play central roles in the formation of the 3D structure, the combined influence of the weak interactions such as C–H?O bonds, carbonyl?π and C–H?π interactions are also evident in the structures. The preliminary investigation on the thermal and fluorescence property of the complexes are presented.     

Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of Some N-Alkyl-N-Phenyl-Dithiocarbamates

The thermal decomposition of Zn(II), Cd(II) and Hg(II) complexes of N-ethyl-N-phenyl and N-butyl-N-phenyl dithiocarbamates have been studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The products of the decomposition, at two different temperatures, were further characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results show that while the zinc and cadmium complexes undergo decomposition to form metal sulphides, and further undergo oxidation forming metal oxides as final products, the mercury complexes gave unstable volatiles as the final product.     

Synthesis and Solution Properties of a Double‐Tailed Quaternary Ammonium Surfactant with a Protrudent Head Group

Modification of the molecular structure of surfactants is an effective method for exploring their self‐assembly. A double‐tailed quaternary ammonium surfactant with a protrudent head group, namely 2‐octyldecyltrimethylammonium bromide (2‐ODTAB) was synthesized, and the solution properties were investigated by surface tension, dynamic light scattering, and cryogenic TEM. A comparative study was also performed on the traditional double‐tailed homologue surfactants dioctyldimethylammonium bromide (8–8), didecyldimethylammonium bromide (10–10), and didodecyldimethylammonium bromide (12–12). The results showed that 2‐ODTAB was more effective at lowering surface tension and in forming stable vesicles than traditional double‐tailed surfactants with similar alkyl chain length. The reason is attributed to the improved structure of 2‐ODTAB, in which the two alkyl tails are connected to the ionic head group by one carbon atom. This structure imparts more freedom to the head group and thus favors formation of more stable aggregates at low concentration. In addition, the lower limit of the alkyl chain length of the double‐tailed surfactants for forming stable vesicles was illustrated.     

Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C(6)H(5))(CH(3))NCS(2)](4)Hg(2)

Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, (1)H and (13)C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films.     

Foam Separation of Mercury Ion with Chelating Surfactant: The Selectivity of the Removal of Cadmium and Mercury lons with 4-Dodecyldiethylenetriamine

Abstract

Foam separation techniques for the removal of mercury ion were studied which employed a surfactant specifically designed to chelate with the ion. The chelating surfactant was 4-dodecyldiethylenetriamine. Mercury ion was found to be removed almost quantitatively from aqueous solution using this surfactant, even in the presence of a large concentration of other metallic ions. Formation constants and surface tensions of Cd and Hg ionic complexes with the surfactant were measured. Selectivity of the removal of Cd and Hg ions is discussed.     

新型含氟季铵盐(C_4H_9)_4NAlF_4的合成、表征及电化学性质

在氮气保护下,四丁基氢氧化铵水溶液与氟铝酸铵进行反应,采用二氯甲烷萃取分离和异丙醇共沸除水方法对反应产物进行处理,制备了高纯的新型含氟季铵盐-四丁基铵的四氟铝酸盐,对其结构进行了表征,并对其物理及电化学性质进行了研究.结果表明,该季铵盐的熔点为204℃,400℃时分解,220℃时的电导率为4.67S/m,电化学窗口为4.7V,具有熔点低、电导率高、热稳定性和电化学稳定性好等优点,是一种很有潜力的低温电解质.     

Solvent-controlled assemblies,structures, and properties of two Hg(II) coordination polymers with a multidentate N-donor tecton 3,4-bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole

Coordination polymers [Hg(L²)Cl₂]_n (1) and {[Hg₂(L²)Cl₄](DMF)}_n (2) have been assembled from Hg(II) chloride and a novel tripyridyltriazole tecton 3,4-bis(2-pyridyl)-5-(4-pyridyl)-1,2,4-triazole (L²) in different solvent media. Both complexes have been characterized by IR, microanalysis, powder X-ray diffraction, and thermogravimetric analysis. Single crystal X-ray diffraction indicates that the L² ligands take the (η³, μ₂) and (η⁴, μ₃) binding modes in 1 and 2, respectively, which connect the Hg(II) centers to afford linear and ladder-like 1D arrays. Interestingly, complex 1 exhibits strong solid state fluorescent emission at room temperature due to the intraligand transitions, whereas complex 2 is non-fluorescent.     

Adsorption of Cd(II), Hg(II) and Zn(II) from aqueous solution using mesoporous activated carbon produced from Bambusa vulgaris striata

Mesoporous activated carbon (surface area of 608 m²/g) has achieved high efficiency in removal of cadmium, mercury and zinc ions from water solution. The proposed low-cost adsorbent was physically activated with water steam from the bamboo species Bambusa vulgaris striata. The batch studies suggested an activated carbon dose of 0.6 g/L, solution pH of 9 and an equilibrium time of 16 h in static conditions. The pseudo-second order equations represented the adsorption kinetics with high correlation. Fitting of the experimental results to the Langmuir, Freundlich, Redlich–Peterson and Toth isotherm models showed an almost homogeneous surface coverage and presence of physical adsorption. The highest adsorption capacities, calculated from the Langmuir model, are 239.45, 248.05 and 254.39 mg/g of cadmium, mercury and zinc, respectively.