Electromagnetic porous lignocellulosic matrix composites: A green electromagnetic shielding material with high absorption efficient electromagnetic interference.

Electromagnetic interference (EMI) shielding materials play a vital role in human society, especially in light of the rapid development of electronic communication equipment. Therefore, it is urgent to develop green, high-efficiency EMI shielding materials. Wood, as a renewable raw material, possesses significant structural advantages in studying EMI materials due to its unique 3D pore structure. Herein, we report magnetoelectric lignocellulosic matrix composites derived from the delignified wood for efficient EMI shielding. The composite was fabricated by in-situ polymerization of PEDOT conductive coating and magnetic Fe3O4 in delignified wood. The conductive 3D pore structure of Fe3O4/PEDOT@wood could effectively cause dielectric loss and multiple internal reflections. Combined with the magnetic loss of Fe3O4, the material exhibited excellent EMI shielding effectiveness (SE), which could be attributed to the synergistic effect of dielectric and magnetic losses. The Fe3O4/PEDOT@wood showed excellent conductivity (103 S/m), good magnetism (26.7 emu/g), the EMI SE up to 59.8 dB, and high SEA/SET ratios of∼84.2 % to 95.7 % at 2 mm in X -band. Moreover, the material exhibited a high compressive strength and tensile strength of 100.8 MPa and 18.1 MPa, respectively. Therefore, this work provided a reference for the preparation of high-efficiency EMI shielding materials.

Core-shell structured lignin-stabilized silver nanoprisms for colorimetric detection of sulfur ions.

Widespread occurrence of sulfides in domestic and industrial wastewater contributes to environmental pollution and poses risks to human health. Therefore, the development of highly selective, sensitive, and rapid sulfur ion (S2-) detection probes in aquatic ecosystems is of paramount importance. In this study, lignin-stabilized silver nanoprisms (EHL@AgNPRs) were prepared using the seed growth and self-assembly methods. Based on this, a novel, high-performance, and environmentally friendly S2- colorimetric detection method was proposed. Lignin is believed to coat the surface of AgNPRs through cation-π and electrostatic interactions, acting as an excellent dispersant and stabilizer to prevent aggregation and shape deformation. This allows AgNPRs to maintain localized surface plasmon resonance (LSPR) characteristics and superior colorimetric sensing sensitivity towards S2- even after 30 d. The EHL@AgNPRs exhibited remarkable selectivity towards S2- with a minimum detection limit of 41.3 nM. The conjugation of lignin with AgNPRs offers a highly promising approach for the rapid detection of S2- in natural aquatic environments and for the valorization of lignin.

Structure-property-degradability relationships of varisized lignocellulosic biomass induced by ball milling on enzymatic hydrolysis and alcoholysis.

BACKGROUND: Valorization of lignocellulosic biomass to obtain clean fuels and high-value chemicals is attractive and essential for sustainable energy and chemical production, but the complex structure of biomass is recalcitrant to catalytic processing. This recalcitrance can be overcome by pretreating biomass into deconstructable components, which involves altering the structural complexities and physicochemical properties. However, the impact of these alterations on biomass deconstruction varies considerably, depending on the pretreatment and subsequent conversion type. Here, we systematically describe the changes in structure and properties of corn stover after ball milling as well as their influence on the following enzymatic saccharification and acid-catalyzed alcoholysis, with the aim of elucidating the relationships between structures, properties and deconstructable potential of lignocellulosic biomass. RESULTS: Ball milling causes dramatic structural changes, since the resistant plant cell walls are destroyed with size reduction to a cellular scale, leading to the increase in surface area and reducing ends, and decrease in crystallinity and thermal stability. As a result, ball-milled corn stover is more susceptible to enzymatic saccharification to fermentable sugars and provides more industrially viable processing approaches, as it is effective at high solids loading and minor enzyme loading, without any other pretreatment. Acid-catalyzed alcoholysis of corn stover to biofuels, on the other hand, is also enhanced by ball milling, but additional processing parameters should be tailored to the needs of efficient conversion. Further, a detailed examination of process variables coupled with a kinetic study indicates that acid-catalyzed alcoholysis is limited by the process variables rather than by the substrate parameters, whereas ball milling facilitates this reaction to some extent, especially under mild conditions, by lowering the activation energy of corn stover decomposition. CONCLUSIONS: The efficient catalytic conversion of biomass is closely related to its structure and properties, an understanding of which offers prospects for the rational improvement of methods aimed at more economic commercial biorefineries.

High-solids enzymatic hydrolysis of ball-milled corn stover with reduced slurry viscosity and improved sugar yields.

BACKGROUND: High-solids enzymatic hydrolysis has attracted increasing attentions for the production of bioethanol from lignocellulosic biomass with its advantages of high product concentration, water saving, and low energy and capital costs. However, the increase of solids content would worsen the rheological properties, resulting in heat/mass transfer limitation and higher mixing energy. To address these issues, ball milling was applied to corn stover prior to enzymatic hydrolysis, and the rheological behaviors and digestibility of ball-milled corn stover under high-solids loading were investigated. RESULTS: Ball milling significantly modified the physicochemical properties of corn stover. The apparent viscosity of slurries at 30% solid loading decreased by a factor of 500 after milling for 60 min, and the yield stress was less than 10 Pa. The dramatic decrease of viscosity and yield stress enabled the hydrolysis process to be conducted in shake flask, and remained good mixing. Meanwhile, the estimated energy consumption for mixing during saccharification decreased by 400-fold compared to the untreated one. The resultant hydrolysate using 10 FPU g-1 solids was determined to contain 130.5 g L-1 fermentable sugar, and no fermentation inhibitors were detected. CONCLUSIONS: The proposed ball milling pretreatment improved rheological behavior and sugar yield of high-solids corn stover slurry. Ball milling enables high-solids slurry to maintain low viscosity and yield stress while obtaining a non-toxic high-concentration fermentable syrup, which is undoubtedly of great significance for inter-unit processing, mixing and downstream process. In addition, the energy input for ball milling could be balanced by the reduced mixing energy. Our study indicates ball milling a promising pretreatment process for industrial bioethanol production.

Comparison and intrinsic correlation analysis based on composition, microstructure and enzymatic hydrolysis of corn stover after different types of pretreatments.

Pretreatment is a key step in the energy utilization of lignocellulosic biomass. Different types of pretreatments (ultrafine grinding pretreatment, alkaline hydroxide peroxide pretreatment, dilute acid pretreatment, and ammonia fiber expansion pretreatment) were conducted on corn stover. The lignocellulosic composition, microstructural parameters, and glucose yield of differently pretreated corn stover were characterized and compared. Then qualitative and quantitative correlation analyses of the parameters were carried out to explore the correlations among the composition, microstructure properties, and enzymatic hydrolysis efficacy of corn stover after different types of pretreatments and identify the main properties affecting enzymatic hydrolysis. Qualitative correlation analysis found that cellulose content, specific surface area, pore volume, enzyme-accessible pore volume, and surface area of cellulose had significant positive correlations with glucose yield. The results of quantitative correlation analysis were GY = 15.01 × cellulose content-339.05, GY = 13.06 × SSA + 172.35, GY = 7226.27 × PV + 129.14, GY = 8628.61 × EAPV + 125.61, and GY = 1.18 × SAC-287.21.

Determination of Solute Diffusion Properties in Artificial Sebum.

Despite a number of studies showed that hair follicular pathway contributed significantly to transdermal delivery, there have been limited studies on the diffusion properties of chemicals in sebum. Here, the diffusion property of 17 chemical compounds across artificial sebum has been measured using diffusion cell. The diffusion flux showed 2 types of distinctive behaviors: that reached steady state and that did not. Mathematical models have been developed to fit the experimental data and derive the sebum diffusion and partition coefficients. The models considered the uneven thickness of the sebum film and the additional resistance of the unstirred aqueous boundary layer and the supporting filter. The derived sebum-water partition coefficients agreed well with the experimental data measured previously using equilibrium depletion method. The obtained diffusion coefficients in artificial sebum only depended on the molecular size. Change in pH for ionic chemicals did not affect the diffusion coefficients but influenced their diffusion flux because of the change of sebum-water partition coefficients. Generally, the measured diffusion coefficients of chemicals in artificial sebum are about one order of magnitude higher than those in the stratum corneum lipids, suggesting the hair follicle might have a non-negligible contribution to the overall permeation.

An aggregated understanding of cellulase adsorption and hydrolysis for ball-milled cellulose.

This study evaluated the effects of physicochemical properties of a series of ball-milled cellulose on cellulase adsorption and glucose yield. The relationship between cellulase adsorption and initial hydrolysis rate was also discussed. We found that hydrophobicity and surface charge are the key factors affecting cellulase adsorption on ball-milled cellulose. The results demonstrated that glucose yield had a positive correlation with specific surface area, while showed a negative correlation with particle size, degree of polymerization and crystallinity. Among these properties, specific surface area and crystallinity are the key factors affecting glucose yield. As ball milling progressed, cellulose showed lower enzyme adsorption capacity/amount of bound enzyme during initial stage of hydrolysis, but had higher initial hydrolysis rate. The enhanced rate is attributed to the fact that the amorphous region produced by ball milling reduces the free energy required for decrystallization thus increases the catalytic efficiency of the bound enzyme.

Insights into the improvement of alkaline hydrogen peroxide (AHP) pretreatment on the enzymatic hydrolysis of corn stover: Chemical and microstructural analyses.

The alkaline hydrogen peroxide (AHP) pretreatment (0.5 g H2O2/g corn stover, 30 °C, 24 h) removed 91.53% of the initial lignin and 55.77% of the initial hemicellulose in corn stover and afforded a considerable glucose yield (88.34%) through enzymatic hydrolysis. A combination of chemical and microstructural analyses was used to illustrate the mechanism of the effect of AHP pretreatment on enzymatic hydrolysis. During pretreatment, H2O2-derived radicals effectively spread into and destroyed the cell wall of various parts (vascular bundle sheath, xylem vessels, tracheid, phloem, and parenchyma) of corn stover to remove most of the lignin, acetyl group, and partial hemicellulose. They destroyed the compact structure of the cellulose-hemicellulose-lignin network, increased the cellulase-accessible pore volume by 6 times, doubled the area of exposed cellulose, and decreased the unproductive adsorption of enzymes onto lignin. Combining all the effects, AHP pretreatment effectively improved the cellulose accessibility to enhance the subsequent enzymatic hydrolysis efficiency.

Quantitative characterization of enzyme adsorption and hydrolytic performance for ultrafine grinding pretreated corn stover.

Quantitative analysis of enzyme adsorption and hydrolysis were performed for sieve-based grinding corn stover (SGCS) and ultrafine grinding corn stover (UGCS)1 with different enzyme consumptions. The UGCS presented significantly higher enzyme adsorption quantity (5.15mg/g for UGCS, 1.33mg/g for SGCS), higher glucose yield (49.75% for UGCS, 28.75% for SGCS) under 20FPU/g and higher binding enzyme proportion (41.32% for UGCS, 10.64% for SGCS under 5FPU/g) which can be attributed to the more accessible microstructure properties. The relationship between enzyme adsorption and hydrolytic production was directly proportional for SGCS (GY1=21.04×AQ1+1.86 (R2=0.95)) while was exponential for UGCS (GY2=49.42×(1-e-0.57×AQ2) (R2=0.99)),2 indicating that overmuch enzyme consumption was not advisable for UGCS at economical aspect.

A novel film-pore-surface diffusion model to explain the enhanced enzyme adsorption of corn stover pretreated by ultrafine grinding.

BACKGROUND: Ultrafine grinding is an environmentally friendly pretreatment that can alter the degree of polymerization, the porosity and the specific surface area of lignocellulosic biomass and can, thus, enhance cellulose hydrolysis. Enzyme adsorption onto the substrate is a prerequisite for the enzymatic hydrolysis process. Therefore, it is necessary to investigate the enzyme adsorption properties of corn stover pretreated by ultrafine grinding. RESULTS: The ultrafine grinding pretreatment was executed on corn stover. The results showed that ultrafine grinding pretreatment can significantly decrease particle size [from 218.50 µm of sieve-based grinding corn stover (SGCS) to 17.45 µm of ultrafine grinding corn stover (UGCS)] and increase the specific surface area (SSA), pore volume (PV) and surface composition (SSA: from 1.71 m(2)/g of SGCS to 2.63 m(2)/g of UGCS, PV: from 0.009 cm(3)/g of SGCS to 0.024 m(3)/g of UGCS, cellulose surface area: from 168.69 m(2)/g of SGCS to 290.76 m(2)/g of UGCS, lignin surface area: from 91.46 m(2)/g of SGCS to 106.70 m(2)/g of UGCS). The structure and surface composition changes induced by ultrafine grinding increase the enzyme adsorption capacity from 2.83 mg/g substrate of SGCS to 5.61 mg/g substrate of UGCS. A film-pore-surface diffusion model was developed to simultaneously predict the enzyme adsorption kinetics of both the SGCS and UGCS. Satisfactory predictions could be made with the model based on high R (2) and low RMSE values (R (2) = 0.95 and RMSE = 0.16 mg/g for the UGCS, R (2) = 0.93 and RMSE = 0.09 mg/g for the SGCS). The model was further employed to analyze the rate-limiting steps in the enzyme adsorption process. Although both the external-film and internal-pore mass transfer are important for enzyme adsorption on the SGCS and UGCS, the UGCS has a lower internal-pore resistance compared to the SGCS. CONCLUSIONS: Ultrafine grinding pretreatment can enhance the enzyme adsorption onto corn stover by altering structure and surface composition. The film-pore-surface diffusion model successfully captures features on enzyme adsorption on ultrafine grinding pretreated corn stover. These findings identify wherein the probable rate-limiting factors for the enzyme adsorption reside and could, therefore, provide a basis for enhanced cellulose hydrolysis processes.

Integrated chemical and multi-scale structural analyses for the processes of acid pretreatment and enzymatic hydrolysis of corn stover.

Corn stover was pretreated with acid under moderate conditions (1.5%, w/w, 121°C, 60min), and kinetic enzymolysis experiments were performed on the pretreated substrate using a mixture of Celluclast 1.5L (20FPU/g dry substrate) and Novozyme 188 (40CBU/g dry substrate). Integrated chemical and multi-scale structural methods were then used to characterize both processes. Chemical analysis showed that acid pretreatment removed considerable hemicellulose (from 19.7% in native substrate to 9.28% in acid-pretreated substrate) and achieved a reasonably high conversion efficiency (58.63% of glucose yield) in the subsequent enzymatic hydrolysis. Multi-scale structural analysis indicated that acid pretreatment caused structural changes via cleaving acetyl linkages, solubilizing hemicellulose, relocating cell wall surfaces and enlarging substrate porosity (pore volume increased from 0.0067cm(3)/g in native substrate to 0.019cm(3)/g in acid-pretreated substrate), thereby improving the polysaccharide digestibility.

A novel diffusion-biphasic hydrolysis coupled kinetic model for dilute sulfuric acid pretreatment of corn stover.

Kinetic experiments on the dilute sulfuric acid pretreatment of corn stover were performed. A high xylan removal and a low inhibitor concentration were achieved by acid pretreatment. A novel diffusion-hydrolysis coupled kinetic model was proposed. The contribution to the xylose yield was analyzed by the kinetic model. Compared with the inhibitor furfural negatively affecting xylose yield, the fast and slow-hydrolyzing xylan significantly contributed to the xylose yield, however, their dominant roles were dependent on reaction temperature and time. The impact of particle size and acid concentration on the xylose yield were also investigated. The diffusion process may significantly influence the hydrolysis of large particles. Increasing the acid concentration from 0.15 M to 0.30 M significantly improved the xylose yield, whereas the extent of improvement decreased to near-quantitative when further increasing acid loading. These findings shed some light on the mechanism for dilute sulfuric acid hydrolysis of corn stover.