Cellulose Nanocrystals Content Research Articles

Encapsulation of Camphor in Nanocellulose based Pickering Emulsion and Study of its Antibacterial Activity

Abstract: Camphor is a natural and renewable antimicrobial agent. However, it is highly sublime, which limits its practical application as an effective antibacterial agent. To improve camphor's stability and retention properties, we have microencapsulated camphor into an almond essential oil-based Pickering emulsion (AO-PE), stabilized by cellulose nanocrystals (CNC). The CNC was synthesized from corn husk using an eco-friendly homogenization approach to stabilize the AO-PE. Various factors affecting the formation and stability of Pickering emulsions (PE) were studied, such as the source of cellulose (corn husk and mung hull), oil type (sesame oil and almond oil), oil in water concentration, and stability with time and shear. Camphor-loaded CNC-stabilized AO-PE exhibited a small droplet size and had long-term stability at 6.67% by volume oil concentration, owing to the presence of 0.2 g of CNC at droplet interfaces. The results showed that the PE exhibited better antibacterial performance against Staphylococcus aureus than the equivalent concentrations of camphor, almond oil, CNC, and camphor dissolved in almond oil, individually. This research shall provide fresh insights into the significant enhancement of the antimicrobial properties of medicinal natural products by incorporating them into PEs. Graphical abstract

3D printed protein/polysaccharide food simulant for dysphagia diet: Impact of cellulose nanocrystals

With the intensified aging population, the demand for dysphagia diet is growing rapidly. The food texture in a dysphagia diet needs to be adjusted to be easy-to-swallow. Thus, most food is transformed in mashed form, which is not visually appealing and reduces patients’ appetite, resulting in a malnutrition risk. Three-dimensional (3D) food printing is an efficient technique to fabricate food designs with an attractive appearance and tailored nutritional content. In this work, we developed cellulose nanocrystal (CNC)-based protein/polysaccharide aqueous food inks using two commonly used proteins, namely gelatin B (GB) and whey protein isolate (WPI) for 3D printing, in combination with a polysaccharide frequently found in dysphagia diet, i.e. xanthan gum (XG). To ensure proper printability and shape retention, 2 wt% GB, 8 wt% XG and 8 wt% WPI were selected. Adding 1.0 wt% CNC in GB/XG and 1.5 wt% in WPI/XG improved the viscosity, yield stress and self-supporting ability of the inks, leading to higher shape fidelity right after printing and better shape retention for at least 96 h when stored at 4 °C. Additionally, the thermal stability of GB/XG mixed gels was also largely enhanced by CNC addition, resulting in a high shape retention with ∼90% of its original side area even at 50 °C. As a demonstration, some complex 3D shapes fabricated using both GB/XG/1.0CNC and WPI/XG/1.5CNC inks by single and multi-material DIW printing could also well retain their structures after heating at 50 °C for 5 min. Texture profile can also be tailored by both CNC concentrations and post-processing temperatures. Holding the temperature at 4 °C on the GB/XG/1.5CNC sample turned it from a non-approved classification into a level 5-minced and moist dysphagia diet formulation, according to the International Dysphagia Diet Standardization Initiative (IDDSI) test framework. This work provides rheological and processing guidelines for designing attractive food creations for dysphagic patients using 3D printing.

Pipe Flow of Suspensions of Cellulose Nanocrystals

The pipeline flow behavior of suspensions of cellulose nanocrystals (CNCs) was investigated over the CNC concentration range of 0.24 to 3.65 wt% in different diameter pipelines. The CNC suspensions were Newtonian below the CNC concentration of 1 wt%. At higher concentrations, the CNC suspensions were non-Newtonian power-law fluids. For Newtonian CNC suspensions, the experimental friction factor–Reynolds number data were obtained only in the turbulent regime, and the data followed the Blasius equation closely. For power-law CNC suspensions, the experimental data of friction factor–Reynolds number covered both laminar and turbulent regimes. The experimental data followed the friction factor–Reynolds number relationships for power-law fluids reasonably well.

Compressible, elastic and 3D porous Ti3C2Tx MXene/RGO/CNCs composite aerogel for electromagnetic wave absorbing

Incorporating compressibility, elasticity, and porous structures into microwave- absorbing materials will facilitate electromagnetic wave absorption (EMA) and improve environmental adaptability for practical applications. Herein, a strategy to prepare Ti3C2Tx MXene/reduced graphene oxide (RGO)/ cellulose nanocrystals (CNCs) aerogels via a directed freezing method to design three-dimensional structures and strengthen the interaction between Ti3C2Tx MXene and RGO lamellae is demonstrated. Oriented structures and the addition of CNCs benefit structural stability while achieving superior absorption performance by forming perfect impedance matching and multiple polarization effects. Interestingly, the prepared MXene/RGO/CNCs (MRC-20) aerogel delivers the prominent EMA performance in reported MXene-based absorbing materials, with a minimal reflection loss (RLmin) of − 72.32 dB at 12.0 GHz corresponding to a matching thickness of 2.56 mm and an effective absorption bandwidth (EAB) of 4.96 GHz at 1.88 mm with an RLmin of − 59.87 GHz. Furthermore, by tuning the content of CNCs, the MRC-20 aerogel exhibits the highest stress (37.2 kPa) at 70% compressive strain and demonstrates the stability of the compression cycle. These intriguing features make the hybrid aerogel stand out among numerous absorbers.

Apparent Failures in Interpretation of Interfacial Characterization When Formulating Emulsions Stabilized by Cellulose Nanocrystals.

Cellulose nanocrystals (CNCs) are sustainable particles that are effective at stabilizing emulsions by adsorbing at droplet interfaces and providing a steric barrier to coalescence. However, CNCs have surface charges that reduce the coverage of the emulsion droplets due to the electrostatic repulsion between CNCs. In such cases, adding salt is a typical (and straightforward) way to adjust the formulation so that the charges are screened, allowing increased coverage of the droplets. At the outset of this work, we hypothesized that characterization of the interfacial tension and interfacial shear rheology of the oil-water interface would be correlated to interfacial coverage and therefore predictive of the optimal salt concentration for emulsion stability. Included in the methods section as a useful reference to others is the presentation of a detailed derivation for the equations needed to compute interfacial shear moduli in a custom, double-gap geometry. In contrast to our hypothesis, we found that interfacial tension did not correlate well with emulsion stability and that the native surface-active compounds in corn oil overwhelmed any influence of the CNCs on the interfacial tension. Additionally, we found that interfacial shear rheology (which can be painstakingly difficult to measure) was not a useful tool for formulating these emulsions. This is because at commonly used concentrations of CNCs, the bulk rheology is increased to a much greater degree than that of the interface, making the details of the interfacial rheology unimportant. Finally, we found that at concentrations of CNCs that are typical in industrial processes, characterizing the bulk viscoelastic properties of the aqueous suspending phase without added oil (a relatively simple measurement) is sufficient to predict the influence of NaCl concentration on charge screening between the CNCs and, by extension, increased surface coverage of droplets for greater emulsion stability.

Thermoplastic Starch Biocomposite Films Reinforced with Nanocellulose from Agave tequilana Weber var. Azul Bagasse.

In this work, cellulose nanocrystals (CNCs), bleached cellulose nanofibers (bCNFs), and unbleached cellulose nanofibers (ubCNFs) isolated by acid hydrolysis from Agave tequilana Weber var. Azul bagasse, an agro-waste from the tequila industry, were used as reinforcements in a thermoplastic starch matrix to obtain environmentally friendly materials that can substitute contaminant polymers. A robust characterization of starting materials and biocomposites was carried out. Biocomposite mechanical, thermal, and antibacterial properties were evaluated, as well as color, crystallinity, morphology, rugosity, lateral texture, electrical conductivity, chemical identity, solubility, and water vapor permeability. Pulp fibers and nanocelluloses were analyzed via SEM, TEM, and AFM. The water vapor permeability (WVP) decreased by up to 20.69% with the presence of CNCs. The solubility decreases with the presence of CNFs and CNCs. The addition of CNCs and CNFs increased the tensile strength and Young's modulus and decreased the elongation at break. Biocomposites prepared with ubCNF showed the best tensile mechanical properties due to a better adhesion with the matrix. Images of bCNF-based biocomposites demonstrated that bCNFs are good reinforcing agents as the fibers were dispersed within the starch film and embedded within the matrix. Roughness increased with CNF content and decreased with CNC content. Films with CNCs did not show bacterial growth for Staphylococcus aureus and Escherichia coli. This study offers a new theoretical basis since it demonstrates that different proportions of bleached or unbleached nanofibers and nanocrystals can improve the properties of starch films.

Mechanical Properties and Non-Isothermal Crystallization Kinetics of Polylactic Acid Modified by Polyacrylic Elastomers and Cellulose Nanocrystals.

In this paper, a polyacrylic elastomer latex with butyl acrylate (BA) as the core and methyl methacrylate (MMA) copolymerized with glycidyl methacrylate (GMA) as the shell, named poly(BA-MMA-GMA) (PBMG), was synthesized by seeded emulsion polymerization. Cellulose nanocrystal (CNC) was dispersed in the polyacrylic latex to prepare PBMG/CNC dispersions with different CNC contents. The dried product was mixed with polylactic acid (PLA) to fabricate PLA/PBMG/CNC blends. The addition of PBMG and PBMG/CNC improved the mechanical properties of the PLA matrix. Differential scanning calorimetry (DSC) was used to investigate the non-isothermal crystallization kinetics. The Avrami equation modified by the Jeziorny, Ozawa and Mo equations was used to analyze the non-isothermal crystallization kinetics of PLA and its blends. Analysis of the crystallization halftime of non-isothermal conditions indicated that the overall rate of crystallization increased significantly at 1 wt% content of CNC. This seemed to result from the increase of nucleation density and the acceleration of segment movement in the presence of the CNC component. This phenomenon was verified by polarizing microscope observation.

Fabrication of Bio-Nanocomposite Packaging Films with PVA, MMt Clay Nanoparticles, CNCs, and Essential Oils for the Postharvest Preservation of Sapota Fruits.

Sapota is an important climacteric fruit with limited shelf life. A special system must be employed to extend the shelf life of sapota fruits. In the present study, polyvinyl alcohol (PVA) and montmorillonite clay (MMt)-based bio-nanocomposite films (BNFs) were integrated at various concentrations (2%, 4%, 6%, and 8%) into cellulose nanocrystals (CNCs), produced from garlic peels (GPs). The BNF loaded with 8% CNC has a better crystallinity index and mechanical properties than the other concentrations of CNC. Therefore, the 8% CNC-incorporated BNF (BNF-8) was selected for further packaging studies. The combined effect of BNF-8 with ajwain essential oil (AO) and oregano essential oil (OO) vapors and BNF-8 with carbendazim (commercial fungicide-CARB) were investigated. In this study, the BNF-based packagings are categorized into five types, viz: BNF+8% CNC (BNF-8), BNF-8+AO, BNF-8+OO, BNF-8+CARB and the non-packaged fruits (control). The shelf-life duration, antioxidant activity, firmness, decay index, and sensory quality were evaluated in order to identify the effectiveness of packaging treatment on sapota fruits. BNF-8+CARB, BNF-8+AO, and BNF-8+OO packaging extended the shelf life of sapota fruits to up to 12 days and maintained the overall physiochemical parameters and sensory qualities of the fruits. Therefore, the BNF-8+AO and BNF-8+OO packaging materials are appropriate alternatives to commercial fungicides for the preservation of sapota during postharvest storage.

Antibacterial and antioxidant lemongrass essential oil Pickering emulsion stabilized by cellulose nanocrystals

An effective antibacterial system was developed by using cellulose nanocrystals (CNC) to stabilize lemongrass essential oil Pickering emulsion (PE-LEO) through ultrasonication technology. The factors affecting the formation and stability of PE-LEO were studied, such as ultrasonication times, CNC concentrations, lemongrass essential oil (LEO) concentrations. By size and zeta index, the most suitable sample was 8 ultrasonication times, 0.8% CNC, 15% LEO. The antibacterial and anti-fungal performance of PE-LEO was investigated by determining the minimal inhibitory concentrations (MIC). The results showed that for gram-positive bacteria (E.faecalis, S.aureus, MRSA), the MIC of PE-LEO was much higher than LEO, the opposite was true for gram-negative bacteria (E. coli) and fungi. Based on the concentrations of LEO, with IC50 of PE-LEO is 0.30% vLEO/v, which is significantly lower than that of LEO (0.99%). The CNC-stabilized PE-LEO exhibited higher antioxidation activity at equivalent LEO concentrations. The fabricated CNC based Pickering emulsions provide a promising alternative for the delivery of antimicrobial essential oils in the food industries.

3D-Printed Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)-Cellulose-Based Scaffolds for Biomedical Applications.

While biomaterials have become indispensable for a wide range of tissue repair strategies, second removal procedures oftentimes needed in the case of non-bio-based and non-bioresorbable scaffolds are associated with significant drawbacks not only for the patient, including the risk of infection, impaired healing, or tissue damage, but also for the healthcare system in terms of cost and resources. New biopolymers are increasingly being investigated in the field of tissue regeneration, but their widespread use is still hampered by limitations regarding mechanical, biological, and functional performance when compared to traditional materials. Therefore, a common strategy to tune and broaden the final properties of biopolymers is through the effect of different reinforcing agents. This research work focused on the fabrication and characterization of a bio-based and bioresorbable composite material obtained by compounding a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) matrix with acetylated cellulose nanocrystals (CNCs). The developed biocomposite was further processed to obtain three-dimensional scaffolds by additive manufacturing (AM). The 3D printability of the PHBH-CNC biocomposites was demonstrated by realizing different scaffold geometries, and the results of in vitro cell viability studies provided a clear indication of the cytocompatibility of the biocomposites. Moreover, the CNC content proved to be an important parameter in tuning the different functional properties of the scaffolds. It was demonstrated that the water affinity, surface roughness, and in vitro degradability rate of biocomposites increase with increasing CNC content. Therefore, this tailoring effect of CNC can expand the potential field of use of the PHBH biopolymer, making it an attractive candidate for a variety of tissue engineering applications.

A study on the crystallization and melting of PLA nanocomposites with cellulose nanocrystals by DSC

AbstractPoly(lactic acid) (PLA)/cellulose nanocrystal (CNC) nanocomposites with 1 or 3 phr of CNC were prepared by melt mixing and compression molding then their % crystallinities as well as crystallization and melting behavior during the first heating/cooling/second heating process were investigated by differential scanning calorimetry (DSC). Isothermal crystallization at 80–130°C for 5 min was performed during the cooling process to see how the isothermal crystallization affects % crystallinity at 25°C. The % crystallinity at 25°C as well as the crystallization rate of the nanocomposite increased with CNC content and showed a maximum at the isothermal crystallization temperature of 105°C regardless of CNC content. The bimodal DSC melting peaks observed during the second heating process were considered due to the crystals with many defects (α′) and the crystals with more perfect structure (α), respectively. Isothermal crystallization kinetic analysis by Avrami equation showed that the Avrami exponents of the nanocomposites were about 1, meaning a rod‐ or disc‐shaped crystal growth mechanism. Improving the mechanical properties of the PLA/CNC nanocomposite would be possible because the % crystallinity at 25°C could be effectively increased by changing CNC content and cooling history.Highlights PLA/CNC nanocomposites. Crystallization and melting behavior analysis of the nanocomposites by DSC. Isothermal crystallization at 80–130°C for 5 min during cooling by DSC. Crystallization degree was maximum for the isothermal crystallization at 105°C. Isothermal crystallization kinetic analysis by Avrami equation.

Cellulose nanocrystal and Pluronic L121-based thermo-responsive composite hydrogels

Cellulose nanocrystal (CNC) is a promising sustainable material with its biocompatibility, high aspect ratio, and mechanical strength. CNC-based systems have potential applications in various fields including biosensors, packaging, coating, energy storage, and pharmaceuticals. However, turning CNC into smart systems remains a challenge due to the lack of stimuli-responsiveness, limitation in compatibility with hydrophobic matrices, and their agglomeration tendency. In this work, a thermo-responsive nanocomposite system is constructed with CNCs and polymersome forming Pluronic L121 (L121), and its phase behavior and mechanical properties are investigated in detail. Two different CNC concentration (4 % and 5 %) is studied by changing the L121 concentration (1–20 %) to understand the effect of unimers and polymersomes on the CNC network. At dilute L121 concentrations (1–5 %), the composite system becomes softer but more fragile below the transition temperature. However, it becomes much stronger at higher L121 concentrations (10–20 %), and a gel network is obtained above the transition temperature. Interestingly, the elastically reinforced CNC gels exhibit greater resistance to microstructural breakdown at large strains due to the soft and deformable nature of the large polymersomes. It is also found that the gelation temperature for hydrogels is tunable with increasing L121 concentration, and the nanocomposite hydrogels displayed thermo-reversible rheological behavior.

Assessing the Effect of Cellulose Nanocrystal Content on the Biodegradation Kinetics of Multiscale Polylactic Acid Composites under Controlled Thermophilic Composting Conditions.

This work studied the effect of cellulose nanocrystal (NCC) content on the biodegradation kinetics of PLA-based multiscale cellulosic biocomposites (PLAMCBs). To facilitate biodegradation, the materials were subjected to thermo-oxidation before composting. Biodegradation was carried out for 180 days under controlled thermophilic composting conditions according to the ASTM D 5338 standard. A first-order model based on Monod's kinetics under limiting substrate conditions was used to study the effect of cellulose nanocrystal (NCC) content on the biodegradation kinetics of multiscale composite materials. It was found that thermo-oxidation at 70 °C for 160 h increased the biodegradability of PLA. Also, it was found that the incorporation of cellulosic fibrous reinforcements increased the biodegradability of PLA by promoting hydrolysis during the first stage of composting. Likewise, it was found that partial substitution of micro cellulose (MFC) by cellulose nanocrystals (NCCs) increased the biodegradability of the biocomposite. This increase was more evident as the NCC content increased, which was attributed to the fact that the incorporation of cellulose nanocrystals facilitated the entry of water into the material and therefore promoted the hydrolytic degradation of the most recalcitrant fraction of PLA from the bulk and not only by surface erosion.

Colloidal Stability Window for Carboxylated Cellulose Nanocrystals: Considerations for Handling, Characterization, and Formulation.

The scale of production of cellulose nanocrystals (CNCs) has increased dramatically to meet the growing demand for sustainably sourced materials. This work defines the colloidal stability window for commercially produced carboxylated CNCs (DextraCel) compared to the more traditional sulfated CNCs. Phase diagrams showing the stable, reversibly agglomerated, irreversibly aggregated/sedimented, and colloidal glass "zones" as a function of suspension pH, ionic strength, CNC surface charge content, counterion, and concentration are presented. The pKa of carboxylated CNCs was measured to be 5.1, and suspensions of carboxylated CNCs (0.5-1.5 wt %) were visually stable from pH 3 to 11 (without salt). Carboxylated CNCs were highly sensitive to ionic strength, demonstrating some agglomeration with as little as 5 mM NaCl, supporting that weak acid surface groups and lower charge contents make CNCs more sensitive to solution conditions. Surface charge content had the greatest influence on colloidal stability followed by the counterion; carboxylated CNCs were more stable in the "as-received" sodium form, whereas sulfated CNCs had improved stability in acid form after ion exchange. The stability of carboxylated CNCs with industrially relevant additives (ionic and nonionic surfactants and initiators) was also investigated. Less concentrated suspensions were more colloidally stable, emphasizing that characterization and processing of CNCs favor dilute conditions. If carboxylated CNCs are subjected to conditions outside of their colloidal stability window, simple dilution or pH adjustment does not return them to colloidally stable discrete nanoparticles; however, ultrasonication can redisperse agglomerates. This study offers guidelines for handling carboxylated CNCs to broaden the range of products that can be improved by their incorporation.

Optimization of Geopolymer Compressive Strength Using Response Surface Methodology

Geopolymers have issues related to cracking resistance and pore filling, decreasing their mechanical strength. However, the addition of nanosilica and Cellulose Nanocrystals (CNCs) has been found to enhance their mechanical properties. This study focused on optimizing the utilization of nanosilica and CNCs to enhance the compressive strength of geopolymers. This research employed Response Surface Methodology (RSM) with Central Composite Design (CCD). The concentrations of nanosilica and CNCs used in the experiments ranged from 2% to 4% and 1% to 3%, respectively. The experimental results consist of 13 runs, including 5 center point runs. The model suggested concentrations of nanosilica and CNCs of 3.98% and 1%, respectively, for an optimal compressive strength of 22.20 MPa. The proposed quadratic model exhibited high accuracy, as evidenced by an R2 of 0.9865, Adj- R2 of 0.9769, and predicted R2 of 0.9168. The closeness of R2 to 1 indicates a strong correlation between the actual and predicted values, thus highlighting the model's significant relevance. Ultimately, the model developed in this study holds the potential for predicting the compressive strength of geopolymers incorporating nanosilica and CNCs.

Sugarcane Bagasse-Derived Cellulose Nanocrystal/Polyvinyl Alcohol/Gum Tragacanth Composite Film Incorporated with Betel Leaf Extract as a Versatile Biomaterial for Wound Dressing.

In this study, nanocomposite film was fabricated using cellulose nanocrystals (CNCs) as nanofiller in a polymer matrix of polyvinyl alcohol (PVA) and gum tragacanth (GT) via solution casting. CNCs were extracted from sugarcane bagasse using a steam explosion technique followed by acid hydrolysis. Initial analysis of CNCs by transmission electron microscopy (TEM) showed nanosized particles of 104 nm in length and 7 nm in width. Physical and chemical characteristics of neat PVA, PVA/GT, and PVA/GT/CNC films with varying concentrations of CNCs (from 2% to 10%) were analyzed by the scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrometry, mechanical test, and swelling test. The SEM analysis showed cluster formation of CNCs in the polymer matrix at high concentration. The developed films were transparent. FTIR spectrometry analysis confirmed the chemical functional groups of the various components in the film. The presence of GT and CNCs in the polymer matrix improved the characteristics of films as evident in the prolonged stability for 7 days and increased mechanical properties. The highest elastic modulus of 1526.11 ± 31.86 MPa and tensile strength of 80.39 MPa were recorded in PVA/GT/CNC2 film. The swelling ability, however, decreased from 260% to 230%. Cytotoxicity analysis of the PVA/GT/CNC film showed that it is nontoxic to mouse fibroblast cells L929 with 95% cell viability. Films loaded with betel leaf extract exhibited excellent antibacterial activities against Staphylococcus aureus DMST 8840 and Pseudomonas aeruginosa TISTR 781 with 28.20 ± 0.84 mm and 23.60 ± 0.55 mm inhibition zones, respectively. These results demonstrate that PVA/GT/CNC loaded with the betel leaf extract could act as promising and versatile wound dressings to protect the wound surface from infection and dehydration.

On the Roles of Cellulose Nanocrystals in Fiber Cement: Implications for Rheology, Hydration Kinetics, and Mechanical Properties.

Fiber cement reinforced with pulp fibers is one of the key drivers for the decarbonization of nonstructural building materials, where the inclusion of sustainable pulp fibers at high proportions (i.e., > 8 wt %) renders poor workability of fiber-cement slurry with a concomitant loss in mechanical strength. Petrochemical-derived superplasticizers, i.e., polycarboxylates (PCEs), are predominantly used in fiber cement (including cement mortars) because they dramatically improve (content <0.5 wt %) the slurry rheology but reduce the rate of hydration and weaken the strength of the cured composite. Thus, it is crucial to explore renewable and bio-based superplasticizers devoid of any negative traits (if possible) of the conventional PCEs. In this study, we examined wood-derived cellulose nanocrystals (CNCs) as a multifunctional additive in fiber cement (bleached pulp fiber content: 8 wt %). In fiber cement, variation of the content (0.02-4 wt %) of CNCs resulted in improvement in the shear thinning behavior of the fiber-cement slurry and thereafter increased the hydration kinetics at high CNC contents (2-4 wt %). Notably, the flexural strength of the composite also exhibited improvement upon the addition of CNCs; the maximum strength was observed at 4 wt % of CNCs. Overall, the beneficial roles of CNCs afforded >10 wt % (in-total) bio-based content in fiber cement without compromising the mechanical strength and curing time (compared to PCEs); hence, the findings of this study could unravel new avenues in interface engineering of cement composites leveraging the multifunctional features of biomaterials, thus enhancing sustainability.

Influence of dope composition of polyethersulfone membrane blend with cellulose nanocrystal and carboxylated multi-walled carbon nanotube on humic acid rejection

A full factorial experimental design was employed to investigate the dope composition of a membrane made of cellulose nanocrystal (CNC), multi-walled carbon nanotube (MWCNT), and polyethersulfone (PES) for its ability to reject humic acid (HA). Four factors were screened, including PES composition, polyvinylpyrrolidone content, CNC content, and carboxylated MWCNT content. The membranes were tested for HA rejection using a 10-ppm aqueous feed solution. The results indicated that the percentage of MWCNT had the most significant impact, contributing 72.31% to the overall contribution. The fabricated membranes exhibited high HA removal capacity of up to 90% for the membrane embedded with MWCNT. The model's predicted values agreed reasonably with the experimental data, indicating the model's validity. This study provides insights into the development of CNC/MWCNT/PES membranes for efficient HA rejection in water treatment applications.

Pelindung Dinding Terhadap Hujan Asam Menggunakan Geopolimer Berbasis Nanosilika dan Cellulose Nanocrystals

Geopolymers have a weakness in durability against exposure to acid rain. Nano-silica and Cellulose Nanocrystals (CNCs) can be incorporated to enhance the acid rain resistance of geopolymers. This study aims to investigate the durability of geopolymer-based nano-silica and CNCs against exposure to acid rain. This study employed a rain simulation infiltration method. The concentrations of nano-silica and CNCs used were 4% and 1%, respectively. The compressive strength of the geopolymer specimens was tested before and after exposure to assess the effects of acid rain. Additionally, SEM and XRD tests were conducted to analyze microstructural changes. The results revealed a significant reduction in the compressive strength of the geopolymer without nano silica and CNCs (36.14% and 26.73% at pH 4 and 5, respectively). In contrast, the geopolymer paste containing nano-silica and CNCs exhibited lower reductions of 22.93% and 19.77% at pH 4 and 5, respectively. These findings indicate that the addition of nano-silica and CNCs contributes to the preservation of compressive strength. The observed effect is attributed to the ability of nano-silica and CNCs to impede acid attack on the geopolymer paste, thereby preventing the degradation of calcium levels present in the fly ash within the geopolymer. The strength degradation of the geopolymer paste resulted from the breakdown of Al–O, Si–O, and calcium bonds within the system, triggered by the reaction with H2SO4 from the acid rain. Nano-silica and CNCs-based geopolymers exhibit positive effects and can be utilized as a coating on the walls of buildings.

Cellulose Nanocrystal-Based Gradient Hydrogel Actuators with Controllable Bending Properties.

Stimuli-responsive hydrogel actuators are being increasingly used in microtechnology, but typical bilayer hydrogel actuators have significant drawbacks due to weak adhesive interface between the two layers. In this study, thermoresponsive single-layer hydrogel actuators are produced by generating a gradient distribution of cellulose nanocrystals (CNCs) in a poly(N-isopropylacrylamide) (PNIPAAm) hydrogel network by electrophoresis. Tunable bending properties of the composite hydrogels, such as the thermoresponsive bending speed and angle, are realized by varying the electrophoresis time, applied voltage, and CNC concentration. By varying these conditions, the gradient distribution of the CNCs can be optimized, leading to fast bending and large bending angles of the hydrogels. Bending properties are attributed to the gradient distribution of CNCs causing different deswelling rates across the hydrogel network owing to reinforcing effects. Bending ability is also influenced by differences in the CNC dimensions based on the sources of cellulose, which determine the rigidity of the CNC-rich layer of the polymer composite. It is thus shown that thermoresponsive single-layer gradient hydrogels with tunable bending properties can be realized.