Dongjie Yang

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.

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.

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.

A novel and efficient polymerization of lignosulfonates by horseradish peroxidase/H 2 O 2 incubation

Lignosulfonates(LSs), by-products from chemical pulping processes, are low-value products with limited dispersion properties. The ability of commercially available horseradish peroxidase (HRP) to polymerize LS macromolecules and improve the dispersion properties of LSs was investigated. The polymerization of LSs proceeded efficiently under mild reaction conditions in an aqueous solution with HRP/H2O2. Gel permeation chromatography showed a significant increase in weight-average molecular weight (Mw) of sulfonated kraft lignin and sodium lignosulfonate (NaLS) by 8.5-fold and 4.7-fold, respectively. The mechanism of polymerization was investigated by elemental analysis, surface charge measurement, headspace gas chromatography, infrared spectroscopy (IR), and hydrogen nuclear magnetic resonance spectrometry (1H-NMR). The functional group measurements indicated that HRP incubation did not reduce the sulfonic group content. However, it decreased the phenolic and methoxyl group contents. As the phenolic group content decreased, Mw increased as a power function. The polymerization was proposed to involve the random coupling of phenoxy radical intermediates. The radicals coupled with each other to form different inter-unit linkages, most of which were the β-O-4’ type, as the 1H-NMR spectra indicated. Moreover, the HRP/H2O2 incubation induced a significant improvement in the adsorption and dispersion properties of LSs. Therefore, the HRP/H2O2 incubation is a promising approach for industrial applications of LSs.

Lignin-based polyoxyethylene ether enhanced enzymatic hydrolysis of lignocelluloses by dispersing cellulase aggregates.

Water-soluble lignin-based polyoxyethylene ether (EHL-PEG), prepared from enzymatic hydrolysis lignin (EHL) and polyethylene glycol (PEG1000), was used to improve enzymatic hydrolysis efficiency of corn stover. The glucose yield of corn stover at 72h was increased from 16.7% to 70.1% by EHL-PEG, while increase in yield with PEG4600 alone was 52.3%. With the increase of lignin content, EHL-PEG improved enzymatic hydrolysis of microcrystalline cellulose more obvious than PEG4600. EHL-PEG could reduce at least 88% of the adsorption of cellulase on the lignin film measured by quartz crystal microbalance with dissipation monitoring (QCM-D), while reduction with PEG4600 was 43%. Cellulase aggregated at 1220nm in acetate buffer analyzed by dynamic light scattering. EHL-PEG dispersed cellulase aggregates and formed smaller aggregates with cellulase, thereby, reduced significantly nonproductive adsorption of cellulase on lignin and enhanced enzymatic hydrolysis of lignocelluloses.

Physicochemical Properties of Calcium Lignosulfonate with Different Molecular Weights as Dispersant in Aqueous Suspension

Five purified calcium lignosulfonate (CL) fractions with different molecular weights were obtained by fractionation using ultrafiltration and dialysis. The influence of molecular weight on their physicochemical properties was investigated by determining the properties of five fractions. TEM and ESEM imaging indicated that CL has a globular structure to form locally regular colloidal assemblies with the diameter of approximately 200 ∼ 300 nm. Fraction3 (M w is 7621) with the molecular weight of 5,000–l0,000 has more sulfonic and carboxyl group, so the highest zeta potential (−36 mV) can be charged on the TiO2 particles. With the increase of molecular weight, the hydrophobicity and surface activity of CL in aqueous solution increase, so Fraction5 (M w is 21646) which molecular weight is more than 30000 has the biggest adsorption amount. The adsorption characteristic of CL on solid-water interface have great impact on the dispersive properties of TiO2 particle in aqueous solution and the higher adsorption capacity is helpful to improve the dispersive ability of CL. On the other hand, the surface charge of TiO2 particle absorbing CL is another important factor to the dispersive ability of CL. Furthermore, when the CL concentration in TiO2 suspension is less than 4 mg/mL, Fraction3 has the best dispersive ability because the electrostatic repulsion effect is controlling factor. The dispersive ability of CL increases with the increase of molecular weight when the CL concentration in TiO2 suspension is more than 4 mg/mL, so Fraction5 has the best dispersive ability owing to the steric hindrance effect.

Preparation and Evaluation of Carboxymethylated Lignin as Dispersant for Aqueous Graphite Suspension Using Turbiscan Lab Analyzer

Carboxymethylated lignin (CML) was prepared from wheat straw alkali lignin (WAL) via carboxymethylation modification. The characterizations using FTIR, 13C NMR, and 1H–13C HSQC NMR suggest that carboxyl groups are introduced into WAL structure successfully and there are two different active sites substituted by carboxymethyl groups. Moreover, the dispersion efficiency of CML was evaluated using the Turbiscan Lab analyzer. Effects of CML dosage and suspension pH on the dispersion stability of aqueous graphite suspension were investigated. The result shows that the dispersion stability of aqueous graphite suspension prepared with CML of 1.0% dosage at suspension pH 6.7 is obviously improved.

Reduction of lignin color via one-step UV irradiation

The dark color of industrial lignin is the main obstacle for their high value-added use in areas such as sunscreen or dyestuff dispersants. Here, a one-step method for reducing the color of lignin is presented and the structural changes of the whitened lignin are characterized by UV, FTIR, NMR, GPC, DLS, AFM, HS-GC and potentiometric titration. The results show that the content of aromatic ring, methoxyl and phenolic hydroxyl groups in the alkali lignin (AL) decreases, while the content of carboxylic groups increases when it is exposed to UV in THF. AL experiences a darkening process before it is gradually whitened. The blue shift of the UV spectrum and the decrease in size and molecular weight indicate AL is not only intermolecular and intramolecular disaggregated, but also partially depolymerized when light colored lignin is obtained. This simple but efficient whitening method is successfully practised in bleaching. The white degree of raw paper increases from 0.438 to 0.917 after being irradiated under sunshine for 3 days.