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  • 1.
    Barghi, H.
    et al.
    University of Borås, School of Engineering.
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Synthesis of an electroconductive membrane using poly(hydroxymethyl-3,4-ethylenedioxythiophene-co-tetramethylene-N-hydroxyethyl adipamide)2013In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 1, no 39, p. 6347-6354Article in journal (Refereed)
    Abstract [en]

    Synthesis of a novel electroconductive membrane (ECM) was studied with the aim of producing an electroconductive membrane (ECM) with low electrical resistance and appropriate mechanical properties. The method was based on copolymerization of a highly electroconductive monomer (hydroxymethyl-3,4-ethylenedioxythiophene) with highly mechanical resistant hydrophilized polyamide 46 (polytetramethylene-N-hydroxyethyl adipamide). Due to the lack of hydroxyl groups, polyamide 46 does not have the tendency to take part in any chemical reactions, therefore prior to copolymerization, PA 46 was hydrophilized with acetaldehyde to create reactive sites, which allowed copolymerization to occur. At the final stage, a very thin layer, 566 nm conductive poly(hydroxymethyl-3,4-ethylenedioxythiophene) homopolymer was localised using in situ plasma polymerization in order to improve the electrical conductivity of the obtained copolymer. The result was an adherent, highly conductive, semi-hydrophilic and flexible ECM. The presence of hydroxyl groups in the final product led to improved hydrophilicity of the conductive membrane with a surface tension of 41 mJ m−2. The electrical resistance of PA 46 was dramatically reduced after copolymerization, to 202 in dry and 54 kΩ cm−2 in wet conditions; furthermore, after plasma treatment, this reduction continued to 105 in dry and 2 kΩ cm−2 in wet conditions. Other parameters such as flux flow, roughness, pore size, pore distribution, contact angle, surface energy and thermal stability of the ECM were also investigated.

  • 2.
    Barghi, Hamidreza
    University of Borås, School of Engineering.
    Functionalization of Synthetic Polymers for Membrane Bioreactors2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Membrane bioreactors (MBRs) show great promise for productivity improvement and energy conservation in conventional bioprocesses for wastewater reclamation. In order to attain high productivity in a bioprocess, it is crucial to retain the microorganisms in the bioreactors by preventing wash out. This enables recycling of the microorganisms, and is consequently saving energy. The main feature of MBRs is their permeable membranes, acting as a limitative interface between the medium and the microorganisms. Permeation of nutrients and metabolites through the membranes is thus dependent on the membrane characteristics, i.e. porosity, hydrophilicity,and polarity. The present thesis introduces membranes for MBRs to be used in a continuous feeding process, designed in the form of robust, durable, and semi-hydrophilic films that constitute an effective barrier for the microorganisms, while permitting passage of nutrients and metabolites. Polyamide 46 (polytetramethylene adipamide), a robust synthetic polymer, holds the desired capabilities, with the exception of porosity and hydrophilicity. In order to achieve adequate porosity and hydrophilicity, bulk functionalization of polyamide 46 with different reagents was performed. These procedures changed the configuration from dense planar to spherical, resulting in increased porosity. Hydroxyethylation of the changed membranes increased the surface tension from 11.2 to 44.6 mJ/m2. The enhanced hydrophilicity of PA 46 resulted in high productivity of biogas formation in a compact MBR, due to diminished biofouling. Copolymerization of hydrophilized polyamide 46 with hydroxymethyl 3,4-ethylenedioxythiophene revealed electroconductivity and hydrophilic properties, adequate for use in MBRs. To find either the maximal pH stability or the surface charge of the membranes having undergone carboxymethylation, polarity and the isoelectric point (pI) of the treated membranes were studied by means of a Zeta analyzer. The hydroxylated PA 46 was finally employed in a multilayer membrane bioreactor and compared with hydrophobic polyamide and PVDF membranes. The resulting biogas production showed that the hydroxylated PA 46 membrane was, after 18 days without regeneration, fully comparable with PVDF membranes.

  • 3.
    Barghi, Hamidreza
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Catalytic Synthesis of Bulk Hydrophilic Acetaldehyde-Modified Polyamide 462014In: Current Organic Synthesis, ISSN 1570-1794, E-ISSN 1875-6271, Vol. 11, no 6, p. 288-294Article in journal (Refereed)
    Abstract [en]

    Hydrophilization of Polyamide 46 (PA46) via modification with acetaldehyde in continuous phase was studied. The chemical modification of PA 46 with acetaldehyde resulted in a water-swollen polymer with hydrophilic property. The polyamide 46 undergoes a nucleophilic addition with acetaldehyde in the presence of aluminum chloride as a catalyst. The extent of bulk hydroxyethylation using AlCl3 resulted in 95.65% modification counted as total N-hydroxyethylated polyamide 46. The modification resulted in improved hydrophilic properties, and a maximum surface free energy of 44.6 mJ/m2 was achieved after 3 h reaction, whereas the unmodified PA46 had a surface free energy of 11.2 mJ/m2. In addition, thermal properties of the polymers were studied using differential scanning calorimetry and thermogravimetric analyses. The functionalization leads to decrease in the crystallization energy from 88 J/g to 51 J/g, while the melting energy is changed from 110 J/g to 53 J/g. Furthermore, the thermal stability of the PA46 to pyrolysis was diminished after hydroxylation.

  • 4.
    Barghi, Hamidreza
    et al.
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Synthesis and characterization of novel bulk hydrophilic acetaldehyde modified polyamide 462011Conference paper (Other academic)
  • 5.
    Barghi, Hamidreza
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Taherzadeh, Mohammad J.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bulk Hydrophilic Functionalization of Polyamide 462013Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    (EN)A modified polymer as result of a bulk functionalization of polyamide 46 (PA 46) is presented, as well as methods for synthesizing the modified polymer. This functionalization of PA 46 is performed to provide a homogenous semi-permeable polyamide 46 capable of different charges and different porosities with particles of nanoscale size in order to replace or improve other polyamide fibers used in the textile industry, filtering processes, selective sorption, controlled release devices, phase transfer catalysts, chromatography media, biocompatible capsules, artificial skins, organs, bone void repair as well as in cell bioreactors and incubators, dental impliments, medical devices, clothing, detectors, perfusion devices, in regenerative medicine, and fuel cells. (FR)Un polymère modifié comme résultat d'une fonctionnalisation en masse de polyamide 46 (PA 46) est présenté, ainsi que des procédés de synthèse du polymère modifié. Cette fonctionnalisation de PA 46 est effectuée pour fournir un polyamide 46 semi-perméable homogène apte à des différentes charges et de différentes porosités avec des particules d'une dimension à l'échelle nanométrique afin de remplacer ou d'améliorer d'autres fibres de polyamide utilisées dans l'industrie textile, les procédés de filtration, la sorption sélective, les dispositifs à libération entretenue, les catalyseurs de transfert de phase, les supports de chromatographie, les capsules biocompatibles, les peaux artificielles, les organes, la réparation de cavités osseuses ainsi que les bioréacteurs et incubateurs de cellules, les implants dentaires, les dispositifs médicaux, les vêtements, les détecteurs, les dispositif de perfusion, en médecine régénérative et dans les piles à combustible.

  • 6. Majdejabbari, Sara
    et al.
    Barghi, Hamidreza
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Synthesis and Characterization of Biosuperabsorbent Based on Ovalbumin Protein2010In: Journal of macromolecular science. Pure and applied chemistry (Print), ISSN 1060-1325, E-ISSN 1520-5738, Vol. 47, no 7, p. 708-715Article in journal (Other academic)
    Abstract [en]

    A biosuperabsorbent (Bio-SAP) hydrogel from ovalbumin (egg protein) was synthesized via modification with an acylating reagent and a bifunctional crosslinker, and its swelling behavior was investigated. The protein was acylated using ethylenediaminetetraacetic dianhydride (EDTAD), and then crosslinked by glutaraldehyde and dried. Bio-SAP provided through this method includes modification of lysyl residues in the unfolded protein by adding one or more hydrophilic carboxyl groups to increase the hydrophilicity of protein. The water binding capacity was measured in deionized water, 0.9% NaCl solution and synthetic urine, which under the best conditions were 296, 64 and 56 g/g after 24 h, respectively. In addition, the effects of EDTAD/protein ratio on the chemical modification of the protein, the various chemical neutralization agents, pH sensitivity and ionic strength, as well as temperature and particle size on the water absorption capacity with and without load and its kinetic were also investigated.

  • 7.
    Ylitervo, Päivi
    et al.
    University of Borås, School of Engineering.
    Barghi, Hamidreza
    University of Borås, School of Engineering.
    Franzén, Carl Johan
    Taherzadeh, Mohammad J.
    University of Borås, School of Engineering.
    Improving the stability and mechanical resistance of capsules for encapsulation of S. cerevisiae2010Conference paper (Other academic)
    Abstract [en]

    Nowadays, fuel ethanol is both used as a substitute and an additive to the conventional fossil fuels and the interest in converting lignocellulose to fuel ethanol has expanded in the last few decades. Lignocellulose is attractive as raw material due to its high abundance and low price. However, chemical hydrolysis or pre-treatment of lignocelluloses creates several components that are toxic to fermenting organisms and makes cultivation complicated. By using encapsulated yeast, one can overcome this problem. In encapsulation, the yeast cells are confined inside a capsule composed of an outer semi-permeable membrane and an inner liquid core (Fig. 1). Encapsulation is an attractive method since it can improve the cell stability and inhibitor tolerance, increase the biomass concentration, and decrease the cost of cell recovery, recycling, downstream processing, and fermentation time. Mechanical resistance is a key parameter together with permeability for the success of an encapsulation system. In order to improve the robustness of the capsules we are testing different cross linkers to introduce covalent bonds to the chitosan-alginate matrix. By treating chitosan covered alginate capsules with glutaraldehyde the capsules became harder and less elastic. One big disadvantage in using crosslinking agent is, however, that they are toxic for the yeast. If the encapsulated yeast is treated at too harsh conditions they will die. Although, to improve the capsules mechanical strength the membrane have to be crosslinked to a satisfying degree. We have examined different capsule-treatments and found some encouraging results when applying repetitive treatments with crosslinking agent.

  • 8.
    Youngsukkasem, Supansa
    et al.
    University of Borås, School of Engineering.
    Barghi, Hamidreza
    University of Borås, School of Engineering.
    Rakshit, Sudip K.
    Taherzadeh, Mohammad T.
    University of Borås, School of Engineering.
    Rapid Biogas Production by Compact Multi-Layer Membrane Bioreactor: Efficiency of Synthetic Polymeric Membranesane Reactor for Rapid Biogas Production2013In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 6, no 12, p. 6211-6224Article in journal (Refereed)
    Abstract [en]

    Entrapment of methane-producing microorganisms between semi-permeable synthetic membranes in a multi-layer membrane bioreactor (MMBR) was studied and compared to the digestion capacity of a free-cell digester, using a hydraulic retention time of one day and organic loading rates (OLR) of 3.08, 6.16, and 8.16 g COD/L·day. The reactor was designed to retain bacterial cells with uprising plug flow through a narrow tunnel between membrane layers, in order to acquire maximal mass transfer in a compact bioreactor. Membranes of hydrophobic polyamide 46 (PA) and hydroxyethylated polyamide 46 (HPA) as well as a commercial membrane of polyvinylidene fluoride (PVDF) were examined. While the bacteria in the free-cell digester were washed out, the membrane bioreactor succeeded in retaining them. Cross-flow of the liquid through the membrane surface and diffusion of the substrate through the membranes, using no extra driving force, allowed the bacteria to receive nutrients and to produce biogas. However, the choice of membrane type was crucial. Synthesized hydrophobic PA membrane was not effective for this purpose, producing 50–121 mL biogas/day, while developed HPA membrane and the reference PVDF were able to transfer the nutrients and metabolites while retaining the cells, producing 1102–1633 and 1016–1960 mL biogas/day, respectively.

1 - 8 of 8
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