Preparation and adsorption performance of cellulose nanofibrils/polyvinyl alcohol composite gel spheres with millimeter size.

Wastewater treatment is a huge problem facing human beings. The development of recyclable and efficient adsorption materials is of great benefit to solve the problem. Based on the biodegradable cellulose nanofibers (CNFs) derived from biomass resources, the large sized CNFs/PVA composite hydrogel spheres (CV-HSs, 1-3 mm) were successfully prepared by the inverse suspension pellet-forming technology using the polymers as raw materials, and another hydrophobic CNFs/PVA composite aerogel spheres (HCV-ASs) were also obtained by lyophilization and followed silylation of as-prepared CV-HSs. The CV-HSs showed excellent adsorption properties for simulated pollutants, including Cu2+, phenol and aniline in water. The maximum absorption capacity of CV-HSs was 17.22 mmol/g for Cu2+, 176.72 mg/g for phenol and 341.93 mg/g for aniline respectively. The HCV-ASs exhibited good absorption properties for weak polar organic solvents, such as petroleum ether, ethyl acetate and toluene. In summary, two kinds of large-sized CNFs/PVA composite gel spheres were successfully fabricated, and exhibited good adsorption properties for organic pollutants and heavy metal ions, indicating their potential for wastewater treatment.

Water-soluble nanocrystalline cellulose films with highly transparent and oxygen barrier properties.

By mixing a guar gum (GG) solution with a nanocrystalline cellulose (NCC) dispersion using a novel circular casting technology, we manufactured biodegradable films as packaging materials with improved optical and mechanical properties. These films could act as barriers for oxygen and could completely dissolve in water within 5 h. We also compared the effect of nanocomposite films and commercial food packaging materials on the preservation of food.

Using carboxylated nanocrystalline cellulose as an additive in cellulosic paper and poly (vinyl alcohol) fiber paper.

Specialty paper (e.g. cigarette paper and battery diaphragm paper) requires extremely high strength properties. The addition of strength agents plays an important role in increasing strength properties of paper. Nanocrystalline cellulose (NCC), or cellulose whiskers, has the potential to enhance the strength properties of paper via improving inter-fibers bonding. This paper was to determine the potential of using carboxylated nanocrystalline cellulose (CNCC) to improve the strength properties of paper made of cellulosic fiber or poly (vinyl alcohol) (PVA) fiber. The results indicated that the addition of CNCC can effectively improve the strength properties. At a CNCC dosage of 0.7%, the tear index and tensile index of the cellulosic paper reached the maximum of 12.8 mN m2/g and 100.7 Nm/g, respectively. More importantly, when increasing the CNCC dosage from 0.1 to 1.0%, the tear index and tensile index of PVA fiber paper were increased by 67.29%, 22.55%, respectively.

The migration of styrene butadiene latex during the drying of coating suspensions: when and how does migration of colloidal particles occur?

Surface elemental compositions of model latex clay coatings on an impervious substrate consolidated under various conditions were measured using the XPS technique, in order to clarify when and how colloidal latex particles migrate to the surface during drying. Under similar drying conditions, surface carbon content decreased with the addition of a water-soluble polymer to the coating colors, while remaining virtually unchanged for coatings of different coat weights made with a given color, indicating that surface carbon content variation is mainly caused by migration of latex rather than of water-soluble polymer. The results also showed that for coatings made with a given suspension, surface carbon content decreased with increasing delay time between coating and heating. For coatings frozen during consolidation and dried by sublimation, surface carbon content increased with increasing drying time before freezing. These results suggest that for the model coatings studied, latex migration mainly occurs after coating application before capillary formation during the initial drying stage when coatings are in the liquid phase, contradicting both the conventional capillary transport and boundary wall migration mechanisms. An alternative mechanism which attributes latex migration to surface trapping effect and to higher Brownian mobility of the smaller latex particles compared with pigment appears to provide a systematically consistent explanation to those phenomena. The new particle migration mechanism implies that segregation of colloidal particles is a ubiquitous phenomenon that would occur not only during the drying of paper coatings but also during consolidation of colloidal films containing particles of different sizes. This is of great importance in the control of surface compositions of nanocomposite coatings.

The synergistic effect between hydrophobic and electrostatic interactions in the uptake of amino acids by strongly acidic cation-exchange resins.

The goal of this work was to investigate the synergistic effect between the electrostatic and hydrophobic interactions upon the uptake of organic ions with hydrophobic moieties by ion-exchange resins with hydrophobic matrixes. The uptake of neutral amino acids by a macroporous polystyrene-based strongly acidic cation-exchange resin (D001) and two strongly acidic cation-exchange resins (poly(2-acrylamido-2-methyl propanesulfonic acid) and poly(vinylsulfonic acid)) with much less hydrophobic matrixes essentially follow an ion exchange stoichiometry. However, the thermodynamic parameters of the uptakes indicate that besides electrostatic interaction, hydrophobic interaction also contributes to the affinity of the amino acids with hydrophobic side chains for D001. No detectable uptake capacities for the amino acids by D001AM, which was obtained by amidation of the sulfonic acid groups of D001, can be determined. Thus, it is deduced that the hydrophobic interaction alone contributes little to the uptake of these amino acids by D001, of which hydrophobicity is the same with or lower than that of D001AM. These results indicate that synergistic effect exists between the electrostatic and hydrophobic interactions when the two interactions exist in a chelate manner and the hydrophobic interaction contributes to the uptake even if the hydrophobic interaction is so weak that it contributes little to the uptake when it acts alone.