Zhouyang Xiang

Polyethyleneimine-bacterial cellulose bioadsorbent for effective removal of copper and lead ions from aqueous solution

Bacterial cellulose (BC) is a green biopolymer suitable for heavy metal ion removal from aqueous solution due to its nano-porous microstructure. Polyethyleneimine-bacterial cellulose (PEI-BC) was prepared by reductive amination of dialdehyde BC with polyethyleneimine. The capacity of PEI-BC in Cu(II) and Pb(II) adsorption from aqueous solution was investigated. The adsorption kinetics could be well expressed by pseudo-second-order model and the adsorption isotherm data were well fitted with Freundlich model. Adsorption processes of Cu(II) and Pb(II) by PEI-BC reached equilibrium very rapid in 30 and 60min, respectively. The maximum adsorption capacity of PEI-BC on Cu(II) and Pb(II) was found to be 148 and 141mg/g, respectively, which was higher than that of unmodified BC and other modified BC reported. PEI-BC also showed good reusability in the adsorption of Cu(II) and Pb(II). This study demonstrates that polyethyleneimine modification makes BC a potential bioadsorbent for heavy metal ion removal in waste water.

A highly recyclable dip-catalyst produced from palladium nanoparticle-embedded bacterial cellulose and plant fibers

Bacterial cellulose (BC) with its ultrafine nano-reticular structure may provide great support and distribution to metal nanoparticles. In this study, polyethylenimine was introduced into dialdehyde BC to improve the binding stability between BC and palladium (Pd) nanoparticles. The Pd nanoparticle-embedded BC (Pd-BC) was further composited with plant fibers to fabricate a paper-like “dip-catalyst” through a paper handsheet making method. This catalyst has structural features including the fact that PEI-BC provides a great distribution and binding stability to Pd particles, while plant fibers as a supporting component may reduce the cost of fabrication, provide mechanical strength, and improve the contact between the reactants and Pd particles due to their porosity. The dip-catalyst or catalyst sheet was employed in the Suzuki–Miyaura reaction, providing a high reaction rate, a yield of nearly 100% and a high turnover frequency (TOF). It demonstrated an easy reusability and an extensive recycling capability with the same catalyst sheet being used 26 times and still having a yield of nearly 90%. This catalyst sheet produced from sustainable materials is expected to play an important role in organic synthesis.

Glutaraldehyde crosslinking of arabinoxylan produced from corn ethanol residuals

This study investigated the possibility of substituting petroleum-based polymers with biopolymers for films and paper coatings. Arabinoxylan (AX) was extracted from distillers’ grains, a low-value corn ethanol byproduct, and modified through crosslinking with glutaraldehyde (GA) which was made into films and paper coatings. The effects of degree of substitution (DS) on film and coating properties of GA cross-linked AX, referred to as GAX, were investigated. The GAX films had markedly higher tensile strength, approximately 3 times higher than the unmodified AX films at low DS, with higher DS causing a negative effect on the film tensile strength. Compared to unmodified AX coating, paper coated with GAX also had significantly higher tensile index, presumably due to high adhesion between the coating and paper interface. When used as a coating binder with calcium carbonate pigments, GAX showed comparable performance to polyvinyl alcohol, a common industrial binder, demonstrating the potential to be substituted for the petroleum-based paper coating binder.

Deconstruction of cellulosic fibers to fibrils based on enzymatic pretreatment

Enzymatic pretreatment has shown great potential in making the disintegration of cellulosic fibers to fibrils cost-effectively and environmental-friendly. In this study, an extensive commercial endoglucanase was used to pretreat cellulosic fibers for fibrillation. The pretreatment time and the enzyme dosage were optimized using response surface methodology. A 100% fiber recovery was obtained at endoglucanase usage of 9.0 mg/g (substrate) and pretreatment time of less than 3.0 h. A highly fibrillated and fractured surface of pretreated fibers was observed after 0.5 h of pretreatment compared to native fibers. Meanwhile, the progressive deconstruction of cellulosic fibers was occurred with the enzymatic pretreatment time increasing. The degree of deconstruction of fibers was evidenced by changes of the fiber microstructure, such as the inter-/intra-molecular H-bonds, the β-1,4-glucosidic linkages, crystallinity and crystallite size. These discoveries provide new insights into a more efficient and economic pretreatment methods for the disintegration of fibrils from cellulosic fibers.