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  • 1.
    Farooq, Usman
    et al.
    East China Univ Sci & Technol, China..
    Danish, Muhammad
    East China Univ Sci & Technol, China..
    Lu, Shuguang
    East China Univ Sci & Technol, China..
    Naqvi, Muhammad
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Gu, Xiaogang
    East China Univ Sci & Technol, China..
    Fu, Xiaro
    East China Univ Sci & Technol, China..
    Zhang, Xiang
    East China Univ Sci & Technol, China..
    Nasir, Muhammad
    COMSATS Inst Informat Technol, IRCBM, Lahore, Pakistan..
    Synthesis of nZVI@reduced graphene oxide: an efficient catalyst for degradation of 1,1,1-trichloroethane (TCA) in percarbonate system2017In: Research on chemical intermediates (Print), ISSN 0922-6168, E-ISSN 1568-5675, Vol. 43, no 5, p. 3219-3236Article in journal (Refereed)
    Abstract [en]

    Graphene-oxide-supported nano zero-valent iron (nZVI) composite (nZVI-rGO) was synthesized and tested as an efficient percarbonate activator for degradation of 1,1,1-trichloroethane (TCA). Significant dispersion of nZVI on the surface of reduced graphene oxide (rGO) was observed, with good limitation of nanoparticle agglomeration and aggregation. Good TCA degradation efficiency of 90% was achieved in 2.5 h in presence of 0.8 g/l nZVI-rGO catalyst and 30 mM sodium percarbonate (SPC) oxidant; however, excessive catalyst or oxidant concentration reduced the degradation efficiency. Investigation of reactive oxygen species using radical probe compounds as well as radical scavengers confirmed presence of hydroxyl (OH center dot) and superoxide () radicals that are responsible for the TCA degradation. The morphology and surface characteristics of the heterogeneous catalyst were analyzed by transmission electron microscopy and scanning electron microscopy. Brunauer-Emmett-Teller analysis revealed that the synthesized catalyst had large surface area and small particle size of 299.12 m(2)/g and 20.10 nm, respectively, compared with 5.33 m(2)/g and 1.12 A mu m for bare graphene oxide. X-ray diffraction analysis revealed good dispersion of nZVI on the surface of rGO. Fourier-transform infrared characteristic peaks confirmed strong attachment of Fe onto the rGO surface. Energy-dispersive spectroscopy analysis validated the stoichiometric composition of the prepared Fe/rGO material. In conclusion, use of nZVI-rGO-activated SPC could represent an alternative technique for remediation of TCA-contaminated groundwater.

  • 2.
    Steen, Robert O.
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Nurkkala, Lasse J.
    Bernhardt, Paul V.
    University of Queensland, Dept. of Chemistry, School of Molecular & Microbial Sciences .
    Dunne, Simon J.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Bis-cyclometallated Molecular Switches Based on 4,7-phenantroline and 1,5-naphthyridine ArchitectureManuscript (preprint) (Other academic)
    Abstract [en]

    Two new bis-terdentate ligands,  3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline (L1) and 2,6-bis(6-(thiophen-2-yl)pyridin-2-yl)-1,5-naphthyridine (L2), capable of reversible double cyclometallation have been synthesized. Both syntheses proceeded via a Skraup synthesis followed by Stille cross-coupling with 2-thiophen-2-yl-6-tributylstannylpyridine to yield the final product. The Ru2(tpy)2-complex of L1 was shown to be capable of reversible cyclometallation, where the bis-cyclometallated (C,C) isomer of the complex had an oxidation potential of +249 mV while the oxidation potential of the doubly S-coordinated (S,S) complex was +987 mV. No ground state interaction between the Ru cores was however found. In theory the complex should display a third, mixed, state. An S,C-coordinated isomer would open the way for molecular electronic applications based on ternary logic. However, despite attempts the S,C-coordinated complex could not be generated.

  • 3.
    Steen, Robert O.
    et al.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Nurkkala, Lasse J.
    Mälardalen University, School of Sustainable Development of Society and Technology.
    Hougen, Annett I.
    University of Basel, Dept. of Chemistry.
    Schmitt, Chantal X.
    University of Basel, Dept. of Chemistry.
    Constable, Edwin C.
    University of Basel, Dept. of Chemistry.
    Rees, David G. F.
    University of Basel, Dept. of Chemistry.
    Bernhardt, Paul V.
    University of Queensland, Dept. of Chemistry, School of Molecular & Microbial Sciences .
    Dunne, Simon J.
    Coordination-mode pH-activated Molecular Switches based on Ruthenium(II) Oligopyridine Complex ArchitectureManuscript (preprint) (Other academic)
    Abstract [en]

    A number of [Ru(tpy)L] complexes (where L is a ligand based on the 6-thien-2-yl-2,2’-bipyridine motif) have been generated to study the ability of this terdentate motif to switch between a N,N,C and a N,N,S binding mode as a function of pH and irradiation. Whilst the parent system 6-thien-2-yl-2,2’-bipyridine (1) displayed facile switching between the orange and purple forms, heavier analogues displayed sluggish switching – most likely resulting from a large moment of inertia about the bond between the S/C-bonded thiophene ring and the chelating bipyridine unit. Prototypic unsymmetrical bimetallic complexes (C7S and C7C) have been generated in order to test if the binding mode of the switching unit can affect the oxidation potential of the remote [Ru(bpy)2(L)] unit. The results of cyclic voltammetry studies suggest that only weak electronic coupling between the metal cores exists, and that the coordination mode (N,N,C or N,N,S) of the thiophene moiety only has a small effect on the oxidation potential of the [Ru(bpy)2(L)] unit.

  • 4.
    Waltersson, Johanna
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, Department of Biology and Chemical Engineering.
    The metal binding properties of kraft lignin2009Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There is a strong driving force to increase the competitiveness of the pulping industry by finding new business opportunities. In this context full utilisation of the wood raw material used in conventional pulping mills is of vital importance. One focus area is to increase the utilisation areas of lignin. LignoBoost is a new method to obtain kraft lignin of high purity.

    The aim of the project was to investigate and increase the ability of LignoBoost kraft lignins to bind metals in aqueous solutions.

    The metal binding property of kraft lignins was evaluated using copper (II) ions. The metal binding capacities were 1.76 mg Cu2+/g LignoBoost softwood kraft lignin, 0.96 mg Cu2+/g LignoBoost hardwood kraft lignin and 1.12 mg Cu2+/g condensed softwood kraft lignin. The metal binding capacities of the softwood and hardwood kraft lignins from LignoBoost were lower than expected, when compared to the metal binding capacities of other lignins found in literature. The highest copper binding capacity of a kraft lignin found in literature was almost 50 times greater than that of the LignoBoost softwood kraft lignin.

     

    The Mannich reaction was used to increase the nitrogen content in softwood lignin, and thereby increase its electron-donating capacity. An increase in electron-donating capacity should promote its metal binding capacity.

     

    The Mannich reaction occurs in the vacant ortho position of the phenolic groups of lignin, introducing an aminomethyl group at that position. The only vacant ortho position in the phenol unit for reaction is in the guaicyl unit. Softwood lignin underwent a Mannich reaction, since softwood contains a greater number of guaiacyl units than hardwoods.

     

    A screening of the products from this Mannich reaction on LignoBoost softwood kraft lignin was performed to optimise the reaction conditions. The reaction time, temperature, amount of formaldehyde and dimethylamine were varied. The Mannich products were evaluated by elemental analysis. The conditions giving the highest nitrogen content in the product were used further in a Mannich reaction of condensed softwood kraft lignin. The condensed softwood kraft lignin (7 g) was treated with dimethylamine (0.35 mol) and formaldehyde (0.35 mol) at 80°C for 24 hours.

     

    The metal binding experiment could not be carried out with Mannich-modified condensed softwood kraft lignin since the lignin dissolved in the copper solution.

     

    When introducing nitrogen functionalities into lignin the electron-donating capacity should increase. An increase in donor groups should promote the metal binding capacity of the lignin. A problem that occurred when introducing aminomethyl groups was an increase in solubility of the lignin. Water solubility of the lignin derivative is undesirable in the envisaged utilization area, metal binding in, for example mine deposits, from where contaminated water may be a concentrated source of heavy metals.

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