Browsing by Author "Dimic-Misic, Katarina"

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  • Achieving a Superhydrophobic, Moisture, Oil and Gas Barrier Film Using a Regenerated Cellulose–Calcium Carbonate Composite Derived from Paper Components or Waste
    (2022-08-22) Imani, Monireh; Dimic-Misic, Katarina; Kostic, Mirjana; Barac, Nemanja; Janackovic, Djordje; Uskokovic, Petar; Ivanovska, Aleksandra; Lahti, Johanna; Barcelo, Ernest; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    It has been a persistent challenge to develop eco-friendly packaging cellulose film providing the required multiple barrier properties whilst simultaneously contributing to a circular economy. Typically, a cellulosic film made from nanocellulose materials presents severe limitations, such as poor water/moisture resistance and lacking water vapour barrier properties, related primarily to the hydrophilic and hygroscopic nature of cellulose. In this work, alkyl ketene dimer (AKD) and starch, both eco-friendly, non-toxic, cost-effective materials, were used to achieve barrier properties of novel cellulose–calcium carbonate composite films regenerated from paper components, including paper waste, using ionic liquid as solvent. AKD and starch were applied first into the ionic cellulose solution dope mix, and secondly, AKD alone was coated from hot aqueous suspension onto the film surface using a substrate surface precooling technique. The interactions between the AKD and cellulose film were characterised by Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) showing the formation of a ketone ester structure between AKD and the hydroxyl groups of cellulose. The presence of calcium carbonate particles in the composite was seen to enhance the cellulose crystallinity. The initial high-water vapour and oxygen transmission rates of the untreated base films could be decreased significantly from 2.00 to 0.14 g m−2 d−1, and 3.85 × 102 to 0.45 × 102 cm3 m−2 d−1, respectively. In addition, by applying subsequent heat treatment to the AKD coating, the water contact angle was markedly increased to reach levels of superhydrophobicity (>150°, and roll-off angle < 5°). The resistance to water absorption, grease-permeation, and tensile strength properties were ultimately improved by 41.52%, 95.33%, and 127.33%, respectively, compared with those of an untreated pure cellulose film. The resulting regenerated cellulose–calcium carbonate composite-based film and coating formulation can be considered to provide a future bio-based circular economy barrier film, for example, for the packaging, construction and agriculture industries, to complement or replace oil-based plastics.
  • Acid dissociation of surface bound water on cellulose nanofibrils in aqueous micro nanofibrillated cellulose (MNFC) gel revealed by adsorption of calcium carbonate nanoparticles under the application of ultralow shear
    (2017-08) Liu, Guodong; Maloney, Thaddeus; Dimic-Misic, Katarina; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    At ultralow shear rate (similar to 0.01 s(-1)), acting below the yield stress of the aqueous gel, adsorption of calcium carbonate nanoparticles (<~100 nm) onto cellulose nanofibrils is induced without pigment–pigment preflocculation. Dispersant-free and polyacrylate treated dispersed carbonate particles are compared. Initially, it is seen that the polyacrylate dispersed material does not adsorb, whereas the dispersant-free carbonate adsorbs readily under the controlled ultralow shear conditions. However, repeated cycles of ultralow shear with intermittent periods in the rest state eventually induce the effect as initially seen with the dispersant-free calcium carbonate. The fibril suspension in the bulk is slightly acidic. The addition of buffer to a controlled pH in the case of the dispersant treated particles maintained a similar delay in the onset of adsorption, but adsorption occurred eventually after repeated cycles. During this cycling process, in parallel, the pH gradually drops under repeated cycles of ultralow shear, opposite to expectation, given the buffering capacity of calcium carbonate. The conductivity, in turn, progressively increases slightly at first and then significantly. The action of surface bound water on the nanofibril is considered key to the action of adsorption, and the condition of ultralow shear suggests that the residence time of the particle in contact with the nanofibril, acting under controlled strain against diffusion in the gel, is critical. It is proposed that under these specific conditions the calcium carbonate nanoparticles act as a probe of the nanofibril surface chemistry. The hydrogen bonded water, known to reside at the nanofibril surface, is thus considered the agent in the carbonate-surface interaction, effectively expressing an acid dissociation, and the calcium carbonate nanoparticles act as the probe to reveal it. An important phenomenon associated with this acid dissociation behaviour is that the adsorbed calcium carbonate particles subsequently act to flocculate the otherwise stable cellulose material, leading to release of water held in the aqueous gel matrix structure. This latter effect has major implications for the industrial ease of use of micro and nanofibrillar cellulose at increased solids content. This novel mechanism is also proposed for use to enhance the dewatering capability in general of complex cellulose-containing gel-like water-holding suspensions.
  • Effects of Hydroxyapatite Additions on Alginate Gelation Kinetics During Cross-Linking
    (2025-01-19) Dimic-Misic, Katarina; Imani, Monir; Gasik, Michael
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Alginate hydrogels have gathered significant attention in biomedical engineering due to their remarkable biocompatibility, biodegradability, and ability to encapsulate cells and bioactive molecules, but much less has been reported on the kinetics of gelation. Scarce experimental data are available on cross-linked alginates (AL) with bioactive components. The present study addressed a novel method for defining the crosslinking mechanism using rheological measurements for aqueous mixtures of AL and calcium chloride (CaCl2) with the presence of hydroxyapatite (HAp) as filler particles. The time-dependent crosslinking behaviour of these mixtures was exploited using a plate–plate rheometer, when crosslinking occurs due to calcium ions (Ca2+) binding to the guluronic acid blocks within the AL polymer, forming a stable “egg-box” structure. To reveal the influence of HAp particles as filler on crosslinked sample morphology, after rheological measurement and crosslinking, crosslinked samples were freeze-dried and their morphology was assessed using an optical microscope and SEM. It was found that the addition of HAp particles, which are known to enhance the mechanical properties and biocompatibility of crosslinked AL gels, significantly decreased (usually rapidly) the interaction between the Ca2+ and AL chains. In this research, the physical “shielding” effect of HAp particles on the crosslinking of AL with Ca2+ ions has been observed for the first time, and its crosslinking behaviour was defined using rheological methods. After crosslinking and rheometer measurements, the samples were further evaluated for morphological properties and the observations were correlated with their dewatering properties. While the presence of HAp particles led to a slower crosslinking process and a more uniform development of the rheological parameters, it also led to a more uniform porosity and improved dewatering properties. The observed effects allow for a better understanding of the crosslinking process kinetics, which directly affects the physical and chemical properties of the AL gels. The shielding behaviour (retardation) of filler particles occurs when they physically or chemically block certain components in a mixture, delaying their interaction with other reactants. In hydrogel formulations, filler particles like hydroxyapatite (HAp) can act as barriers, adsorbing onto reactive components or creating physical separation, which slows the reaction rate and allows for controlled gelation or delayed crosslinking. This delayed reactivity is beneficial for precise control over the reaction timing, enabling the better manipulation of material properties such as crosslinking distribution, pore structure, and mechanical stability. In this research, the physical shielding effect of HAp particles was observed through changes in rheological properties during crosslinking and was dependent on the HAp concentration. The addition of HAp also enabled more uniform porosity and improved dewatering properties. The observed effects allow for a better understanding of the crosslinking process kinetics, which directly affects the physical and chemical properties of the AL gels.
  • Heterogeneous Hierarchical Self-Assembly Forming Crystalline Nanocellulose–CaCO3 Hybrid Nanoparticle Biocomposites
    (2023-08-16) Liukko, Sirje; Dimic-Misic, Katarina; Ge, Yanling; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Nanocellulose is increasingly proposed as a sustainable raw material having strong interparticle bonding. However, cellulose alone has limited bending and impact resistance. We newly observe self-assembly between crystalline nanocellulose (CNC) and ultrafine ground chemical-free calcium carbonate nanoparticles (UGCC). The suspension displays an intrinsic gel-like state, and heterogeneous adsorption occurs under the specific conditions where Brownian motion of both species is arrested by application of ultralow shear (0.01 s−1). In contrast, simple static aging of the mixture leads to autoflocculation of each species independently. The heterogeneous adsorption results in compound particle self-assembly leading to multi-level hierarchical structures depending on relative species size and concentration ratio. Fine particles from species 1 adsorb onto the coarser complementary particles of species 2 and vice versa. Depending also on whether CNC or UGCC particles are in excess, the structural assembly occurs primarily through either CNC–CNC hydrogen bonding or CaCO3–CaCO3 autogenous flocculation, respectively. Controlling the hierarchical composite structure bonding in this way, the resulting morphology can express dual or predominantly single either mineralic or cellulosic surface properties. Novel complex hybrid biocomposite materials can therefore be produced having designable compatibility across a broad range of both natural and oil-based polymeric materials. Both CNC and UGCC are exemplified here via commercial products.
  • Identifying the Challenges of Implementing a European Bioeconomy based on Forest Resources: Reality Demands Circularity
    (2019-01-01) Dimic-Misic, Katarina; Barcelo, Ernest; Brkic, Vesna Spasojevic; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Greenhouse gas emission reduction is strongly advocated within the European Union (EU). Biomass has emerged as a renewable energy source and as manufacturing raw material with ecological credentials to mitigate carbon imbalance. The EU has defined the bioeconomy encompassing these material sources as a basis for technological and economic development. Biocenology, describing the study of natural communities, however, additionally demands inclusion of a circular economy, in which it needs to be assumed that endless renewable products are kept in continuous circulation of use and reuse. Thus, there arises the question whether the bioeconomy route alone, promoted by the EU, is sustainable. Using research literature, based on the Delphi method, and EU documents, we discuss the importance of sustainable management of bioresources. Short term solutions may remain necessary to ensure economic stability but, without embracing the circular economy, only limited mitigation of greenhouse gas emissions can be expected.
  • Improved stabilisation of graphite nanoflake dispersions using hydrothermally-produced nanocellulose
    (2021-02-05) Dimic-Misic, Katarina; Buffiere, Jean; Imani, Monireh; Nieminen, Kaarlo; Sixta, Herbert; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Dispersing graphite nanpoflakes in aqueous suspension is essential both during their processing and to realise the high level of functionality they offer. In this study two types of chemical-free nanocelluloses were assessed as possible dispersing agent for graphite nanoflakes. Hydrothermally-produced nanocellulose (HTC) obtained by supercritical water treatment of microcrystalline cellulose, showed superior dispersing than the more conventional, mechanically-produced microfibrillated nanocellulose (MFC) alternative, effectively preventing nanoflake agglomeration. Thanks to the specific processing method, the HTC material displayed higher total surface energy and a favourable particle morphology. These properties resulted in a 2-fold reduction in the volume median colloidal particle size of nanographite in suspension upon addition of only 2 w/w% nanocellulose. The improved single particle dispersion within the suspension matrix could be observed microscopically and was reflected rheologically. The latter was achieved by parameterising the stress-shear rate response and fitting the linear segments displaying the suspension coupling response. Using chemical-free nanocellulose as dispersant in aqueous medium is a positive step toward the exfoliation of nanographite into graphene in a more affordable and environmentally-friendly way.
  • Influence of fibrillar cellulose on pigment coating formulation rheology
    (2012) Dimic-Misic, Katarina
     School of Chemical Engineering | Licentiate thesis
    Coating suspension rheology influences the coating performance at high speeds. The quality of the coated and printed papers is also affected by the rheology of the suspension. For good coating results, it is crucial to optimize the water retaining properties of coating colours. The observation that fibrillar cellulose (MFC) could be used in paper coating formulations as a co-binder, since it is biodegradable and has good shear thinning properties, raises a question about the process ability of coating colours which have cobinder substituted with fibrillar cellulose. In this study, fibrillar cellulose is used to substitute the standard, synthetic co-binder material, carboxymethyl cellulose thus affecting both dewatering and rheological properties of coating colours. Reactivity of the MFC fibers in coating colour formulation is strongly dependent on the fineness of the fibrillar material as well as on its consistency, pre-treatment and refining route. In the present study the consolidation of coating colour layers has been studied using rheology as the main tool. This method combines the use of standard viscoelastic and static dewatering tools, Åbo Academy Gravimetric Dewatering Device and Brookfield viscometer, with the use of MRC300 Rheometer accompanied with an Immobilization cell. The rheological behaviour of all coating colours that have fibrillar cellulose as co-binders was found to be similar. Lower water retention and faster immobilization of filter cake were accompanied with higher shear thinning behaviour. This conclusion was strengthened by the recovery measurements, which showed that the fibrillar material containing coatings have a prolonged recovery time after high shear. A linear correlation between gravimetric (static) water retention and immobilization time, on the one hand and elasticity and prolonged recovery time on the other was found for fibrillar cellulose containing coating colours, regardless of the type of fibrillar material or pigment blend.
  • Micro and nanofibrillated cellulose (MNFC) as additive in complex suspensions: influence on rheology and dewatering
    (2014) Dimic-Misic, Katarina
     School of Chemical Technology | Doctoral dissertation (article-based)
    The traditional forest products, such as paper, packaging and viscose products, have their well-established place, but further efforts urgently need to be made to meet growing ecological demands, increasing economic pressure and to develop new technologies for utilisation of high performance materials. Nanocellulose applied in paper making suspensions and as water retention control aids may introduce additional strength properties in traditional products, and when considered for coatings may deliver oil and gas barrier properties as well as targeted liquid interactions based on surface energy criteria and designed pore and gel network structures. The properties increase the potential for their use in a broad range of novel products. The processes, firstly by which nanocellulose is both created, as part of cellulose structures in nature, and subsequently produced determine their aqueous suspension rheology and dewatering behaviour, and thus, by using knowledge of their rheological behaviour when utilised in complex suspensions, will support the creation of new controls in water-based production processes. The use of rheology for the characterisation of nanocellulose suspensions and their applications in a range of industries as diverse as the oil and papermaking industries has been the subject of numerous studies in recent years. Although many studies have been conducted relating to papermaking furnishes and their water suspensions while including nanocellulose containing materials, these rheological investigations were conducted independently from conditions of dynamic dewatering. For the first time, this work sets out to observe and try to overcome experimental difficulties related to rheometry and dynamic dewatering of high consistency viscoelastic gel-like nanocellulose suspensions using a variety of experimental techniques and methods. Once reliable rheological measurements were designed and the methodology established, the work goes on to analyse the possible structures attained by nanocellulose containing suspensions in combination with macroscopic fibres, pigments and fibril dispersing polymers, which traditionally are used as pigment flocculant water retention aids. These analyses are used to support and challenge the basic hypotheses of the thesis in relation to the impact these structures will have on properties such as process applicability, phase separation, substrate coverage, coating and material uniformity.  
  • Micro Nanofibrillated Cellulose as Functional Additive Supporting Processability of Surface-Active Mineral Suspensions: Exemplified by Pixel Coating of an NOx-Sorbent Layer
    (2023-02) Dimic-Misic, Katarina; Imani, Monireh; Barac, Nemanja; Janackovic, Djordje; Uskokovic, Petar; Barcelo, Ernest; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Unlike established coating formulations, functional particulate coatings often demand the omission of polymer dispersant so as to retain surface functionality. This results in heterogeneous complex rheology. We take an example from a novel development for an NOx mitigation surface flow filter system, in which ground calcium carbonate (GCC), applied in a coating, reacts with NO2 releasing CO2. Inclusion of mesoporous ancillary mineral acts to capture the CO2. The coating is applied as droplets to maximize gas-contact dynamic by forming a pixelated 2D array using a coating device consisting of protruding pins, which are loaded by submersion in the aqueous coating color such that the adhering droplets are transferred onto the substrate. The flow is driven by surface meniscus wetting causing lateral spread and bulk pore permeation. Filamentation occurs during the retraction of the pins. Stress-related viscoelastic and induced dilatancy in the suspension containing the ancillary mesoporous mineral disrupts processability. Adopting shear, oscillation and extensional rheometric methods, we show that the inclusion of an ancillary mineral that alone absorbs water, e.g., perlite (a naturally occurring porous volcanic glass), is rheologically preferable to one that in addition to absorbing water also immobilizes it on the mineral surface, e.g., sepiolite. When including micro-nanofibrillated cellulose (MNFC), critical for maintaining moisture to support NO2 sorption, it is observed that it acts also as a flow modifier, enabling uniform coating transfer to be achieved, thus eliminating any possible detrimental effect on mineral surface activity by avoiding the use of soluble polymeric dispersant.
  • Nitrogen plasma surface treatment for improving polar ink adhesion on micro/nanofibrillated cellulose films
    (2019-04-15) Dimic-Misic, Katarina; Kostić, Mirjana; Obradović, Bratislav; Kramar, Ana; Jovanović, Stevan; Stepanenko, Dimitrije; Mitrović-Dankulov, Marija; Lazović, Saša; Johansson, Leena Sisko; Maloney, Thad; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    We find that nitrogen plasma treatment of micro/nanofibrillated cellulose films increases wettability of the surface by both liquid polar water and nonpolar hexadecane. The increased wetting effect is more pronounced in the case of polar liquid, favouring the use of plasma treated micro/nanofibrillated cellulose films as substrates for a range of inkjet printing including organic-based polar-solvent inks. The films were formed from aqueous suspensions of progressively enzymatic pretreated wood-free cellulose fibres, resulting in increased removal of amorphous species producing novel nanocellulose surfaces displaying increasing crystallinity. The mechanical properties of each film are shown to be highly dependent on the enzymatic pretreatment time. The change in surface chemistry arising from exposure to nitrogen plasma is revealed using X-ray photoelectron spectroscopy. That both polar and dispersive surface energy components become increased, as measured by contact angle, is also linked to an increase in surface roughness. The change in surface free energy is exemplified to favour the trapping of photovoltaic inks.
  • Novel device for determining the effect of jetting shear on the stability of inkjet ink
    (2021-03-31) Gane, Patrick A. C.; Imani, Monireh; Dimic-Misic, Katarina; Kerner, Enn
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Inkjet printing is a rapidly expanding technology for non-contact digital printing. The focus for the technology has changed from office printing of text and image documents increasingly toward wider applications, including large-scale printing of on demand books and packaging or ultra-small-scale functional printing of microscopic volumes of precious/rare materials formulated for use in precisely printed digitally defined patterning arrays, such as printed diagnostics, flexible electronics, anti-counterfeiting, etc. For efficiency, as well as resource management and conservation, predicting the stable runnability of an inkjet ink remains largely a key unknown. Today the only way to know often means simply trialling it, which at best takes time, and at worst incurs costs rectifying possible equipment damage. We propose a mechanically driven displacement device providing constant high-shear flow rate through an extended capillary. This differs from a standard capillary viscometer, which is commonly pressure driven only and lacks the ability to mimic consistent volume flow inkjetting. The novel method is used to study the aqueous colloidal stability of polymer solution, latex polymer suspensions and complete pigment-containing inks, including a reference pigment only comprising suspension. The results reveal the tendency to build agglomerates, determined by dynamic light scattering particle size distribution, optical and electron microscopy. Liquid phase parameters, including surface tension, and suspension intrinsic viscosity are also studied. Repeated application of high shear is seen to act as a milling process for pigment and agglomerate building tendency for latex binder. Consequences for ink jettability are discussed.
  • Production of Micro Nanofibrillated Cellulose from Prerefined Fiber via a Dry Dielectric Barrier Discharge (DBD) Oxygen Plasma-Treated Powder Precursor
    (2024) Dimic-Misic, Katarina; Obradovic, Bratislav; Kuraica, Milorad; Kostic, Mirjana; Lê, Huy Quang; Korica, Matea; Imani, Monireh; Gane, Patrick
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cellulose is a strong contender for the development of sustainably resourced biodegradable material composites supporting circular economy. Nanofibrillar cellulose-comprising materials are among the most promising lignocellulose derivatives. Currently, their production capacity and economy are hindered by high chemical and energy consumption, the latter primarily during mechanical fibrillation of native fiber in aqueous suspension and the negative limitation of very low solid content associated with the gel-like properties of the resulting final product. The application of oxygen gas barrier discharge (DBD) plasma on dry cellulose fiber, as reported here, is considered novel in achieving onward nanofibrillation. At this early stage, though, simple laboratory DBD equipment precludes the study of overall efficiency. Example fiber was taken from paper pulp manufacture but may not be limited to wood source. The oxygen plasma was seen to etch the microcellulose fiber structure, simultaneously oxidizing the glue-functioning hemicellulose, rendering it soluble, so that nanopolymer crystalline-based cellulose fibrils can be readily released at the surface of the host refined microfiber at the point of application, forming micro nanofibrillated cellulose structure (MNFC) at previously uneconomic higher solid content. Eliminating the need for liquid water during precursor process treatment is considered potentially transformative with respect to production feasibility, end-product transportation and application.
  • Rheology of nanocellulose-rich aqueous suspensions: A review
    (2017-11-01) Hubbe, Martin A.; Tayeb, Pegah; Joyce, Michael; Tyagi, Preeti; Kehoe, Margaret; Dimic-Misic, Katarina; Pal, Lokendra
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    The flow characteristics of dilute aqueous suspensions of cellulose nanocrystals (CNC), nanofibrillated cellulose (NFC), and related products in dilute aqueous suspensions could be of great importance for many emerging applications. This review article considers publications dealing with the rheology of nanocellulose aqueous suspensions in the absence of matrix materials. In other words, the focus is on systems in which the cellulosic particles themselves "dependent on their morphology and the interactive forces between them" largely govern the observed rheological effects. Substantial progress in understanding rheological phenomena is evident in the large volume of recent publications dealing with such issues including the effects of flow history, stratification of solid and fluid layers during testing, entanglement of nanocellulose particles, and the variation of inter-particle forces by changing the pH or salt concentrations, among other factors. Better quantification of particle shape and particle-to-particle interactions may provide advances in future understanding. Despite the very complex morphology of highly fibrillated cellulosic nanomaterials, progress is being made in understanding their rheology, which supports their usage in applications such as coating, thickening, and 3D printing.
  • The Role of Bioeconomy in the Future Energy Scenario: A State-of-the-Art Review
    (2022-01-05) Perišić, Martina; Barceló, Ernest; Dimic-Misic, Katarina; Imani, Monireh; Spasojević Brkić, Vesna
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    The bioeconomy aims at decreasing reliance on fossil fuels, preventing or reducing climate change, eliminating insecurity, and efficiently using resources; however, fierce controversy exists on conceivable pathways to accomplish these objectives. The transport sector alone, which encompasses all other industrial sectors, has grown with regard to its energy demand by 50% over the past 30 years. The aim of this paper is to promote a dialogue as to whether an economy based on biomass can be more sustainable than today’s existing economies, considering that the economy needs to expand and be boosted, while creating a cascading and recycling system. This semi-systematic review paper discusses four research questions based on findings from the last 20 years: (i) What are the crucial issues in the ongoing debate on the development of a sustainable bioeconomy concept? (ii) Where are the major conflicting points and focuses? (iii) How does the bioeconomy follow current urbanization and land-abandonment trends? (iv) How will the crisis linked to the COVID-19 pandemic change these previous scenarios? As it is not easy to currently predict which pathway will be the most effective, whether it be the one taken as of now or a specific novel pathway, this article recommends following a strategy that is diverse regarding its approaches to shaping the bioeconomy and further funding of renewable energy sources, along with the involvement of urban planning. In addition, conclusions are validated through a questionnaire completed by 51 experts in the field.
  • Stochastic transient liquid-solid phase separation reveals multi-level dispersion states of particles in suspension
    (2019-01-01) Gane, Patrick; Dimic-Misic, Katarina; Hummel, Michael; Welker, Matthias; Rentsch, Samuel
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Wall slip or, more usually, liquid-solid phase separation at the boundary wall when measuring the rheological properties of particulate suspensions is normally considered an undesirable source of error.However, exclusion of a structure consisting of multiple particulates at a planar boundary can, in turn, reveal the nature of that structure and the way it interacts with other elements in the dispersion. Using a system of surface-treated ground calcite particles, designed to control lyophilicity, dispersed, respectively, in two comparative liquids, hexadecane (dispersive surface tension component only) and linseed oil (both dispersive and polar surface tension components), the relative wettability of the particulate surface can be studied. The static state is viscoelastic, with the elastic component reflecting the network of interacting forces acting to structure the particles together and/or to trap liquid within the long-range particle-particle matrix. As strain is applied under plate-plate geometry, selected aggregate structures become size-excluded at the wall, leading to a loss of shear coupling with the bulk polydisperse suspension. At high strain, given optimal solids content, this results in a stochastic transition between two discrete stress data sets, i.e. that with full shear coupling and that with only partial coupling. Stress recovery is subsequently monitored as strain is step-wise reduced, and the progress toward loss of the stochastic transient phenomenon, together with its parallel change in magnitude, is used to describe the re-formation of primary agglomerates. Cessation of the phase separation indicates re-build of the close-to-static structure. Under certain conditions it is observed that the cessation may be accompanied by a secondary relaxation of state, indicating the build of a secondary but weaker structure, likened to the well-known dual-level flocculation in aqueous colloidal suspension. Rheo-optical observations using small angle light scattering illumination (SALS) are used to confirm a structure model switching from static (uncoupled with shear) to rotating (fully coupled to the boundary-defined shear) and finally uniformly sheared.
  • Unveiling a Recycling-Sourced Mineral-Biocellulose Fibre Composite for Use in Combustion-Generated NOx Mitigation Forming Plant Nutrient: Meeting Sustainability Development Goals in the Circular Economy
    (2020-06-05) Gane, Patrick; Dimic-Misic, Katarina; Bara´c, Nemanja; Imani, Monireh; Jana´ckovi´c, Djordje; Uskokovi´c, Petar; Barceló Rodriguez, Ernesto
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    NOx is unavoidably emitted during combustion in air at high temperature and/or pressure, which, if exceeding recommended levels, has a negative impact on the population. The authors found that when moist, limestone (CaCO3) readily sorbs NO2 to form calcium nitrate, which provides the basis for developing a surface flow filter. The substrate was made from “over-recycled” cellulose fibres such as newsprint, magazines, or packaging fibre, which are too weak to be used in further recycling. The substrate was specially-coated with fine-ground calcium carbonate and micro-nano-fibrillated cellulose, which was used as a binder and essential humectant to avoid formation of a stagnant air layer. Pre-oxidation countered the action of denitrification bacteria colonising the cellulose substrate. The by-product CO2 produced in situ during carbonate to nitrate conversion was adsorbed by perlite, which is an inert high surface-area additive. After use, the nitrate-rich CaCO3-cellulose-based filter was proposed to be mulched into a run-o resistant soil fertiliser and micronutrient suitable, e.g., for renewable forestry within the circular economy. Belgrade, Serbia, which is a highly polluted city, was used as a laboratory test bed, and NO2 was successfully removed from an inlet of city air. A construct of street-side self-draughting or municipal/commercial transport vehicle-exterior motion-draught filter boxes is discussed.