Liulian Huang

Preparation of Microfibrillated Cellulose/Chitosan–Benzalkonium Chloride Biocomposite for Enhancing Antibacterium and Strength of Sodium Alginate Films

The nonantibacterial and low strength properties of sodium alginate films negatively impact their application for food packaging. In order to improve these properties, a novel chitosan-benzalkonium chloride (C-BC) complex was prepared by ionic gelation using tripolyphosphate (TPP) as a coagulant, and a biocomposite obtained through the adsorption of C-BC complex on microfibrillated cellulose, MFC/C-BC, was then incorporated into a sodium alginate film. The TEM image showed that the C-BC nanoparticles were spherical in shape with a diameter of about 30 nm, and the adsorption equilibrium time of these nanoparticles on the surface of MFC was estimated to be 6 min under the driving forces of hydrogen bonds and electrostatic interactions. According to the disc diffusion method, the MFC/C-BC biocomposite-incorporated sodium alginate film exhibited remarkable antibacterial activity against Staphylococcus aureus and certain antibacterial activity against Escherichia coli . The strength tests indicated that the tensile strength of the composite sodium alginate film increased about 225% when the loading of MFC/C-BC biocomposite was 10 wt %. These results suggested that the MFC/C-BC biocomposite-incorporated sodium alginate film with excellent antibacterial and strength properties would be a promising material for food packaging, and the MFC/C-BC may also be a potential multifunctional biocomposite for other biodegradable materials.

Immobilization of pectinase and lipase on macroporous resin coated with chitosan for treatment of whitewater from papermaking

Anionic residues and pitch deposits in whitewater negatively impact the operation of paper-forming equipment. In order to remove these substances, a macroporous resin based on a methyl acrylate matrix was synthesized and coated with chitosan of various molecular weights through glutaraldehyde cross-linking. Pectinase from Bacillus licheniformis and lipase from Thermomyces lanuginosus were immobilized on the resin coated with chitosan by a Schiff base reaction. The highest hydrolysis activities of the immobilized enzymes were achieved by using chitosan with 10×10(5)DaMW for coating and 0.0025% glutaraldehyde for cross-linking chitosan. The cationic demand and pitch deposits in whitewater were reduced by 58% and 74%, respectively, when treating whitewater with immobilized dual-enzymes for 15min at 55°C and pH 7.5. This method is useful for treatment of whitewater in the papermaking industry.

Enhancing antibacterium and strength of cellulosic paper by coating triclosan-loaded nanofibrillated cellulose (NFC)

The nanofibrillated cellulose (NFC) was used as substrates to carry triclosan (TCS), which was then applied as a coating agent for impacting antibacterial property to paper while also improving its strength. The TCS-loaded NFC material was further characterized. UV-vis spectra results showed that a characteristic absorption band at 282 nm was observed, which was attributed to triclosan, confirming its successful loading onto NFC. The antibacterial activity tests indicated that the coated paper exhibited excellent antibacterial activity against Escherichia coli, and the growth inhibition of bacteria (GIB) increased as the loading amount of triclosan coated on paper increased. The GIB can reach 98.7% when the 0.023 g TCS-loaded NFC was coated on paper. Meanwhile, the tensile and tear index of the coated paper increased by 18.0% and 26.4%, respectively compared to the blank paper. Therefore, the triclosan-loaded paper could be potentially used in the medical field.

Degradation and dissolution of hemicelluloses during bamboo hydrothermal pretreatment.

To elucidate the hemicelluloses degradation and dissolution during hydrothermal pretreatment, hemicelluloses separated from both hydrolysate and pretreated substrate were investigated. Along with the pretreatment proceeding, some hemicelluloses fractions dissolved and diffused into the bulk liquor; MW (molecular weight) of these hemicelluloses fractions increased first and then decreased as well as amount of the fractions. Based on the definition of MW of the soluble hemicellulose, it has been concluded that some insoluble hemicellulose fractions appeared in the hydrolysate. In contrast, the hemicellulose degradation occurred continually and had been observed by the gradual decrease of MW of the hemicellulose isolated from pretreated substrate. Lingering dissolution at the later stage might attribute to the facts that some soluble fractions were still entrapped in the substrate. 5-15% hemicellulose fractions remained in the pretreated substrate at the later stage were composed of soluble species.

Hydrothermal pretreatment of bamboo and cellulose degradation

A systematic hydrothermal pretreatment of bamboo chips had been conducted with an aim to trace the cellulose degradation. The results showed that cellulose chain cleavage basically occurred when the temperature exceeded 150°C. A slightly higher DP (degree of polymerization) than starting material had been observed at low temperature pretreatment. Treatment at higher temperature (≥ 170°C) caused severe cleavage of cellulose and therefore gave rise to low DP with more soluble species. DP of cellulose declined drastically without additional hemicelluloses dissolution when hemicelluloses removal reached to the limit level. Cellulose degradation under hydrothermal pretreatment generally followed the zero reaction kinetics with the activity energy of 121.0 kJ/mol. Besides, the increase of cellulose crystalline index and the conversion of Iα-Iβ had also observed at the hydrothermal pretreatment.

Evaluation of ethylenediamine-modified nanofibrillated cellulose/chitosan composites on adsorption of cationic and anionic dyes from aqueous solution

A multi-functional adsorbent was prepared by modifying nanofibrillated cellulose/chitosan composites with ethylenediamine (E-NFC/CS). The E-NFC/CS was characterized by FTIR and used for adsorption of cationic dye methylene blue (MB) and anionic dye new coccine (NC) from aqueous solution. The FTIR results showed that the E-NFC/CS contained more amino groups than the NFC/CS due to the modification for the NFC/CS with ethylenediamine. The results indicated that the maximum adsorption capacities occurred at pH 4.0 for MB and pH 2.0 for NC, respectively. The adsorption equilibrium time for MB and NC was 30 and 50min, respectively. In addition, the regenerated E-NFC/CS exhibited excellent adsorption performance for NC. It can keep almost 98% of the adsorption capacity after reused three times. Therefore, the E-NFC/CS can be potentially used as an effective adsorbent of cationic and anionic dyes in industrial effluents.

Versatile fabrication of a superhydrophobic and ultralight cellulose-based aerogel for oil spillage clean-up

To deal with marine oil spillage and chemical leakage issues, a highly efficient absorbent (cellulose based aerogel) with a low density (ρ < 0.034 g cm-3, φ > 98.5%) and high mechanical strength was fabricated via a novel physical-chemical foaming method, plasma treatment and subsequent silane modification process. This aerogel has a perfect 3D skeleton and interconnected pores similar to honeycomb, which are favorable to oil adsorption and storage. More importantly, without introducing additional micro/nanoparticles, the rough micro/nano structure of the surface was directly constructed using plasma irradiation in this study. The low surface energy substrate was further introduced using a simple physical-soaking method and the resulting aerogel exhibited excellent superhydrophobicity (WCA > 156°) and superoleophilicity (OCA = 0°), which can selectively and efficiently absorb various oils or organic solvents from polluted water. In addition, this aerogel has a high storage capacity and absorption capacity (up to 4300% and 99% of its weight and volume, respectively). More interestingly, this aerogel exhibits excellent mechanical abrasion resistance and corrosion resistance even in strong acid, alkali solution and salt marine environment. The aerogel could be reused more than 30 times after removal of the absorbed oil by rinsing with ethanol.

Effect of the degree of substitution on the hydrophobicity of acetylated cellulose for production of liquid marbles

Acetylated cellulose powders with varying degree of substitution (DS) were prepared by reacting cellulose with acetic anhydride. The effect of DS on the hydrophobic properties of acetylated cellulose was examined based on contact angle and mechanical stability measurements. The surface energy of the acetylated cellulose decreases with increasing DS, and for DS of 0.39, the acetylated cellulose was able to encapsulate a water droplet to form a liquid marble. The corresponding cellulose acetate powder-over-water spreading coefficient was ca. 8.9. Increasing DS also improved the mechanical stability of the liquid marble. This study opens important perspectives for the precise control of DS of cellulose acetate for various practical applications in membranes, filters, scaffolds, and textiles.

Preparation of CNC-dispersed Fe3O4 nanoparticles and their application in conductive paper

Well-dispersed Fe3O4 nanoparticles (NPs) were synthesized by a co-precipitation method in the presence of cellulose nano-crystals (CNC) as the template. The thus prepared Fe3O4 NPs were then used as a coating agent for the preparation of conductive paper. Fourier transform infrared spectroscopy (FTIR) results revealed that the Fe3O4 NPs were immobilized on the CNC through interactions between the hydroxyl groups of CNC and Fe3O4. Scanning transmission electron microscopy (STEM) images showed that the Fe3O4 NPs prepared in the presence of CNC can be dispersed in the CNC network, while the Fe3O4 NPs prepared in the absence of CNC tended to aggregate in aqueous solutions. The conductivity of the Fe3O4 NPs coated paper can reach to 0.0269 S/m at the coating amount of 14.75 g/m(2) Fe3O4/CNC nanocomposites. Therefore, the thus obtained coated paper can be potentially used as anti-static packaging material in the packaging field.

Surface characterizations of bamboo substrates treated by hot water extraction

Environment Scanning Electron Microscopy (ESEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface morphology and chemical changes on both the interior and exterior surface of bamboo (Dendrocalamopsis oldhami) substrates treated by hot water extraction. ESEM results showed the visible changes between exterior and interior surface of the treated substrates, in where spherical droplets did not extensively appear on both the surfaces at start of the pretreatment; nevertheless the droplets formation on the exterior surface occurred more rapidly than that of the interior surface. Results from XPS examination that the increase of C1 (C-C, C-H) concentration and decrease of O/C ratio and O1 (C=O) concentration of the samples on the both surfaces further demonstrated that both surfaces consisted of increasing amount of lignin as the extraction continued, especially for exterior surface. The O/C ratios finally reached to a level-off value with exterior surface 0.34 and interior surface 0.37.