Pretreatment Temperature Research Articles

Pretreatment of Arundo donax L. for photo-fermentative biohydrogen production by ultrasonication and ionic liquid

Combined pretreatment methods were assumed to further enhance photo-fermentative biohydrogen production (PFHP) from lignocellulosic biomass. For this purpose, an ultrasonication assisted ionic liquid pretreatment was applied to Arundo donax L. biomass for PFHP. The optimal condition for the combined pretreatment was 16 g/L of 1-Butyl-3-methylimidazolium Hydrogen Sulfate ([Bmim]HSO4) combined with ultrasonication at a solid to liquid ratio (SLR) of 1:10 for 1.5 h under 60 °C. Under this condition, the maximum delignification of 22.9 % was obtained, in addition, the hydrogen yield (HY) and energy conversion efficiency (ECE) were enhanced by 1.5-fold and 46.4 % (p < 0.05) compared to untreated biomass, respectively. Moreover, heat map analysis was performed to evaluate the correlation between pretreatment conditions and corresponding results, suggesting pretreatment temperature had the strongest (absolute value of Pearson’s r was 0.97) linear correlation with HY. Combined multiple energy production approaches might be useful for further improved ECE.

Study on mechanism of cellulose hydrolysis during alkali thermal pretreatment of lignocellulose by density functional theory

Alkali thermal pretreatment can effectively destroy the compact three-dimensional aggregated structure of lignocellulose, and further promote the production of high value-added chemicals. Cellulose is an important component of lignocellulose, and in this study the mechanism of cellulose hydrolysis in alkali thermal pretreatment was studied by density functional theory. The hydrolysis was divided into two steps, firstly the hydroxide ion captured a proton from the hydroxyl of which had most positive potential value of 1.23 eV. Subsequently, the glycosidic bond was cleaved to form a new C–O bond, and the hydroxide ion attacked the intermediate forming a glucose residue by a new covalent. The amount of electron transfer of the two steps were natural orbitals for chemical valence eigenvalue 0.31 and 0.34, and the corresponding energy barriers were 147.11 and 101.17 kJ/mol at 298.15 K, respectively. With the increase of pretreatment temperature from 298.15 to 413.15 K, the enthalpy and Gibbs free energy change of cellobiose hydrolysis decreased by 2.97 and 2.34 kJ/mol and the thermodynamic feasibility and reaction rate increased. This study will providing an important guidance for the process control, reactor design and performance enhancement of lignocellulose pretreatment.

An innovative study for pretreatment of high-phosphorus oolitic hematite via high-temperature heating: phase, microstructure, and phosphorus distribution analyses

To investigate the effects of heating pretreatment on the distribution of phosphorus elements, phase transformation, and microstructure evolution mechanisms of high-phosphorus oolitic hematite (HPOH), particularly from the Tindouf regions of Algeria, several analyses, including HSC Chemistry software, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Image-Pro Plus software, specific surface area, pore size distribution (BJH), and N2 adsorption–desorption isotherms. The results show that the conventional heating pretreatment has a significant effect on the phase and microstructure of HPOH. Cracks appeared within mineral phases and around the interphase boundaries owing to the co-promotion of different thermal expansions of minerals and dehydration and chemical reactions via the heating treatment of ore samples. As the pretreatment temperature increased within the studied range, increases in crack perimeter (from 8.062 to 87.236 μm), percentage of crack area (from 0.135 to 7.988 %), and BJH desorption average pore diameter (from 6.1788 to 23.4384 nm) were observed. The specific surface area and pore volume decreased from 23.2054 to 1.0661 m2/g and 0.0237 to 0.0017 cm3/g, respectively. In addition, the distribution of phosphorus did not change or repartition during the heating pretreatment period in the mineral phases.

Effects of high temperature pretreatment and inoculation of Bacillus coagulans on promoting aerobic composting of chicken manure

Effects of high temperature pretreatment and inoculation of Bacillus coagulans were determined relative to the physicochemical properties and bacterial community of aerobic composting of chicken manure. Chicken manure was pretreated with high temperature for 0 h (CJ), 0.5 h (T-0.5h), 1.0 h (T-1.0h), 1.5 h (T-1.5h), and 2.0 h (T-2.0h) and then inoculated with B. coagulans. Chicken manure without high temperature pretreatment was included as control (CK). The results showed that the temperature of manure in CJ, T-0.5h, T-1.0h, T-1.5h, and T-2.0h groups was 2.2 to 8.4 °C higher than the chicken manure in CK within 1 day. On day 3, the chicken manure temperature reached a peak, which was 1.5 to 7.7 °C higher than that in the CK (56.8 °C). Both inoculation of B. coagulans and high temperature pretreatment increased the abundance and diversity of the bacterial community. The abundance of Firmicutes in T-1.5h was significantly higher than that in CJ. In the temperature decreasing period, the abundance of Bacillus in T-1.5h group was significantly higher than that in the CK and CJ. Overall, it was concluded that high temperature pretreatment and B. coagulans inoculation can accelerate the temperature elevation, increase the temperature of compost, and regulate the structure of bacterial community.

Optimizing the mechanical properties of coal-fines briquettes produced with steam-exploded sugarcane bagasse as a binder

ABSTRACT Co-briquetting of coal fines and lignocellulosic biomass is a possible path for incorporating biomass energy into the current coal-based infrastructure, although the cost and performance of conventional binders remain problematic. The use of steam-exploded sugarcane bagasse (SE SCB) as a binder for coal fines briquetting was therefore investigated. SE SCB (produced at 140–220°C for 15 min) was mixed with high-ash bituminous coal-fines at various concentrations (0–18%), and briquetted at a pressure value of 24 MPa and at various temperatures (25–180°C). Following multivariate optimization, an optimal steam explosion temperature range of 185–195°C was found. At these pretreatment temperatures, sufficient disruption of the lignocellulosic structure occurred, resulting in increased binding between coal fines and SCB, while higher temperatures resulted in detrimental destruction of fiber structure and reduction in binding performance. A synergistic interaction between briquetting temperatures and SE SCB content above 100°C and 13%, respectively, substantially improved briquette properties. At these optimum conditions, the briquettes had a compressive strength of 1205 kPa, an abrasion resistance of 97%, water absorption index of 82%, and a wet compressive strength of 501 kPa. Briquettes maintained structural integrity when pyrolyzed at 700°C and had a post-pyrolysis compressive strength of 134 kPa, indicating that SE SCB could potentially be a suitable binder for coal fines briquetting.

A novel method of strong and tough Si3N4 ceramic from the particle‐stabilized foam

AbstractThe brittleness of Si3N4 ceramics has always limited its wide application. In this paper, Si3N4 ceramics were prepared based on foam. Combining the unique honeycomb structure of the ceramic foams and the self‐toughening mechanism of Si3N4, the strengthening and toughening of Si3N4 ceramics can be further achieved by adjusting the microstructure of Si3N4 ceramic foams. The powder particles are self‐assembled by particle‐stabilized foaming to form a foam body with a honeycomb structure. It was pretreated at different temperatures (1450–1750°C). The microstructure evolution of foamed ceramics at different pretreatment temperatures and the conversion rate of α‐Si3N4 to β‐Si3N4 at different pretreatment temperatures were explored. Then the foamed ceramics with different microstructures are hot‐press sintered to prepare Si3N4 dense ceramics. The effects of different microstructures of foamed ceramics on the strength and toughness of Si3N4 ceramics were analyzed. The experimental results show that the relative density of Si3N4 ceramics prepared at a particle pretreatment temperature of 1500°C is 97.8%, and its flexural strength and fracture toughness are relatively the highest, which are 1089 ± 60 MPa and 12.9 ± 1.3 MPa m1/2, respectively. Compared with the traditional powder hot‐pressing sintering, the improvement is 21% and 33%, respectively. It is shown that this method of preparing Si3N4 ceramics based on foam has the potential to strengthen and toughen Si3N4 ceramics.

A Comparison of Histological Staining Methods for Pathogenic Fungi in Humans

Background: Using special stains to detect fungus is an essential diagnostic tool in histology. Because microbiology cultures can take over a month for a definitive diagnosis, rapid detection and treatment of fungal infections are necessary for patient care, particularly in immunocompromised patients when infections may lead to life-threatening complications. Objective: A comparison of various classic special stain methods along with more recent modifications on those staining methods was performed to evaluate the effectiveness of fungal detection while attempting to ameliorate the dangers associated with certain chemicals used in histochemical procedures. Methods: Twenty-five formalin-fixed paraffin-embedded archived tissue blocks containing the genera <i>Aspergillus, Blastomyces, Candida, Cryptococcus, Histoplasma, Mucor, </i>and <i>Pneumocystis</i> were stained with periodic acid Schiff light green (PAS-LG) and Grocott methenamine silver (GMS) using standard methods. Modifications of these and other protocols found in the literature to include altering the oxidizing reagent, time in oxidizer, temperature of oxidizer, pretreatment, and counterstain applied were made and the results were compared. Results: <i>Cryptococcus</i> and <i>Candida</i> were the most readily labeled fungal genera with detection rates of 92% and 85%, respectively across all staining protocols assayed. <i>Histoplasma</i>, however proved to be the most difficult genus to successfully label with only a 21% sensitivity across all staining protocols. Conclusion: While several procedures which included altering oxidizers, incubation periods, and temperatures were variably successful, the original Grocott method with chromic acid as the oxidizer remained the most effective protocol in the detection of fungal elements with 96% sensitivity.

Modulation of stress factors for cryopreservation of Paracentrotus lividus (Lamarck 1816) larvae

In the present work we modulated two stress factors salinity and temperature, whose ranges have been previously determined by bioassays using six pre-treatments (18 °C-29.5‰; 18 °C-35‰; 18 °C-39‰ and 20 °C-29.5‰; 20 °C-35‰; 20 °C-39‰), in order to obtain a successful cryopreservation protocol for pluteus larvae of the sea urchin P. lividus (Lamarck 1816). Toxicity tests were performed with different cryoprotectants in a range of 0.5–3 M. Best results pointed out to METH and Me2SO as those more suitable for cryopreservation. First an exploratory cryopreservation experiment with Me2SO supplemented with 0.04 M trehalose (TRE) was tested following the protocol for cryopreservation of embryos (8-h blastula) of Bellas and Paredes, 2011, which did not give satisfactory results. A cryopreservation experiment was performed with both cryoprotectants supplemented with 0.04 M trehalose on 4-arm pluteus larvae (48 h-old) developed in these pre-treatment conditions, followed by a simpler and shorter protocol with a cooling rate of 1 °C/min to −35 °C, achieving for the first time the successful cryopreservation of P. lividus larvae. When larvae were incubated in low salinity or low temperature pre-treatments, they showed delayed larval development and abnormalities. In contrast, pretreatments with high temperature and salinity showed good results. Dimethyl sulfoxide with trehalose proved to be the only effective cryoprotectant for successful cryopreservation of P. lividus larvae. The success of dimethyl sulfoxide is consistent with that described for other cases in previous literature, where dimethyl sulfoxide, although not the least toxic compound, gave the best cryopreservation result.

High Temperature Lignin Separation for Improved Yields in Ethanol Organosolv Pre-Treatment

The full utilization of renewable raw materials is necessary for a sustainable economy. Lignin is an abundant biopolymer, but is currently mainly used for energy production. Ethanol organosolv pre-treatment produces high-quality lignin, but still faces substantial economic challenges. Lignin solubility increases with temperature, and previous studies have shown that it reprecipitates during cooling after the pre-treatment. Thus, a possibility for the optimization of lignin production with this process can be the separation of extract and residual biomass at high temperatures. In this work, lignin was extracted from wheat straw at 180 °C, and the extract was separated from the remaining solids at several temperatures after the pre-treatment. The results show that 10.1 g/kg of lignin and 2.2 g/kg of carbohydrates are dissolved at the pre-treatment temperature of 180 °C, which is reduced to 8.6 g/kg of lignin and 1.2 g/kg of carbohydrates after cooling. The precipitation of lignin separated from the extracts at 180 °C showed that a higher lignin concentration at high temperatures results in a 46% improvement in the yield of solid lignin, while there was no significant impact on the lignin purity.

One-pot generation of lignin microspheres and digestible substrate with a polyol-DES pretreatment in high solid loading

Previous lignin microspheres (LMS) preparation needs multiple steps with very low yield and high cost. Herein, we developed a high-solid deep eutectic solvent (DES) pretreatment for an effective lignin fractionation and enzymatic saccharification of moso bamboo under mild temperature (110 °C) with high-solid loading. Lignin was significantly removed from the plant cell wall, and cellulose properties (e.g., crystallinity and degree of polymerization) were also altered during the pretreatment. As a result, the enzymatic digestibility of the pretreated bamboo was dramatically increased. Uniform micro-spherical lignin was directly produced from the pretreatment system, and its particle size could be regulated by controlling the solid loadings and pretreatment temperatures. The lignin microspheres formation mechanism was investigated by analyzing the lignin's size distribution, molecular weight distribution, chemical structure, and hydrophobicity. The DES showed excellent recyclability, and the recycled DES could still remove 42.78% lignin even after 7th circulation associated with 100% glucan saccharification. The mass balance based on 1000 g biomass showed that 196.28 g LMS was directly recovered, which exhibited a high RhB adsorption. Besides, 404.91 g glucose and 36.67 g xylose were obtained after the enzymatic saccharification process. Specifically, GAPI analysis exhibited a near total green and yellow portions of the pictogram, indicating our DES process was green enough to make this biorefinery sustainable. Overall, the proposed DES generated synergistic productions of digestible solid and LMS which could contribute to establish a green and sustainable biorefinery sequence with diverse outputs in one pot.

The effect of nanocrystalline TiO2 on structure and catalytic activity of CuO–ZnO in combined methanol reforming

CuO–ZnO (CZ) and CuO–ZnO/TiO2 (CZT) catalysts have been prepared by co-precipitation, characterized by X-ray diffraction, surface area measurements and chemical analysis and tested in the combined methanol reforming reaction. Catalytic tests have been performed in the temperature range 200–400 °C with a GHSV = 55.000 h−1, after H2 reducing pretreatment at 250 °C or 450 °C. It is shown that nanocrystalline TiO2 influences the CuO–ZnO nanosized structure, reducibility and reactivity. TiO2 slightly increases ZnO crystallite size of the fresh catalyst. Moreover, it causes the CuO chemical reduction to nanosized Cu2O on exhaust catalyst pretreated in hydrogen at 250 °C, this improves the reaction with higher methanol conversion and hydrogen production. On the contrary, TiO2 reduces CuO to submicron Cu0 and greatly increases ZnO crystallite size on the exhaust catalyst pretreated in hydrogen at 450 °C, this treatment weakens the reaction, with lower methanol conversion and hydrogen production. In both cases, nanocrystalline TiO2 presence is able to decrease the CO formation: independently of the hydrogen pretreatment temperature. This ability of the nanocrystalline TiO2 is ascribed to the presence of the oxygen vacancies, which act as electron donors that contribute to hinder CO2 and H2 surface adsorption for steric, electrostatic and probabilistic factors.

Quantitative structure-property relationships of thermoset pea protein gels with ethanol, shear, and sub-zero temperature pretreatments

Pea protein is often processed to alter the protein's native structure, enhancing desirable textures in meat and dairy analog products. Cold denaturation is a universal phenomenon in protein that exposes hydrophobic amino acids, though little information exists about this in food science research. In this work, ethanol, shear forces, and low temperatures were used to modify the structure of commercial pea protein isolate, and impacts on gelation are characterized. Treatment at −10 °C in ethanol with applied shear forces led to gels with the lowest tan δ values during temperature ramps and frequency sweeps. A quantitative structure-property relationship (QSPR) method found that hydrogen bonding can be derived from secondary structure (R 2 = 0.960), and hydrogen bonding correlated with the temperature dependence of G′ during cooling in treatments. This work suggests cold denaturation forms hydrophobically bound gels that may aid in replacing fatty textures, and a QSPR framework aids in interpreting rheological data. • Ethanol, shear forces, and low-temperature treatment increase pea protein gel strength. • The number of hydrogen bonds can be estimated from protein secondary structure resulting from FTIR. • Hydrogen bonding correlates to the degree of stiffening during gelation. • Hydrogen bonding correlates to the number of crosslinks estimated using rubber elasticity theory. • Cold denaturation facilitates the design of new cold processing methods to enhance functionality of proteins.

Comparison of coupled chemical pretreatment and mechanical refining of spruce sawdust: fiber network properties and initial production of lignin-bonded biocomposites

AbstractAround 50% of sawn wood remains as a by-product during the processing into timber. A large part of these by-products consists of sawdust, which still contains a lot of intact fibers and would have great potential to be used for biocomposite materials. This study investigates the influence of different pretreatments on spruce sawdust in a two-step process, where chemical pretreatments like liquid hot water (LHW), organosolv (OS), and alkali (NaOH) are coupled with a mechanical pretreatment (refining). The idea is to customize a suitable fibrous material for creating a biocomposite with a natural binder as lignin instead of synthetic binders. The first part of the study focused on comparing the different chemical pretreatments and the influence of the refining time. Each chemical pretreatment resulted in a different partially solubilized lignocellulosic matrix profile, making the matrix’s fibers less or more accessible. In the second step, the material was treated in a refiner to fibrillate the embedded fibers, enhancing the flexibility and bonding properties. Paper sheets were produced to evaluate the mechanical properties of the obtained fibrous materials. Based on the results, the most promising material was selected for further investigation. The second part of the study focused on the initial testing of the produced fibrous materials as composites. First, the fibers produced in the first part were impregnated with lignin, forming composite bars through hot-compression molding. Finally, the tensile strength of the composites was determined. Especially with higher pretreatment temperatures and longer refining times, several promising combinations could be found for the two-step process.

Second Generation Bioethanol Production from Soybean Hulls Pretreated with Imidazole as a New Solvent

Soybean hulls (SH) are the main industrial waste from soybean processing, representing 5–8% of the whole grain. Imidazole was employed for the hydrothermal pretreatment of SH and further bioethanol production. Different pretreatment temperatures (120 and 180 °C) and times (1 and 3 h) were tested. Lignin removal and glucose yield were significantly influenced by temperature. After 48 h of enzymatic hydrolysis of imidazole-treated SH (120 °C, 1 h), 32.7 g/L of glucose and 9.4 g/L of xylose were obtained. A maximum bioethanol yield of 78.9% was reached after 12 h of fermentation by Saccharomyces cerevisiae using SH enzymatic hydrolysate. Imidazole appears to be a potential alternative to pretreat lignocellulosic wastes such as SH for the production of second-generation biofuels and other biomolecules.

Enhanced enzymolysis and bioethanol yield from tobacco stem waste based on mild synergistic pretreatment

The use of mild pretreatment conditions can significantly lower the cost of the biorefining process. This study evaluated a mild pretreatment approach for tobacco stem waste using a combination of dilute acid and dilute alkali. By optimizing the pretreatment conditions, we obtained a high reducing sugar concentration at a pretreatment temperature &amp;lt;100°C. Increasing the acid or alkali strength in a single pretreatment step did not always improve the result; instead, the synergistic effect of both pretreatment components was important. To increase the bioethanol titer, a high solid loading, 30%, was used for bioethanol fermentation. Compared with batch fermentation, enzyme feeding with a shorter feeding period (24 h) enhanced the bioethanol production by 4.32%, generating 86.88 g/L bioethanol. The results provide valuable insights into the effects of two-step acid/alkali pretreatment on enzymolysis. The findings suggest that the optimized synergistic pretreatment process is efficient for bioethanol fermentation.

Optimization of Vibration Pretreatment Microwave Curing in Composite Laminate Molding Process.

Vibration pretreatment microwave curing is a high-quality and efficient composite out-of-autoclave molding process. Focusing on interlaminar shear strength, the effects of pretreatment temperature, pretreatment time and vibration acceleration on the molding performance of composite components were analyzed sequentially using the orthogonal test design method; a scanning electron microscope (SEM) and optical digital microscope (ODM) were used to analyze the void content and fiber-resin bonding state of the specimens under different curing and molding processes. The results show that the influence order of the different vibration process parameters on the molding quality of the components was: vibration acceleration > pretreatment temperature > pretreatment time. Within the parameters analyzed in this study, the optimal vibration pretreatment process parameters were: pretreatment temperature of 90 °C, pretreatment time of 30 min, and vibration acceleration of 10 g. Using these parameters, the interlaminar shear strength of the component was 82.12 MPa and the void content was 0.37%. Compared with the microwave curing process, the void content decreased by 71.8%, and the interlaminar shear strength increased by 31.6%. The microscopic morphology and mechanical properties basically reached the same level as the standard autoclave process, which achieved a high-quality out-of-autoclave curing and molding manufacturing of aerospace composite components.

Effect of pretreatment process on microstructure and mechanical properties in Inconel 718 alloy

The residual stress reduction, the precipitation behavior of γ" phase and the evolution of mechanical properties of Inconel 718 alloy in solid solution annealed with different pretreatment were investigated. The results show that the pretreatment process can effectively reduce the quenching residual stresses. With the increase of pretreatment temperature from 680 °C to 720 °C, the residual stress reduction rate increased from 52% to 65%, and the corresponding stress relaxation mechanism changed from dislocation slip dominated to both dislocation slip and grain boundary migration. Meanwhile, the pretreatment process promotes the nucleation and precipitation of the γ" phase, which is uniformly nucleated and always consistent with the matrix. The yield strength of the pretreated samples was slightly increased compared to the purely aged state, with an extreme value of 5.1%. The increase in strength is mainly attributed to the coherent hardening effect associated with the morphology and distribution of the γ" phase.

Elucidating the inhibiting mechanism of pseudo-lignin on the enzymatic digestibility of cellulose by surface plasmon resonance

To explore the interaction mechanism of pseudo-lignin (PL) with cellulase and its influence on cellulose hydrolysis, different PLs were extracted from pretreated bamboo holocellulose (HC) using different organic solvents. Meanwhile, the real-time interaction of PL and cellulase was analyzed using surface plasmon resonance (SPR). The results showed that the extraction effect of the tetrahydrofuran and 1, 4-dioxane/water solution on PL was more effective than the ethanol/water solution. The inhibition of PL fraction obtained from HC by acid pretreatment with higher temperature showed less effect on Avicel’s enzymatic hydrolysis. SPR analysis revealed that PL formed at higher pretreatment temperature had a lower dissociation rate after adsorption with cellulase. Besides, the binding affinity of PL (160 °C) to cellulase was much greater than that of PL obtained from 180 °C, indicating PL extracted at higher temperature treated biomass is more easily dissociated from cellulase after binding.

Long-lasting low temperature pretreatment of soybean seeds enhance plant field performance and content of free metabolites

Long-lasting low temperature pretreatment of soybean seeds enhance plant field performance and content of free metabolites

Development of lutetium oxide continuous fibers with excellent mechanical properties

The difficulty of reducing the diameter of lutetium oxide (Lu₂O₃) continuous fibers below 50 μm not only limits the flexibility of the sample but also seriously affects their application and development in high-energy lasers. In this work, a Lu-containing precursor with high ceramic yield was used as raw material, fiberized into precursor fibers by dry spinning. The pressure-assisted water vapor pretreatment (PAWVT) method was creatively proposed, and the effect of pretreatment temperature on the ceramization behavior of the precursor fibers was studied. By regulating the decomposition behavior of organic components in the precursor, the problem of fiber pulverization during heat treatment was effectively solved, and the Lu₂O₃ continuous fibers with a diameter of 40 μm were obtained. Compared with the current reported results, the diameter was reduced by about 50%, successfully breaking through the diameter limitation of Lu₂O₃ continuous fibers. In addition, the tensile strength, elastic modulus, flexibility, and temperature resistance of Lu₂O₃ continuous fibers were researched for the first time. The tensile strength and elastic modulus of Lu₂O₃ continuous fibers were 373.23 MPa and 31.55 GPa, respectively. The as-obtained flexible Lu₂O₃ continuous fibers with a limit radius of curvature of 3.5–4.5 mm had a temperature resistance of not lower than 1300 ℃, which established a solid foundation for the expansion of their application form in the field of high-energy lasers.