Determination of heavy metal concentration in feed and permeate streams of polymer enhanced ultrafiltration process

Polymer enhanced ultrafiltration (PEUF) is a newly developed method for the removal of heavy metals from aqueous solutions. This method was applied for the removal of mercury and cadmium with the presence of polyethyleneimine (PEI) as a water soluble polymer. After ultrafiltration experiments for metal–polymer mixtures, two separate streams, namely, retentate and permeate, former of which contains mainly metal–polymer complex and free polymer molecules while latter of which mainly contains free metal ions, were obtained. At the end of PEUF experiments, performance of operation was determined by concentration analyses which was achieved by atomic absorption spectroscopy (AAS) applied in a different way for permeate and retentate streams considering the effect of presence of polymer. For mercury analysis, cold vapor AAS was applied. It was observed that the presence of PEI did not affect the atomic absorption signal when 10% HCl was added to the sample solutions. For calcium and cadmium, flame AAS was used. It was observed that change in PEI concentration results in change in measured concentration of calcium and cadmium. Therefore, two new approaches were developed for accurate measurement of concentrations of calcium and cadmium. It was also observed that presence of other metals did not affect the accuracy of the measurement of a particular metal in the concentration range studied.     

A novel synthesis of (3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-(4-vinylbenzyl)-9H-carbazole), alternating polymer formation, characterization, and capacitance measurements

In this work, (3,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-9-(4-vinylbenzyl)-9H-carbazole) (EDOTVBCz) comonomer was chemically synthesized and characterized by Fourier transform infrared (FTIR), proton nuclear magnetic resonance, and carbon nuclear magnetic resonance spectroscopy. EDOTVBCz was electrocoated on glassy carbon electrode (GCE) in various initial molar concentrations ([EDOTVBCz]₀?=?1.0, 1.5, 2.0, and 3.0) in 0.1 M lithium perchlorate (LiClO₄)/acetonitrile (CH₃CN). P(EDOTVBCz)/GCE was characterized by cyclic voltammetry, FTIR reflectance-attenuated total reflection spectroscopy, scanning electron microscopy–energy dispersive X-ray analysis, atomic force microscopy, and electrochemical impedance spectroscopy (EIS). EIS was used to determine the capacitive behaviors of modified GCE via Nyquist, Bode magnitude, Bode phase, and admittance plots. The highest low-frequency capacitance value was obtained as C _LF?=?～2.35 mF cm^?2 for [EDOTVBCz]₀?=?3.0 mM. Double-layer capacitance of the polymer/electrolyte system was calculated as C _dl?=?～2.78 mF cm^?2 for [EDOTVBCz]₀?=?1.0 and 3.0 mM. The maximum phase angle was obtained as θ?=?～76.7^o for [EDOTVBCz]₀?=?1.0, 1.5, 2.0, and 3.0 mM at the frequency of 20.6 Hz. AC impedance spectra of P(EDOTVBCz)/LiClO₄/CH₃CN was obtained by performing electrical equivalent circuit model of R(Q(R(CR))) with linear Kramers–Kronig test.

An Efficient Synthesis of Nitriles from Aldoximes in the Presence of Trifluoromethanesulfonic Anhydride in Mild Conditions

Russian Journal of Organic Chemistry - A new and convenient protocol has been proposed for the transformation of aldoximes to nitriles using trifluoromethanesulfonic anhydride and triethylamine....     

The effect of fermentation (retting) time and harvest time on kudzu (Pueraria lobata) fiber strength

Applied Biochemistry and Biotechnology - The noncommercial kudzu plant has been growing wild in the southern United States since the 1930s. In this article, the kudzu fibrous vine is investigated...     

Conjugation of arginine–glycine–aspartic acid peptides to thermoreversible N‐isopropylacrylamide polymers

Thermoreversible polymeric biomaterials are finding increased acceptance in tissue engineering applications. One drawback of the polymers is their synthetic nature, which does not allow direct interaction of mammalian cells with the polymers. This limitation may be alleviated by grafting arginine–glycine–aspartic acid (RGD) containing peptides onto the polymer backbone to facilitate interactions with cell‐surface integrins. Toward this goal, N‐isopropylacrylamide (NiPAM)‐based thermoreversible polymers containing amine‐reactive N‐acryloxysuccinimide (NASI) groups were synthesized. Conjugation of RGD‐containing peptides to polymers was demonstrated with ¹H NMR spectroscopy and reverse‐phase high‐pressure liquid chromatography. The conjugation reaction was optimal at 4 °C and pH of 8.0, and increased with the increasing NASI content of polymers. With a peptide grafting ratio of 0.25 mol %, there was no significant change in the lower critical solution temperature of the polymers. Finally, the NASI‐containing polymers, cast as films, on tissue culture polystyrene, were shown to conjugate to RGD‐containing peptides and support C2C12 cell attachment. We conclude that NASI‐containing thermoreversible polymers are amenable for grafting biomimetic peptides to impart cell adhesiveness to the polymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3989–4000, 2003     

Studies on the synthesis of the azocino[4,3‐b]indole framework and related compounds

An efficient method for the synthesis of C‐4 position alkylated azocino[4,3‐b]indole 13 and 18 is described. Reduction of compounds 5, 6, 7 and 8 yielded the corresponding alcohols. Compounds 5, 6, 7 and 8 were synthesized through several steps starting from 1 . The resulting alcohols underwent acid catalyzed ring closure to give tetracyclic azocino[4,3‐b]indole 9, 10, 11 and 12 . Finally, compounds 9 and 17 were alkylated at C‐4 position to the corresponding products 13 and 18 . The structure of the compounds 13 and 18 has been confirmed by X‐ray single crystal analysis.     

Development of surface chemistry for surface plasmon resonance based sensors for the detection of proteins and DNA molecules

The immobilisation of biological recognition elements onto a sensor chip surface is a crucial step for the construction of biosensors. While some of the optical biosensors utilise silicon dioxide as the sensor surface, most of the biosensor surfaces are coated with metals for transduction of the signal. Biological recognition elements such as proteins can be adsorbed spontaneously on metal or silicon dioxide substrates but this may denature the molecule and can result in either activity reduction or loss. Self assembled monolayers (SAMs) provide an effective method to protect the biological recognition elements from the sensor surface, thereby providing ligand immobilisation that enables the repeated binding and regeneration cycles to be performed without losing the immobilised ligand, as well as additionally helping to minimise non-specific adsorption. Therefore, in this study different surface chemistries were constructed on SPR sensor chips to investigate protein and DNA immobilisation on Au surfaces. A cysteamine surface and 1%, 10% and 100% mercaptoundecanoic acid (MUDA) coatings with or without dendrimer modification were utilised to construct the various sensor surfaces used in this investigation. A higher response was obtained for NeutrAvidin immobilisation on dendrimer modified surfaces compared to MUDA and cysteamine layers, however, protein or DNA capture responses on the immobilised NeutrAvidin did not show a similar higher response when dendrimer modified surfaces were used.