Mingsong Zhou

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.

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.

Effect of the molecular structure of lignin-based polyoxyethylene ether on enzymatic hydrolysis efficiency and kinetics of lignocelluloses

Effect of the molecular structure of lignin-based polyoxyethylene ether (EHL-PEG) on enzymatic hydrolysis of Avicel and corn stover was investigated. With the increase of PEG contents and molecular weight of EHL-PEG, glucose yield of corn stover increased. EHL-PEG enhanced enzymatic hydrolysis of corn stover significantly at buffer pH 4.8-5.5. Glucose yield of corn stover at 20% solid content increased from 32.8% to 63.8% by adding EHL-PEG, while that with PEG4600 was 54.2%. Effect of EHL-PEG on enzymatic hydrolysis kinetics of cellulose film was studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). An enhancing mechanism of EHL-PEG on enzymatic hydrolysis kinetics of cellulose was proposed. Cellulase aggregates dispersed by EHL-PEG excavated extensive cavities into the surface of cellulose film, making the film become more loose and exposed. After the maximum enzymatic hydrolysis rate, the film was mainly peeled off layer by layer until equilibrium.

Structure and photoluminescence characteristics of europium(III) doped in CaAl2Si2O8 phosphors

A series of Eu3+ activated CaAl2Si2O8 phosphors have been synthesized at 1350 °C in air, and their photoluminescence properties have been investigated as a function of activator concentrations. The results show that the dominant emission peak of the phosphors Ca1−3x/2Al2Si2O8:xEu3+ is located at ∼611 nm due to Eu3+ transition (5D0 → 7F2). The reduction reaction from Eu3+ to Eu2+ is observed by the luminescent spectra because of the charge compensation mechanism and the special structure of the CaAl2Si2O8 host lattice even when synthesized in air. The energy transfer rate between the Eu3+ pairs is not very high as proved by the results of the decay lifetimes and the efficiency of Eu3+ 5D0 → 7F2 emissions. The thermal quenching behaviour is attributed to the crossover process from the 5D0 to the charge transfer state (Eu3+–O2−) band. The CIE chromaticity coordinates of the red emission of the Ca0.925Eu0.05Al2Si2O8 phosphor is (0.59, 0.28), which is the NTSC system standard for red chromaticity. With enhanced properties (i.e., colour render property) and the ability to be efficiently stimulated by NUV and blue UV LEDs, this kind of phosphor can be used in developing novel types of flat panel and projection displays.

Preparation of a new lignin-based anionic/cationic surfactant and its solution behaviour

The lignin-based polyoxyethylene (SL–PEG) was synthesized by grafting sodium lignosulphonate (SL) with polyethylene glycol (PEG) long chains. The obtained SL–PEG was formulated with cetyltrimethylammonium bromide (CTAB) at different mass ratios to prepare different lignin-based cationic/anionic surfactants (CA-SLs). The solution behaviour of CA-SL with different mass ratios of CTAB/SL–PEG was studied. The particle size of the CA-SL aggregates was highest when the zeta potential is zero and then becomes small when the zeta potential is positive. It is concluded that the electrical properties and hydrophobic properties of the CA-SL molecules are the fundamental reasons which induce the aggregation behaviour to change. Besides, the results about the Critical Aggregation Concentration (CAC) and surface tension indicate that CA-SL has a stronger ability to lower the surface tension at the air/water interface compared with SL–PEG, but a weaker one than CTAB. However, the CACs of CA-SLs inside the solution are lower than those of both SL–PEG and CTAB. In conclusion, the CA-SL exhibits more obvious physical and chemical properties of polymeric surfactants than SL–PEG whether on the solution surface or inside the solution. The successful preparation of water-soluble lignin-based anionic/cationic surfactants may be a useful method in the efficient utilization of SL.

Physicochemical Behavior of Sulphonated Acetone-Formaldehyde Resin and Naphthalene Sulfonate-Formaldehyde Condensate in Coal-Water Interface

This article studies the physicochemical characteristic of two anionic dispersants—sulphonated acetone-formaldehyde resin (SAF) and naphthalene sulfonate-formaldehyde condensate (FDN)—at coal-water interface, including contact angle, adsorption amount, thickness of adsorbed film, and zeta potential, using four different ranks of coals. The results show that SAF has better wetting property than FDN on coal surface. The adsorption amount of SAF in coal-water interface is greater than that of FDN, and that the thickness of adsorbed films of SAF and FDN on Datong coal measured by x-ray photoelectron spectroscopy (XPS) are respectively 6.38 nm and 2.11 nm. Moreover, the measurements of zeta potentials in coal-water interface show that SAF has greater capacity in charging coal surface with electronegativity. Based on the investigation, the adsorption models of SAF and FDN on different rank of coals are presented.