Ngoc Huynh

The growing environmental and health concerns associated with synthetic dyes have increased interest in natural alternatives. This study investigates the multifunctional properties of yellow onion skin extract as a sustainable dye source for cellulosic substrates, assessing the extract's functional properties beyond coloration. The extract was applied to premordanted cellulose nanofiber films (CNF) with a concentration of 2 g/L and knitted cotton fabric 0.125 g/L at 80 °C for 60 min, and its impact on UV protection, antioxidant properties, and dye stability was investigated. To enhance adsorption, biobased polyelectrolytes, including chitosan, tannic acid, and organic acids, were used as mordants and compared to metal mordants. Surface interactions between the cellulosic substrate and dye were studied using in situ monitoring to obtain data on the dyeing conditions for optimization. The dyed CNF films demonstrated excellent UV-shielding properties with up to 90% UV blocking and 82% DPPH radical scavenging activity, making them promising for protective packaging solutions. For cotton fabric, the dye concentration was low (0.125 g/L), resulting in relatively low color depth (K/S 1.33-5.59) with moderate (LF 3-5) fastness properties. Our study of KeratinoSens (OECD Test Guideline 442D equivalent) suggests a potential skin sensitizing effect of the yellow onion dye at higher concentrations. This needs further evaluation and studies. All together, these findings highlight the potential of yellow onion skin waste as a functional dye for applications in textiles and packaging that require enhanced surface properties.

Cellulose-based materials are gaining increasing attention in the packaging industry as sustainable packaging material alternatives. Lignocellulosic polymers with high quantities of surface hydroxyls are inherently hydrophilic and hygroscopic, making them moisture-sensitive, which has been retarding the utilization of cellulosic materials in applications requiring high moisture resistance. Herein, we produced lightweight all-cellulose fiber foam films with improved water tolerance. The fiber foams were modified with willow bark extract (WBE) and alkyl ketene dimer (AKD). AKD improved the water stability, while the addition of WBE was found to improve the dry strength of the fiber foam films and bring additional functionalities, that is, antioxidant and ultraviolet protection properties, to the material. Additionally, WBE and AKD showed a synergistic effect in improving the hydrophobicity and water tolerance of the fiber foam films. Nuclear magnetic resonance (NMR) spectroscopy indicated that the interactions among WBE, cellulose, and AKD were physical, with no formation of covalent bonds. The findings of this study broaden the possibilities to utilize cellulose-based materials in high-value active packaging applications, for instance, for pharmaceutical and healthcare products or as water-resistant coatings for textiles, besides bulk packaging materials.

In this work, MXene as a hydrophilic 2D nanosheet has been suggested to tailor the polyphenylsulfone (PPSU) flat sheet membrane characteristics via bulk modification. The amount of MXene varied in the PPSU casting solution from 0–1.5 wt.%, while a series of characterization tools have been employed to detect the surface characteristics changes. This included atomic force microscopy (AFM), scanning electron microscopy (SEM), contact angle, pore size and porosity, and Fourier-transform infrared spectroscopy (FTIR). Results disclosed that the MXene content could significantly influence some of the membranes’ surface characteristics while no effect was seen on others. The optimal MXene content was found to be 0.6 wt.%, as revealed by the experimental work. The roughness parameters of the 0.6 wt.% nanocomposite membrane were notably enhanced, while greater hydrophilicity has been imparted compared to the nascent PPSU membrane. This witnessed enhancement in the surface characteristics of the nanocomposite was indeed reflected in their performance. A triple enhancement in the pure water flux was witnessed without compromising the retention of the membranes against the Cu²⁺, Cd²⁺ and Pd²⁺ feed. In parallel, high, and comparable separation rates (>92%) were achieved by all membranes regardless of the MXene content. In addition, promising antifouling features were observed with the nanocomposite membranes, disclosing that these nanocomposite membranes could offer a promising potential to treat heavy metals-containing wastewater for various applications.

Membrane contactor technology affords great opportunities for nitrogen recovery from waste streams. This study presents a performance comparison between lab- and pilot-scale membrane contactors using landfill leachate samples. Polypropylene (PP) and polytetrafluoroethylene (PTFE) fibers in different dimensions were compared in terms of ammonia (NH₃) recovery on a lab scale using a synthetic ammonium solution. The effect of pre-treating the leachate with tannin coagulation on nitrogen recovery was also evaluated. An ammonia transfer on the lab and pilot scale was scrutinized using landfill leachate as a feed solution. It was found that PTFE fibers performed better than PP fibers. Among PTFE fibers, the most porous one (denoted as M1) had the highest NH₃ flux of 19.2 g/m².h. Tannin pre-treatment reduced fouling and increased NH₃, which in turn improved nitrogen recovery. The mass transfer coefficient of the lab-scale reactor was more than double that of the pilot reactor (1.80 × 10⁻⁷ m/s vs. 4.45 × 10⁻⁷ m/s). This was likely attributed to the difference in reactor design. An analysis of the membrane surface showed that the landfill leachate caused a combination of inorganic and organic fouling. Cleaning with UV and 0.01 M H₂O₂ was capable of removing the fouling completely and restoring the membrane characteristics.

Plants, animals, and humans use camouflage to blend in with their surroundings. The camouflage is achieved with different combinations of colors, patterns, and morphologies. In stealth applications, the simplest camouflage uses textiles colored similarly to the environment to create an illusion. However, often, visible light range camouflage is not enough since the multispectral detection technologies of today are readily utilized for identification. Foams can be created with a straightforward fabricating process, and lightweight material exhibits good thermal insulation properties, providing stealth in the infrared light region. Herein, we produce cellulosic wet foams from surfactant and bleached pulp or cellulose nanofibrils. The visible light camouflage is created with green microalgae, Chlorella vulgaris, and brown kraft lignin, which also stabilized the foams. The thermal and spectral camouflage performance of foams was influenced by the cellulose content as well as the stability and water content of foams. Overall, these results give insight into how stability impacts the thermal and spectral properties of wet foams and provide a solid base for further material development to improve camouflage performance. While there is plenty of data on dry foams, the functional behavior of wet foams is currently not well known. Our method, using plant-based components can be exploited in a variety of other applications where simplicity and scalability are important.