Capture of toxic gases in MOFs: SO2, H2S,NH3 and NOx

MOFs are promising candidates for the capture of toxic gases since their adsorption properties can be tuned as a function of the topology and chemical composition of the pores. Although the main drawback of MOFs is their vulnerability to these highly corrosive gases which can compromise their chemical stability, remarkable examples have demonstrated high chemical stability to SO₂, H₂S, NH₃ and NO_x. Understanding the role of different chemical functionalities, within the pores of MOFs, is the key for accomplishing superior captures of these toxic gases. Thus, the interactions of such functional groups (coordinatively unsaturated metal sites, μ-OH groups, defective sites and halogen groups) with these toxic molecules, not only determines the capture properties of MOFs, but also can provide a guideline for the desigh of new multi-functionalised MOF materials. Thus, this perspective aims to provide valuable information on the significant progress on this environmental-remediation field, which could inspire more investigators to provide more and novel research on such challenging task.

MOFs are promising candidates for the capture of toxic gases such as SO₂, H₂S, NH₃ and NOx. Understanding the role of different chemical functionalities, within the pores of MOFs, is the key for accomplishing superior captures of these toxic gases.     

Fast HPLC Method for Determination of Fenoxycarb and Permethrin in Antiparasitic Veterinary Shampoo Using Fused-Core Column

A new and fast high-performance liquid chromatography (HPLC) method using technology of fused-core columns for separation of fenoxycarb and cis-, trans-permethrin has been developed and used for their determination in antiparasitic veterinary shampoo. Separation of insecticides and internal standard sudan II was achieved on the fused-core column Ascentis Express RP-Amide (100 × 3.0 mm), particle size 2.7 μm, with mobile phase acetonitrile/water (55:45, v/v) at a flow rate of 1.0 mL min⁻¹ and at temperature 60 °C. The detection wavelength of detector was set at 225 nm for both compounds and internal standard sudan II. Under the optimum chromatographic conditions standard calibration curves were measured with good linearity [r ² = 0.99991 for fenoxycarb, r ² = 0.99987 for trans-permethrin, and r ² = 0.99984 for cis-permethrin (n = 8)]. Commercial samples of antiparasitic veterinary shampoo were extracted with ethanol in ultrasound bath for 5 min. A 2-μL sample volume of the filtered solution was directly injected into the HPLC system. Accuracy of the method defined as a mean recovery of insecticides from shampoo matrix was in the range 100.43–103.85 % for both insecticides.

     

Taxicab geometry in table of higher-order elements

Nonlinear Dynamics - The paper deals with the analysis of the order of the differential equation of motion describing the dynamics of a one-port network compounded of series or parallel connections...     

Green chromatography separation of analytes of greatly differing properties using a polyethylene glycol stationary phase and a low-toxic water-based mobile phase

A simple, rapid, and environmentally friendly HPLC method was developed and validated for the separation of four compounds (4-aminophenol, caffeine, paracetamol, and propyphenazone) with different chemical properties. A “green” mobile phase, employing water as the major eluent, was proposed and applied to the separation of analytes with different polarity on polyethylene glycol (PEG) stationary phase. The chromatography separation of all compounds and internal standard benzoic acid was performed using isocratic elution with a low-toxicity mobile phase consisting of 0.04 % (v/v) triethylamine and water. HPLC separation was carried out using a PEG reversed-phase stationary phase Supelco Discovery HS PEG column (15?×?4 mm; particle size 3 μm) at a temperature of 30 °C and flow rate at 1.0 mL min^?1. The UV detector was set at 210 nm. In this study, a PEG stationary phase was shown to be suitable for the efficient isocratic separation of compounds that differ widely in hydrophobicity and acid–base properties, particularly 4-aminophenol (log P, 0.30), caffeine (log P, ?0.25), and propyphenazone (log P, 2.27). A polar PEG stationary phase provided specific selectivity which allowed traditional chromatographic problems related to the separation of analytes with different polarities to be solved. The retention properties of the group of structurally similar substances (aromatic amines, phenolic compounds, and xanthine derivatives) were tested with different mobile phases. The proposed green chromatography method was successfully applied to the analysis of active substances and one degradation impurity (4-aminophenol) in commercial preparation. Under the optimum chromatographic conditions, standard calibration was carried out with good linearity correlation coefficients for all compounds in the range (0.99914–0.99997, n?=?6) between the peak areas and concentration of compounds. Recovery of the sample preparation was in the range 100?±?5 % for all compounds. The intraday method precision was determined as RSD, and the values were lower than 1.00 %.

HPLC column-switching technique for sample preparation and fluorescence determination of propranolol in urine using fused-core columns in both dimensions

A new and fast high-performance liquid chromatography (HPLC) column-switching method using fused-core columns in both dimensions for sample preconcentration and determination of propranolol in human urine has been developed. On-line sample pretreatment and propranolol preconcentration were performed on an Ascentis Express RP-C-18 guard column (5?×?4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water (5:95, v/v) at a flow rate of 2.0 mL min^?1 and at a temperature of 50 °C. Valve switch from pretreatment column to analytical column was set at 4.0 min in a back-flush mode. Separation of propranolol from other endogenous urine compounds was achieved on the fused-core column Ascentis Express RP-Amide (100?×?4.6 mm), particle size, 2.7 μm, with mobile phase acetonitrile/water solution of 0.5 % triethylamine, pH adjusted to 4.5 by means of glacial acetic acid (25:75, v/v), at a flow rate of 1.0 mL min^?1 and at a temperature of 50 °C. Fluorescence excitation/emission detection wavelengths were set at 229/338 nm. A volume of 1,500 μL of filtered urine sample solution was injected directly into the column-switching HPLC system. The total analysis time including on-line sample pretreatment was less than 8 min. The experimentally determined limit of detection of the method was found to be 0.015 ng mL^?1.

Sulphur distribution in the products of waste tire pyrolysis

The aim of the presented work was to investigate the distribution of sulphur in tire pyrolysis products as well as the influence of process parameters (temperature and residence time) on sulphur distribution due to environmental concerns. Among modern methods used for waste tire recycling, pyrolysis is one of the most reasonable alternatives meeting current environmental standards. However, waste tire sulphur content can be a potential drawback for pyrolysis products utilisation as fuels. Sulphur is present in tires in different concentrations, depending on the type and age of the tires. Typical sulphur content in tires is about 1.6 mass %. In this paper, the distribution of sulphur in tire pyrolysis products was investigated. Tire pyrolysis yields three different products: liquid, gaseous, and solid residue composed mostly of carbon black (chars). Temperature and residence time are the two most important parameters affecting the yield and composition of the volatile fraction and they are therefore expected to affect the sulphur content in residues. Pyrolysis experiments were carried out in a laboratory pyrolysis reaction unit in the temperature range of 650°C to 750°C at different residence times: 88.6 s, 80.2 s, and 73.9 s. Liquid and solid products were analysed by elemental analysis and the distribution of total sulphur in tire pyrolysis products was calculated.     

Application of Novel Zn‐Ferrite Modified Glassy Carbon Paste Electrode as a Sensor for Determination of Cd(II) in Waste Water

This paper describes the preparation of a new sensor based on Zn‐ferrite modified glassy carbon paste electrode and its electrochemical application for the determination of trace Cd(II) ions in waste waters using differential pulse anodic stripping voltammetry (DPASV). Different Zn/Ni ferrite nanoparticles were synthesized and characterized using scanning electron microscopy (SEM) and X‐ray powder diffraction (XRPD). The prepared ferrite nanoparticles were used for the preparation of Zn‐ferrite‐modified glassy carbon paste electrode (ZnMGCPE) for determination of Cd(II) at nanomolar levels in waste water at pH 5. The different parameters such as conditions of preparation, Zn²⁺/Ni²⁺/Fe²⁺ ratio and electrochemical parameters, percentage of modifier, accumulation time, pH and accumulation potential were investigated. Besides, interference measurements were also evaluated under optimized parameters. The best voltammetric response was observed for ZnFe₂O₄ modifier, when the percentage of modifier was 3 %, accumulation time 9 min, pH of supporting electrolyte 5 and accumulation potential ?1.05 V. Thus prepared electrode displays excellent response to Cd(II) with a detection limit of 0.38 ppb, and selective detection toward Cd(II) was achieved.     

One-phase supported titanium-based catalyst for polymerization of ethylene. IV. Effect of alkyl group at organoaluminium compound on catalyst performance

The effect of a basic layer (SiO₂—R₃Al intermediate) in the one-phase silica supported titanium-based catalyst was investigated using the simple model catalyst systems obtained by reacting the activated silica gel consecutively with R₃Al and TiCl₄. Mode of the interaction of SiO₂ with R₃Al—resulting in the formation of the basic layer—was observed via analysis of the concentration of the unreacted OH groups on the silica surface employing IR spectroscopy and via analysis of the concentration of aluminium in solvent using AA spectroscopy. It was found that nature of the alkyl group in R₃Al modified the structure of the basic layer, thus influencing the catalyst performance including the concentration of both the sum of Ti²⁺ and Ti³⁺ and the ESR-active Ti (III) centers. The sum of Ti²⁺ and Ti³⁺ ranged from 45 to 52 mol % and the amount of the ESR-active Ti (III) species ranged from 6 to 17 mol % of the all titanium content. A significant effect of alkyl group at organoaluminium compound on the molecular weight distribution of the resulting polymer was observed. © 1996 John Wiley & Sons, Inc.