Destruction Of Lignin Research Articles

Enhancing photocatalytic destruction of lignin via cellulose derived carbon quantum dots/g-C3N4 heterojunctions

Lignocellulosic biomass exhibits a promising potential for production of carbon materials. Nitrogen and phosphorus co-doped carbon quantum dots (N,P-CQDs) were fabricated via (NH4)2HPO4 assisted hydrothermal treatment of cellulose pulp fibers. The as-prepared N,P-CQDs were characterized by HRTEM, FTIR, fluorescence and UV–vis, and then incorporated into g-C3N4 (CN) through sonication and liquid deposition, forming N,P-CQDs/sonication treated g-C3N4 (C-SCN) composites, which were then explored as photocatalysts. The photocatalytic ability of C-SCN towards model lignin was further analyzed. The results showed that, the fluorescence intensity and photoluminescence performance of N,P-CQDs were much higher than that of CQDs; the heterojunction was successfully constructed between the composites of N,P-CQDs and SCN; the incorporation of N,P-CQDs enhanced the visible light absorption, but reduced the band gap of the composite heterojunction; the resultant photocatalysts exhibited a good photocatalytic ability of model lignin via catalyze the fracture of β–O–4′ ether bond and CC bond, i.e., the photocatalytic degradation ratio reached up to 95.5 %; and the photocatalytic reaction generated some valuable organics such as phenyl formate, benzaldehyde, and benzoic acid. This study would promote the high value-added utilization of lignocellulosic resources especially in the transformation of lignin, conforming the concept of sustainable development.

ANALYSIS OF SPENT LIQUOR OF LOW-TEMPERATURE ALKALINE DELIGNIFICATION OF HARDWOOD

Complex and deep processing of wood raw materials to produce products with high added value while reducing the amount of waste is one of the urgent tasks of the modern pulp and paper industry. The search for economically profitable, but at the same time resource-, energy-saving and environmentally friendly technologies for processing wood raw materials in the modern world is becoming the most important means of ensuring the sustainable development of the industry. An alternative innovative method for the production of high-yield fibrous semi-finished products is the production of an extrusion chemical-thermomechanical mass as a result of low-temperature (90 °C) at atmospheric pressure alkaline delignification of hardwood. The liquor obtained in the process of delignification is a complex complex of mineral compounds and products of destruction of lignin, polysaccharides, extractives and products of their.

The structure and properties of lignin isolated from various lignocellulosic biomass by different treatment processes

The structure and properties of lignin can vary depending on the type of lignocellulosic biomass it comes from and the separation techniques used, and also affects its suitability for different applications. In this work, the structure and properties of lignin isolated from moso bamboo, wheat straw, and poplar wood by different treatment processes were compared. Results show that deep eutectic solvent (DES) extracted lignin exhibits well-preserved structures (including β-O-4, β–β, and β-5 linkages), a low molecular weight (Mn = 2300–3200 g/mol), and relatively homogeneous lignin fragments (1.93 < PDI < 2.33) compared to dealkaline lignin (DL) and milled wood lignin (MWL). Besides, lignin samples extracted by DES have a regular nanostructure, higher carbon residue content (>40 %), and excellent antioxidant properties (the free radical scavenging index >20). Among the three types of biomass, the structural destruction of lignin in straw is the most obvious, which is due to the degradation of β-O-4 and β-β linkages during DES treatment. These findings can contribute to a better understanding of the structural changes that occur in various treatment processes from different lignocellulosic biomass, and help maximize the targeted development of their applications based on the characteristics of lignin.

ASSESSMENT OF THE EFFECT OF BIOCHAR ON THE PROCESS OF THERMOLISIS OF BIOMASS OF PLANTS GROWN ON RECLAIMED LANDS

Samples of soil contaminated with heavy metals for pot experiments with annual crops (maize, sweet and sudan sorghum) were taken near the mines "Pavlogradska" and "Blagodatna" in the coal-mining region of Western Donbass. The basis of the reclaimed areas was an 8-10 m thick mine rock (MR) dump, covered with different layers of black soil or red-brown clay by creating two types of soil artificial profiles with the addition of 30 cm of black soil (30 cm of BS +MR) and 50 cm red-brown clay (50 cm RBC + MR). Experimental soil samples were treated with 3.0% (w/w) biochar. The purpose of the study was to study the effect of the addition of biochar on the process of thermal destruction of the biomass of maize, sweet and sudan sorghum, grown on different substrates - components of artificial reclaimed profiles (upper layers of chernozem mass and red-brown clay). The process of thermolysis of biomass components of three agricultural crops was studied by the method of thermogravimetric analysis. Thermal destruction of the biomass of the three studied plant species occurred in two stages: evaporation of water and volatile compounds (stage 1) and decomposition of the main components: hemicellulose, cellulose and lignin (stage 2). The first stage took place in the temperature range of 50-180°С. The process was slow, the maximum speed did not exceed 5-8%/min, the extreme point was observed at a temperature of 100-110°C. Loss of body weight is insignificant, 4.5–7.5%. The second stage is divided into two phases: the decomposition of holocellulose with the beginning of lignin decomposition (phase 1) and the cessation of lignin decomposition, and the formation of non-combustible residue (phase 2). Destruction of holocellulose occurred in the temperature range of 190-390°С. Due to the large amount of hemicellulose in the biomass of the studied plants, its decomposition was shifted to the region of higher temperatures. Therefore, the degradation ranges of hemicellulose and cellulose overlapped, and only one extreme point was observed in the DTG curves. The process proceeded at high speeds with the peak of destruction in the temperature range of 280-310°C. Weight loss was also the most significant and was between 50 and 55%. Decomposition of lignin occurred rather slowly, with one insignificant peak in the temperature range of 420-440°C. A weight loss of 26-30% has been established. At the first stage, the process proceeded mainly with heat absorption; the reactions of the second stage were exothermic with noticeable thermal effects in the zones of cellulose and lignin decomposition. Differences in thermal characteristics of sugar sorghum biomass grown on different substrates and with the addition of biochar were determined in the process of thermolysis. Degradation of holocellulose occurred more slowly in biomass collected from a vessel with red-brown clay, in contrast to lignin, which decomposed faster than in the experiment where the substrate was a loose layer of chernozem. The share of non-combustible residues was almost 2 times smaller. A slight increase in the rate of the cellulose decomposition reaction (1,2 times) and a significant increase in the rate of the lignin destruction reaction (5 times) was observed. In the treatment with biochar, a more complete combustion of biomass was observed. The rate of cellulose decomposition in the experiment with red-brown clay became somewhat higher, although the decomposition of lignin occurred more slowly. The share of non-combustible residues increased by 1,8 times. Thermal destruction of Sudan grass biomass on both substrates occurred in a similar manner. The addition of biochar did not reveal significant deviations in the thermal behavior of biomass grown on chernozem, in contrast to the experiment with red-brown clay, where the addition of biochar contributed to a significant reduction in the duration of thermolysis. The first stage of thermolysis of corn biomass was somewhat shorter in the experiment with a bulk layer of chernozem compared to red-brown clay and was accompanied by a lower mass loss. The same trend was observed in the decomposition of holocellulose. At the same time, the destruction of lignin in the version with chernozem lasted longer, the extremum point was shifted to the region of higher temperatures, the speed of the process was almost twice as low as in the version with clay, and the proportion of non-combustible residue was 1,7. times higher. More complete combustion of corn biomass was also observed in the version with biochar.

Ensiling Improved the Colonization and Degradation Ability of Irpex lacteus in Wheat Straw.

To develop a non-thermal method to replace steam autoclaving for white-rot fungi fermentation, Irpex lacteus spawn was inoculated in wheat straw (WSI) or ensiled WS (WSI) at varying ratios of 10%, 20%, 30%, 40%, and 50%, and incubated at 28 °C for 28 days to determine the effects of the ensiling and inoculation ratio on the colonization and degradation ability of Irpex lacteus in wheat straw (WS). The results demonstrate that ensiling effectively inhibited the growth of aerobic bacteria and molds, as well as other harmful microorganisms in WS, which created a favorable condition for the growth of I. lacteus. After the treatment of I. lacteus, the pH of EWSI decreased to below 5, while that of WSI, except for the feedstocks of WSI-50%, was around 7, indicating that I. lacteus colonized well in the ensiled WS because the substrates dominated by I. lacteus are generally acidic. Correspondingly, except for the molds in WSI-50% samples, the counts of other microorganisms in WSI, such as aerobic bacteria and molds, were significantly higher than those in EWSI (p < 0.05), indicating that contaminant microorganisms had a competitive advantage in non-ensiled substrates. Incubation with I. lacteus did not significantly affect the cellulose content of all samples. However, the NDS content of EWSI was significantly higher than that of WSI (p < 0.05), and the hemicellulose and lignin contents were significantly lower than the latter (p < 0.05), except for the NDS and hemicellulose contents of WSI-50% samples. Correlation analysis revealed a stronger negative correlation between NDS content and the contents of hemicellulose, cellulose, and lignin in EWSI, which could be caused by the destruction of lignin and hemicellulose and the conversion from structural carbohydrates to fungal polysaccharides or other compounds in NDS form. Even for WSI-50% samples, the sugar yield of WS treated with I. lacteus improved with an increasing inoculation ratio, but the ratio was not higher than that of the raw material. However, the sugar yield of EWSI increased by 51–80%, primarily owing to the degradation of lignin and hemicellulose. Above all, ensiling improves the colonization ability of I. lacteus in WS, which promotes the degradation of lignin and hemicellulose and the enzymic hydrolysis of cellulose, so combining ensiling and I. lacteus fermentation has promising potential in the pretreatment of WS.

Degradation of the Pine Wood Structure in Ozonolytic Delignification

Transformations of pine wood during exposure to ozone were studied. The content of lignin and cellulose in the cellulose-containing material (CCM) from ozonated wood was determined. The polymerization degree (PD) of cellulose from CCM was determined. The CCM samples were examined by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and X-ray diffraction (XRD) analysis. HPLC analysis of water-soluble lignin ozonolysis products was performed. Wood ozonation leads to lignin destruction; 40–42% delignification degree is achieved. The destruction of aromatic components is confirmed by DRIFT spectra. A decrease in the intensity of skeletal vibrations of aromatic ring at 1511 and 1598 cm–1, bands at 1662 cm–1, and an increase in the intensity of stretching C=O vibrations of lignin and hemicelluloses (HCs) at 1736 cm–1 were observed. The stoichiometric ratio of the amount of absorbed ozone and the destroyed guaiacyl units, as well as the composition of water-soluble products, shows that ozonolysis is the main mode of wood lignin destruction. The XRD data and a decrease in PD of cellulose show that, in addition to lignin, HCs and amorphous cellulose are also destroyed during ozonation. It has been found that the region of ozone specific absorption ≤1.5 mmol O3/g corresponds to the most efficient destruction of lignin with the lowest degradation of cellulose fiber.

Study of Reducing Destruction of Lignin by FT-IR Spectroscopy

Study of Reducing Destruction of Lignin by FT-IR Spectroscopy

Features of Lignin Destruction in Wood under the Action of Ozone

Samples of pine wood ozonated with different contents of water are studied via UV diffuse reflectance spectroscopy. It is shown that polyaromatic and stilbene structures, guaiacyl derivatives, and carbonyl- and carboxyl-containing aromatic structures of lignin are destroyed during ozonation of pine wood. The destruction of aromatic structures proceeds efficiently in wood with a moisture content of more than 60–65% in the 2–3 mmol/g range of ozone consumption. When the moisture content is below 40%, ozone treatment of pine wood at low ozone consumption allows us to obtain different modifications of oxygen-containing aromatic and polyaromatic structures on surfaces of lignocellulosic material (LCM). IR absorption spectra of dioxane lignin obtained from the initial and ozonated wood samples confirm the different direction of lignin transformations, depending on the content of moisture in the wood.

Dynamics of Lignin Destruction in Pine Wood under the Action of Ozone

The destruction of lignin in pinewood during ozonization is studied via diffuse reflection IR spectroscopy (DRIFT) and Raman spectroscopy. The DRIFT spectra are deconvoluted into Lorentz components. Samples of dioxanlignin obtained from wood are analyzed by means of UV spectroscopy (second derivatives). Based on the DRIFT, Raman, and UV spectra, specific rates of ozone (Qr) consumption corresponding to the oxidation of different structures on the wood surface are determined. In the range of Qr ≤ 1.5 mmol/g, the predominant process is the breakdown of aromatic rings. In the range of 1.5–3.0 mmol/g, hydroxyaromatic compounds formed at the first stage of ozonization are oxidized. At Qr higher than 2.0 mmol/g, aliphatic structures of lignin are also oxidized by ozone, along with carbonyl and carboxylic oxidation products occurring on the surface. These lignin oxidation products block to some extent the accessibility of lignin for ozone.

Pretreatment of sweet sorghum straw and its enzymatic digestion: insight into the structural changes and visualization of hydrolysis process

BackgroundThe efficient utilization of lignocellulosic biomass for biofuel production has received increasing attention. Previous studies have investigated the pretreatment process of biomass, but the detailed enzymatic hydrolysis process of pretreated biomass remains largely unclear. Thus, this study investigated the pretreatment efficiency of dilute alkali, acid, hydrogen peroxide and its ultimate effects on enzymatic hydrolysis. Furthermore, to better understand the enzymatic digestion process of alkali-pretreated sweet sorghum straw (SSS), multimodal microscopy techniques were used to visualize the enzymatic hydrolysis process.ResultAfter pretreatment with alkali, an enzymatic hydrolysis efficiency of 86.44% was obtained, which increased by 99.54% compared to the untreated straw (43.23%). The FTIR, XRD and SEM characterization revealed a sequence of microstructural changes occurring in plant cell walls after pretreatment, including the destruction of lignin–polysaccharide interactions, the increase of porosity and crystallinity, and reduction of recalcitrance. During the course of hydrolysis, the cellulase dissolved the cell walls in the same manner and the digestion firstly occurred from the middle of cell walls and then toward the cell wall corners. The CLSM coupled with fluorescent labeling demonstrated that the sclerenchyma cells and vascular bundles in natural SSS were highly lignified, which caused the nonproductive bindings of cellulase on lignin. However, the efficient delignification significantly increased the accessibility and digestibility of cellulase to biomass, thereby improving the saccharification efficiency.ConclusionThis work will be helpful in investigating the biomass pretreatment and its structural characterization. In addition, the visualization results of the enzymatic hydrolysis process of pretreated lignocellulose could be used for guidance to explore the lignocellulosic biomass processing and large-scale biofuel production.

Biomodification of Flax Fibrous Materials for Increase of Sorption to Organic Compounds

This paper was focused on the method to increase of the sorption properties in the flax fibrous material. This method was based on the original approach which includes the application of enzymatic catalysis as a destruction regulator of the polycarbohydrate components in the bast. The formed reaction products were used as reagents for reductive destruction of lignin. The changes in the fiber sorption capacity to the molecular markers were controlled after changing both the polymer composition of the fiber and the size of its pore. It was determined that the flax sorbents increase the adsorption of phenol vapors to 9–12 times and organic dyes from aqueous solutions to 4 times.

Destruction of Lignin during the Ozonation of Pine Wood

The consumption of ozone by pine wood with a water content of 7 to 85% is investigated. The specific ozone consumption and degree of ozone conversion during the ozonation of wood with different contents of water are determined. IR absorption spectra of ozonated lignocellulosic material (LCM) produced from wood are analyzed. Destruction of the lignin aromatic structure and the formation of carbonyl- and carboxyl-containing compounds are observed. The content of cellulose in a sample of ozonated LCM grows along with the specific ozone consumption. Products of the ozonolysis of lignin (glyoxylic, formic, and oxalic acids) form during ozonation of the wood, as determined via HPLC. It is shown that the oxidation of acids by ozone proceeds in the water phase of the sample. Based on the data for the destruction of lignin and the results from investigating the process of wood ozonation, it is concluded that the optimum content of water for wood treatment is 60–63%. It was shown that the destruction of lignin during wood ozonation proceeds via ozonolysis and with the participation of radicals formed in the reaction between ozone and water.

Potentials of using mixed culture bacteria incorporated with sodium bicarbonate for hydrogen production from water hyacinth

The aim of this study is to assess the potentials of using mixed culture bacteria incorporated with different concentrations of NaHCO3 for hydrogen production from water hyacinth (WH). The lowest hydrogen yield (HY) of 30.4 ± 1.9 mL/gTVS, H2 content (HC) of 19.5 ± 1.5% and hydrogenase enzyme (HE) activity of 0.06 ± 0.01 mgM.Breduced/min were registered for the cultures without supplementation of NaHCO3. The HY, HC, and HE activity were maximized at levels of 69.2 ± 4.3 mL/gTVS, 58.4 ± 3.6% and 0.18 ± 0.01 mgM.Breduced/min. respectively for the anaerobes supplied with 3.0 g NaHCO3/L. Furthermore, cellulose, hemicellulose, and lignin destruction efficiencies were 37.2 ± 2.3, 30.0 ± 1.9 and 20.9 ± 1.3% respectively due to the increase of cellulase and xylanase activities up to 2.73 ± 0.17 and 1.87 ± 0.12 U/mL, respectively. Moreover, the abundance of Firmicutes was substantially increased and accounted for 71% of the total OTU’s. Microbes belonging to the order Clostridiales and OPB54 were particularly enriched in the medium supplemented with NaHCO3.

The diversity of microorganisms inhabiting the sludge tanks of Baikalsk pulp and paper plant (BPPP)

The wastes from the Baikalsk pulp and paper plant, including the by-products of the plant’s bleaching unit are stored in the special disposal reservoirs in the form of a sludge-lignin, which consists of lignin, polyacrylamide and flocculants. Here, we report on microbiological composition of sludge-lignin: we detected fungi hyphae, actinomycete hyphae, long and short rods as well as coccal forms of bacteria. Interestingly, despite the diversity of bacterial, cyanobacterial and fungal communities no noticeable destruction of lignin was observed. We recommend to use specific chemical compounds and microbiological agents for destruction of sludge-lignin.

Maximization of hydrogen fermentative process from delignified water hyacinth using sodium chlorite

This study investigated the direct supplementation of sodium chlorite (NaClO2) in acidic fermentation process rather than using NaClO2 as a pretreatment agent. This approach targets saving both of the cost of external acetic acid that needs to be added in pretreatment and the loss of polysaccharide, which simultaneously occurs during pretreatment process. Whereas, fermentation of water hyacinth (WH) provided quite low H2 yield (HY) of 39.7 ± 2.5 mL/gTVS and lignin destruction of 2.6 ± 0.2%. Cellulase and xylanase enzymes amounted to 2.15 ± 0.18 and 1.81 ± 0.14 U/mL, respectively. Enterobacter and Clostridium sp. accounted for 2.41 ± 0.15 × 105 and 4.02 ± 0.27 × 104 cfu/mL, respectively. However, NaClO2 addition significantly augmented HY, cellulase and xylanase enzymes to 119.6 ± 7.8 mL/gTVS, 3.46 ± 0.21 and 2.09 ± 0.23 U/mL at dosage of 8.0 mg/L, respectively. Moreover, cellulose, hemicellulose and lignin degradation efficiencies were maximized to 57.8 ± 3.1, 46.3 ± 3.8 and 31.6 ± 1.6%, respectively. Enterobacter and Clostridium sp. counts were 4.23 ± 0.28 × 105 and 9.75 ± 0.52 × 104 cfu/mL, respectively in the batches supplemented with NaClO2. Nevertheless, at a dosage exceeding 8.0 mg/L, the HY (26.1 ± 2.0 mL/gTVS) and bacterial count was highly deteriorated due to the excessive production of inhibitory phenolic compounds of 1.61 ± 0.12 g/L in the medium where the destruction of lignin was quite high (38.8 ± 2.4%).

A novel oxidative destruction of lignin and enzymatic digestibility of hazelnut shells

This study investigated the effect of sequential oxidative (ozonolysis) pretreatment and enzymatic hydrolysis of hazelnut shells on production of fermentable sugars. Two factors (ozone concentration and pretreatment time), which were determined to be significant by the Box-Behnken response surface methodology, were further maximized for total lignin removal, solid recovery, and total reducing sugar yield via enzymatic hydrolysis of the pretreated biomass using full-factorial design. The ozonolysis was performed by passing 30, 40, and 50 mg/L of ozone gas through a packed bed of ground hazelnut shells for up to 120 min at a flow rate of 0.25 L/min. The highest lignin reduction (20.5%) was obtained in the shells with 30% moisture content subjected to ozone concentration of 50 mg/L for 120 min, which corresponded to a high biomass recovery (94%). The reducing sugar yield also increased from 119.9 mg/g dry untreated biomass to 284.6 mg/g dry untreated biomass for hazelnut shells ozonated at 30 mg/L for 60 min. Thus, these results indicate remarkable benefits of ozonolysis during pretreatment of hazelnut shells.

Impact of hot water pretreatment temperature on the pyrolysis of birch wood

Hydrothermal treatment of wood is an integral part of a modern biorefinery concept. Our research is devoted to the study of properties of birch wood and lignocelluloses at its base after hydrothermal treatment at various temperatures using TG and Py-GC/FID/MS. It was found that treatment in temperature range 150–200°C led to increase of the content of pyrolysis volatiles due to the increase of the content of the main cellulose product—levoglucosan, while the content of the phenolic products was practically constant. Due to hydrolytic processes and condensation reactions in the temperature range 200–250°C the content of all carbohydrate derived volatiles decreased and the content of lignin destruction products increased mainly at the expense of dimethoxylated derivatives.

Fundamental and molecular composition characteristics of biochars produced from sugarcane and rice crop residues and by-products

Biochar conversion of sugarcane and rice harvest residues provides an alternative for managing these crop residues that are traditionally burned in open field. Sugarcane leaves, bagasse, rice straw and husk were converted to biochar at four pyrolysis temperatures (PTs) of 450°C, 550°C, 650°C, and 750°C and evaluated for various elemental, molecular and surface properties. The carbon content of biochars was highest for those produced at 650–750°C. Biochars produced at 550°C showed the characteristics of biochar that are commonly interpreted as being stable in soil, with low H/C and O/C ratios and pyrolysis fingerprints dominated by aromatic and polyaromatic hydrocarbons. At 550°C, all biochars also exhibited maximum CEC values with sugarcane leaves biochar (SLB) > sugarcane bagasse biochar (SBB) > rice straw biochar (RSB) > rice husk biochar (RHB). The pore size distribution of biochars was dominated by pores of 20nm and high PT increased both smaller and larger than 50nm pores. Water holding capacity of biochars increased with PT but the magnitude of the increase was limited by feedstock types, likely related to the hydrophobicity of biochars as evident by molecular composition, besides pore volume properties of biochars. Py-GC/MS analysis revealed a clear destruction of lignin with decarboxylation and demethoxylation at 450°C and dehydroxylation at above 550°C. Overall, biochar molecular compositions became similar as PT increased, and the biochars produced at 550°C demonstrated characteristics that have potential benefit as soil amendment for improving both C sequestration and nutrient dynamics.

Straw cellulose obtaining in the isobutanol - hydrazine – KOH system

The delignification process of wheat straw in isobutyl alcohol - hydrazine – KOH system in the range of 140-160 0 C and length 60-150 min is investigated. It is shown that the quality values of obtained cellulose are naturally decreased with increasing of temperature and duration of cooking, due to the intensification of lignin destruction process. Laboratory castings of straw pulp has the following physical and mechanical properties, tensile length of 6200-6900 meters, forcing index 4,2-4,5 kN/g, number of double kinks 520-600, that is higher than the wood cellulose quality obtained by traditional sulfate and sulfite cooking methods. The chemical composition of top layer of worked-out solution is determined by the method of proton magnetic resonance. Four major peaks that correspond to isobutanol groups and confirm ability to use the top layer of worked-out cooking solution to the following cooking are observed in the obtained spectra.

Transformation of wood during ozonization in the presence of hydrogen peroxide

Samples of ozonized aspen wood pretreated with hydrogen peroxide solutions of various concentrations are investigated by UV diffuse reflectance spectroscopy, IR spectroscopy, and X-ray structural analysis. The general course of wood transformation under the action of the O3/H2O2 system is associated with the destruction of lignin and oxidation of carbohydrates, raising the fraction of the crystalline phase in a lignocarbohydrate material. The possibility of varying the depth of the chemical and structural transformation of the substrate upon changing the hydrogen peroxide concentration in the O3/H2O2 system is demonstrated.