| 1. |
- An, Siwen, et al.
(författare)
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Comparison of Elemental Analysis Techniques for Fly Ash from Municipal Solid Waste Incineration using X-rays and Electron Beams
- 2019
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Ingår i: IOP Conference Series. - : Institute of Physics (IOP).
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Konferensbidrag (refereegranskat)abstract
- With the rapid expansion of the waste incineration business both in Europe and globally, there is a growing need for the elemental analysis for fly ash from municipal solid waste incineration. In this work, samples of washed and unwashed ash from municipal solid waste incineration in Sundsvall are evaluated. Qualitative analysis and semi-quantitative analysis are used to compare two elemental analysis methods, scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) and X-ray fluorescence (XRF) measurement. Both methods are used to retrieve the difference in elemental composition between washed and unwashed fly ash. SEM-EDS accurately detects light elements from well-prepared samples in a vacuum environment, while, for online measurements, XRF is a potential method that analyses hazardous metal content in the fly ash.
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| 2. |
- An, Siwen, et al.
(författare)
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Effects of Water Absorption on Mercury Contamination in Fiberbank Sediments using X-ray Fluorescence Spectrometer
- 2021
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Ingår i: IOP Conference Series: Earth and Environmental Science. - : Institute of Physics (IOP). - 1755-1307 .- 1755-1315.
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Konferensbidrag (refereegranskat)abstract
- A large amount of contaminated cellulose and wood fibers were emitted directly onto the seabed by the pulp and paper industry before the year of 1970. This fiber-rich sediment contains concentrations of hazardous substances that cause environmental problems. Mercury (Hg) in the fiber sediment is a worldwide threat because it can bioaccumulate in the aquatic ecosystem and eventually affect human health. X-ray fluorescence (XRF) analysis is anelemental analysis method for earth materials, which is rapid and requires minimal sample preparation. However, for in-situ XRF analyses, constraints in the measurement conditions will strongly affect the measurement sensitivity and accuracy, such as the scattered background and the water content surrounding the sample. In this work, we showed that applying an X-ray beam filter foil, optimized by using the material absorption edge, can improve the sensitivity of the XRF spectrometer system for Hg determination. Furthermore, the influence of water content in XRF measurement for Hg contamination analysis was investigated. The attenuation coefficient in water was determined by simulation of water layer with varying thickness using a Monte Carlo simulation code. The measured intensity for Hg was decreased exponentially asthe water thickness increase, as expected. We propose a method to correct the attenuation in water with XRF analysis and we expect that these findings can contribute to an accurate in-situ Hg detection experiment.
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| 3. |
- An, Siwen, et al.
(författare)
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Full-field X-ray fluorescence imaging with a straight polycapillary X-ray collimator
- 2020
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 15:12
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Tidskriftsartikel (refereegranskat)abstract
- Due to the availability of X-ray imaging detectors, full-field X-ray fluorescence (FF-XRF) imaging technique has become achievable, which provides an alternative to scanning X-ray fluorescence imaging with a micro-focus X-ray beamline. In this paper, we present a setup based on straight capillary optics and an energy-dispersive hybrid pixel detector, which can perform simultaneous mapping of several chemical elements. The photon transmission efficiency and spatial resolution are compared between two X-ray collimation setups: one using pinhole optics and one using straight polycapillary optics. There is a tradeoff between the spatial resolution and transmission efficiency when considering X-ray optics. When optimizing the spatial resolution, using straight capillary optics achieved a higher intensity gain when comparing with the pinhole setup. Characterization of the polycapillary imaging setup is performed through analyzing various samples in order to investigate the spatial frequency response and the energy sensitivity. This developed setup is capable of FF-XRF imaging in characteristic energies below 20 keV, while for higher energies the spatial resolution is affected by photon transmission through the collimator. This work shows the potential of the FF-XRF instrument in the monitoring of toxic metal distributions in environmental mapping measurements.
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| 4. |
- An, Siwen, et al.
(författare)
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Geometrical influence on Hg determination in wet sediment using K-shell fluorescence analysis
- 2023
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Ingår i: X-Ray Spectrometry. - : John Wiley and Sons Ltd. - 0049-8246 .- 1097-4539. ; 52:4, s. 82-196
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Tidskriftsartikel (refereegranskat)abstract
- To quickly identify maritime sites polluted by heavy metal contaminants, reductions in the size of instrumentation have made it possible to bring an X-ray fluorescence (XRF) analyzer into the field and in direct contact with various samples. The choice of source-sample-detector geometry plays an important role in minimizing the Compton scattering noise and achieving a better signal-to-noise ratio (SNR) in XRF measurement conditions, especially for analysis of wet sediments. This paper presents the influence of geometrical factors on a prototype, designed for in situ XRF analysis of mercury (Hg) in wet sediments using a 57Co excitation source and an X-ray spectrometer. The unique XRF penetrometer prototype has been constructed and tested for maritime wet sediment. The influence on detection efficiency and SNR of various geometrical arrangements have been investigated using the combination of Monte Carlo simulations and laboratory experiments. Instrument calibration was performed for Hg analysis by means of prepared wet sediments with the XRF prototype. The presented results show that it is possible to detect Hg by K-shell emission, thus enabling XRF analysis for underwater sediments. Consequently, the XRF prototype has the potential to be applied as an environmental screening tool for analysis of polluted sediments with relatively high concentrations (e.g., >2880 ppm for Hg), which would benefit in situ monitoring of maritime pollution caused by heavy metals. © 2022 The Authors
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| 5. |
- An, Siwen, et al.
(författare)
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Signal-to-Noise Ratio Optimization in X-ray Fluorescence Spectrometry for Chromium Contamination Analysis
- 2021
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Ingår i: Talanta. - : Elsevier BV. - 0039-9140 .- 1873-3573. ; 230
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Tidskriftsartikel (refereegranskat)abstract
- In most cases, direct X-ray fluorescence (XRF) analysis of solutions entails technical difficulties due to a high X-ray scattering background resulting in a spectrum with a poor signal-to-noise ratio (SNR). Key factors that determine the sensitivity of the method are the energy resolution of the detector and the amount of scattered radiation in the energy range of interest. Limiting the width of the primary spectrum by the use of secondary targets, or filters, can greatly improve the sensitivity for specific portions of the spectrum. This paper demonstrates a potential method for SNR optimization in direct XRF analysis of chromium (Cr) contamination. The suggested method requires minimal sample preparation and achieves higher sensitivity compared to existing direct XRF analysis. Two states of samples, fly ash and leachate from municipal solid waste incineration, were investigated. The effects of filter material, its absorption edge and filter thickness were analyzed using the combination of Monte Carlo N-Particle (MCNP) code and energy-dispersive XRF spectrometry. The applied filter removes primary photons with energies interfering with fluorescence photons from the element of interest, thus results in lower background scattering in the spectrum. The SNR of Cr peak increases with filter thickness and reaches a saturation value when further increased thickness only increases the measurement time. Measurements and simulations show that a Cu filter with a thickness between 100 μm and 140 μm is optimal for detecting Cr by taking into account both the SNR and the exposure time. With direct XRF analysis for solutions, the limit of quantitation (LOQ) of the achieved system was 0.32 mg/L for Cr, which is well below the allowed standard limitation for landfills in Sweden. This work shows that XRF can gain enough sensitivity for direct monitoring to certify that the Cr content in leachate is below environmental limits.
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| 6. |
- An, Siwen
(författare)
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Spectroscopic and Microscopic X-ray Fluorescence Analysis for Environmental and Industrial Applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heavy metals are well-known environmental pollutants due to its potential impact on associated ecosystems and human health. Thus, it is important to monitor the levels of heavy metals in the environment. X-ray fluorescence (XRF) analysis is a powerful and effective screening tool in measuring the concentration of multi-elements simultaneously.This thesis provides insight into development and implementation of XRF instruments for environmental monitoring and industrial process control. The XRF method was compared with a commercial scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) for fly ash samples. Qualitative analysis and semi-quantitative analysis of Na, S, Cl, K and Cd in incineration fly ash were performed with these two similar techniques. One of the challenges of using XRF is the scattering background noise from the primary beam, which decreases the detection limit and the sensitivity of the measurement system. Hence, an X-ray beam filter was chosen to suppress the background noise for a specific element, Cr, in leachate. Numerical simulations and experiments were developed to find the proper filter material and thickness by calculating the X-ray fluorescence intensities and the signal-to-noise ratio. The developed system is capable of online monitoring of Cr levels, to certify that the concentration is below the threshold level in leachate. An XRF prototype was built and calibrated for underwater Hg analysis in maritime wet sediment using a radioisotope source. The presented results show that it is possible to detect Hg by K-shell emission thus enabling XRF analysis for sediment underwater.For non-homogeneous samples, an image revealing the elemental distribution can be achieved by micro-XRF (µ-XRF). XRF mapping of element distributions on a microscopic level was obtained by using scanning XRF microscopy and full-field XRF projection microscopy (FF-XRF). The spatial resolution of the scanning XRF imaging setup using an X-ray tube is in the order of 100 µm, but need to be further improved to measure the homogeneity of S on individual fiber level in pulp and paper industry. For the scanning technique, it is a tradeoff between resolution and measurement time. Another technique is FF-XRF imaging, and a setup was implemented using an energy resolving pixel detector and X-ray optics. The capabilities and limitations of using X-ray optics in XRF imaging systems have been identified. These microscopy measurements can guide further comprehensive environmental and industrial monitoring missions, utilizing elemental distribution information.
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| 7. |
- An, Siwen
(författare)
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X-ray Fluorescence Spectrometry for Environmental Applications
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heavy metal contamination in environmental applications is particularly important because of its potential impact on associated ecosystems and human health. At present, monitoring of heavy metals is usually done by taking and preparing samples for off-line laboratory measurements. X-ray fluorescence (XRF) analysis is a powerful and widely used tool for determining the elemental composition and concentration of chemical species in materials. This project is a feasibility study for the possibility of on-line XRF systems for continuousand direct analysis of industrial processes and environmental emissions.The feasibility of such measurements depends on the accuracy with which the concentration can be measured within a given response time. Therefore, this project is focused on investigating possible background suppression of the XRF spectrum. First, an XRF setup has been built, and its capability has been compared to a commercial scanning electron microscope with energy dispersive spectroscopy (SEM-EDS). The qualitative analysis and semi-quantitative analysis of heavy metal contamination in fly ash was performed and compared. Due to minimal sample preparation, the developed XRF system is suitable for in-situ measurements. A series of experiments was performed to optimize the signal-to-noise ratio of the spectra achieved from chromium contaminated liquid samples. The most significant factor turned out to be the primary X-ray source filter. Numerical simulation models have been developed in the Monte Carlo N-particle radiation transport code (MCNP), to calculate the X-ray fluorescence intensities and the detection limit for chromium in liquid samples. The experimental results agree with the results predicted by the simulation model, hence the model is used for optimization of the XRF system. Further, XRF mapping of chemical element distributions on a microscopic level has been obtained by using both X-ray scanning microscopy and full-field projection microscopy. The resultingdata from these microscopy measurements can guide further comprehensive environmental and industrial monitoring missions by providing additional spatial distribution information.In conclusion, the first research contribution presented in this thesis is the demonstration of the possibility to perform in-situ XRF measurements of chromium contamination in leachate with a limit of detection below the legal environmental limits. The second is the demonstration of XRF mapping on amicroscopy level, where a polycapillary X-ray optics setup achieves a similar intensity as a geometrically corresponding pinhole optics setup.
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| 8. |
- Norlin, Börje, associate professor, 1967-, et al.
(författare)
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Visualisation of sulphur on single fibre level for pulping industry
- 2023
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Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 18:01, s. C01012-C01012
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Tidskriftsartikel (refereegranskat)abstract
- In the pulp and paper industry, about 5 Mt/y chemithermomechanical pulp (CTMP) are produced globally from softwood chips for production of carton board grades. For tailor making CTMP for this purpose, wood chips are impregnated with aqueous sodium sulphite for sulphonation of the wood lignin. When lignin is sulphonated, the defibration of wood into pulp becomes more selective, resulting in enhanced pulp properties. On a microscopic fibre scale, however, one could strongly assume that the sulphonation of the wood structure is very uneven due to its macroscale size of wood chips. If this is the case and the sulphonation could be done significantly more evenly, the CTMP process could be more efficient and produce pulp even better suited for carton boards. Therefore, the present study aimed to develop a technique based on X-ray fluorescence microscopy imaging (µXRF) for quantifying the sulphur distribution on CTMP wood fibres. Firstly, the feasibility of µXRF imaging for sulphur homogeneity measurements in wood fibres needs investigation. Therefore, clarification of which spatial and spectral resolution that allows visualization of sulphur impregnation into single wood fibres is needed. Measurements of single fibre imaging were carried out at the Argonne National Laboratory’s Advanced Photon Source (APS) synchrotron facility. With a synchrotron beam using one micrometre scanning step, images of elemental mapping are acquired from CTMP samples diluted with non-sulphonated pulp under specified conditions. Since the measurements show significant differences between sulphonated and non-sulphonated fibres, and a significant peak concentration in the shell of the sulphonated fibres, the proposed technique is found to be feasible. The required spatial resolution of the µXRF imaging for an on-site CTMP sulphur homogeneity measurement setup is about 15 µm, and the homogeneity measured along the fibre shells is suggested to be used as the CTMP sulphonation measurement parameter.
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| 9. |
- Rahman, Hafizur, Researcher, 1978-, et al.
(författare)
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Characterization of impregnation depth in wood fibers related manufacturing of advanced fiber materials replacing fossil-based materials
- 2022
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Ingår i: Proceedings International mechanical Pulping Conference. ; , s. 162-165
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- An underestimated problem in the rapidly growing CTMP industry is uneven sulphonation. Optimizing the unit operations before chip refining, chip washing, steaming, impregnation, and preheating improves efficiency, provides smoother fiber properties, and reduces the cost of certain properties in the final product. Impregnation is crucial to the CTMP quality, and a further improvement in its smoothness requires a careful study of the optimization of pulpwood chipping and the chipping process with reduction technology at sawmills. The CTMP system, however, is difficult to optimize due to the lack of rapid measurement methods for determining the smoothness of the impregnation at the fiber level. The ability to study how the processing system can be optimized requires a robust method of measuring the degree of sulphonation at the fiber level. It is possible to study CTMP's degree of sulphonation at the fiber level by measuring the distribution of elemental sulphur and counterions of the sulphonate groups, such as sodium or calcium. Thus, we are developing an XRF (x-ray fluorescence) technology based on scanning imaging and energy-resolved X-ray spectrum from a collimated X-ray source. The measurement technology is developed so that it can be used in pulp industry laboratories.
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| 10. |
- Rahman, Hafizur, Researcher, 1978-, et al.
(författare)
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Development of improved CTMP with even sulphonate distribution at fibre level using XRF analysis
- 2022
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Ingår i: Transactions of the 17th Fundamental Research Symposium held in Cambridge: August/September 2022. - 9780992616366 ; , s. 3-11
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Konferensbidrag (refereegranskat)abstract
- Optimizing the fiber property distribution could increase the pulp properties as well as the process efficiency of chemimechanical pulps (CMP/CTMP). This can only be achieved with a better understanding of how evenly distributed sulphonate concentrations are between the individual CTMP fibres. Given that the quality of wood chips varies with the chipping methods used in pulpwood processing and sawmill processing, as well as with the chip screening system, it is a challenge to develop an impregnation process that ensures even distribution of sodium sulphite (Na2SO3) in the liquid used to impregnate the chemimechanical pulp (CMP/CTMP). Therefore, the distribution of sulphonate groups within wood chips and individual fibers must be measured at the microscale level. On a micro level, the degree of unevenness, ie, the amount of fiber sulphonation and softening before defibration, cannot be determined due to the use of excessively robust or complex processing methods. By having it, we could better understand how sulphonation occurs before defibration, so we could improve impregnation. Developing a laboratory-scale miniaturized energy dispersive X-ray fluorescence (ED-XRF) method that measures sulfur distribution at the fiber level can enable us to study the influence of impregnation on improving processes.
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| 11. |
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| 12. |
- Rahman, Hafizur, Research Engineer, 1978-, et al.
(författare)
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Improve the competitive advantages of pulp fiber-based products over fossil-based materials
- 2021
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Ingår i: Accelerating the progress towards the 2030 SDGs in times of crisis. - Östersund : Mid Sweden University. - 9789189341173 ; , s. 2133-2145
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Konferensbidrag (refereegranskat)abstract
- To improve the competitive advantages of pulp fibre based materials such as tissue and packaging products over the fossil-based products, it is of key importance to improve the knowledge of the selectivity of the cooking process. There is also demand to expand the fundamental scientific understanding of pulp and paper manufacturing systems because of growing demand for replacing plastics. However, it is challenged to improve the selectivity of the cooking process by optimizing unit operation such as impregnation, cooking and refining. For pulp production based on chips regardless of chemical (kraft or sulphite) or high-yield (chemimechanical or semi-chemical pulp) pulping process, the efficiency of the impregnation is always crucial. To improve impregnation uniformity, we need to study how even distribution of lignin releases down to fibre level via easily impregnated wood chips. It can be achieved, using classic measures such as; equalized hydroxide ion concentration, increased initial sulphide ion concentration, low sodium ion concentration and low boiling temperature combined with the oxidative and reductive environment to understand how the chemicals quickly enter and distribute in the chips. However, we have studied the uniformity of impregnation at fibre level by the possibility of accurately measuring S and Na content by collimating the X-ray beam into a ~200 µm spot in diameter using energy-dispersive X-ray fluorescence (ED-XRF) spectrometry. In addition, we have also studied improved impregnation by selective cooking systems for sulphate pulp in oxidative (polysulfide) and reductive (sodium borohydride, NaBH4) environments. Our aim is to develop standard measurement methods to improve the smoothness of fibre properties for tissue and packaging products to reach the sustainable development goal (SDG) stated by the UN at target 9.5 “Enhance research and upgrade industrial technologies”.
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| 13. |
- Rahman, Hafizur, Research Engineer, 1978-, et al.
(författare)
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Maximized wood chip impregnation efficiency validated by new miniaturized X-ray fluorescence techniques
- 2019
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Konferensbidrag (refereegranskat)abstract
- 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 boxHowever, 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.
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| 14. |
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| 15. |
- Rahman, Hafizur, Research Engineer, 1978-, et al.
(författare)
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Measurement of S and Na distribution in impregnated wood chip by XRF
- 2021
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Ingår i: TAPPICon Virtual 2021. - : TAPPI Press. - 9781713829683 ; , s. 547-553
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Konferensbidrag (refereegranskat)abstract
- As there are increasing demands to replace plastics especially as packaging material with renewable, easy to recycle and compostable materials as those produced by paper industry, there is an increasing demand also to improve the fundamental scientific understanding of pulp and paper manufacturing systems. High yield pulping (HYP) processes, such as CTMP, are increasingly interesting for packaging material as well as manufacturing of hygiene paper. The yield from wood chips to final fiber is about 90%-98% and due to that, the lignin (28% of coniferous wood) plays a key role when designing properties of packing materials. A key unit operation when producing CTMP is the pre-treatment of wood chips before defibration. In order to separate the wood to individual fibers with a minimum amount of electricity it is necessary to soften the lignin. The lignin is softened by means of a combination of sulphonation at high pH and elevated temperatures in the preheater and in the refiner, where the fiber separation occurs. As the size of wood chips is normally about 20 mm in length, 3-4 mm in thickness at the same time the fiber size is 20-40 μm in width with 1.5-5 mm in length, it is challenging to create a process technology that gives an even distribution across the wood chips of the sodium sulphite (Na2SO3) containing liquid used for impregnation. In order to improve the impregnation technology, it is valuable to measure the sulphonation degree on a detailed level. Our XRF imaging system using a collimated X-Ray source and an energy-dispersive X-Ray spectroscopy can make an image of sulphur (S) and sodium (Na) across wood chips or in individual fibers.
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| 16. |
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| 17. |
- Rahman, Hafizur, Researcher, 1978-, et al.
(författare)
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On-Site X-ray Fluorescence Spectrometry Measurement Strategy for Assessing the Sulfonation to Improve Chemimechanical Pulping Processes
- 2022
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Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 7:51, s. 48555-48563
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Tidskriftsartikel (refereegranskat)abstract
- Minimizing the fiber property distribution would have the potential to improve the pulp properties and the process efficiency of chemimechanical pulp. To achieve this, it is essential to improve the level of knowledge of how evenly distributed the sulfonate concentration is between the individual chemimechanical pulp fibers. Due to the variation in quality between pulpwood and sawmill chips, as well as the on-chip screening method, it is difficult to develop an impregnation system that ensures the even distribution of sodium sulfite (Na2SO3) impregnation liquid. It is, therefore, crucial to measure the distribution of sulfonate groups within wood chips and fibers on a microscale. Typically, the degree of unevenness, i.e., the amount of fiber sulfonation and softening prior to defibration, is unknown on a microlevel due to excessively robust or complex processing methods. The degree of sulfonation at the fiber level can be determined by measuring the distribution of elemental sulfur and counterions of sulfonate groups, such as sodium or calcium. A miniaturized energy-dispersive X-ray fluorescence (ED-XRF) method has been developed to address this issue, enabling the analysis of sulfur distributions. It is effective enough to be applied to industrial laboratories for further development, i.e., improved image resolution and measurement time.
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| 18. |
- Zeeshan, Faisal, et al.
(författare)
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Study of heavy metals including mercury within Fiber Banks of Västernorrland and Norrbotten counties by portable X-RayFluorescence (pXRF) spectrometry
- 2021
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Ingår i: Accelerating the progress towards the 2030 SDGs in times of crisis. - 9789189341173 ; , s. 265-276
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Konferensbidrag (refereegranskat)abstract
- Discharge of waste water from pulp and paper industries has led to environmental impact in the formation of sediment layers, so called fiber banks, on the coast of Västernorrland and Norrbotten counties in Sweden. These fiber banks are thick underwater deposits which are highly contaminated with some toxic metals such as Al, Cr, Fe, Cu, Zn, As, Pb, Hg. These metals can lead to several consequences for the environment, thus ultimately having harmful effects on living organisms. Our purpose is to study several of these toxic metals and analyze the concentration level by using portable X-ray Fluorescence (pXRF) spectrometry for rapid sample characterization of wet samples. Field analyses are highly affected by moisture and it is difficult to obtain measurement accuracy. Therefore, moisture tests were performed by air drying samples at room temperature from 0 to 24 h. Some of the samples were oven dried for 48 h at 950 C, dried, grinded and turned into pellets and performed laboratory measurements to compare results with field measurements. Our aim is to provide an improved state of facts for decision makers to prevent and reduce marine pollution and to protect and restore ecosystems in order to avoid significant adverse impacts, and take actions for their restoration in order to achieve healthy and productive oceans. A future outcome is to reach the sustainable development goal (SDG) stated by the UN at target 14.1 and 14.2 “Life below water”.
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| 19. |
- Zeeshan, Faisal, et al.
(författare)
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Synchrotron measurements of Sulphonation degree from Chemimechanical pulp (CTMP) to optimize the pulping process for packaging products
- 2022
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The manufacturing of CTMP has a significant role in producing sustainable packaging products. But the strategy to improve the impregnation technology is still challenging due to the uneven distribution of Na2SO3. Our aim was to investigate the oxidation states of Sulphonate present in our handmade paper samples which consist of different CTMP percentages. Therefore, XANES measurements were done to investigate the oxidation states and XRF measurements were done to see the presence of other elements. XRF mapping was also done to know the distribution of Na in the samples.
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| 20. |
- Zhang, Renyun, et al.
(författare)
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Triboelectric biometric signature
- 2022
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Ingår i: Nano Energy. - : Elsevier BV. - 2211-2855 .- 2211-3282. ; 100
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Tidskriftsartikel (refereegranskat)abstract
- Biometric signatures based on either the physiological or behavioural features of a person have been widely used for identification and authentication. However, few strategies have been developed that combine the two types of features in one signature. Here, we report a type of biometric signature based on the triboelectricity of the human body (TEHB) that combines these two types of features. This triboelectric biometric signature (TEBS) can be accomplished by anyone regardless of the physical condition, as it can be performed by many parts of the body. Different TEBS can be identified using a convolutional neural network (CNN) model with a test accuracy of up to 1.0. The TEBS has been further used for text encryption and decryption with a high sensitivity to changes. Moreover, a dual signed digital signature for enhanced security has been proposed. Our findings provide a new type of TEBS that can be generally used and demonstrated in applications.
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