Xueqing Qiu

Sulfonation of Alkali Lignin and Its Potential Use in Dispersant for Cement

Sulfonation modification of alkali lignin from wheat straw pulping spent liquid, carried out under normal pressure and medium temperature, was investigated, and the properties of the resulting sulfonated lignin were characterized. It was found that condensed lignin was degraded into lignin fragments with lower molecular weight by oxidation reaction, producing more active sites to react with formaldehyde, consequently forming more active hydroxymethyl groups for sulfonation. Therefore, it is feasible to carry out the sulfonation of alkali lignin under conditions of normal pressure and medium temperature. As higher contents of sulfonic group were introduced, sulfonated lignin with 1.49 mmol/g of sulfonation degree exhibits 96.9% of solubility at neutral aqueous solution and good surface activity. Compared to commercial lignosulfonate, sulfonated lignin produced by the present work contributes higher adsorption amount and zeta potential to cement particles, and hence shows better dispersion effect to the cement matrix.

Formation of uniform colloidal spheres from lignin, a renewable resource recovered from pulping spent liquor

Alkali lignin, recovered from the pulping black liquor, was chemically modified by acetylating, and then used as a biomass resource to prepare uniform colloidal spheres via self-assembly. The self-assembled structure and colloid formation mechanism of the acetylated lignin (ACL) were investigated by DLS, SLS, TEM, AFM, XPS, FTIR, elemental analysis and contact angle measurements. Results show that ACL colloidal spheres are obtained from gradual hydrophobic aggregation of ACL molecules, induced by continuously adding water into the ACL–THF solution. ACL molecules start to form colloidal spheres at a critical water content of 44 vol% when the initial concentration of ACL in THF is 1.0 mg mL−1, and the colloidization process is completed at a water content of 67 vol%. An excessive amount of water is added into the dispersions to “quench” the structures formed and then the ACL dispersion is treated by rotary evaporation for recycling THF and acquiring colloidal spheres. The ACL colloidal spheres have an of 110 nm with a polydispersity (μ2/Γ2) of 0.022. The average aggregated number ( ) in each colloidal sphere and the average density ( ) are estimated to be 1.0 × 105 and 0.187 g cm−3. Preparation of water-dispersive lignin nanoparticles opens up a green and valuable pathway for value-added utilization of lignin biomass recovered from pulping spent liquor, which is of great significance for both the utilization of renewable resources and environmental protection.

Lignin: a nature-inspired sun blocker for broad-spectrum sunscreens

We report the evaluation of lignin for the development of high-performance broad-spectrum sunscreens. Lignin is added into several commercial sunscreen products. Significant enhancements in ultraviolet (UV) absorbance are observed. The results show that the sunscreen effect of sun protection factor (SPF) 15 could reach that of SPF 30 with the addition of 2 wt% lignin. Adding 10 wt% lignin makes SPF 15 outperform SPF 50. It is also interesting to find that the sunscreen performance improves with UV-radiation time. After 2 h of UV radiation, the UV absorbance of the 10 wt% lignin SPF 15 lotion increases dramatically. This has been attributed to certain synergistic effects between lignin and other sunscreen actives in the lotions, as well as the antioxidant property of lignin. This nature-inspired lignin system may provide a green alternative to replace some synthetic sunscreen actives.

Investigation of Aggregation and Assembly of Alkali Lignin Using Iodine as a Probe

Molecular iodine has been introduced into the alkali lignin (AL) solutions to adjust the π-π aggregation, and the effect of lignin-iodine complexes on the aggregation and assembly characteristics of AL have been investigated by using fluorescence, UV-vis spectroscopy, light scattering, and viscometric techniques. Results show that AL form π-π aggregates (i.e., J-aggregates) in THF driven by the π-π interaction of the aromatic groups in AL, and the π-π aggregates undergo disaggregation in THF-I(2) media because of the formation of lignin-iodine charge-transfer complexes. By using iodine as a probe to investigate the aggregation behaviors and assembly characteristics, it is estimated that about 18 mol % aromatic groups of AL form π-π aggregates in AL molecular aggregates. When molecular iodine is introduced into the AL solutions, lignin-iodine complexes occur with charge-transfer transition from HOMO of the aromatic groups of AL to the LUMO of iodine. The formation of lignin-iodine complexes reduces the affinity of the aromatic groups approaching each other due to the electrostatic repulsion and then eliminates the π-π interaction of the aromatic groups. The disaggregation of the π-π aggregates brings a dissociation behavior of AL chains and a pronounced molecular expansion. This dissociation behavior and molecular expansion of AL in the dipping solutions induce a decrease in the adsorbed amount and an increase in the adsorption rate, when AL is transferred from the dipping solution to the self-assembled adsorbed films. Consequently, the adsorption behavior of AL can be controlled by adjusting the π-π aggregation. Above observations give insight into the occurrence of J-aggregation of the aromatic groups in the AL molecular aggregates and the disaggregation mechanism of AL aggregates induced by the lignin-iodine complexes for the first time. The understanding can provide an academic instruction in the efficient utilization of the alkali lignin from the waste liquor and also leads to further development in expanding functionalities of the aromatic compounds through manipulation of the π-π aggregation.

Reducing non-productive adsorption of cellulase and enhancing enzymatic hydrolysis of lignocelluloses by noncovalent modification of lignin with lignosulfonate

Four fractions of one commercial sodium lignosulfonate (SXP) with different molecular weight (MW) and anionic polymers were studied to reduce non-productive adsorption of cellulase on bound lignin in a lignocellulosic substrate. SXP with higher MW had stronger blocking effect on non-productive adsorption of a commercial Trichoderma reesi cellulase cocktail (CTec2) on lignin measured by quartz crystal microgravimetry with dissipation monitoring. Linear anionic aromatic polymers have strong blocking effect, but they would also reduce CTec2 adsorption on cellulose to decrease the enzymatic activity. The copolymer of lignin and polyethylene glycol (AL-PEG1000) has strong enhancement in enzymatic hydrolysis of lignocelluloses, because it not only improves the cellulase activity to cellulose, but also blocks the non-productive cellulase adsorption on lignin. Apart from improving the cellulase activity to cellulose, the enhancements of enzymatic hydrolysis of lignocellulose by adding AL-PEG1000 and SXPs are the result of the decreased cellulase non-productive adsorption on lignin.

Aggregation Behavior of Sodium Lignosulfonate in Water Solution

Lignosulfonate is a type of macromolecular surfactant widely used as interfacial additive in various industrial fields and it is produced during chemical pulping process. In this paper, we present a new effective method for measurement of the critical aggregation concentration (CAC) of sodium lignosulfonate (SL) in water solution, with which a value of 0.38 g L(-1) was obtained. Through the determination of CAC and observation by DLS, the state and dynamics of the formation of the SL micelles were disclosed. The results showed that SL was the state of individual molecules when its mass concentration was less than CAC; the individual SL molecules started to aggregate above CAC and thus micelles formed and grew with increasing SL concentration. The SL solution was quickly frozen and the structures of SL molecules or micelles were observed by ESEM, revealing that the spherical micelles were the main form of SL in the solution. Based on the results, the spherical hollow vesicular structure is proposed as a model of the aggregated micelles of SL in the solution.

Properties of Different Molecular Weight Sodium Lignosulfonate Fractions as Dispersant of Coal‐Water Slurry

Four purified sodium lignosulfonate (SL) samples with different molecular weights were prepared by fractionation using ultrafiltration. The effect of the molecular weights of SL on the apparent viscosity of coal‐water slurry (CWS) was investigated by studying the adsorption amounts and the zeta potentials in the coal‐water interface. The results show that the adsorption behavior of the dispersants in the coal‐water interface is the key factor to affect the dispersing effect, that the higher adsorption amount and compact adsorption film help reduce the viscosity reduction of CWS, and that the zeta potential is also an important factor influenced by the sulfonic group and carboxy contents of the lignosulfonate molecule. Furthermore, SL with a molecular weight ranging from 10000 to 50000 has both a higher adsorbed amount and zeta potential on the coal surface and the best effect on reducing the viscosity of the coal‐water slurry.

Understanding the effects of lignosulfonate on enzymatic saccharification of pure cellulose

The effects of lignosulfonate (LS) on enzymatic saccharification of pure cellulose were studied. Four fractions of LS with different molecular weight (MW) prepared by ultrafiltration of a commercial LS were applied at different loadings to enzymatic hydrolysis of Whatman paper under different pH. Using LS fractions with low MW and high degree of sulfonation can enhance enzymatic cellulose saccharification despite LS can bind to cellulase nonproductively. The enhancing effect varies with LS properties, its loading, and hydrolysis pH. Inhibitive effect on cellulose saccharification was also observed using LS with large MW and low degree of sulfonation. The concept of “LS-cellulase aggregate stabilized and enhanced cellulase binding” was proposed to explain the observed enhancement of cellulose saccharification. The concept was demonstrated by the linear correlation between the measured amount of bound cellulase and saccharification efficiency with and without LS of different MW in a range of pH.

Study on the stability of coal water slurry using dispersion-stability analyzer

Abstract 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.

Highly Efficient Inverted Perovskite Solar Cells With Sulfonated Lignin Doped PEDOT as Hole Extract Layer

UNLABELLED Sulfonated-acetone-formaldehyde (SAF) was grafted with alkali lignin (AL) to prepare grafted sulfonated-acetone-formaldehyde lignin (GSL). Considering the rich phenolic hydroxyl groups in GSL, we detected a hole mobility of 2.27 × 10(-6) cm(2) V(-1) s(-1) with GSL as a hole transport material by space-charge-limited current model. Compared with nonconjugated poly(styrene sulfonic acid), GSL was applied as p-type semiconductive dopant for PEDOT to prepare water-dispersed PEDOT GSL. PEDOT GSL shows enhanced conductivity compared with that of PEDOT PSS. Simultaneously, the enhanced open-circuit voltage, short-circuit current density, and fill factor are achieved using PEDOT GSL as a hole extract layer (HEL) in sandwich-structure inverted perovskite solar cells. The power conversion efficiency is increased to 14.94% compared with 12.6% of PEDOT PSS-based devices. Our results show that amorphous GSL is a good candidate as dopant of PEDOT, and we provide a novel prospective for the design of HEL based on lignin, a renewable biomass and phenol derivatives.