In this work, lignin/zinc oxide nanocomposites with excellent UV-absorbent performance were prepared through a novel hydrothermal method using industrial alkali lignin (AL) as raw materials. AL was first modified by quaternization to synthesize quaternized alkali lignin (QAL). The QAL/ZnO nanocomposites with different lignin contents were then prepared via a facile one-step hydrothermal method using QAL and zinc nitrate hexahydrate and hexamethylenetetramine in aqueous solution. The prepared nanocomposite possessed an average diameter of ∼100 nm and showed excellent synergistic UV-absorbent performance. The particle morphology and hybrid structure were carefully characterized by SEM, TEM, XRD, FT-IR, XPS, UV–vis, and TG analyses. Interestingly, it was found that the UV transmittance of polyurethane (PU) film was significantly reduced and the mechanical properties of the PU were significantly enhanced when blended with the prepared QAL/ZnO nanocomposite. The results of this work were of practical importance for high value-added application of industrial lignin in the field of functional materials.

•Lignin from pulping black liquor was used to prepare lignin-based carbon/ZnO.•The LC/ZnO nanocomposites were prepared by a simple and novel one-pot in-situ method.•The LC/ZnO nanocomposites composed of ZnO nanoparticles and carbon nanosheets.•The prepared LC/ZnO nanocomposites exhibited excellent photocatalytic performance.•This work opens a green and valuable pathway for high-valued utilization of lignin.This work demonstrated a facile one-pot in-situ method to prepare lignin-based carbon/ZnO (LC/ZnO) nanocomposites by using lignin that was extracted from paper pulping waste liquor as the carbon source. The morphological, physical and optical properties of the prepared LC/ZnO nanocomposites was characterized with Scanning electron microscope (SEM), Transmission electron microscopy (TEM), Thermal-gravimetric analysis (TGA), Raman, X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses. The resulting LC/ZnO is composed of highly dispersed ZnO nanoparticles embedded on a lignin-based carbon nanosheet. The typical D and G bonds of carbon materials obviously appeared. The TGA shows that the LC contents could be controlled. The BET surface area of the LC/ZnO was much larger than the BET surface area of the pure ZnO. The prepared LC/ZnO nanocomposites exhibited excellent photocatalytic performance for the degradation of organic dyes. LC/ZnO that contained ∼6.38% lignin-based carbon exhibited an excellent photo-degradation efficiency of methyl orange as high as 98.9% under sunlight irradiation for 30 min, superior to the performance of pure ZnO and other reported ZnO/GRs. The improved photocatalytic performance was attributed to a homogeneous structure and stronger absorption ability for organic dyes. The mechanism exploration experiment showed that h+ was the main active specie. Meanwhile, the photocatalytic electron transfer mechanism was also investigated. In addition, this work demonstrates a green and valuable pathway for the high-value-added utilization of lignin.Download high-res image (307KB)Download full-size image

•1 The LC/ZnO hybrid was synthesized using industrial lignin by a simple carbonization method.•2 The LC/ZnO hybrid is composed of ZnO nanoparticles and carbon nanosheets.•3 The LC/ZnO hybrid exhibited excellent surface contact and photocatalytic performance.•4 The LC/ZnO hybrid showed photocatalytic mechanism for the different charged dyes.In this work, a novel lignin-based carbon/ZnO (LC/ZnO) hybrid composite with excellent photocatalytic performance was prepared through a convenient and environment friendly method using alkali lignin (AL) as carbon source. The morphological, microstructure and optical properties of the as-prepared LC/ZnO hybrid composite was characterized with scanning electron microscope (SEM), X-ray diffraction (XRD), Raman and UV–vis. The resulting LC/ZnO hybrid is composed of highly dispersed ZnO nanoparticles embedded on a lignin-based carbon nanosheet, showing excellent photogenerated electrons and holes separation and migration efficiency. The photocatalytic activity of LC/ZnO was much higher than the pure ZnO. The LC/ZnO hybrid composite showed different photocatalytic mechanism for degradation of negative methyl orange (MO) and positive Rhodamine B (RhB). It showed that h+ was the main photocatalytic active group during the degradation of MO, ·O2− and ·OH were the photocatalytic active groups during degradation of RhB. This reported photocatalyst with selective degradation of positive and negative organic dyes may have a great application prospect for photoelectric conversion and catalytic materials. Results of this work were of practical importance for high-valued utilization of lignin for carbon materials.Download high-res image (130KB)Download full-size image

Two biorefinery lignosulfonates (LSs), Ca-LS-DF and Na-LS-LP, were, respectively, isolated from pilot-scale sulfite-pretreated spent liquor of lodgepole pine and fermentation residue of Douglas-fir harvest forest residue. The molecular weights of Na-LS-LP and Ca-LS-DF were approximately 9 000 and 11 000 Da, respectively. The two LSs were applied as dispersant for graphite in aqueous suspensions. The dispersion stability was evaluated by a scanning electron microscope and Turbiscan Lab Expert. LS performance in modifying graphite was better than that of a commercial dispersant Reax-85A as indicated by the Turbiscan TSI values, zeta potential of suspension particles, and SEM imaging. The practical importance of this study lies in the fact that the pilot-scale sulfite pretreatments that produced the two LSs also produced excellent bioethanol yields at high titer without detoxification and washing, suggesting the LSs are a true value-added coproduct for high yield biofuel production.Keywords: Biorefinery; Dispersion stability; Graphite; Lignin-coproducts; Lignosulfonate;

Lignosulfonates (SLs) are widely used as dye dispersants. However, they have some disadvantages, including poor high temperature dispersibility and severe fiber staining resulting from the abundant phenolic hydroxyl content in the SL molecules. In this work, etherified lignosulfonates (ESLs) were obtained by using epichlorohydrin to reduce the content of phenolic hydroxyl while increasing the molecular weight. ESLs with lighter color can reduce fiber staining rate by 52% due to whitening by the epichlorohydrin process. The lower adsorption capacity of ESLs onto the surface of fibers can reduce the fiber staining effect, owing to the lower phenolic hydroxyl content. The ESLs also exhibit superior high temperature stability to SL because of their higher adsorption capacity and more rigid adsorption films.

Wheat straw alkali lignin (WAL), byproducts from the alkali pulping process, is a low-value product with poor water solubility and limited dispersion performance. Sulfomethylated wheat straw alkali lignin (SWAL) was first prepared by sulfomethylation. In order to further improve the dispersion performance of WAL, a commercially available horseradish peroxidase (HRP) was then used to modify SWAL. Gel permeation chromatography showed an obvious increase in molecular weight after HRP modification by approximately 6 fold and 18 fold, compared with SWAL and WAL, respectively. The structural characterization was investigated by functional group content measurements and IR and 1H NMR analyses. After the HRP modification, the phenolic and methoxyl group content decreased, while the sulfonic and carboxyl group content increased. Because of the higher molecular weight and hydrophilic group content, the HRP modification induced a significant improvement in adsorption and dispersion performance of WAL.Keywords: Adsorption and dispersion performance; Horseradish peroxidase; Molecular weight; Structural characterization; Wheat straw alkali lignin

Effect of modified lignin series and naphthalene series dispersants on the stability of coal water slurry (CWS) and sedimentation behavior of coal particles were investigated using Turbiscan Lab dispersion-stability analyzer. The results indicate that the sedimentation behavior of coal particles of CWS belongs to differential sedimentation and there is a conglobation between coal particles in CWS preparation. Stability of CWS prepared with lignin series dispersants is better than that prepared with naphthalene series, and the height and mean sedimentation rate of clarifying zone is about 68% of that of FDN when the dosage of additives is 1.0%. The Turbiscan Lab dispersion-stability analyzer can analyze the stability of CWS and also can be useful to investigate the stability mechanism of CWS.