A fluorescence ratiometric detection scheme for ammonium ions based on the solvent sensitive dye MC 540

Principles of wavelength ratiometric evaluation of fluorescence have been extensively used to cancel out and reference sensor response not associated with the analyte. Main limitations of this technique include wavelength ratiometric properties inherent only to a restricted number of solute specific fluorescent dyes. This study presents a dual-excitation/dual-emission ratiometric detection scheme applied on a two-phase coextraction based fluorosensor. Rather than utilizing spectral shifts associated with various complexation and acid–base equilibria of solute specific indicators, we made use of the fluorescence shift induced by the phase transfer of the solvent sensitive dye merocyanine 540 (MC 540) upon ammonium–nonactin coextraction in a hydrogel–ether emulsion. The two-phase ratiometric fluorosensor was exposed to conditions frequently reported to alter performance of fluorescence based optical sensors. Sensor response was unaffected by O₂ concentrations, and signals caused by variations in excitation light intensity and pH were found more or less completely eliminated by the ratiometric procedure. Selectivity towards NH₄⁺ and possible interferences from K⁺ were more accurately evaluated using the dual-excitation/dual-emission ratio, compared to a single-excitation/single-emission fluorescence scheme. It was not possible to eliminate artifacts associated with fluctuations in temperature, effective MC 540 concentrations and sample ionic strength by the ratiometric reference scheme, most likely due to monomer–dimer complexation of the indicator dye and the formation of larger aggregates at concentrations exceeding the critical salt concentration of MC 540. Principles described for a two-phase ratiometric detection procedure associated with solvent sensitive dyes rather than solute specific fluorescent dyes may provide a powerful tool for direct solute detection. Thus, the limited versatility of wavelength ratiometric fluorescence detection to specially designed compounds with wavelength ratiometric properties directly linked to interactions with the analyte, may be overcome.     

Growth and Solvent Effects of a Promising Nonlinear Optical Sodium Paranitrophenolate Dihydrate (NO2-C6H4-ONa∙2H2O) Single Crystal

Sodium paranitrophenolate dihydrate (NPNa∙2H2O) is an excellent semiorganic nonlinear optical (NLO) material, crystallizes both in water and methanol with high degree of transparency. Good optical quality single crystals of dimension upto 18 mm×6 mm×3 mm are obtained by sothermal solvent evaporation technique. The solubility of the crystal in different solvents was measured gravimetrically. The single crystals of NPNa∙2H2O show variation in physical properties and growth rate in different solvents. Methanol or ethanol solution yields crystals of bipyramidal shape with clear morphology. However, methanol grown crystal is exhibiting improved hardness parameters and possesses excellent thermal stability as compared to water grown crystals. The effects of solvent on hardness parameter along with thermal and optical properties of NPNa∙2H2O was revealed in this paper.     

Characterization study and recovery of copper from low grade copper ore through hydrometallurgical route

Characterization studies were conducted on low grade copper ore with the aid of standard approaches. The Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS) study specifies the semi-quantitative data of qualitatively analyzed chemical elements present in the ore sample. Optical Microscopy (OM) and X-Ray Diffraction (XRD) endorse the presence of chalcopyrite (CuFeS₂) and pyrites along with other different mineral phases in the ore sample. Thermo Gravimetric Analysis (TGA) and Mossbauer spectroscopy studies confirm the formation of CuO and Fe₂O₃ after roasting at 700 °C. The better copper recovery from low grade copper ore was achieved through optimized leaching parameters. It was found that the particle size of ?63+53 µm can be leached up to 94.96 % of copper using a lixiviant reagent mixture (30 vol. % hydrogen peroxide and 0.5 M sulfuric acid) under magnetic stirring for 30 min at a constant speed of 300 rpm, by keeping the liquid/solid (L/S) ratio at 20/2 ml/g. Moreover, the solvent extraction process works well with the pregnant leach solution, whereby, 98.9 % of copper extraction is possible, and the loading time is less than a minute. Meanwhile, 93.91 % of overall copper extraction efficiency was achieved through optimized leaching parameters and solvent extraction method.     

粗苯加氢精制技术比较

本文介绍了莱托法高温加氢、萃取蒸馏低温加氢和溶剂萃取低温加氢工艺.阐述了加氢原理,列出了产品质量、收率、能耗指标,对3种粗苯加氢工艺进行了比较,认为粗苯精制改造宜采用低温加氢精制工艺.     

Silver modified porous silica from rice husk and its catalytic potential

Rice husk silica modified with Ag (RH-Ag) and its calcined form, RH-Ag(C) are heterogeneous catalysts prepared from rice husk. The sodium silicate was extracted from rice husk using a simple solvent extraction technique. Silver was added during the precipitation of the gel to form RH-Ag. Calcination of RH-Ag yielded RH-Ag(C). RH-Ag and RH-Ag(C) was found to have a well defined amorphous phase and a crystalline phase. TEM analysis showed that silver was encapsulated into the silica matrix. Well defined mesoporous channels were found in RH-Ag(C). The EDX analysis showed that silver was indeed incorporated in the matrix of RH-Ag but it was not homogenously distributed. The specific surface area of RH-Ag and RH-Ag(C) was found to be 447 and 419 m² g⁻¹ respectively. The cation exchange capacity (CEC) for RH-Ag was found to be 0.470 mmol g⁻¹ which was higher than that of RH-Ag(C) with 0.273 mmol g⁻¹. Both the CEC and the BET values for RH-Ag(C) was consistent with the calcination process. Catalysis of benzyl alcohol using RH-Ag and RH-Ag(C) gave two products which were identified as benzaldehyde and dibenzyl ether. Percentage conversion was higher when the reaction was conducted with pure oxygen (14.0%) than in open air (0.60%). Overall, RH-Ag(C) was found to be a better catalyst for the formation of dibenzyl ether. The optimum weight and time of reaction for the oxidation was found to be 0.3 g and 3 h respectively for both catalysts. It was found that even in an inert atmosphere, 13% of benzaldehyde was obtained with RH-Ag(C) as catalyst. Mechanisms for the formation of benzaldehyde under oxygen and inert atmosphere and the condensation mechanism assisted by the presence of the Ag on the surface of the catalyst have been suggested.     

Recovery of 1-butanol from a model pharmaceutical aqueous waste by pervaporation

Pervaporation experiments were conducted to recover 1-butanol from model pharmaceutical aqueous waste using a surface modified poly(vinylidene difluoride) membrane. The surface modification of the membrane was made using silicone grease as an ultra-thin layer on the surface to improve the pervaporation performance of the membrane. The effect of operating variables such as feed composition, feed temperature and feed flow rate on permeation fluxes, separation factor and pervaporative separation index were studied in order to optimize the operating variables. The experimental results showed that surface modified poly(vinylidene difluoride) membrane was 1-butanol permselective, especially for low feed compositions. 1-Butanol separation factor of 6.4 and a total flux of have been obtained at a feed composition of 7.5 wt%, feed temperature of , feed flow rate of and permeate pressure of 50 mmHg. The total flux of the surface modified membrane increased with increasing the feed composition, feed temperature, feed flow rate of the mixture whereas the separation factor follows a reversed order except for flow rate. The influence of operating variables such as feed composition and temperature on partial flux and permeate composition was modelled based on Fick's first law to understand the process behaviour and it will be very useful for design purpose. These models will be used to predict the required membrane surface area for recovery of 1-butanol for the range of experimental feed compositions.     

Measurement and correlation of the solubility of sodium acetate in eight pure and binary solvents

The knowledge of solubility of a salt in either the pure solvent or blend solvent is of great importance for studying or operating the crystallization, extraction, and distillation processes. The solubility of sodium acetate (NaAc) in four pure solvents (water, ethanol, acetic acid and 2,2,2-trifluoroethanol) and four binary solvents (water–ethanol, water-acetic acid, acetic acid–ethanol, and acetic acid-ethyl acetate) were measured by using the laser dynamic method at temperatures from 288.15 K to 338.15 K at 0.1 MPa. The results showed that the solubility of NaAc was influenced by either the solution temperature or solvent composition. The aqueous sodium acetate solution possessed the maximal solubility under the experimental conditions. The solubility of NaAc in 2,2,2-trifluoroethanol was found to be decreased with the increase of the solution temperature. While, the solubilities of NaAc in other seven solvents increased as the solution temperature was elevated. Besides, five correlation models, including the van't Hoff model, modified Apelblat model, Yaws model, λh model, and modified Apelblat-Jouyban-Acree model were used to correlate the solubility data of those sodium acetate solutions with acceptable deviation, respectively. Finally, van't Hoff analysis method was selected to analyze the change law of thermodynamic properties of a salt during the dissolution process.     

煤化工废水中二元酚处理方法的研究进展

介绍了含二元酚废水处理方法的研究现状,主要包括吸附法、乳状液膜分离法、溶剂萃取法、焚烧法、酚醛缩合法、化学氧化法、蒸汽脱酚法、臭氧氧化法和高级氧化技术等,分析比较了各种处理方法的优缺点和应用前景,重点介绍了目前工业上常用的溶剂萃取法、溶剂的选择及其影响因素,展望了含二元酚废水处理技术的发展方向,提出多种技术联用是今后处理含二元酚废水的趋势.     

聚烯烃塑料溶剂提取物影响因素研究

目的研究并建立测定聚烯烃树脂二甲苯和正己烷溶剂提取物的最佳方法。方法通过实验研究试样质量与溶剂体积比、过滤方式、样品粒径、蒸干方式、残渣干燥方式和干燥时间对烯烃聚合物树脂正己烷和二甲苯溶剂提取物的影响,确定最佳实验方案。结果聚烯烃溶剂提取物实验的最佳条件为试样质量/溶剂体积比为1 g/100 mL、试样粒径为小于8目筛网孔(二甲苯提取物可不受此限)、二甲苯物实验可不添加抗氧化剂、正己烷提取物过滤方式为滤纸过滤、二甲苯提取物过滤方式为布氏漏斗减压过滤、蒸干方式为水浴蒸干、干燥条件为普通烘箱干燥2h。结论优化实验条件下所得结果与标准条件一致,但优化实验条件成本低、且操作更为简单、快捷。     

丙烯酸酯共聚物压敏胶的研制

研究了丙烯酸酯共聚物压敏胶的单体组成、合成工艺及其产品性能,目的是为了探索一种原料品种少、生产工艺简单、产品性能优良的方法。实验结果令人满意。