Facilitated oxygen transport through a Nafion membrane containing cobaltporphyrin as a fixed oxygen carrier

A Nafion membrane containing a cobaltporphyrin (CoP) complex as a fixed oxygen carrier was prepared with a view to facilitate oxygen transport through the membrane. The design concept of the CoP-loaded Nafion membrane was based on the CoP's modification to place the CoP complex in a hydrophobic domain of the microphase-separated structure, in order to facilitate the oxygen transport and to maintain proton conductivity. The oxygen permeability through the CoP-loaded Nafion membrane was higher than the nitrogen permeability, and significantly enhanced at relatively-low oxygen pressures of the upstream, indicating that the fixed CoP complex acted as an oxygen hopping site to facilitate the oxygen transport. The oxygen/nitrogen permselectivity increased with the content of CoP in the Nafion membrane. Electrochemical reduction of oxygen at a glassy carbon electrode, modified with a Pt/C catalyst and the CoP-loaded Nafion membrane, provided additional support for the facilitated oxygen transport by the membrane. Increased current for the reduction of oxygen on the modified electrode by loading CoP indicated that the CoP offered the oxygen hopping site in the Nafion membrane.     

Tris(dithiocarbamato)iron(III) complexes as precursors for iron sulfide nanocrystals and iron sulfide-hydroxyethyl cellulose composites

Iron(III) complexes of dimethyldithiocarbamate and imidazolyl dithiocarbamate were synthesized and characterized by elemental analyses, FTIR, UV–VIS and the ligands by NMR spectroscopy. The complexes were thermolysed as single molecule precursors at 180°C to prepare octadecylamine (ODA) capped iron sulfide nanocrystals and iron sulfide-hydroxyethyl cellulose (HEC) composites. UV–VIS, PL, FTIR, P-XRD, HRTEM, FESEM and EDS were used to characterize the iron sulfide nanocrystals and corresponding HEC nanocomposites. XRD confirmed iron sulfide nanocrystal (NP1) from dimethyldithiocarbamate to be hexagonal pyrrhotite-5H, Fe₉S₁₀ crystalline phase while iron sulfide nanocrystals (NP2) from imidazolyl dithiocarbamate is in pyrrhotite, Fe₁₁S₁₂ crystalline phase. TEM images show that the iron sulfide nanocrystals have particle sizes in the range 24–32?nm for NP1 and 18–25?nm for NP2 iron sulfide nanocrystals. The optical band gaps of the iron sulfide nanocrystals obtained from Tauc plots are 3.83 and 4.16?eV for NP1 and NP2, respectively. IR spectra, FESEM surface morphology and EDS spectra of iron sulfide/HEC composites confirmed dispersion of the iron sulfide nanocrystals within the hydroxyethyl cellulose (HEC) matrix.     

Selective transport of cobalt (II) from ammoniacal solutions containing cobalt (II) and nickel (II) by emulsion liquid membranes using 8-hydroxyquinoline

The selective transport of cobalt (II) from ammoniacal solutions containing nickel (II) and cobalt (II) by emulsion liquid membranes (ELMs) using 8-hydroxyquinoline (8-HQ) as extractant has been presented. Membrane solution consists of a diluent (kerosene), a surfactant (ECA 4360J), and an extractant (8-HQ). Very dilute sulphuric solution buffered at pH 5.0 has been used as a stripping solution. The ammoniacal feed solution pH was adjusted to 9.0 with hydrochloric acid. The important variables governing the permeation of cobalt (II) have been studied. These variables are membrane composition, pH of the feed solution, cobalt (II) and nickel (II) concentrations of the feed solution, stirring speed, surfactant concentration, extractant concentration, complexing agent concentration and pH of the stripping solution, and phase ratio. After the optimum conditions had been determined, it was possible to selectively transport 95.0% of cobalt (II) from ammoniacal feed solution containing Co²⁺ and Ni²⁺ ions. The separation factors of cobalt (II) with respect to nickel (II), based on initial feed concentration, have experimentally found to be of as high as 31 for equimolar Co(II)–Ni(II) feed solution.     

Selective low temperature hydroxylation of isobutane by molecular oxygen catalyzed by an iron perhaloporphyrin complex

Irontetrakis(pentafluorophenyl)-octabromoporphyrinato complexes have been synthesized for the first time and shown to have unprecedented catalytic activity for the reaction of molecular oxygen with isobutane to givetert-butyl alcohol. This is the first report of the use of a perhaloporphyrin complex for mild, selective air-oxidation of an alkane and extends the trend of increased activity with halogen substitution established previously. Replacing the eight -(pyrrolic) hydrogens in Fe(TPPF₂₀) complexes with bromines gives catalysts having twice the room temperature air-oxidation activity of the Fe(TPPF₂₀) complexes. Room temperature reaction of isobutane with oxygen catalyzed by Fe(TPPF₂₀6-Br₈)Cl produces 190 moles product per mole catalyst per hour with over 90% selectivity to the alcohol. The catalyst activity is unchanged after 74 hours.     

Facilitated oxygen transport in a novel silicone polymer membrane containing carboxylic cobalt groups

A novel silicone polymer membrane with facilitated oxygen transport properties was prepared by using 11‐alkene acid cobalt, a silicone rubber containing vinyl groups of 5 mol %, a hydrogen‐containing silicon oil, and chlorine platinum acid. The solution casting and the vulcanization were carried out simultaneously at room temperature. Investigation showed that PO ₂ increased and PN ₂ did not change with decreasing gas pressure difference. This facilitated oxygen transport behavior was contributed by a polymeric cobalt complex formed from carboxylic groups and cobaltous ions in the membrane to result in the simultaneous increase of both PO ₂ and αO ₂/N ₂ under lower gas pressure difference. For example, the PO ₂ and αO _2/N ₂ of the membrane containing 11‐alkene acid cobalt of 2.5 wt% were 750 Barrer and 3.09 under a gas pressure difference of 0.05 mPa. As much as 5 wt% 11‐alkene acid cobalt could be added to the membranes; PO ₂ and αO _2/N ₂ increased to 802 Barrer and 3.34 respectively when the membrane contained 11‐alkene acid cobalt of 5 wt %. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1038–1044, 2003     

Electrospun poly(2‐aminothiazole)/cellulose acetate fiber membrane for removing Hg(II) from water

Fiber membrane adsorbent not only has the advantage of ease of handling, but also offers high specific surface area that can benefit the adsorption process when compared with powdered adsorbent. In this work, a poly(2‐aminothiazole) (PAT)/cellulose acetate (CA) composite fiber membrane is prepared by a coaxial electrospinning process, and used as adsorbent for removing Hg(II) from water. The adsorption processes are investigated as functions of pH value, contact time and temperature. The results suggest that the Hg(II) adsorption is preferred to be conducted at pH 6.5 and the adsorption is a monolayer process through chemical interaction. The maximum adsorption capacity in theory is 177 mg/g at 298 K with a very low PAT percentage (6.5 wt %), which is much higher than that of the nanoparticle‐type PAT through conversion. Desorption results exhibit excellent reusability of the composite fiber membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44879.     

Electropolymerization and characterization of terpyridinyl iron (II) and ruthenium (II) complexes

Electroactive 2,2′: 6,2″-terpyridinyl ligands ( 3, 5, 6 ) and their iron(II) ( 7a–9a ) and ruthenium(II) complexes ( 7b–9b ) were synthesized. Bis[3-(aminophenyl)-2,2′ :6,2″-terpyridinyl]metal(II) complexes ( 7a, 7b ) and bis[2-(hydroxyphenyl)-2,2′ :6,2″-terpyridinyl]metal(II) complexes ( 8a, 8b ) were electropolymerized on to the surface of Pt or In-SnO₂ (ITO) electrodes in acetonitrile containing Bu₄NCIO₄ by scanning the potential between O and + 1.6V (for 7a and 7b ), and ?0.8 and +1.6V (for 8a and 8b ) versus saturated calomel electrode. The electrodes obtained by electropolymerization exhibited reversible electrochromism based on Fe(II)/Fe(III) or Ru(II)/Ru(III) redox couple. Photoresponses to visible light were found in the modified electrode obtained by electropolymerization of ruthenium complex 7b in an aqueous LiClO₄ solution containing methylviologen (cation MV²⁺) under an O₂ atmosphere. The mechanism for the photoresponded cathodic current was explained in terms of an excitation of bis(terpyridinyl)ruthenium(II) complex [Ru(terpy)²₂⁺] by visible light, an electron transfer from the excited state [Ru(terpy)^2+*₂] to MV²⁺, reduction of Ru(terpy)³⁺₂ at an electrode, and oxidation of MV^+* with O₂.     

Copper(II) and cadmium(II) complexes with an imide tethered imidazole and a copper(II) coordination polymer through ring opening reaction

The reactions of 2-(3-(1H-imidazol-1-yl)propyl)isoindoline-1,3-dione (L) with copper (II) chloride or copper(II) nitrate resulted in mononuclear complexes [CuL₄Cl₂]·12H₂O (1) or [CuL₄(H₂O)NO₃]NO₃·2H₂O (2) respectively; whereas the copper(II) acetate reacted with L to give a three dimensional coordination polymer {[Cu(L′)₂]·4H₂O}n (3), (where L′ = 2-(3-(1H-imidazol-1-yl)propylcarbamoyl)benzoate). The reaction of cadmium(II) acetate with L led to the formation of a seven-coordinated complex [CdL₃(O₂CCH₃)₂]·2H₂O (4).     

Preparation and characterization of carboximidate iron(II) complexes

The reactions of C₅H₄NCHNNHC(O)Ph (1) with Fe(II) chloride gave [Fe₂(C₅H₄NC(OEt)NNHC(O)Ph)₂(μ-OEt)₂Cl₂]) (2) in ethanol and [Fe₂(C₅H₄NC(OMe)NNHC(O)Ph)₂(μ-OMe)₂Cl₂] (3) in methanol as well as [Fe(C₅H₄NCHNNHC(O)Ph)Cl₂] (4) in tetrahydrofuran, respectively. The X-ray diffraction analysis reveals their structures and complex 4 is proposed as an intermediate of formation of complexes 2 and 3.     

Cyanide binding to iron in a highly distorted porphyrin macrocycle: Synthesis and structure of low-spin Fe(II) dicyano porphyrin

Dark brown crystals of [K(18-crown-6)(H₂O)₂]₂[Fe^II(tn-OEP)(CN)₂] are grown by slow diffusion of cyclohexane into the THF solutions of the molecule generated via auto reduction of [Fe^III(tn-OEP)Cl] in the presence of KCN and 18-crown-6 at room temperature in air and structurally characterized. The complex represents the first structurally characterized dicyano Fe(II) porphyrins in a highly distorted and sterically crowded macocyclic environment. The metal iron is on the plane of the four porphyrinic nitrogens which are accompanied by the decrease of the saddle distortion with a clear and significant increase in ruffling.     

Transport of mercury(II) ion through a supported liquid membrane containing a triisobutylphosphine sulfide (Cyanex 471X) as a mobile carrier

Carrier‐facilitated transport of mercury(II) against its concentration gradient from aqueous 0.1 mol dm^?3 hydrochloric acid solution across a flat‐sheet supported liquid membrane (SLM) containing triisobutylphosphine sulfide (Cyanex 471X) as the mobile carrier in kerosene as diluent has been investigated. Dilute sodium thiocyanate solution (0.11 mol dm^?3) was the most efficient stripping agent among several aqueous reagents tested. Various parameters such as stirring rate, concentration of HCl in the feed solution, concentration of NaSCN in the strippant, concentration of Cyanex 471X in the membrane, and contact time were investigated. Under optimum conditions the transport of Hg(II) across the liquid membrane is about 100% after 6 h. The carrier, Cyanex 471X, selectively and efficiently transported Hg(II) ions in the presence of other associated metal ions. The method has been demonstrated to recover selectively mercury from waste samples and mercurochrome solution. © 2002 Society of Chemical Industry     

Enantiomer enrichment of oxprenolol through cellulose tris(3,5-dimethylphenylcarbamate) membrane

Enantioselective enrichment of racemic oxprenolol dissolved in a hexane-2-propanol mixture was achieved with a solid chiral polymer membrane consisting of cellulose tris(3,5-dimethylphenylcarbamate) coated on a Teflon membrane filter. The oxprenolol obtained through the membrane was rich in (S)-isomer up to about 50% ee at initial stage and (R) enrichment of a source phase (23% ee) was achieved. © 1994 John Wiley & Sons, Inc.     

Polymerization of methyl methacrylate by iron(II) pyridinebisimine complexes

Fe(II) pyridinebisimine complexes activated with trialkylaluminium or modified methylaluminoxane (MMAO) as catalysts were employed for the polymerization of methyl methacrylate. Polymer yields, activities and polymer molecular weights as well as molecular weight distributions can be controlled over a wide range by the variation of the structures of the Fe(II) pyridinebisimine complexes and the reaction parameters such as Al/Fe molar ratio, monomer/catalyst molar ratio, monomer concentration, reaction temperature and time applied to the polymerization of methyl methacrylate. Under optimum condition, the catalytic activity of Fe(II) complex is of up to 74.5 kg_polym/mol_Fe h.     

Structure and physical properties of cellulose acetate/poly(butylene succinate) blends containing a transition metal alkoxide

Two biodegradable polymers, that is, poly(butylene succinate) (BN) and cellulose acetate (CA), were solvent‐cast blended with chloroform. Homogeneous films were obtained from the blend by the addition of tetraisopropyl titanate (TP) as a compatibilizer. We measured the viscosity of the blend solution to investigate the function of TP during the blending process. From the measurement, we conclude that there are interactions among TP, BN, and CA. From optical observation and thermal measurements of the blend films, we found that the structure of blends is in a pseudostable state and that the addition of TP makes the structure units small. From thermogravimetric analyses, we found that the addition of TP decreases the thermal decomposition temperature of the BN/CA blends. From the measurements of mechanical properties of the blends, we found that changing the blend ratio can produce the materials with a wide range of mechanical properties. The hydrolysis of the blends was investigated. The molecular scission of BN/CA blends takes place uniformly not only from the outside but also from the inside of the films. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1750–1758, 2002     

Carrier-facilitated transport of Cd(II) from a high-salinity chloride medium across a supported liquid membrane containing Cyanex 923 in Solvesso 100

The transport of cadmium (II) from a high-salinity chloride medium across a flat-sheet supported liquid membrane containing Cyanex 923 in Solvesso 100 supported on a PVDF membrane into a strip solution with water was investigated. Permeability coefficients of metal increased with decreasing the pH of feed from 2.0 to 0.5. It also increases with increasing carrier concentration in the membrane phase, whereas the permeation is dependent on the organic phase diluent but independent of metal concentration in the feed phase. The performance of the present system against other carriers was also studied.     

Selective permeation across a blend film of cellulose acetate and polymer or copolymer of c-(Nε-AcrLys-Sar)

A blend film of cellulose acetate and the homopolymer (PCP) or the copolymer with styrene [P(CP_ST)] or 4-vinylpyridine [P(CP_VP)] of $\text{cyclo(}\text{N}{}^{\mathrm{\epsilon }}\text{-}\text{acryloyl-}\text{l}\text{-lysylsarcosyl}\text{)}$ [c-(N^ε-AcrLys_Sar)], which is a vinyl compound carrying a cyclic dipeptide in the side chain, was prepared and investigated as a selectively permeable film for ions and polar substances. For the permeation of alkali metal chlorides, the solubility coefficient S increased in proportion to the content of PCP in the blend film, whereas the diffusion constant D_s increased up to 20 wt% of PCP content and levelled off beyond it. D_s of Rb⁺ was greatest for any blend film regardless of the composition. It was considered that the hydrophilic PCP forms water channels in the blend film and metal salts diffuse by coordination with cyclic dipeptide ligand groups which are arrayed along the water channels. In this process, the cooperative interaction of the ligand groups with a metal ion along the flexible polymer chain should work most efficiently with Rb⁺, leading to the Rb⁺ selectivity in the permeation. A similar ion selectivity was observed with the blend film of P(CP_ST). For the blend film of P(CP_VP), S increased in proportion to the content of P(CP_VP), where D_s was a minimum at 20 wt% of P(CP_VP) content. The ion selectivity was not observed with either S or D_s. For the permeation of alkali metal salts across the blend film of PCP, D_s and the ion selectivities were compared for chlorides and thiocyanates, and no remarkable difference was observed. D_s for the permeation of alkaline earth metal salts across various blend films were smaller than those for alkali metal salts. A blend film containing 20 wt% of PCP was found to permeate l-phenylalanine about three times as fast as d-phenylalanine. The optical resolution of racemic phenylalanine by the permeation across the blend film was possible. With increasing content of PCP in the blend film, the urea permeability increased but the oxygen permeability decreased.     

High performance forward osmosis cellulose acetate (CA) membrane modified by polyvinyl alcohol and polydopamine

Cellulose acetate (CA) is a low cost and readily available material widely used in forward osmosis (FO) membranes. However, the performance of pure CA membranes is not good enough in salt separation and the traditional modification methods are generally multistep and difficult to control. In this paper, we reported high performance cellulose acetate (CA) composite forward osmosis (FO) membranes modified with polyvinyl alcohol (PVA) and polydopamine (PDA). PVA was first cross-linked onto the surface of CA membranes, and then PDA was coated with a rapid deposition method. The membranes were characterized with respect to membrane chemistry (FTIR and XPS), surface properties comprising wettability (by water contact angle), and osmosis performance. The modified membrane coated by PVA and PDA shown better hydrophilicity and exhibited 16.72 LMH osmotic water flux and 0.14 mMH reverse solute flux with DI water as feed solution and 2.0 M NaCl as draw solution and active layer facing the feed solution. This simple and highly effective modification method makes it as an excellent candidate for further exploration for FO.     

Dyeing of cotton with indigo using iron(II) salt complexes

The use of gluconic acid as a ligand for complexing iron(II) salts and for vat dyeing of cotton has been reported previously. The present paper reports the observations on the use of iron(II) salts complexed with such ligands as tartaric acid and citric acid for the reduction of indigo at room temperature and subsequent cotton dyeing. This study includes the measurement of reduction potentials of various iron complexes, their effect on dye uptake and the deposition of iron on dyed fabric.