Mid Sweden University

Chitosan films with potential application in triboelectric nanogenerators (TENGs) represent a promising approach to replace non-biobased materials in these innovative devices. In the present work, chitosan with varying molecular weights (MW) and degrees of deacetylation was dissolved in aqueous acetic acid (AA) at different acid concentrations. It was observed that the MW had a greater influence on the viscosity of the solution compared to either the acid concentration or deacetylation degree. Gel formation occurred in high-MW chitosan solutions prepared with low AA concentration. Films prepared from chitosan solutions, through solvent-casting, were used to prepare TENGs. The power output of the TENGs increased with higher concentrations of AA used in the chitosan dissolution process. Similarly, the residual AA content in the dried films also increased with higher initial AA concentrations. Additionally, hot-pressing of the films significantly improves the TENG power output due to the decrease in morphological defects of the films. It was demonstrated that a good selection of the acid concentration not only facilitates the dissolution of chitosan but also plays a key role in defining the properties of the resulting solutions and films, thereby directly impacting the performance of the TENGs. 

Asplund fibers are manufactured using low-energy thermomechanical pulping. They have traditionally been used in fiberboard applications. Since Asplund fibers have a high specific surface area (SSA), they can find new uses as biorefinery feedstock. However, little is known about how the Asplund process parameters affect the chemical and physical structure of the fibers. This research examined the effect of refining temperature and pressure on softwood fiber properties at refining temperatures ranging from 170 degrees C to 200 degrees C. Spruce chips were subjected to a pilot-scale Asplund refining process. FTIR analyses revealed ordering of cellulose macromolecules at elevated temperatures up to 190 degrees C. Ordering of cellulose was confirmed by XRD analyses. FTIR analyses also suggested lignin condensation at elevated temperatures. SEM images showed improved fiber separation at higher temperatures when compared to the temperatures of 170 degrees C and 180 degrees C. These findings are useful when developing novel biorefinery concepts, where Asplund fibers are used as feedstock.

Fiberbanks are organic-rich sediment deposits in aquatic environments, primarily formed through historical pulp and paper mill activities. These deposits consist of wood-derived fibrous materials and are contaminated with potentially toxic elements (PTEs) such as vanadium, chromium, cobalt, nickel, copper, zinc, arsenic, cadmium, and lead. The leaching of these contaminants into surrounding waters poses significant environmental and health risks, impacting aquatic ecosystems and potentially entering the food chain. Effective remediation of fiberbanks is crucial, particularly in Sweden and other regions with extensive wood-pulping industries. This study aims to evaluate the bioaccumulation capacities of 26 native Swedish white-rot fungi (WRF) species for the remediation of PTEs in fiberbank material. Fiberbank samples were collected from Sundsvall’s Bay in the Baltic Sea, while the fungal species were isolated from boreal forests in Västernorrland, Sweden. The fungi were cultured on Hagem agar medium with sterilized fiberbank material as the substrate. After two months, fungal biomass was analyzed for PTE uptake using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed significant variability (p < 0.001) in PTE uptake among fungal species. Phlebia tremellosa consistently demonstrated the highest bioconcentration factors for analyzed elements, with values for V (0.39), Cr (0.10), Co (1.81), Cu (1.54), Pb (1.65), Ni (1.28), As (0.83), Zn (3.61), and Cd (5.56). Other species, including Laetiporus sulphureus (0.09–4.78), Hymenochaete tabacina (0.08–4.52), and Diplomitoporus crustulinus (0.08–4.48), also exhibited significant bioremediation potential. These findings highlight the potential of native WRF species for PTEs remediation in fiberbanks and provide a foundation for mycoremediation strategies in contaminated environments. 

Cellulose regeneration is a critical step in the production of textiles, cellulose derivates, edible films for packaging or biomedical products because the regeneration process alters the cellulose properties. Cellulose regeneration involves complex intermolecular interactions and kinetics that determine the structure and properties of the regenerated cellulose products. Homogeneous quality is crucial for meeting market demands, but it is challenging due to variations in raw materials, process conditions, and other factors. On-line real-time monitoring of the cellulose regeneration process will allow researchers to optimize the process and producers to assess and control the key parameters involved during the regeneration process, ensuring both optimal product quality and process efficiency. This paper describes for the first time the potential of using focused beam reflectance measurements (FBRM) to monitor the evolution of cellulose regeneration under different conditions. The analysis of the evolution of the cellulose particle growth under different conditions allow us to confirm that the mechanism of cellulose aggregation is initiated by hydrophobic interactions and to understand the contribution of the different processes involved during the regeneration such as nucleation, particle growing, cellulose flocculation and floc break down. The results indicate that hydrolysis of urea in alkaline conditions, accelerated by elevated temperatures, has a major impact on the regeneration process confirming the idea that urea prevents hydrophobic interactions. The effects of temperature, initial cellulose concentration, seeding and aging have been quantified. FBRM analysis offers crucial insights that enhance understanding of the regeneration process, enabling its optimization and facilitates the creation of customized cellulose-based materials tailored for specific applications. 

Background

Wastewater discharges from the old pulp and paper industry led to the accumulation of contaminated wood pulping fbers and debris—referred to as fberbanks (FB)—in the Baltic Sea and freshwater bodies across Sweden and other pulp-producing countries. These anthropogenic sediments are polluted with toxic metal(oid)s and persistent organic pollutants, and their decomposition releases greenhouse gases. Phytoremediation ofers a nature-based solution for the ex-situ treatment of these fbrous sediments, but they present unique challenges due to the abundant and unstable organic matter and aged pollution. This study aims to identify potential plant candidates and to address the limitations of fberbanks as a plants growing media for phytoremediation.In a greenhouse experiment, we assessed the performance of fve plant species (Brassica juncea, Brassica napus, Helianthus annuus, Hordeum vulgare, and Poa annua) grown in substrates formulated with fberbank. The evaluation included plant growth parameters, bioconcentration and uptake efciency of metal(oid)s (V, Cr, Co, Ni, Cu, Zn, As, Cd, and Pb), and the degradation of polycyclic and linear hydrocarbons.

Results

Despite initial concerns, fberbanks displayed favorable physical characteristics and a degree of fertility conducive to plant growth. Even though all tested species seeds could cope with fberbanks acute toxicity, H. vulgare and P. annua showed better tolerance to the fberbanks substrates and superior aerial biomass development, which promoted a highest toxic metal(oid)s uptake efciency, regardless of lower bioconcentration factors for most of the target elements. Zn (17.16–23.25 mg/kg of FB), Cu (4.18–6.48 mg/kg of FB) and Cr (1.05–1.36 mg/kg of FB) were most efectively taken up by these plants. The uptake of Co (0.04–0.18 mg/kg of FB) and Ni (0.05–0.17 mg/kg of FB) was lower. As (0.01–0.02 mg/kg of FB), Cd (0.02–0.06 mg/kg of FB), Pb (0.02–0.04 mg/kg of FB) and V (0.02–0.03 mg/kg of FB) phytoextraction was not signifcant. None of the species exhibited a signifcant removal of targeted organic pollutants.

Conclusions

Phytoremediation, either on its own or in combination with other strategies, shows promise for the remediation of fberbanks. However, further research is needed to understand how the organic matrix and long-term underwater aging of fberbanks afect pollutants bioavailability.

Chelating surfactants are amphiphilic molecules capable of forming coordination complexes with metal ions and self-assembling into organized structures. These compounds have gained significant attention in recent years due to their multifaceted applications in environmental remediation, industrial processes, and material sciences. This review provides an overview of the characterization techniques and recent advancements in the applications of chelating surfactants over the past few years. The review begins by elucidating the characterization methods employed to understand the physicochemical properties of chelating surfactants and gain insight into their complex behavior and interactions in various systems. The applications of chelating surfactants in remediation of wastewater and soil, flotation of minerals, oil recovery processes, and corrosion inhibition in metallic structures are explored. Through examination of recent fundamental research activities, innovative approaches, mechanisms of action, and advancements in the different application domains are highlighted. Lastly, some recent progress in the related field of metallosurfactants is explored, even though not all metallosurfactants are chelating. 

Worldwide, populations face issues related to water and energy consumption. Water scarcity has intensified globally, particularly in arid and semiarid regions. Projections indicate that by 2030, global water demand will rise by 50%, leading to critical shortages, further intensified by the impacts of climate change. Moreover, wastewater treatment needs further development, given the presence of persistent organic pollutants, such as dyes and pharmaceuticals. In addition, the continuous increase in energy demand and rising prices directly impact households and businesses, highlighting the importance of energy savings through effective building insulation. In this regard, tannin-furanic foams are recognized as promising sustainable foams due to their fire resistance, low thermal conductivity, and high water and chemical stability. In this study, tannin and lignin rigid foams were explored not only for their traditional applications but also as versatile materials suitable for wastewater treatment. Furthermore, a systematic approach demonstrates the complete replacement of the tannin-furan foam phenol source with two lignins that mainly differ in molecular weight and pH, as well as how these parameters affect the rigid foam structure and methylene blue (MB) removal capacity. Alkali-lignin-based foams exhibited notable MB adsorption capacity (220 mg g−1), with kinetic and equilibrium data analysis suggesting a multilayer adsorption process. The prepared foams demonstrated the ability to be recycled for at least five adsorption-desorption cycles and exhibited effective flame retardant properties. When exposed to a butane flame for 5 min, the foams did not release smoke or ignite, nor did they contribute to flame propagation, with the red glow dissipating only 20 s after flame exposure.

Currently, industrial water pollution represents a significant global challenge, with the potential to adversely impact human health and the integrity of ecosystems. The continuous increase in global consumption has resulted in an exponential rise in the use of dyes, which have become one of the major water pollutants, causing significant environmental impacts. In order to address these concerns, a number of wastewater treatment methods have been developed, with a particular focus on physicochemical approaches, such as adsorption. The objective of this study is to investigate the potential of a bio-based material derived from olive oil pomace (OOP) as an environmentally friendly bio-adsorbent for the removal of methylene blue (MB), a cationic dye commonly found in textile effluents. The biobased material was initially characterized by determining the point of zero charge (pHpzc) and using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Subsequently, a comprehensive analysis was conducted, evaluating the impact of specific physicochemical parameters on MB adsorption, which included a thorough examination of the kinetic and thermodynamic aspects. The adsorption process was characterized using Langmuir, Freundlich, Brunauer-Emmett-Teller (BET), and Dubinin Radushkevich (D-R) isotherms. The results suggest that the equilibrium of adsorption is achieved within ca. 200 min, following pseudo-second-order kinetics. The optimal conditions, including adsorbent mass, temperature, bulk pH, and dye concentration, yielded a maximum adsorption capacity of ca. 93% (i.e., 428 mg g−1) for a pomace concentration of 450 mg L−1. The results suggest a monolayer adsorption process with preferential electrostatic interactions between the dye and the pomace adsorbent. This is supported by the application of Langmuir, BET, Freundlich, and D-R isotherm models. The thermodynamic analysis indicates that the adsorption process is spontaneous and exothermic. This work presents a sustainable solution for mitigating MB contamination in wastewater streams while simultaneously valorizing OOP, an agricultural by-product that presents risks to human health and the environment. In conclusion, this approach offers an innovative ecological alternative to synthetic adsorbents. 

Poly(butylene succinate) (PBS) has been drawing attention as a reliable biodegradable and sustainable alternative to synthetic petroleum-based polymers. In this study, PBS-lignin composites were developed using a recently extracted lignin (LA-lignin) from pine wood residues employing an innovative sustainable approach. These composites were systematically compared with PBS-based composites formed with commonly used technical lignins. The molecular weight of the lignins was evaluated, along with various structural and performance-related properties. The LA-lignin/PBS composites display a remarkably low water solubility (ca. < 2%), water uptake (<ca. 1%), and high contact angle (>ca. 100°). Moreover, the rigidity and thermal stability of the LA-lignin-PBS composites were higher than those of the systems formed with technical lignins. Although all composites studied present remarkable antioxidant features, the novel LA-lignin-PBS systems stand out in terms of antiadhesion activity against both Gram-positive and Gram-negative bacteria. Overall, the systematic analysis performed in this work regarding the impact of various lignins on the formed PBS composites enables a better understanding of the essential structural and compositional lignin features for achieving biobased materials with superior properties. 

Cellulose has shown great potential in the development of green triboelectric nanogenerators. Particularly, regenerated cellulose (R-cellulose) has shown remarkably high output power density but the structural features and key parameters that explain such superior performance remain unexplored. In this work, wood cellulose fibers were dissolved in a LiOH(aq)-based solvent to produce a series of R-cellulose films. Regeneration in different alcohols (from methanol to n-pentanol) was performed and the films’ structural features and triboelectric performance were assessed. Nonsolvents of increased hydrophobicity led to R-cellulose films with a more pronounced (1–10) diffraction peak. An open-circuit voltage (VOC) of up to ca. 260 V and a short-circuit current (ISC) of up to ca. 150 µA were measured for R-cellulose against polytetrafluoroethylene (as negative counter-layer). However, R-cellulose showed an increased VOC of 175% (from 88.1 V) against polydimethylsiloxane when increasing the alcohol hydrocarbon chain length from methanol to n-pentanol. The corresponding ISC and output power also increased by 76% (from 89.9 µA) and by 382% (from 8.8 W m–2), respectively. The higher R-cellulose hydrophilicity, combined with soft counter-tribolayer that follow the surface structures increasing the effective contact area, are the leading reasons for a superior triboelectric performance.