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  • 1.
    Hague, Enamul
    et al.
    University of Dhaka, Bangladesh .
    Islam, Nahidul
    University of Dhaka, Bangladesh .
    Rahman, Hafizur
    University of Dhaka, Bangladesh .
    Uddin Mohamad, Akim
    University of Dhaka, Bangladesh .
    Antimicrobial and Cytotoxic Activities of the Crude Extracts and Isolated Compounds of Xylocarpus mollucensis2008In: Dhaka University Journal of Pharmaceutical Sciences, Vol. 6, no 2, p. 109-112Article in journal (Refereed)
    Abstract [en]

    The fractionated crude extracts and three isolated pure compounds XM-1, XM-2 and XM-3 from stem bark of Xylocarpus mollucensis were screened for their antibacterial and antifungal activities and cytotoxicity against brine shrimp nauplii. Petroleum ether, ethyl acetate (EtOAc) and methanol (MeOH) extracts and the compounds isolated from EtOAc fractions were studied for their antimicrobial activities. Cytotoxic activities were conducted only with EtOAc extract and its selected fractions. The EtOAc extract showed promising antimicrobial activities against all the gram positive and gram negative bacteria whereas petroleum ether extract showed moderate activities and the MeOH extract did not show any antimicrobial activities. The isolated pure compounds XM-1, XM-2 and XM-3, whose structures were not elucidated, exhibited activities against most of the bacterial strains. The cytotoxicity towards brine shrimp nauplii of the crude EtOAC extract and its selected fractions were studied. The LC50 values of the EtoAc extract was 12.6 µg/ml and for the fractions 2, 5, 8 and 13 were 17.78, 13.34, 14.13 and 15.85 µg/ml, respectively.

  • 2.
    Haque, Enamul
    et al.
    University of Dhaka, Bangladesh.
    Uddin Shekhar, Hussain
    University of Dhaka, Bangladesh.
    Uddin Mohamad, Akim
    University of Dhaka, Bangladesh.
    Rahman, Hafizur
    University of Dhaka, Bangladesh.
    Islam, Mydul
    University of Dhaka, Bangladesh.
    Hossain, Sabir
    University of Dhaka, Bangladesh.
    Triterpenoids from the Stem Bark of Avicennia officinalis2006In: Dhaka University Journal of Pharmaceutical Sciences, Vol. 5, no 1-2, p. 53-57Article in journal (Refereed)
    Abstract [en]

    The triterpinoids, betulinic acid, lupeol and betulinaldehyde, were isolated from the ethyl acetate extract of the stem bark of Avicennia officinalis (Avicenniaceae) by a combination of column and preparative thin- layer chromatography over silica gel. The structures of these compounds were determined by spectroscopic analysis (UV, IR, 1 H NMR, 13 CNMR and EIMS). This is the first report of a systematic phytochemical investigation and the presence of these triterpoids from this plant.

  • 3.
    Rahman, Hafizur
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Modification of Softwood Kraft Pulp is Better for Tissue Paper2018Other (Other (popular science, discussion, etc.))
  • 4.
    Rahman, Hafizur
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Modification of softwood kraft pulp requiring less energy in tissue paper production2019Conference paper (Refereed)
    Abstract [en]

    Modification of softwood kraft pulp by the addition of either polysulfide (PS) or sodium borohydride (NaBH4) has been shown to increase pulp yield due to a higher retention of hemicellulose. The modified pulps showed higher tensile index, especially at lower refining. It also showed a greater porosity of the fibre wall, indicating an increase in the swelling potential of the fibres thus helping to increase fibre flexibility, increase joint strength between the fibres and to raise the tensile index. However, the swelling increase associated with the higher hemicellulose content could also make dewatering more challenging because of the higher water retention of pulp. But recent studies showed the positive influence of increase pulp yield dominates over the negative influence of the higher hemicellulose content on dewatering properties, especially at lower refining. Studies simulating full-scale tissue dewatering conditions showed that pulps with higher hemicellulose content had a higher tensile index at the same dryness which was achieved in a shorter dwell-time. A given tensile index was also achieved with less refining energy. Therefore modification of the kraft pulping process is now a way to give high quality fibres for tissue paper production with less refining energy and lower drying energy costs.

  • 5.
    Rahman, Hafizur
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Modify or optimize the Kraft pulping process to produce more refining energy efficient fibers at the final functional product properties of Tissue Papers2015In: Cellulose Materials Doctoral Students Summer Conference 2015 / [ed] Hauhio, Leena, Aalto University, Finland, 2015Conference paper (Refereed)
  • 6.
    Rahman, Hafizur
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Modifying kraft pulping to produce a softwood pulp requiring less energy in tissue paper production2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Modification of softwood kraft pulp by the addition of either polysulfide (PS) or sodium borohydride (NaBH4) has been shown to increase the pulp yield due to a higher retention of glucomannan.  The pulps with higher yield gave a paper with higher tensile index than reference pulp, especially at lower degrees of refining. The higher yield pulps also showed a greater porosity of the fibre wall, indicating an increase in the swelling potential of the fibres. This can lead to increased fibre flexibility and increased joint strength between the fibres and to the higher handsheet tensile index. However, the swelling increase associated with the higher hemicellulose content could also make dewatering more challenging because of the higher water retention of the pulp. The results of this study show however that the positive influence of the increase in yield (fewer fibres and a more open sheet structure) dominates over the negative influence of the higher hemicellulose content on the dewatering properties, especially at lower refining energy levels. Studies simulating full-scale tissue machine dewatering conditions showed that pulps with a higher yield and a higher hemicellulose content had a higher tensile index at the same dryness. Moreover, the same dryness level was achieved in a shorter dwell-time. A given tensile index was also achieved with less refining energy.

    Increasing the yield and hemicellulose content by the addition of either an oxidizing or a reducing agent in the softwood kraft pulping process thus has a potential for giving high quality fibres for tissue paper production with less refining energy and lower drying energy costs.

     

  • 7.
    Rahman, Hafizur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    An, Siwen
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Persson, Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Maximized wood chip impregnation efficiency validated by new miniaturized X-ray fluorescence techniques2019Conference paper (Refereed)
    Abstract [en]

    Manufacturing of chemi-thermomechanical pulp (CTMP) is increasing due to increased demand for packaging materials such as cardboard as well as tissue and other hygiene products. Today high yield pulp (HYP) is produced from different wood species. It is well-known that chip-refining is normally responsible for more than 60% of the electric energy consumption in most high yield pulping process. There are opportunities to improve energy efficiency and quality stability in defibration processes by means of optimizing impregnation. Impregnation is a key unit operation in CTMP production as well as in all chemical pulping and biorefinery systems. The efficiency of the impregnation is known to be crucial (Ferritsius et al. 1985; Gorski et al. 2010). Early research showed difficulties to achieve even distribution of sulphite and sodium ions in wood chips resulting in inhomogeneous fibre properties (Bengtsson et al. 1988). Increased and homogenous sulphonation leads to reduced shive content, which is a key factor in all end product applications. To address this issue developing a new type miniaturized X-ray based technique (XRF) to measure local concentration of sulphur and sodium across wood chips and in individual fibres could become a key tool.

     

    The presence of elements as sulphur and sodium can be detected by X-ray fluorescence (XRF) or spectral absorption. At the XRF, images the surface of the sample using specific energies from K-shell or L-shell fluorescence. This method is investigated at the X-ray laboratory in Mid Sweden University research centre STC (Sensitive Things that Communicate) (Norlin et al. 2018). At the spectral absorption, images specific K-shell absorption energies in transmission X-ray images of the sample, a method widely used in medical diagnosis. This transmission method might also be further investigated for this application in the future (Frojdh et al. 2013; Reza et al. 2013). Both methods can be validated by using monoenergetic radiation from synchrotron facilities.

     

    An XRF imaging system uses a collimated X-ray source and a spectroscopic detector. The sample is scanned to make an image of the content of the substances of interest. A specific challenge in this case is that the low energy fluorescence photons from sulphur (S) and sodium (Na) are easily absorbed in air, which makes imaging in a different atmosphere necessary.

     

    The measurement setup has been simulated using MCNP (C. J. Werner, 2017) to validate the system setup and to select the correct, geometry, shielding, filtering and atmosphere for the measurement. The solution was to use a titanium box flooded with helium to minimise the absorption of fluorescence photons and to shield from scattered photons that might disturb the measurement, fig 1. A filter has been added to the X-ray source to make it nearly monoenergetic and to avoid emission of photons with energies close to the expected fluorescence. The system has been used to estimate sodium and sulphur content in low grammage handsheet (CTMP) or single wood chip samples. It is possible to build a laboratory instrument similar to the prototype setup to obtain the distribution of sodium and sulphur in XRF imaging.

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

     

    Figure 1: Photograph of XRF measurement setup with of moveable Helium atmosphere Ti box

    However, the technique we are developing can become useful in mills to improve and control process efficiency, product properties and to find solutions to process problems in future. In addition, a more even distribution of the sulphonation can reduce specific energy demand in chip refining at certain shive content.

     

    References

     

    1.      Bengtsson, G., Simonson, R., Heitner, C., Beatson, R., and Ferguson, C. (1988): Chemimechanical pulping of birch wood chips, Part 2: Studies on impregnation of wood blocks using scanning electron microscopy and energy dispersive x-ray analysis, Nord. Pulp Paper Res. J. 3 (3), 132-138.

    2.      C. J. Werner, (2017): MCNP User's manual, Code Version 6.2, Los Alamos National Laboratory report, LA-UR-17-29981.

    3.      Ferritsius, O., and Moldenius, S. (1985): The effect of impregnation method on CTMP properties. In International Mechanical Pulping Conference Proceedings, SPCI, Stockholm (p. 91).

    4.      Frojdh, C., Norlin, B. and Frojdh, E. (2013): Spectral X-ray imaging with single photon processing detectors, Journal of Instrumentaion, Volume 8, Article number C02010.  

    5.      Gorski, D., Hill, J., Engstrand, P., and Johansson, L. (2010): Reduction of energy consumption in TMP refining through mechanical pre-treatment of wood chips, Nord. Pulp Paper Res. J, 25(2), 156-161.

    6.      Norlin, B., Reza, S., Fröjdh, C. and Nordin, T. (2018): Precision scan-imaging for paperboard quality inspection utilizing X-ray fluorescence, Journal of Instrumentation, Volume: 13, Article number C01021.

    7.      Reza, S., Norlin, B. and Thim, J. (2013): Non-destructive method to resolve the core and the coating on paperboard by spectroscopic x-ray imaging, Nord. Pulp Paper Res. J. 28 (3), 439-442.

     

  • 8.
    Rahman, Hafizur
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. SCA R & D Centre, Sundsvall.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Sandström, Peter
    SCA R & D Centre, Sundsvall.
    Sjöstrand, B.
    Karlstad University, Karlstad.
    Dewatering properties of low grammage handsheets softwood kraft pulps modified to minimize the need for refining2018In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 33, no 3, p. 397-403Article in journal (Refereed)
    Abstract [en]

    Previous paper (Rahman et al. 2017) showed that the yield of softwood kraft pulp increased by the addition of either polysulfide or sodium borohydride because of higher hemicellulose retention. An increase in hemicellulose content can make dewatering more difficult as WRV of the pulp increases, but instead, an overall increase in pulp yield could improve dewatering as a sheet of a certain weight will contain fewer fibres, giving a more open sheet structure. It was therefore of interest to measure the dewatering properties of low grammage handsheets (20 g/m2) under conditions mimicking the tissue paper machine dewatering processes, and sheet strength properties, WRV, °SR and fibre dimensions were also studied. The results showed that the positive influence of overall yield increase dominated over the negative influence of an increase in hemicellulose content on the dewatering properties, particularly at lower refining energy levels. Moreover, higher yield and higher hemicellulose content pulps had a higher tensile index at the same dryness. A given tensile index was achieved with less refining energy. The results indicate that increased yield and hemicellulose content by modification of the kraft pulping process will result in a pulp with a potential to improve tissue paper quality.

  • 9.
    Rahman, Hafizur
    et al.
    SCA R&D Ctr, Sundsvall.
    Lindström, Mikael E.
    KTH Royal Inst Technol, Stockholm.
    Sandström, Peter
    SCA R&D Ctr, Sundsvall.
    Salmen, Lennart
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering. Res Inst Sweden, RISE Bioecon Cellulose Sci & Technol, Stockholm.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    The effect of increased pulp yield using additives in the softwood kraft cook on the physical properties of low-grammage handsheets2017In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 32, no 3, p. 317-323Article in journal (Refereed)
    Abstract [en]

    The effect of increasing the pulp yield by the addition of sodium borohydride (NaBH4) or polysulfide (PS) in softwood kraft cooking, i.e. enhancing the retention of glucomannan, on the physical properties of low-grammage handsheets was studied. In addition to the yield improvement, an increase in tensile index was observed, especially at lower degrees of beating. These higher yield pulps showed an increase in pore volume, indicating an increased degree of swelling of the fibres. Presumably, the increased flexibility of the fibres affects the bonding strength and leads to the higher tensile index observed.

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