Guihua Yang

Cationic polyacrylamide enhancing cellulase treatment efficiency of hardwood kraft-based dissolving pulp

Cellulase treatment for decreasing viscosity and increasing Fock reactivity of dissolving pulp is a promising approach to reduce the use of toxic chemicals, such as hypochlorite in the dissolving pulp manufacturing process in the industry. Improving the cellulase treatment efficiency during the process is of practical interest. In the present study, the concept of using cationic polyacrylamide (CPAM) to enhance the cellulase treatment efficiency was demonstrated. This was mainly attributed to the increased cellulase adsorption onto cellulose fibers based on the patching/bridging mechanism. Results showed that the cellulase adsorption was increased by about 20% with the addition of 250 ppm of CPAM under the same conditions as those of the control. It was found that the viscosity decrease and Fock reactivity increase for the cellulase treatment was enhanced from using CPAM. The CPAM-assisted cellulase treatment concept may provide a practical alternative to the present hypochlorite-based technology for viscosity control in the industry.

Efficient and selective adsorption of multi-metal ions using sulfonated cellulose as adsorbent.

Contamination of heavy metal in wastewater has caused great concerns on human life and health. Developing an efficient material to eliminate the heavy metal ions has been a popular topic in recent years. In this work, sulfonated cellulose (SC) was explored as efficient adsorbent for metal ions in solution. Thermo gravimetric analyzer (TGA), X-ray diffraction (XRD) and Fourier-transform infrared spectrometer (FTIR) first analyzed the characterizations of SC. Subsequently, effects of solution pH, adsorbent loading, temperature and initial metal ion concentration on adsorption performance were investigated. The results showed that sulfonated modification of cellulose could decrease the crystallinity and thermostability of cellulose. Due to its excellent performance of adsorption to metal ions, SC could reach adsorption equilibrium status within as short as 2min. In multi-component solution, SC can orderly removes Fe(3+), Pb(2+) and Cu(2+) with excellent selectivity and high efficiency. In addition, SC is a kind of green and renewable adsorbent because it can be easily regenerated by treatment with acid or chelating liquors. The mechanism study shows that the sulfonic group play a major role in the adsorption process.

LiFePO4/NaFe3V9O19/porous glass nanocomposite cathodes for Li+/Na+ mixed-ion batteries

The discovery and optimisation of high performance cathode materials are critical to future breakthroughs for next-generation rechargeable batteries. LiFePO4 (LFP)/NaFe3V9O19 (NFV)/Na2O–FeO–V2O3–P2O5–biocarbon (NFVPB) porous glass nanocomposites (LFP/NFV/NFVPB) offer new possibilities for Li+/Na+ mixed-ion batteries with high-rate capability and high discharge voltage plateaus. Here we have successfully synthesized these nanocomposites via self-assembly of adenosine disodium triphosphate (Na2ATP) biotemplates and a carbon thermal reduction method. As a novel cathode material, LFP/NFV/NFVPB delivers a reversible capacity of 202.8 mA h g−1 at 0.1C in the Li+/Na+ mixed-ion cell with the electrochemically active redox reactions of Fe2+/Fe3+ and V3+/V4+, which is far higher than the theoretical capacity of LiFePO4 (170 mA h g−1). The cell exhibits two high voltage plateaus with well-defined discharge voltage near 3.4 and 3.7 volts, and a coulombic efficiency of approximately 90 percent. Because the low-energy nonequilibrium paths of the fast phase transformation process in LFP/NFV composite nanoparticles can improve the high-rate performance, the cell still exhibits a higher specific capacity of about 100.4 mA h g−1 at 10C. These results are attributed to the nanocomposite structure of LiFePO4 and NaFe3V9O19 and better percolation of electrochemically active glass with a hierarchical pore structure. This work will contribute to the development of Li+/Na+ mixed-ion batteries.

Highly selective and efficient extraction of lignin in kraft pulp by aqueous ionic liquids for enhanced bleaching properties

Aqueous ionic liquids (ILs) that selectively extract lignin in kraft pulp under benign conditions were reported. This study provided an innovative idea to isolate the three-dimensional lignin from a recalcitrant matrix with the benefits of decreased dosage of bleaching chemicals, degradation of cellulose and toxicity of bleaching effluent.

High selective delignification using oxidative ionic liquid pretreatment at mild conditions for efficient enzymatic hydrolysis of lignocellulose.

Herein, the oxidative ionic liquid (IL) pretreatment for overcoming recalcitrance of lignocellulose with selective delignification was investigated, and the subsequent enzymatic hydrolysis was evaluated. IL pretreatment incorporating oxygen delignification could enhance lignin extraction with high selectivity at low carbohydrate loss. The dual-action of oxidative decomposition and dissolution by 1-butyl-3-methlimidazolium chloride (BmimCl) on biomass were synergistically acted, accounting for efficient recalcitrance removal. In addition, the mild oxidative IL treatment only slightly converted crystalline cellulose into amorphous structure, and the extensive extraction of the amorphous lignin and carbohydrate resulted to the expose of cellulose with high susceptibility. Correspondingly, the enzymatic hydrolysis of the pretreated lignocellulose was greatly enhanced. The oxidative IL treatment at mild conditions, collaborating BmimCl treatment with oxygen delignification is a promising and effective system for overcoming the robust structure of lignocellulose.

Recycling cellulase towards industrial application of enzyme treatment on hardwood kraft-based dissolving pulp.

Cost-effectiveness is vital for enzymatic treatment of dissolving pulp towards industrial application. The strategy of cellulase recycling with fresh cellulase addition was demonstrated in this work to activate the dissolving pulp, i.e. decreasing viscosity and increasing Fock reactivity. Results showed that 48.8-35.1% of cellulase activity can be recovered from the filtered liquor in five recycle rounds, which can be reused for enzymatic treatment of dissolving pulp. As a result, the recycling cellulase with addition fresh cellulase of 1mg/g led to the pulp of viscosity 470mL/g and Fock reactivity 80%, which is comparable with cellulase charge of 2mg/g. Other pulp properties such as alpha-cellulose, alkaline solubility and molecular weight distribution were also determined. Additionally, a zero-release of recycling cellulase treatment was proposed to integrate into the dissolving pulp production process.

Thermogravimetric kinetics of sugarcane bagasse pretreated by hot-water.

The thermogravimetric of sugarcane bagasse pretreated by hot-water has been studied in this paper. Results indicated that residual solid pretreatment by hot water could decrease the activation energy of phase 2 (270-350 °C) obviously, which makes the pyrolysis more energy-saving. By hot water pretreatment, the hemicellulose, especially xylose (9.78%/o.d. dry mass at 170 °C and 1 h) was greatly extracted into hydrolyzates liquor. Greatly minimized hemicellulose waste at low temperature during pyrolysis also agreed with biorefinery concept. Therefore, bagasse with hot-water pretreatment should be a good pyrolysis material for value-added material.

SiO2-carbon nanocomposite anodes with a 3D interconnected network and porous structure from bamboo leaves

To seek for a low-cost, green and sustainable method of preparing nanostructured carbon electrode materials, we are inspired by natural biomaterials. An amorphous SiO2–carbon nanocomposite (SiO2–C/NCs) with three-dimensional (3D) interconnected network and hierarchical porous structure is synthesized by thermal decomposition of abandoned bamboo leaves at 700 °C in N2 atmosphere. The characterization results indicate that the SiO2–C/NCs inherited the natural hierarchical structure of the bamboo leaves. Compared with the commercialized graphite anode and other artificial nanostructured carbon materials, the SiO2–C/NCs anode shows a high lithium-storage capacity of 586.2 mA h g−1 at 200 mA g−1, with impressive good cycle stability (294.7 mA h g−1 after 190 cycles) and ultra-high coulombic efficiency close to 100%. After 160 cycles at varied current densities from 200 mA g−1 to 2000 mA g−1, this anode still maintains a high discharge of 117.4 mA h g−1. This simple, green and sustainable strategy will open a new avenue for large-scale preparation and application of nanostructured electrode materials from biomass materials.

3D porous Li3V2(PO4)3/hard carbon composites for improving the rate performance of lithium ion batteries

In this paper, three dimensional (3D) porous Li3V2(PO4)3 (LVP)/hard carbon (HC) composites have been synthesized via a simple method at 800 °C. The XRD, SEM, HRTEM, XPS, Raman spectra, TG, and BET show that the 3D LVP/HC composite is composed of monoclinic LVP nanocrystals (50–100 nm in size) and 3D HC (about 9 wt%) with a pore size range of 2–200 nm. The LVP nanoparticles were conglutinated and uniformly coated by HC. We have clarified the formation mechanism of the nanocomposite structure and the influences of the calcination temperature on the structure and electrochemical properties of 3D porous LVP/HC composites. As a novel cathode for lithium ion batteries, the 3D LVP/HC composites exhibit desired electrochemical performances with a discharge capacity of 143 mA h g−1 at the rate of 0.1C and excellent cycle stability at high rate (the retention capacity is about 92 mA h g−1 after 1000 cycles at 10C).

High consistency cellulase treatment of hardwood prehydrolysis kraft based dissolving pulp.

For enzymatic treatment of dissolving pulp, there is a need to improve the process to facilitate its commercialization. For this purpose, the high consistency cellulase treatment was conducted based on the hypothesis that a high cellulose concentration would favor the interactions of cellulase and cellulose, thus improves the cellulase efficiency while decreasing the water usage. The results showed that compared with a low consistency of 3%, the high consistency of 20% led to 24% increases of cellulase adsorption ratio. As a result, the viscosity decrease and Fock reactivity increase at consistency of 20% were enhanced from 510 mL/g and 70.3% to 471 mL/g and 77.6%, respectively, compared with low consistency of 3% at 24h. The results on other properties such as alpha cellulose, alkali solubility and molecular weight distribution also supported the conclusion that a high consistency of cellulase treatment was more effective than a low pulp consistency process.