Use of Al2O3 in an automated on-line pre-concentration system for determination of cadmium(II) by FAAS

This paper presents the development of an on-line pre-concentration system to determine cadmium(II) in aqueous samples. The analyte was trapped in a mini-column filled with Al(2)O(3) in the form of macro-spheres obtained by the mixture of Al(NO(3))(3).9H(2)O(aq) and chitosan dissolved in acetic acid. The mixture was dropped into an NH(4)OH aqueous solution under rigorous agitation using a peristaltic pump, the macro-spheres were separated from alkaline solution and dried, and finally were submitted to thermal treatment. The pre-concentration system was linear between 1.0 and 100 microg L(-1), with a linearity of 0.999, sensitivity of 3.58 x 10(-3)L microg(-1) and enrichment factor of 21.9. The limits of detection and quantification were 0.08 microg L(-1) and 0.28 microg L(-1), respectively. The repeatability was between 2.6 and 5.9%. Recovery tests were carried out with a real aqueous sample.     

Functionalized diatom silica microparticles for removal of mercury ions

Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH₂) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g⁻¹ for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.     

Functionalized diatom silica microparticles for removal of mercury ions

Abstract

Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH₂) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g^?1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.     

Solid phase extraction of ultra traces mercury (II) using octadecyl silica membrane disks modified by 1,3-bis(2-ethoxyphenyl)triazene (EPT) ligand and determination by cold vapor atomic absorption spectrometry

A facile and highly efficient method was developed for the preconcentration of the ultra trace amounts of mercury (II) ions. Octadecyl silica membrane disk was modified by the recently synthesized triazene ligand, 1,3-bis(2-ethoxyphenyl)triazene (EPT), and cold vapor atomic absorption spectrometry was used to determine the resultant preconcentrated Hg(II) ions. Solution studies with EPT and a series of metal ions were done in advance, and the results showed a strong affinity of EPT to the mercury ions. To perform solid phase extraction, various parameters such as pH of the sample, flow rates and the amount of the ligand were optimized. A linear calibration curve was obtained in the range of 0.02-1.90 μg L⁻¹ with r² = 0.9990 (n = 8), and the limit of detection (LOD) based on three times the standard deviation of the blank was 10.6 ng L⁻¹. The relative standard deviation (RSD) for the determination of 0.1 μg L⁻¹ Hg(II) found to be 2.9% while a RSD value of 1.1% was obtained for the determination of 1.0 μg L⁻¹ Hg(II) (n = 8). The preconcentration and improvement factors were 380 and 74, respectively. The newly developed method was successfully applied to the determination of mercury ions in real water samples.     

硅胶固载酸功能化离子液体催化剂的制备和应用

将带有酸官能团的离子液体固载到具有高表面积的硅胶上,制备的硅胶固载酸功能化离子液体可作为催化剂用于多种有机反应。该新型催化剂具有高效、高选择性、离子液体用量少、产品易分离和催化剂易回收等优点,因有望用于化工过程的固定床反应器而受到关注。     

Preparation of xylenol orange functionalized silica gel as a selective solid phase extractor and its application for preconcentration--separation of mercury from waters

A new selective solid phase extractor was prepared from silica gel modified with xylenol orange (SGMXO). The solid phase extractor is stable in 6molL(-1) HCl, common organic solvents, and pH 1.0-9.0 buffer solutions. In the batch experiments, Hg(II) can be adsorbed on SGMXO at pH 1.0 with 90.0% retention, whereas the retention of other common coexisting metal ions such as Cd(II), Pb(II), Cu(II), Ni(II), Co(II), Mn(II), Zn(II), and Fe(III) is less than 4.1%.. The adsorption equilibration for Hg(II) was achieved within 3min. At optimum conditions, the adsorption capacity of the extractor is 18.26micromolg(-1) of dry modified silica gel, and the preconcentration factor is as high as 333. The recovery is still higher than 95% for the preconcentration of 10ngmL(-1) Hg(II). The new solid phase extractor has been used for the preconcentration of low level of Hg(II) in surface water, tap water in chemistry laboratory and student's dormitory and a simulated sea water samples, recoveries of 98.2-100.6% were obtained. It is showed that low level of Hg(II) can be effectively preconcentrated by this new selective solid phase extractor.     

Fabrication of silica glass containing yellow oxynitride phosphor by the sol–gel process

Abstract

We have prepared silica glass by the sol–gel method and studied its ability to disperse the Ca-α-SiAlON:Eu²⁺ phosphor for application in white light emitting diodes (LEDs). The emission color generated by irradiating doped glass with a blue LED at 450 nm depended on the concentration of SiAlON and the glass thickness, resulting in nearly white light. The luminescence efficiency of 1-mm-thick glass depended on the SiAlON concentration, and was highest at 4 wt% SiAlON.     

Separation, preconcentration and determination of silver ion from water samples using silica gel modified with 2,4,6-trimorpholino-1,3,5-triazin

A new modified silica gel using 2,4,6-trimorpholino-1,3,5-triazin was used for separation, preconcentration and determination of silver ion in natural water by atomic absorption spectrometry (AAS). This new bonded silica gel was used as an effective sorbent for the solid-phase extraction (SPE) of silver ion from aqueous solutions. Experimental conditions for effective adsorption of trace levels of silver ion were optimized with respect to different experimental parameters in column process. Common coexisting ions did not interfere with the separation and determination of silver at pH 3.5 so that silver ion completely adsorbed on the column. The preconcentration factor is 130 (1 mL elution volume for a 130 mL sample volume). The relative standard deviation (R.S.D.) under optimum conditions is 3.03% (n=5). The accuracy of the method was estimated by using spring and tap water samples that were spiked with different amounts of silver ion. The adsorption isotherm of silver ion was obtained. The capacity of the sorbent at optimum conditions has been found to be 384 microg of silver per gram of sorbent.     

固体超强酸于多孔高硅氧纤维的负载及其在酯化中的应用

以溶胶浸渍法,将SO42-/ZrO2固体超强酸负载到由酸沥滤工艺制备的多孔高硅氧纤维上,并用于催化合成乙酸正丁酯。研究结果表明,该催化剂具有用量少,酯收率较高,产物易于分离等优点;而且使用寿命长,重复用于5次合成后,酯化率仍高于70%。     

Fabrication of silica glass containing yellow oxynitride phosphor by the sol–gel process

We have prepared silica glass by the sol–gel method and studied its ability to disperse the Ca-α-SiAlON:Eu²⁺ phosphor for application in white light emitting diodes (LEDs). The emission color generated by irradiating doped glass with a blue LED at 450 nm depended on the concentration of SiAlON and the glass thickness, resulting in nearly white light. The luminescence efficiency of 1-mm-thick glass depended on the SiAlON concentration, and was highest at 4 wt% SiAlON.     

Preparation of DNA–cyclodextrin–silica composite by sol–gel method and its utilization as an environmental material

A DNA–cyclodextrin–silica composite was prepared by the sol–gel method. This composite possessed the bi-functions of double-stranded DNA, such as intercalation into DNA, and cyclodextrin, such as inclusion into its intramolecular cavity. Therefore, we demonstrated the accumulation of harmful compounds from an aqueous multi-component solution using a DNA–cyclodextrin–silica composite column. As a result, the DNA–cyclodextrin–silica composite column can effectively accumulate not only planar structure-containing harmful compounds, such as dioxin and polychlorobiphenyl (PCB) derivatives, but also non-planar structure containing compounds, such as bisphenol A and diethylstilbestrol, from an aqueous multi-component solution. The accumulated amount of these harmful compounds was more than 90%. Additionally, the DNA–cyclodextrin–silica composite column was recycled by the application of methanol. Therefore, the DNA–cyclodextrin–silica composite may have the potential to be used as an environmental material for the accumulation of harmful compounds from industrial or experimental waste.     

Study of optimum growth condition and characterization of zinc mercury thiocyanate (ZMTC) single crystals in silica gel

Some bimetallic thiocyanate complexes exhibit excellent nonlinear optical properties. Single crystals of one such material, zinc mercury thiocyanate ZnHg(SCN)₄ have been grown in silica gel with gel technique by the process of diffusions and the optimum growth condition has been studied. Crystals of 4 mm length have been obtained. Their structural, optical and thermal properties have been studied. Structural analysis was carried out using an X-ray diffractometer and the crystal structure was confirmed to be tetragonal. Fourier transform infrared spectrum was obtained to confirm the functional groups. Transmission spectrum has been recorded in the solution state and the cut-off wavelength has been determined. Thermal stability of the grown crystal has been investigated by thermogravimetric and differential thermal analyses. Nonlinear optical property of the crystal has been confirmed using the Kurtz powder technique and a study of its second harmonic generation efficiency in comparison with urea has been made.     

Examination of the concrete from an old Portuguese dam: Texture and composition of alkali–silica gel

Exudations and pop-outs were identified in the interior galleries of a large dam built in the 1960s. The samples collected were examined by a Scanning Electron Microscope. A dense material with a smooth surface and drying shrinkage cracks or a spongy texture were observed in the samples. The semi-quantitative composition was obtained by energy dispersive spectrometry (EDS) and it was concluded that this material corresponds to alkali–silica gel, composed of SiO₂–Na₂O–K₂O–CaO. A viscous white product in contact with an aggregate particle in a cone sampled from a pop-out was observed through use of the scanning electron microscope and it has characteristics similar to the gel present in the exudations and cavities. Reference is made to the potential alkali reactivity of the aggregate present in the concrete. The texture and composition of the products probably resulting from an alkali–silica reaction are presented, set out in ternary diagrams, and discussed.     

Enrichment of trace amounts of copper(II) ions in water samples using octadecyl silica disks modified by a Schiff base ionophore prior to flame atomic absorption spectrometric determination

Bis(5-bromo-2-hydroxybenzaldehyde)-1,2-propanediimine is synthesized by the reaction of 5-bromo-2-hydroxybenzaldehyde and 1,2-diaminopropane in ethanol. This ligand is used as a modifier of octadecyl silica disks for preconcentration of trace amounts of copper(II) ions, followed by nitric acid elution and flame atomic absorption spectrometric (FAAS) determination. The effect of parameters influencing the extraction efficiency, i.e. pH of the sample solutions, amount of the Schiff base, type and volume of stripping reagent, sample and eluent flow rates were evaluated. Under optimum experimental conditions, the capacity of the membrane disks modified by 4mg of the ligand was found to be 247.7 (+/-2.1)mug of copper. The detection limit and the concentration factor of the presented method are 2.4ng/l and greater than 400, respectively. The method was applied to the extraction, recovery and detection of copper in different synthetic and water samples.     

具有有序宏观结构纳米碳纤维的制备及其性能应用

以CH4为碳源,金属Ni为催化剂,采用化学气相沉积法(CVD)在有序宏观基体材料(SiO2纤维,Al2O3纤维)上制备出纳米碳纤维。利用场发射扫描电镜(FE-SEM)、透射电镜(TEM)、拉曼光谱(Raman)以及热重分析(TG)对产物进行了微观形貌和结构的检测。结果表明,所制备的纳米碳纤维具有取向性,能够在有序宏观基体材料上形成致密有序的纳米碳纤维层;与Al2O3纤维相比,SiO2纤维更易于生成高质量的纳米碳纤维;所制备的纳米碳纤维遵循顶端生长模式。此外,采用纳米碳纤维作模板可以原位合成出具有有序宏观结构的纳米LaMnO3,它能明显降低碳黑颗粒的起燃温度,具有潜在的应用前景。     

聚甲基丙稀酸羟乙酯甘油凝胶仿软骨材料的制备与性能

为了使人体关节软骨损伤后得到修复,采用热聚合的方法制备了一种新型人工仿软骨材料。在水浴保温和引发剂条件下,采用甲基丙稀酸羟乙酯(CH2CCH3COOCH2CH2OH,HEMA)和医用甘油(C3H8O3)聚合成一种新型凝胶,并对其分别进行了表面形貌观察和猪软骨硬度的对比,以及抗压性、弹性等力学性能测试。使用FTIR红外光谱对其作分析表征,结果表明:凝胶主体仍然是聚甲基丙稀酸羟乙酯(PHEMA),甘油以凝胶态存在;凝胶硬度随甘油比例增加而下降,但凝胶表面粗糙度却增加;当HEMA与甘油质量比例为1∶1~1∶3时,凝胶的硬度较为接近猪软骨;在比例为1∶1和1∶2的条件下,表面光滑。4种比例下的凝胶都具有良好的抗压性和弹性,当质量比为1∶1时抗压性能和综合性能最好。实验结果表明PHEMA与甘油的凝胶聚合物如果作为人工仿软骨材料,具有力学性能良好的优点,将可能提供给临床实验作进一步考察。     

Use of 8-hydroxyquinoline-chitosan chelating resin in an automated on-line preconcentration system for determination of zinc(II) by F AAS

This study presents the development of an on-line preconcentration system for zinc(II) determination in aqueous samples. The analyte was trapped in a mini-column filled with a chelating resin based on a chitosan biopolymer modified with 8-hydroxyquinoline obtained by the diazotization reaction. Flow and chemical variables of the system, as well as the potential interference ions, were optimized through a multivariate procedure. The factors selected were sample pH, eluent concentration (HNO(3)), and sample and eluent flow rates. It was verified through a full factorial design that the sample pH and eluent flow rate factors were statistically significant at the 95% confidence level. A final optimization of the significant factors was carried out using a Doehlert matrix. The preconcentration system was linear between 2.5 and 75 microgL(-1), with a regression coefficient of 0.9995. The enrichment factor was 17.6. The limits of detection and quantification were 0.8 and 2.5 microgL(-1), respectively. The repeatability and the analytical frequency were, respectively, 2.7 (25.0 microgL(-1), n=8) and 18 samples per hour. Results for recovery tests using mineral water samples were between 85 and 93%. Certified reference materials were analyzed in order to check the accuracy of the proposed method.     

Solid-phase extraction of technetium--amine complexes onto C18 silica and its application to the isolation of 99Tc

The extraction of Tc-tripentylamine complexes onto C18 silica solid-phase extraction columns is evaluated for the selective removal of 99Tc from other isotopes. The Tc-amine complex is quantitatively extracted from sulfuric acid and can be recovered from the column by elution with dilute alkali. A clean separation of Tc from all likely contaminants, including Ru, is achieved showing that C18 silica solid-phase extraction columns are a viable and attractive alternative to the solvent extraction of 99Tc.     

Preparation of halloysite nanotubes supported 2-mercaptobenzimidazole and its application in natural rubber

To improve the antioxidative efficiency of 2-mercaptobenzimidazole (MB) and strengthen the interaction between halloysite nanotubes (HNTs) and natural rubber (NR), HNTs supported 2-mercaptobenzimidazole (HNTs-s-MB) was prepared by reacting MB with chlorosilane modified HNTs (m-HNTs). FTIR, XPS and TGA confirmed that MB was chemically bonded onto the surface of HNTs. HNTs-s-MB could be homogeneously dispersed in the NR matrix and there was a strong interfacial interaction between HNTs-s-MB and NR, leading to the better mechanical performances of NR/HNTs-s-MB nanocomposites than those of NR/HNTs nanocomposites. Based on the measurements of the thermo-oxidation activation energy of NR/HNTs-s-MB and NR/m-HNTs/MB nanocomposites containing equivalent antioxidant component, it was found that the antioxidative efficiency of HNTs-s-MB was superior to that of the corresponding low molecular MB owing to the much lower migration and volatility of HNTs-s-MB than those of MB.     

Extraction behaviour of 2-octylaminopyridine towards lead(II) from succinate media and its separation from other toxic metals

Liquid-liquid extraction of lead(II) from succinate media was carried out with 2-octylaminopyridine (2-OAP) in chloroform. Lead(II) was quantitatively extracted with 0.036 M 2-OAP in chloroform from 0.005-0.007 M sodium succinate when equilibrated for 5 min. Lead(II) from the organic phase was stripped with three 10 mL portions of 0.4M acetic acid and determined titrimetrically with EDTA. The nature of extracted species was determined from the log-log plot. The optimum conditions have been evaluated based on a critical study of weak acid concentration, extractant concentration, period of equilibration and effect of diluents. The metal loading capacity of the reagent was found to be 8 mg of lead(II) with 10 mL 0.036 M of the extractant. The extraction of the lead(II) was carried out in presence of various ions to ascertain the tolerance limit of individual. Temperature dependence of the extraction equilibrium constants was examined to estimate the apparent thermodynamic functions (Delta H, DeltaS and Delta G) for extraction reaction. Lead(II) was successfully separated from commonly associated metal ions such as Bi(III), Hg(II), Cr(VI), Cd(II), Zn(II), Al(III), Ca(II), Ba(II) and from binary and ternary mixtures. The method was extended for determination of lead(II) in real samples.