[diss] Kemian tekniikan korkeakoulu / CHEM

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  • Techno-economic assessment at different production scales for sustainable production of bio-based products
    (2025) Khalati, Elham
     School of Chemical Engineering | Doctoral dissertation (article-based)
    This research assesses different aspects of eco-friendly production plants on pilot and commercial scales and develops technical and efficient processes that produce value-added sustainable products. It begins from a lignin-based production plant on pilot scale. The process involves the formation of colloidal lignin particles (CLPs) via self-assembly when lignin dissolution contacts water. This transformation improves the dispersibility of lignin in different media, thereby enabling its application in various areas. This research takes a systematic approach to design a safe and viable pilot plant to optimize the production process. Such an approach allows testing and validating the setup in conditions that closely mirror a full-scale production environment. For detailed design, the technical, safety, and environmental aspects of the pilot plant were examined. Process models were created to conduct process simulation and optimization, perform process safety analysis, and consider regulations to protect human health and the environment. Process safety analysis was conducted by classifying hazardous areas based on the incident rate and extent of the explosive gas atmosphere. In addition, European Union chemicals legislation was considered to assess health and environmental impacts. In the next research phase, the focus moved to developing a commercial-scale closed-cycle extraction process with supercritical CO2 (scCO2). Compared to conventional techniques, scCO2 extraction is considered a clean technology that mitigates environmental issues and enhances extraction yields. Similarly to the pilot plant, after developing process models, the process plant was simulated. Based on the generated technical diagrams, a structured and systematic system examination and risk analysis were performed. Compared to pilotscale setup, a commercial production plant requires more comprehensive techno-economic assessments to develop a viable and safe process. Therefore, cost assessments were conducted via estimating capital and total operating costs. The profitability of the process was also assessed based on calculating the net present value, payback period, and internal rate of return. Conducting sensitivity analysis also facilitated the determination of important variables impact on the process profitability. This investigation has led to thoroughly evaluating different aspects of pilot-scale CLP production as well as commercial multiproduct scCO2 extraction plants. The assessment results provide the opportunity to show their similar and distinct design aspects, which emphasize their roles in developing eco-friendly feasible processes. The approach applied to the CLP production covers new aspects of process design, which are not generally considered for technical, safety, and environmental features of the bench-scale process. This research can be applied in similar processes that involve lignin dissolution and solvent recovery unit optimization before scale-up. In the case of the full-scale plant, developing a mobile and multiproduct scCO2 extraction plant constitutes a new design concept which was developed and assessed in this study. This safe and eco-friendly process not only economically competes with conventional extraction techniques but also provides novel employment opportunities in rural areas.
  • Fractionation of softwood into lignin-containing fibres and fibrils and lignosulphonates through neutral sulphite pulping
    (2025) Hanhikoski, Saara
     School of Chemical Engineering | Doctoral dissertation (article-based)
    The forest industry plays an important role in the production of sustainable materials, chemicals, and energy to meet current and future demands. Driven by economic and environmental factors, the forest industry is increasingly focused on enhancing resource efficiency and developing higher value-added products. In the wood pulping industry, maximising pulp yield and optimising the use of dissolved organic residues represent complementary strategies for the comprehensive utilisation of wood raw material. In this context, the potential of semi-chemical pulping processes, such as the commercial neutral sulphite semi-chemical (NSSC) pulping, to implement these strategies remains largely unexplored. Thus, this thesis provides insights into the fractionation of Scots pine using sodium-based neutral sulphite (NS) pulping within a pH range of 7‒10, as an alternative process to produce lignin-containing high-yield fibres and recoverable organic compounds in the spent liquor. The various sodium sulphite cooking conditions investigated enabled the production of pulp with yields ranging from 80% to 55% on o.d. wood. The analysed compositions showed that a high content of carbohydrates was preserved in the pulps, largely due to the stabilisation of galactoglucomannan. In contrast, delignification under the applied conditions was limited, and to achieve a pulp yield lower than that of typical NSSC pulps (<70% o.d. wood) required long cooking times at high temperatures or the use of anthraquinone as a catalyst. In the spent liquors, lignosulphonates and carboxylic acids, mainly acetic and formic acids, constituted the primary dissolved components. The lignin balances, compiled from lignosulphonates in the pulps and spent liquors, revealed that the pulps contained a residual lignosulphonate fraction that was readily alkali-soluble. The characteristics of this fraction were close to those of spent liquor lignosulphonates, indicating the potential for recovering and utilising both as by-products. Due to their high hemicellulose content and anionic charge, the fibres were relatively easy to fibrillate into nanosized material, although their fibrillation behaviour varied depending on lignin content. As a result of this characteristic, the fibres presented a promising source for lignin-containing cellulose nanofibrils, which may create new application opportunities for the fibres. The findings on Scots pine fractionation under various NS pulping conditions, summarised in this thesis, provide a basis for evaluating softwood NS pulping as an alternative process for producing lignin-containing high-yield fibres and fibrils, as well as lignosulphonates. In addition, the analysed characteristics of fibres and lignosulphonates facilitate the identification of their potential end-use applications. Considering the forest industry's emphasis on strategies to enhance resource efficiency through comprehensive utilization of wood, semi-chemical pulping processes present a viable option.
  • Fabrication of bio-inspired films and surfaces
    (2025) Daghigh Shirazi, Hamidreza
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Nature provides a wealth of optimized principles and functional structures that inspire the development of advanced materials to meet the demands of future technologies. This thesis explores bio-inspired approaches for fabricating films and surfaces using three distinct methods: direct replication of natural surface structures, independent tailoring of hierarchical surface structures, and film production via a spinning technique. These fabrication strategies aim to harness nature-inspired functionalities to advance material design and performance. The replication of leaf surface structures, specifically leek leaves, was achieved through soft lithography, enabling the transfer of superhydrophobic and anisotropic wetting properties of the leaves to the replicas. Furthermore, the replicated surface structures lead to additional optical functionalities. Three approaches were employed: all-biobased replicas using cellulose-based substrates coated with carnauba wax, elastomeric replicas coated with a candle soot layer, and elastomeric encapsulation for solar cells. The results demonstrated improvements in the efficiency of perovskite solar cells through light management. Furthermore, self-cleaning functionalities derived from the leaf structures was enabled owing to the superhydrophobic surfaces, in which dust and dirt are removed when water droplets roll off the surface. In the case of solar cells, this selfcleaning property ensures maximum incident light exposure and along with suitable encapsulation can promote both the lifetime and efficiency of photovoltaic systems. The thesis further delves into independently tailoring hierarchical surface structures by coupling optical patterning of azopolymers with thermal shrinkage of a bilayer with mismatching mechanical properties, combining surface features in two distinct length scales. This method provided anisotropic wetting properties and can also pave the path toward facile fabrication of templates, instead of direct usage of leaves, to transfer the surface structure. Additionally, a cellulose nanofibril (CNF) film-spinning approach was introduced to produce partial CNF alignment, inspired by cellulose orientation in natural systems like wood. The films showed optical transparency and anisotropic humidity actuation reminiscent of, e.g., pine cones. The developed fabrication routes highlight the potential of bio-inspired strategies to produce multifunctional films and surfaces in straightforward and simple manners. The versatility of the presented methods allows for their integration with a wide range of techniques and materials by researchers in future studies, enabling the potential to achieve even more impactful outcomes.
  • The Potential of Lignocellulosic Materials for Supercapacitors and Hydrogen Storage: Activated Carbon Synthesis and Cellulose Separator Development
    (2025) Selinger, Julian
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Energy storage devices are in growing demand, driven by the transition towards a more sustainable future and the increasing use of electronic devices, increasing use of electric and hydrogen−powered vehicles, as well as renewable energy systems. However, energy storage devices are often linked with environmental concerns, as they may contain non−biobased and non−degradable components. This concern is addressed in the following dissertation by exploring the use of bio−based materials for supercapacitor electrodes, hydrogen storage materials and separators. In a first phase optimized activation parameters for bio−based activated carbons were investigated using cellulose−chitosan IONCEL fibers as model precursors to achieve the best balance between surface area, pore size distribution and yield. Optimal conditions were identified with an activation temperature of 800 °C and pre−carbonized material−to−KOH ratio of 1:5. Industrial side streams from the coffee and sugar producing industries were subsequently activated under these conditions. Specific BET surface areas of up to 3,300 m2g−1 could be achieved, with pore size distributions favorable for hydrogen adsorption capacities of up to 2.8 wt.% at 1 bar and 5.8 wt.% at 37 bar, both measured at 77 K. Additionally, the microporous structures of the activated carbons significantly enhanced the performance of aqueous supercapacitors, achieving capacitances of up to 236 F g−1 (at 5 mV s−1). These results outperformed the benchmark material (YP80F) by approximately 100%. To increase the share of bio−based materials in supercapacitors, the aim was to produce cellulose−based separators while considering key design aspects. By incorporating microfibrillated cellulose into paper hand sheets, the thickness was reduced to below 40 μm, and pore sizes were adjusted to fulfill the requirements for supercapacitor separators. A crosslinking−approach using butanetetracarboxylic acid significantly enhanced the wet strength, increasing it by over 6,000%, while maintaining the dimensional stability under wet conditions. The electrochemical characterization demonstrated that the cellulose based separators perform comparable to that of commercial benchmark materials. This dissertation highlights that bio−based materials are a sustainable resource and can reach parity with or even outperform commercial benchmarks. It offers a path for the development of more environmentally friendly energy storage technologies.
  • Lignin-derived compounds valorization on metal-free carbon catalysts
    (2025) Yang, Mingze
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Biomass is a promising alternative to fossil fuels, addressing rising energy demands and supporting carbon neutrality. Among biomass components, lignin is abundant but challenging to utilize fully, making its valorization an important focus. Common methods like oxidative dehydrogenation (ODH) and alkylation-hydrodeoxygenation often require toxic agents or noble metal catalysts, which present environmental concerns. Metal-free, sustainable routes are needed, and carbon catalysts show potential as eco-friendly substitutes. This thesis investigated lignin valorization pathways using carbon catalysts, discussing the mechanisms and comparing their performance with traditional metal-based methods. The biaryl structural unit was synthesized using an air-oxidized activated carbon (oACair) catalyst in an ODH reaction from lignin-derived ketones. The oACair catalyst demonstrated a 74% biphenyl yield with a 9.1×10-2 h-1 reaction rate constant, showing excellent recyclability over six runs and a broad substrate scope across 15 substituted compounds. The quinoidic carbonyl active site and positively charged intermediated were proposed based on surface oxygen functional group analysis, model compound, functional group blocking, and Hammett plot. Similarly, the diaryl amine N-phenyl-1-naphthylamine (P1NA) was produced from lignin-derived aniline and 1-tetralone via an oACair-catalyzed tandem ODH (TODH) reaction, achieving a 71% yield of P1NA with a 0.23 h-1 Max. TOF. The reaction’s robustness was confirmed by its five-run recyclability and compatibility with 10 substrates, with the carboxylic acid group exhibiting cocatalytic effects. Free radical scavenger tests and simulations suggest a single-electron transfer free-radical mechanism for the TODH reaction. The alkylation of alcohols and phenolic compounds was another pathway explored in this thesis. Lignin-derived acidic carbon (SLC400) displayed a high acid density of 2.92 mmol·g-1 with dominated Bronsted acid sites. SLC400 exhibited good catalytic performance in the alkylation with a Max. TOF of 14.2 h⁻¹ in the dehydration step and a Max. TOF of 0.5 h⁻¹ in the alkylation step. Additionally, zeolite-supported tungsten oxide (WO₃/HY500) was applied for guaiacol ethanol alkylation (GEA), confirming pentaethylphenol as the main product and suggesting an alkylation-demethylation mechanism based on product structure and reaction monitoring. Surface acid analysis identified weak and strong Lewis acid sites as the primary active sites for this reaction. These routes offer practical methods to valorize lignin-derived compounds in an environmentally friendly and sustainable way, emphasizing the importance of metalfree carbon catalysts. The investigation of the kinetics, active site, and mechanism enhances the understanding of carbon catalysts and contributes to the further optimization of these routes.
  • Dewatering of single- and multilayer nanopapers
    (2025) Ahadian, Hamidreza
     School of Chemical Engineering | Doctoral dissertation (article-based)
    During the past decade, the paper and board industry has increasingly explored the application of nanomaterials in furnish components. This is due to their potential to create innovative, high-value products that will dominate future markets. This includes cellulosic nanomaterials such as microand nanofibrillated cellulose (MNFC). MNFC consists of cellulose micro- and nanofibrils obtained by deaggregating cellulose macrofibers. These fibrils are considerably smaller and bind more water than the parent pulp fibers. MNFC presents opportunities to innovate natural fiber products with enhanced performance characteristics, including greater mechanical and barrier properties. However, the small size, high swelling, and large surface area of MNFC causes processing issues such as poor water removal properties. This thesis focuses on forming and dewatering sheets containing cellulose nanomaterials and investigates possible solutions to overcome the dewatering challenges. The main hypothesis is to help dewatering by restructuring the fiber network and increasing the permeability of the wet web. The reduced permeability of the wet web is directly related to sheet sealing, which is an established phenomenon in the papermaking process. Different mechanisms of sheet sealing are presented, and we propose approaches to prevent sheet sealing. We show that the enrichment of small fibrils on the exit layer should be avoided. MNFC/fiber flocs and their agglomeration in the suspension are modified through the addition of cationic micro-and nanobubbles. This also changes the z-distribution (localized concentration) of the MNFC fibrils in the web so that there will be more located in the upper layers, which reduces sheet sealing. This method allows for easier dewatering and producing samples with up to 25% MNFC content. Multilayer forming of sheet is suggested as a direct way of structuring. We show that the application of a very thin fibre layer (as thin as 5 gsm) on the screen has a significant effect on the dewatering rate. We also investigate the application of engineered fibers that provide desired functional properties and maintain dewatering properties. This material involves enhanced external fibrillation of fibers without generating excess flake fines and fiber fragments. The composition of this highly swelling material with parent pulp fibers provides low-density, highstrength paperboards. The work summarized in this thesis delivers new insights into dewatering challenges of novel paper/board grades containing nanomaterials and identifies potential routes to overcome these challenges.
  • Superstructured wood-based carbon materials for broadband light absorption and CO2 capture
    (2025) Zhao, Bin
     School of Chemical Engineering | G5 Artikkeliväitöskirja
    Light is an abundant resource; however, stray light can significantly impact the performance and longevity of optical systems. Adverse effects such as reduced image contrast and signal degradation highlight the need for advanced solutions to effectively mitigate these challenges. Superblack materials, with near-zero light reflectance, are in high demand to enhance several light-based technologies. In this study, we developed wood-based spectral shielding materials with exceptionally low reflectance across the UV-VIS-NIR (250–2500 nm) and MIR (2.5–15 μm) ranges. Using a straightforward top-down approach, we produced robust superblack materials by removing lignin from wood and carbonizing the delignified wood at 1500 °C. This process induced shrinkage stresses in subwavelength severed wood cells, forming vertically aligned carbon microfiber arrays (~100 μm thick) with light reflectance as low as 0.36 %. We further synthesized multiscale carbon supraparticles (SPs) through a soft-templating process involving lignin nano- and microspheres bound with cellulose nanofibrils (CNFs). Following oxidative thermostabilization, these lignin SPs exhibited high mechanical strength due to their interconnected nanoscale networks. In further work, by inserting lignin particles (LPs) into delignified wood and carbonizing the structure, we created a carbonized reconstituted wood (cRW) system with enhanced dimensional fidelity and finely tuned light-absorbing fibrillar microstructures. They resulted in broadband light traps that achieved superabsorbance, exceeding 99.8% across a wide range of wavelengths, from infrared to ultraviolet. Tiled cRW structures, optically welded for customizable size and shape, demonstrated superior laser beam reflectivity compared to commercial light stoppers, eliminating thermal ghost reflections. This makes them promising candidates as reference infrared radiators for thermal imaging device calibration. Beyond optical applications, the carbon SPs also offer hierarchical adsorption sites, achieving a CO₂ adsorption capacity of 77 mg CO2·g-1. This innovation in the area of carbon capture was shown to solve the diffusion and kinetic limitations of conventional nanoparticle-based systems. Overall, this thesis summarizes wood-derived solutions that go from multispectral shielding to carbon capture technologies.
  • Advanced Characterization for Studying Ni-rich Cathode Materials for Li-ion Batteries
    (2025) Colalongo, Mattia
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Li-ion batteries (LiBs) are energy storage devices which are able to convert chemical energy into electrical energy. Due to the recent excessive consumption of fossil fuels resulted in the uncontrolled release of carbon dioxide and significant amounts of greenhouse gases into the atmosphere, the need for sustainable energy growth becameevident. Hence, there is a critical need for high-performance energy storage devices exhibiting both high energy and power density to ensure the sustainability and safety of storing renewable energy. In this thesis, by means of synchrotron radiation facility we explored the most efficient way to Zr bulk doping a Ni-rich layered cathode material upon two different pathways, during lithiation and co-precipitation step. High resolution x-ray diffraction and x-ray absorption spectroscopy measurements revealed, for the coprecipitation step, the absence of every Zr based impurity and a local environment compatible with its inclusion in the cathode host structure. Whereas for the lithiation step, Zr tended to only form extra-phase impurities. The Zr-doped Ni-rich cathode material synthesized via the co-precipitation method exhibited improved electrochemical performance compared to the undoped sample. To investigate these enhancements, operando high-energy x-ray diffraction and exsitu x-ray absorption spectroscopy were utilized. X-ray diffraction analysis revealed a reduced formation rate of the detrimental H3 phase in the doped samples, while x-ray absorption spectroscopy indicated a decrease in transition metal dissolution from the cathode material. These findings underline the importance of studying trace amount dopants to advance the development of more robust Ni-rich cathode materials. The undoped material in the operando studies revealed the presence of a phase segregation upon cycling at high voltages. To understand the nature of the phase segregation formation mechanism, a nanobeam approach was involved. An initial operando experiment by means of scanning x-ray diffraction microscopy was carried out to probe multiple single particles and follow the Li+ heterogenities upon cycling. However, the experiment faced challenges due to cell holder instability, and beam damage. Progress continued with further experiments at the IDOl ESRF beamline, allowing successful ex-situ examination of inter- and intra-particle heterogeneities in polycrystalline particles. Up to date, the operando challenges in nanoprobe studies remain a critical area to address in order to advance the research in the field of Li-ion battery materials.
  • Effects of Nickel in Copper Production: Implications for High-Purity Copper Electrorefining
    (2025) Sahlman, Mika
     School of Chemical Engineering | Doctoral dissertation (article-based)
    The demand for high-purity copper is increasing due to the electrification of society. At the same time, the ore bodies are getting poorer, and there has been an increased emphasis on metal recycling. Most of the world’s high-purity copper is produced by electrorefining. Nickel is one of the main impurities in copper electrorefining, and the previously mentioned factors have resulted in increased nickel concentrations at the smelters and tankhouses, especially in operations that specialise in treating complex raw materials. This thesis studies the effects of Ni on Cu electrorefining and discusses the implications of the results for industrial electrorefining plants. Three main themes were investigated: Ni's contamination of the copper cathode, Ni’s effects on anode slime flow behaviour, and the impact of Ni on the physical quality of the cathode, i.e., roughness and nodule formation. Regular laboratory-scale copper electrorefining experiments were performed in traditional sulfuric acid media, with the focus of the thesis being on the behaviour of anode Ni and electrolyte Ni. Both industrial and synthetic electrolytes were used to investigate electrolyte Ni’s effects on copper electrorefining. Industrial anode samples were used to examine the impact of anodes on copper electrorefining. Anode slime detachment and cathode growth study results were verified in a bench-scale electrorefining cell. No definite upper limit for the anode Ni concentration could be determined. An upper limit of 20 g/L of Ni was proposed for the electrolyte due to the increased risk of rougher cathodes and cell passivation. Particle entrapment was the primary contamination mechanism of copper cathodes in the case of Ni. Synthetic anode slime composed of NiO and Fe2O3 did not cause cathode nodulation. Nodulation was observed with industrial anode slimes, but the industrial anode slime with less Ni (10.3 wt.%) resulted in more nodules than the industrial anode slime with higher Ni concentration (20.4 wt.%). Electrolyte inclusions were deemed plausible, but major micronodulation in the presence of conductive graphite was required for significant contamination. The electrodeposition of Ni does not happen in typical Cu electrorefining conditions. Increasing anode and electrolyte nickel concentrations led to an increased upward flow of anode slimes, at least during passivation. Increasing anode Ni concentrations increased upward flow of anode slimes throughout the electrolyte. In the case of the electrolyte, however, this phenomenon occurred only in the vicinity (1 mm) of the anode surface. The impact of electrolyte Ni was attributed to the increased porosity of the anode slime layer, while the changing anode slime mineralogy might explain the effect of anode Ni. Both anode and electrolyte Ni promoted the clustering of anode slime. Average, maximum and minimum anode slime settling velocities were 0.12 mm/s, 1.65 mm/s and -1.08 mm/s, respectively, during anode passivation (at 25 °C). At 60 °C, the anode slimes settled on average with a velocity of 1.4-49.6 mm/s, and upwards-moving slime could flow with a velocity of 2.5 mm/s. Design of Experiments (DOE) was used in combination with partial least square regression (PLSR) modelling to determine the impact of Ni and electrolyte additives (gelatine, thiourea and chloride) on the cathode roughness (Rz and Sm). Ni increased the Rz roughness of the Cu cathodes from 469 μm to 945 μm in the absence of additives. Ni alone did not affect the Sm roughness, but thiourea and Ni were found to have synergistic effects on smoothening the cathode surface. Laboratory cathodes were compared to industrial samples, and samples from both sources had similar surface roughnesses. While increasing Ni might cause rougher cathodes, variable importance in projections (VIP) suggests that additives have a more notable impact on cathode surface quality.
  • Electrochemical CO2 Reduction Mechanism Exploration: An Integrated Thermodynamic and Kinetic Approach
    (2025) Khakpour, Reza
     School of Chemical Engineering | Doctoral dissertation (article-based)
    The electrochemical reduction of CO₂ (eCO₂RR) presents a promising strategy to address sustainable energy challenges by converting CO₂ into value-added chemicals and fuels. This thesis employs density functional theory (DFT) to investigate the reaction mechanisms of eCO₂RR, focusing on enhancing computational mthodologies and understanding catalyst performance. Key challenges such as the low reactivity of CO₂ and competition with the hydrogen evolution reaction (HER) are addressed through a systematic evaluation of molecular catalysts including metal porphyrins and phthalocyanines. The research develops advanced computational approaches to accurately model proton-coupled and decoupled electron transfers, essential for analyzing reaction pathways. The findings highlight bicarbonate as a more favorable intermediate compared to CO₂ under neutral pH conditions. Mechanistic insights into post-CO reactions including the formation of C1, C2, and C2+ products elucidate the role of catalyst design and reaction conditions in achieving multi-carbon product formation form single atom catalysts (SACs). Additionally, the study explores pH-dependent selectivity for formaldehyde and methane which aligns computational results with experimental observations. By providing a comprehensive framework for understanding eCO₂RR pathways, this thesis contributes to the rational design of catalytic systems and optimization of reaction conditions for sustainable energy applications and efficient electrocatalysis.
  • Molecular simulations of crystalline cellulose interfacial interactions
    (2025) Kou, Zhennan
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Crystalline nanocellulose, especially cellulose nanocrystals (CNCs), is widely used in many fields, such as pharmaceutical and biomedicine materials, paper making and alimentation industries, in reinforcement of polymer composites, but also as support matrices and packaging materials. The interactions between CNC surfaces and other materials can influence the properties of CNCbased materials, which can widen the usage of CNC materials. In this thesis, CNC interactions with water, ions, and lignin-carbohydrate complexes (LCCs) are studied, since these interactions can heavily affect the properties of CNC materials but also the wood-like and wood-based materials. We first studied the interactions between CNC surfaces and Na+ and Cl- ions in water solutions. After that, the interactions between CNC surfaces and LCCs were studied. A very small amount of ions can affect CNC surface interactions strongly. In this thesis research, in a 0.6 %wt CNC solution, 0.25 mM NaCl in the solution was sufficient to significantly change the viscosity. Our results show that the presence of NaCl as ions can change the water dipole orientation, which influences the interactions between CNCs. The hydration layer ordering at the position of the ion can increase. The change at the binding sites is enough to change the interaction between CNC surfaces, affecting solution viscosity. This kind of water molecule orientation change can help merge the hydration layers of surfaces, which increases the connections of CNCs in solution. Thus the viscosity increased. The interactions between LCCs and CNCs are dependent on the CNC surface crystal facet. We examined simple model LCCs to obtain insight. The main driving force of interaction between hydrophilic CNC surfaces and the model LCCs was hydrogen bonding, with lignin playing a bigger role when the hemicellulose chains are short. For hydrophobic CNC surfaces, the interaction was more through van der Waals and dipole-dipole forces. In summary, interactions between CNC surfaces common in CNC solutions and in wood-like and wood-based materials are studied in this thesis. This can help understanding and control the properties of these materials. The findings may help product design in these fields to be more productive and environment-friendly.
  • Bioinspired living coating system for wood protection
    (2025) Poohphajai, Faksawat
     School of Chemical Engineering | Doctoral dissertation (article-based)
    The bioinspired living coating system offers an innovative, sustainable approach to wood protection, relying on natural substances with minimal environmental impact and low maintenance requirements. While promising as an alternative to conventional coatings, key aspects remain poorly understood. Although Aureobasidium pullulans (A. pullulans) has been identified as the optimal fungal species, it is essential to further validate that this fungus meets crucial criteria for effective protection. Additionally, the impacts of natural weathering on substrate properties, bioreceptivity, microbial colonization rates, and the survival of fungal cells within the coating under varied conditions require further investigation. This thesis aims to 1) explore A. pullulans' resilience in biofilm formation across different wood substrates and environmental conditions, 2) assess the performance of wood treated with this biofilm-based coating, and 3) examine fungal cell survival throughout its service life. The evaluation of fungal colonisation on wood surfaces exposed to diverse climate conditions and a range of coated and non-coated biobased façade materials revealed that specific species, notably A. pullulans, emerged as predominant primary colonisers on weathered wood surfaces, regardless of geographical location, cardinal direction, and surface treatment. The adaptability and capacity to thrive in a relatively broad range of ecological conditions make this fungal strain suitable as a protective layer for building materials. The assessment of fungal colonisation on wood surfaces coated with Biofinish following a 9-month exposure period revealed that the majority of the detected species belonged to the genera Aureobasidium, specifically A. pullulans. These results indicate the survival and effective antagonistic action of A. pullulans, the living and active ingredient of the coating, against other wooddecaying fungi. The performance of Scots pine (Pinus sylvestris L.) wood treated with Biofinish was evaluated against uncoated reference wood following a 12-month natural weathering trial. Biofinish exhibited superior performance across all examined aspects compared to the uncoated reference. The entirely bio-based composition of the Biofinish coating enhances its sustainability and compatibility with natural environments, rendering it an appealing alternative to contemporary wood surface protection solutions. The results from this thesis will facilitate the control and optimisation of fungal biofilm and contribute to the development of novel bioinspired protection coatings based on optimised fungal biofilm working in synergy and not against nature.
  • Electrochemical Reduction of CO₂ on Molecular Catalyst: Unfolding Operation Parameters Influence on Product Selectivity
    (2025) Hossain, Md Noor
     School of Chemical Engineering | Doctoral dissertation (article-based)
    The electrochemical reduction of CO₂ (eCO₂R) using renewable electricity offers a promising way to convert waste CO₂ into valuable chemicals and fuels, achieving a negative carbon emission footprint. Industrializing eCO₂R for chemical production requires durable, selective, and active electrocatalysts capable of generating high current density at low overpotentials. This thesis focuses on the design and development of a cobalt tetraphenyl porphyrin/multi-walled carbon nanotube (CoTPP/MWCNT) composite for eCO₂R to one-carbon (C₁) chemicals and fuels, and the evaluation of this composite in various electrochemical cells. The electrochemical reduction of CO₂ on CoTPP/MWCNT was investigated in two electrochemical cells: H-cell and industrially relevant flow cell. In both electrochemical cells, selected potential values and a temperature range of 20-50°C were investigated in a 0.1 M KHCO3 electrolyte. The local reaction environment during eCO₂R on the composite was investigated using a differential electrochemical mass spectrometry (DEMS) technique. A similar temperature range as in previous studies was employed. The H-cell studies reveal that the composite produces a mixture of liquid and gas products. The product selectivity strongly depends on the applied potentials and temperatures. At lowest applied temperature, CO₂ is mainly converted to CO and CH3OH while H2 production remains minimal. As the temperature increases H2 production becomes dominant over eCO₂R related products. Flow cell studies reveal that composite mainly produces gas products such as CO and H2 at all applied potentials and temperature. Like H-cell, product selectivity strongly depends on the applied potentials and temperatures. Interestingly, at 20°C and highest applied negative potential, the composite is highly selective for CO formation, reaching a Faradaic efficiency (FE) of 98%. However, increasing the temperature significantly reduces CO selectivity while increasing H2 production. Furthermore, this study demonstrates that the syngas (a mixture of CO and H2) ratio can be controlled by adjusting the temperature. DEMS studies identify key fragments of reaction products evolving from the electrode/electrolyte interface. Experimental results reveal that onset potential of reaction products is strongly affected by temperature, particularly onset potential of CH3OH formation decreased approximately 300 mV at highest temperature. The reduction of onset potential is economically beneficial for large-scale industrial chemicals production. Overall, DEMS studies enhance our knowledge on the mechanisms of CH3OH and CH4 production on the CoTPP/MWCNT composite.
  • Leaching of lithium-ion battery materials in sulfate and chloride media for hydrometallurgical recycling
    (2025) Partinen, Jere
     School of Chemical Engineering | Doctoral dissertation (article-based)
    As a result of the worldwide attempt to phase out fossil fuels and implement cleaner technologies, batteries are becoming increasingly important. One of the most obvious effects of this green transition in everyday life has been the rapid increase in the number of electric vehicles (EVs) over the past few years. Li-ion batteries used in EVs contain high concentrations of valuable materials, many of which are classified as critical. To ensure the circulation of these materials back to reuse after End-of-Life (EoL), efficient recycling is necessary. The most commonly used battery recycling processes are hydrometallurgical and pyrohydrometallurgical. This thesis studies the leaching step of the hydrometallurgical recycling route. Leaching experiments were performed in sulfate and chloride media, using both pure commercial battery cathode chemicals and industrially processed battery waste – black mass – originating from EoL batteries. This allowed for the investigation of both fundamental phenomena associated with cathode materials leaching as well as holistic process considerations related to the presence of other battery components. During the leaching of pure cathode chemicals, Mn was observed to precipitate out of sulfate media at temperatures T ≥ 70 °C in the absence of external reductants. This precipitation was inhibited in chloride-containing lixiviants, where Cl2 gas was formed instead. Moreover, a system utilizing the reductive properties of soluble cuprous chloride complex species was found to be efficient for battery cathode materials leaching, reaching over 90% Co and Li yields under relatively mild conditions (1 M H2SO4, 0.2 M NaCl, 30 °C, 2 h). Nonetheless, observations on the use of real industrial black mass in a similar system raised questions about the compatibility of chloridecontaining lixiviants, as the reactor overflowed due to rapid gas evolution. In studies involving industrial black mass, the reductive properties of Cu were found to be improved in response to an increased solution iron concentration – up to 0.4 g/L Fe – whereas Al reductive properties were only improved as the temperature was increased. Furthermore, Cu was found to be overall a more efficient reductant in terms of electron efficiency when compared with Al. In the presence of both Cu and Al, copper was also found to temporarily cement on Al particle surfaces and redissolve as leaching progressed. Furthermore, Design of Experiments (DoE) methodology was used in combination with regression modeling to derive equations that can predict leaching yields based on input parameters – temperature, solution Fe concentration, Cu amount, and H2O2 amount. This analysis revealed solution Fe concentration and feed Cu amount as more impactful variables in terms of cathode material reduction when compared with the commonly used hydrogen peroxide. This finding was attributed to the various side-reactions associated with H2O2. Existing literature on LIB cathode material and industrial black mass leaching has largely focused on the development of novel leaching systems by the investigation of alternative reductants to H2O2 while often neglecting the role of various metallic components found within industrial black masses. This thesis contributes to the field by providing a detailed comparison of sulfate and chloride media leaching efficiencies, elucidating the capability of soluble cuprous complexes to catalyze the leaching system, and investigating the reductive efficiencies of current collector metals Cu and Al and the role of soluble Fe as an electron transporter between these metals and battery cathode materials. The research presented in this thesis will help future researchers and industrial operators by providing detailed information about the performance of various leaching media and the reductive efficiency of metallic fractions found within industrial black mass.
  • Expanding the toolbox for genetic manipulations in Methanosarcina acetivorans
    (2025) Zhu, Ping
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Methanosarcina acetivorans is a model methane producer that can utilize many different one-carbon substrates. Genetic tools are needed to investigate its physiology and to extend the product scope beyond methane. The development of the current genetic toolbox in this archaeon, however, is far behind compared with those e.g. for acetogenic bacteria or E. coli. In this study, the genetic toolbox for M. acetivorans has been expanded for efficient genome edition and for controlling gene expression. First, a CRISPR/Cas12a-based genome editing system (Publication I) was introduced for efficient marklerless genome editing in M. acetivorans. Different from the previously developed Cas9-editing system, the Cas12a recognizes distinct PAM sequence and demonstrates high efficiency in large DNA fragments deletion and alleviate the cloning efforts on multiplex genome editing. To facilitate a stable and reliable gene expression, four neutral integration sites in M. acetivorans genome were characterized (Publication II) for heterologous genes integration and metabolic pathway constructions. These neutral sites allow gene expression without disrupting cell viability, providing as non-essential loci for stable long-term genetic engineering. Finally, a promoter-RBS library comparing 33 combinations was developed for fine-tuning gene expression in M. acetivorans (Publication III). By evaluating the native and engineered combinations, the library revealed diverse transcriptional regulation mechanisms mediated by RNA secondary structures. With a broad range of expression strength (ca. 140-fold), the library allows precise control of gene expression levels and enables fine regulation of metabolic flux for various synthetic biology applications. The tools developed in the thesis enhance the capacity for genomic manipulation of M. acetivorans and facilitate the development of metabolic engineering for efficient methane production, carbon flux rewiring, and other biotechnological processes in this organism.
  • Carbonyls in Cellulose: An Investigation into Formation Mechanisms, Analytical Methods, and their Consequential Properties for Fiber Engineering Applications
    (2025) Fliri, Lukas
     School of Chemical Engineering | Doctoral dissertation (article-based)
    This thesis focused on the introduction of carbonyls into the cellulose structure with the wider aim to expand the scope of applications of cellulosic fibers. Thereby, two separate reaction classes were critically re-investigated. First, the periodate oxidation of cellulose combined with modification of the resulting aldehyde functionalities. Second, the carbonization mechanism of cellulose with a focus on the thermal dehydration reactions below 300 °C. Periodate oxidation was investigated for its potential to introduce more flexible segments in the rigid cellulose structure. The low temperature dehydration represents a key yield determining step during the preparation of cellulose-based carbon fibers. To obtain further insights into these well researched topics novel analytical techniques were applied. A recently developed solution state NMR method relying on an ionic liquid electrolyte for the dissolution of crystalline cellulosic materials proved to be useful and was further expanded to a full analytical protocol. The studies on periodate oxidation were significantly hampered by different side reactions. Thus, the research focus shifted on their quantification and mitigation. An updated workup scheme for dialdehyde celluloses was elaborated and an indirect size exclusion chromatography protocol allowed to follow the partial depolymerization reactions in the early stages of periodate oxidation. For further modification the applicability of reductive amination and borohydride reduction was screened. Also there, issues with unwanted degradation or incomplete conversion were encountered and could be highlighted. Overall, the studies on periodate oxidation resulted in an improved understanding of the underlying side reactions. However, they ultimately prevented a meaningful application of this modification strategy for fiber engineering purposes. In the fundamental studies on the thermal dehydration reactions of cellulose different reaction intermediates could be isolated and identified. Application of solution state NMR showed that the first thermal transformations result in depolymerization to levoglucosan end capped structures. In contrast to prevailing mechanistic proposals in the cellulose-based carbon fiber community, the initial dehydration reactions do not include elimination reactions in the pyranose structures. Instead, a polyfuran was isolated as first carbonization intermediate and could be thoroughly characterized. This suggested a localized dehydration mechanism occurring on the reducing end groups, as recently postulated in the literature focusing on other fields of cellulose pyrolysis. This observation also suggests that the chemistry of cellulose carbonization is similar to the carbonization reactions of other sugars. Moreover, the occurrence of a polyfuran intermediate has considerable implications for the potential reactions occurring at higher temperatures, which so far evaded proper analytical characterization.
  • Sustainability of Bio-based Plastics and Composites
    (2024) Äkräs, Laura
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Plastics undoubtedly are indispensable and widespread commodities of the modern world, commonly found in a vast range of applications. Nonetheless, the awareness and concerns about the environmental impacts associated with the fossil-based plastics - that is, climate change, depletion of fossil resources, and plastic debris - are continuously on the rise. To efficaciously abate these impacts, different disciplines and approaches are needed to be used in a complementary manner, with contributions derived from the development of novel, bio-based materials as well as analytical and legal tools. To this end, in the present doctoral dissertation, approaches of material synthesis, multi-criteria decision-making (MCDM) analysis, life cycle assessment (LCA), and instruments of private law were combined in an interdisciplinary manner to analyze the selected set of bio-based plastics and composites. Accordingly, the MCDM analysis techniques of Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and Simple Additive Weighting (SAW) were applied to identify the most suitable and interesting raw materials to produce bio-based plastics, which results were further utilized to synthesize a set of selected biocomposites in the laboratory conditions. A widely used methodology of LCA was, subsequently, employed to explore the environmental impacts derived from the developed biocomposites, with a focus on the impact categories of carbon footprint as well as agricultural-related indicators of acidification, eutrophication, and land use. Finally, the potential of a range of private law instruments - ecolabels, certification marks, and European certification marks (EUCM) - was explored as vessels to convey the sustainability information derived from the results of LCA.  MCDM analysis revealed that the cultivation of castor beans and extraction of subsequent castor oil possessed the highest environmental impacts in comparison with other alternatives, despite the popularity of castor oil as a building block for commercial, bio-based polyamides (PAs). Consequently, varying concentrations of biofillers of starch and biochar were blended with the selected, neat PA- and polylactic acid (PLA) -matrices, which substantially reduced the carbon footprint and agricultural-related impacts of the plain plastics. Lastly, integration of LCA-results with different private law instruments were found not only to strengthen the sustainability information they convey, but also to possess potential to shape the behaviour of the targeted stakeholders. Overall, despite the need to enhance certainty, credibility, and comprehensivity of the applied data and methodologies, the present doctoral dissertation offers valuable information about the sustainability of the selected bio-based plastics and composites. 
  • The use of alternative reductants in pyrometallurgical operations
    (2024) Attah-Kyei, Desmond
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Due to the rising concern about climate change in the last few decades, the metallurgical industry is moving toward greener practices. This move is driven by pressing concerns about the reduction of greenhouse gas emissions and environmental footprints of industrial activities. One of the main strategies in this transition is to employ alternative reductants in high temperature processes. Substituting traditional reductants like coal or coke with sustainable alternatives such as hydrogen or biochar minimizes the carbon emission and provides economic benefits in addition. In this thesis work, several non-fossil reductants were applied in high temperature processes for metal recovery from secondary sources. Leach residue of printed circuit board (PCB) was employed as reductant for solid-state reduction of hematite in DSC-TGA coupled with QMS. Hydrogen was utilized in the reduction of zinc leach residue while nickel and copper smelting slag reduction were treated with biochar on laboratory scale in a vertical fur-nace. The feasibility of adopting alternative reductants in ironmaking and pyrometallurgical treatment of secondary resources were determined in this study. The effect of the amount of reducing agent, reduction time, and temperature on the extent of reduction was investigated. The studies revealed that although PCB leach residue can be applied in reduction processes, it can only partially replace conventional reductants. PCB was also found to be effective at lower temperatures (< 1000 oC). Leach residue from zinc processing were reduced with hydrogen at temperatures of 1200 oC, 1250 oC, and 1300 oC using H2 and N2 gases to form the reducing gas atmosphere. The results showed that H2 is an effective reductant because reduction proceeded rapidly, forming speiss droplets within the slag already after 10 minutes. Nickel and copper smelting slags were reacted with biochar which were produced from hydrolysis lignin and black pellet biomass by pyrolysis at 600 and 1200 °C, and with metallurgical coke for comparison. Nickel reduction experiments were done at 1400 °C for 15, 30, and 60 min under inert gas atmosphere. The samples were quickly quenched and analyzed with Electron Probe X-ray Microanalysis. The results showed that the use of biochar resulted in faster reaction kinetics in the reduction process compared to coke. Copper slag reduction experiments were performed at 1250, 1300 and 1350 °C for 60 min in order to investigate the effect of temperature and the effect of time on reduction progress was studied at 1250 °C for 15, 30 and 60 min. The results revealed that reduction rapidly progresses to the formation of metal alloy within 10 min. Valuable metals like copper and nickel were reduced to the metal phase.Thermodynamic simulations were performed with FactSageTM at the experimental conditions and compared with results from the lab scale experiments. FactSageTM predictions were in agreement with the experiments.
  • Synergism with novel expansin-related proteins for cellulose processing
    (2024) Dahiya, Deepika
     School of Chemical Engineering | Doctoral dissertation (article-based)
    The demand for environmentally sustainable materials has accelerated the use of renewable biomass, such as lignocellulose from plant fibers. This study focuses on innovative biotechnological methods to enhance the conversion of lignocellulosic biomass into valuable products, thereby promoting circular economy principles. Specifically, the research investigates the production and application of microbial expansin-related proteins (EXLX), particularly loosenin-like proteins, to improve enzymatic hydrolysis processes for biomass conversion.  The study employs Pichia pastoris strains SMD1168H and KM71H to produce and scale up these proteins, and further assessing their impact on converting softwood kraft pulp to nanocellulose. Key objectives include evaluating these proteins' ability to synergize with cellulolytic enzymes, enhancing sugar release from softwood kraft pulps, and facilitating the production of cellulose nanocrystals (CNCs). Advanced techniques such as Biological Small Angle Neutron Scattering (Bio-SANS) were used to analyze the structural impact of the proteins on holocellulose.  Results demonstrate that recombinant expansin-related proteins can significantly boost enzymatic hydrolysis efficiency. This enhancement is attributed to the proteins' ability to increase enzyme accessibility by modifying fiber morphology. The integration of these proteins in enzymatic cocktails showed a marked improvement in glucose and xylose yields from various cellulosic substrates. Furthermore, the study explores the enzymatic production of CNCs with enhanced stability and dispersibility, suitable for applications in conductive inks and other advanced materials. The findings underscore the potential of these proteins to reduce enzyme loadings, thereby lowering production costs and environmental impact. Future research directions include optimizing process parameters for large-scale applications and investigating synergistic effects with other enzyme systems.  In conclusion, the incorporation of microbial expansin-related proteins in biomass processing holds significant promise for advancing sustainable production technologies. This research provides foundational insights into their mode of action and range of applications, paving the way for more efficient and eco-friendly biomass conversion methods.
  • Role of conserved and non-conserved residues of Escherichia coli formate dehydrogenase H in the CO2–formate interconversion
    (2024) Li, Feilong
     School of Chemical Engineering | Doctoral dissertation (article-based)
    Molybdenum-dependent formate dehydrogenases (Mo-FDHs) have come to prominence as promising electrocatalysts for CO2 conversion owing to their ability to operate at low redox potentials. Nevertheless, engineering of these enzymes is required prior to application in industrial processes as these differ from physiological conditions under which Mo-FDHs have naturally evolved to increase host fitness. These engineering efforts are currently hampered by the limited understanding of the catalysis of the CO2–formate interconversion and motivated the research presented in this thesis.In publication I, the conserved active-site selenocysteine (U) residue 140 of Escherichia coli formate dehydrogenase H (EcFDH-H) was replaced with cysteine (C) and serine to study its role in catalysis. Kinetic characterization of U140C variants indicated that U140 stabilizes the reduced Mo(IV)–SH state that is required for CO2 reduction. Publication II focuses on the conserved residue lysine (K) 44 in EcFDH-H that is proximal to the Mo and [4Fe-4S] cofactors. The study investigates the role of K44 in catalysis by substitution with six structurally diverse residues. Subsequent kinetic characterization and molecular dynamics simulation of K44 variants suggested that K44 may stabilize the active forms of these cofactors. In publication III, a growth-based screening strategy was developed to extend the structure–function analysis of EcFDH-H beyond conserved residues. This strategy employs the complementation of an incomplete E. coli formate hydrogenlyase complex with EcFDH-H to establish a positive correlation between EcFDH-H variant activity and cell growth. As a proof of concept, five non-conserved residues were analyzed by the designed strategy and the variant A12G with an 82% increased formate oxidation activity was identified. Additionally, unpublished research is included in this thesis that aims at resolving the electron transfer conduit between cathodes and the catalytic center of EcFDH-H. This research was initiated by mapping seventeen potential electrode attachment sites on the EcFDH-H surface by individual replacement of non-conserved residues with cysteine. The formate oxidation activity of EcFDH-H variants was determined and was found to be preserved for the majority of them, providing a basis for the planned bio-electrochemical trials. Overall, the presented results increase the understanding of the role of conserved and non-conserved residues in EcFDH-H catalysis, providing important insights into the reaction mechanism of CO2–formate interconversion by Mo-FDHs. Additionally, this thesis identified potential targets for future engineering works aiming at improving the catalytic properties of Mo-FDHs, thereby promoting the development of proficient catalysts for CO2 utilization.