Polytetrafluoroethylene Sputtered PES Membranes for Membrane Distillation: Influence of RF Magnetron Sputtering Conditions

Thin films of fluorocarbon were deposited on polyethersulfone membranes via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target in an RF magnetron plasma reactor. The obtained deposited ultrathin coatings had nanoscale roughnesses and high degrees of fluorination. The intensity of fluorine atom in plasma environment during fluorocarbon deposition was investigated. Depending on the deposition conditions comprising working gas pressure, applied RF power, and distance between the target and the substrate, polymeric films with different chemical compositions and/or morphologies were obtained. The morphologies of the films were analyzed by means of SEM, XPS, and AFM. The results suggested that the sputtered film deposited at a higher pressure and longer target–substrate distance and moderate RF power had a surface composition and chemical structure closer to those of the PTFE film. The treated hydrophobic PES membranes with water contact angles as high as 115° were applied for the first time in an air gap membrane distillation setup for removal of benzene as a volatile organic compound from water. The results showed that the plasma-treated membranes have a comparable or superior performance to that of commercial PTFE used in membrane distillation with similar permeate flux and separation factor after 20 h long term performance.     

Synthesis of dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylates via a one-pot and four-component reaction

A number of new dialkyl 5-(aryl)-1-phenyl-1H-prazole-3,4-dicarboxylate derivatives have been prepared regiospecifically in moderate to good yield from the cyclocondensation reaction of dialkyl (E)-2-(dialkoxyphosphoryl)-3-(aroyl)-2-butenedioate, derived from the reaction between trimethyl phosphite, an acetylenic ester, and an aroyl chloride, with phenylhydrazine. The reaction is four-component and is carried out under reflux conditions in dry toluene.     

Methyl Methacrylate–Ethyleneglycol Dimethacrylate–Acrylic Acid Surface as Stationary Phase for Stir Bar Sorptive Extraction

A novel poly(methyl methacrylate–ethyleneglycol dimethacrylate–acrylic acid) film has been introduced for coating on stir bars to sorptive extraction (SBSE). The effects of different contents of porogen, monomer, cross-linker, modifier and initiator during the solvent or bulk polymerization step on the mechanical property and solvent resistant of prepared sorptive stir bars were investigated. The evaluation of results were caused to obtain the four prepared sorptive stir bars with good mechanical stability and excellent resistance to organic solvents. The extraction efficiency of these prepared sorptive stir bars were investigated by liquid desorption-liquid chromatography-ultraviolet detection (LD-LC-UV) using N-Nitrosodiphenylamine as target analyte. SBSE assays showed the sorptive stir bar that prepared using solution polymerization method had the better recovery for N-Nitrosodiphenylamine in water samples. This sorptive stir bar showed good linearity and acceptable recoveries, as well as advantages such as sensitivity, simplicity, low cost and high feasibility. Based on atomic force microscopy (AFM) results, the average pore size of optimum prepared stir bar using solvent polymerization method was obtained ~9 nm. The thermal gravity (TG) and differential scanning calorimetric (DSC) results showed this polyacrylate film has high thermal stability.     

Fiber optic-linear array detection spectrophotometry in combination with dispersive liquid-liquid microextraction for preconcentration and determination of copper

In this research, simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME) combined fiber optic -linear array detection spectrophotometry (FO-LADS) was developed using a cylindrical micro-cell for preconcentration and determination of Cu(II) in samples. DLLME and FO-LADS methods have good matching conditions for being combined since FO-LADS is a suitable method for the determination of analytes in low volume of the remained phase obtained after DLLME. Molar absorptivity of complex Cu with (4-benzylp iperidineditiocarbamate potassium salt) (BPDC) was determined as 2.75 × 10⁴ L mol^-1 cm^-1 at 7nmax = 436 nm. Under the optimum conditions the calibration graph was linear in the rage of 2–70 fug L^-1 with detection limit of 0.34 fug L^-1. The proposed procedure was successfully applied to the determination of Cu(II) in real water samples and human urine sample.     

On simultaneous weakly-Chebyshev subspaces

In this paper, we shall introduce and characterize simultaneous quasi-Chebyshev (and weakly-Chebyshev) subspaces of normed spaces with respect to a bounded set S by using elements of the dual space.     

On the Reaction between Alkyl Isocyanides and Ethynyl Phenyl Ketone in the Presence of N,N′-Dimethylbarbituric Acid

Summary.  The reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and ethynyl phenyl ketone was trapped with N,N ′-dimethylbarbituric acid to produce alkyl 1,3-dimethyl-2,4-dioxo-7-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-5-carboxamides in good yields. Corresponding author. E-mail: isayavar@yahoo.com Received January 8, 2002. Accepted January 14, 2002     

Liquid-liquid extraction of palladium(II) from hydrobromic acid media by hexadecylpyridinium bromide.

A simple and rapid liquid-liquid extraction of palladium has been studied involving ion-pairing of bromocomplexes of palladium(II) with hexadecylpyridinium bromide (HDPB) dissolved in chloroform. The stoichiometry and distribution of (HDP)2PdBr4 between the aqueous and organic phase was investigated by spectrophotometric mole ratio method. The extraction efficiency of palladium(II) by HDPB was studied as a function of several variables: acid, salt, surfactant concentration and equilibrium time. The results showed that PdBr4(2-) extraction could be explained by assuming the formation of (HDP)2PdBr4 complexes in the aqueous solution and transfer to organic phase. The extraction was fast and the shaking time was only a few min. The average recovery of palladium(II) from an aqueous solution containing 10 microg/ml of analyte was 99% with an RSD% of 0.95. The percentage recovery of 0.2 microg/ml palladium(II) was 96%.