Characterization of coal-based fulvic acid and the construction of a fulvic acid molecular model

Extraction and chemical characterization of humic acid produced from lignite coals of arid region of Gujarat, Western India

In the current study, extraction of humic acid (HAs) from lignite fines of kutch basin of Gujarat (western India) were reported. The extraction was done by International Humic Substances Society (IHSS) method. Several analytical and spectroscopic techniques were used to characterize of extracted HAs. The gravimetric analysis showed (28.5% and 26.4%) of humic acid extraction from panandhro mines (PM) and mata-No-Madh mines (MNMM) respectively. UV-Vis spectroscopy revealed a high degree of humification, higher stability and aromatic nature. FTIR peaks demonstrated the presence of carboxylic, alcoholic, and phenolic functional groups. SEM/EDX analysis revealed that surface were smooth, non-porous and like loose sponge that showed the presence of major elements like C, O, F, Al, Na, S, Si, Ca, Ti and Fe. The combination of results gives a better and improved understanding of the nature of lignite coals of western India. It may be helpful in choosing suitable coals for the extraction of humic acid and using it for enhancing plant growth condition, soil enrichment and creating green energy solution. This study not only helps in the research related to extraction of humic acid from lignite but also creates a new avenue for the efficient and clean use of lignite.

Integrative transcriptome and metabolome analysis reveals the mechanism of fulvic acid alleviating drought stress in oat

Drought stress inhibits oat growth and yield. The application of fulvic acid (FA) can improve the drought resistance of oats, but the corresponding molecular mechanism of FA-mediated drought resistance remains unclear. Here, we studied the effects of FA on the drought tolerance of oat leaves through physiological, transcriptomic, and metabolomics analyses, and identified FA-induced genes and metabolites related to drought tolerance. Physiological analysis showed that under drought stress, FA increased the relative water and chlorophyll contents of oat leaves, enhanced the activity of antioxidant enzymes (SOD, POD, PAL, CAT and 4CL), inhibited the accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and dehydroascorbic acid (DHA), reduced the degree of oxidative damage in oat leaves, improved the drought resistance of oats, and promoted the growth of oat plants. Transcriptome and metabolite analyses revealed 652 differentially expressed genes (DEGs) and 571 differentially expressed metabolites (DEMs) in FA-treated oat leaves under drought stress. These DEGs and DEMs are involved in a variety of biological processes, such as phenylspropanoid biosynthesis and glutathione metabolism pathways. Additionally, FA may be involved in regulating the role of DEGs and DEMs in phenylpropanoid biosynthesis and glutathione metabolism under drought stress. In conclusion, our results suggest that FA promotes oat growth under drought stress by attenuating membrane lipid peroxidation and regulating the antioxidant system, phenylpropanoid biosynthesis, and glutathione metabolism pathways in oat leaves. This study provides new insights into the complex mechanisms by which FA improves drought tolerance in crops.

Fulvic acid application increases rice seedlings performance under low phosphorus stress

BACKGROUND

Fulvic acid enhances plant growth and interacts synergistically with phosphate fertilizer to alleviate the agricultural production problem of low phosphorus fertilizer utilization efficiency. However, the underlying mechanism of its action remains poorly understood. In this study, we investigated the impact of fulvic acid application with varying concentrations (0, 40, 60, 80 and 120 mg/L) on rice performance in plants grown in a hydroponic system subjected to low phosphorus stress. The rice growth phenotypes, biomass, root morphology, phosphorus uptake, and the impact of fulvic acid on the rhizosphere environment of rice, were assessed.

RESULTS

The findings showed that adding appropriate concentrations of exogenous fulvic acid could promote the growth performance of rice under low phosphorus stress. Particularly at T1 (40 mg/L) and T2 (60 mg/L) over the control effectively increased rice biomass by 25.42% and 24.56%, respectively. Fulvic acid treatments stimulated root morphogenesis, up-regulated phosphate transporter genes, and facilitated phosphorus absorption and accumulation. Especially T1 (20.52%), T2 (18.10%) and T3 (20.48%) treatments significantly increased phosphorus uptake in rice, thereby alleviating low phosphorus stress. Additionally, fulvic acid elevated organic acids concentration in roots and up-regulated plasma membrane H+-ATPase genes, promoting organic acids secretion. This metabolic alteration can also alleviate low phosphorus stress in rice.

CONCLUSIONS

The effect of exogenous fulvic acid on physiological indicators is concentration-dependent under low phosphorus stress, enhances rice performance and reduces reliance on phosphorus fertilizer. This provides new insights to shed light on the mechanism of alleviating low phosphorus stress in rice through fulvic acid application, an eco-friendly tool.

Humic Substances as a Versatile Intermediary

Humic substances are organic ubiquitous components arising in the process of chemical and microbiological oxidation, generally called humification, the second largest process of the carbon cycle. The beneficial properties of these various substances can be observed in many fields of life and health, whether it is the impact on the human organism, as prophylactic as well as the therapeutic effects; animal physiology and welfare, which is widely used in livestock farming; or the impact of humic substances on the environment and ecosystem in the context of renewal, fertilization and detoxification. Since animal health, human health and environmental health are interconnected and mutually influencing, this work brings insight into the excellence of the use of humic substances as a versatile mediator contributing to the promotion of One Health.

Construction and verification of vitrinite-rich and inertinite-rich Zhundong coal models at the aggregate level: new insights from the spatial arrangement and thermal behavior perspective

To explore the thermal behavior of Zhundong coal from the perspective of maceral, it is essential to conduct molecular simulations based on constructing a realistic aggregate model of coal. Here, two Zhundong coal samples ZD-V (vitrinite-rich) and ZD-I (inertinite-rich) were collected, and coal models were constructed using elemental analysis, solid-state ¹³C-nuclear magnetic resonance (¹³C-NMR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrometry (FTIR). The chemical formulas of 2D vitrinite-rich coal and inertinite-rich coal constructed are C₁₅₂H₁₆₇NO₃₆ and C₁₅₅H₁₁₉NO₂₈, respectively. The chemical structure information matches well with that determined by those analysis results, including elemental analysis, structural composition, and ¹³C-NMR spectra. The final aggregate models show that the dimension of the unit cell is 2.785 × 2.785 × 2.785 nm for ZD-V and 2.743 × 2.743 × 2.743 nm for ZD-I, including six macromolecules respectively. The final aggregate structure models were verified by comparing experiments and simulation results. In addition to the verification with He density, the spatial arrangement of the aggregate model was verified by simulated XRD spectrum. And moreover, the thermal behavior was verified by ReaxFF MD, and the simulated trend of thermal weight loss and cumulative total molecules released were consistent with TG-MS. The final models show the visual difference between ZD-V and ZD-I, whether the 2D molecular structure or aggregation state. ZD-V is dominated by chain hydrocarbons, while ZD-I is dominated by cyclic hydrocarbons with linked aromatic rings. The aromatic substitution of oxygen atoms is different, ZD-V is mainly composed of ortho-disubstituted arenes, and ZD-I is mainly composed of meta-disubstituted arenes. In addition, ZD-V has a lower ultra-micropore size distribution and porosity than ZD-I. This study presents a comprehensive approach to construct and verify aggregate models from the spatial arrangement and thermal behavior perspective, and the constructed Zhundong coal models can provide a foundation for further exploration of the thermal reactivity (e.g. combustion, liquefaction, etc.) of coal from maceral aspects.

Humus Acids in the Digested Sludge and Their Properties

Fulvic acids, alpha (α) humic acids and hymatomelanic acids were extracted digested sludge in two Cracow sewage treatment plants: Kujawy and Płaszów. Their elemental composition was examined and micropollution and ash content were determined. Based on the IR and UV-VIS spectrum, their similarities were determined with the occurring interactions with micropollution. Strong correlations between the acids coming from different sources depend on acid type and micropollution accompanying them, depending on concentration, influences to a specific extent their IR and UV-VIS spectra. Absorption analysis in infrared constitutes a simple method for characterizing fulvic and humic acids from wastewater treatment plants. The extracted fulvic acids were characterized by moderate maturity, while humus acids were well developed. In the fermentation process, the N bond increases together with the level of humification of the humus acid. The characteristics of the extracted humus acids comply with other humic substances presented in the literature. Quantitative analysis showed that digested sludge contains, on average: FA from 5.07 to 5.30 g/kg dry matter, αHA from 59.22 to 74.72 g/kg dry matter, HMA from 20.31 to 43.66 g/kg dry matter. It was thus demonstrated that wastewater treatment, in particular digested sludge, constitutes an attractive source of humus acids with a wide range of applications in numerous areas, such as agriculture, ecological rehabilitation, environmental protection, animal breeding, aquaculture, veterinary as well as medicine and is a precious source of soil fertilizers.

Exploration of the H2O2 Oxidation Process and Characteristic Evaluation of Humic Acids from Two Typical Lignites

To study the effect of H2O2 on the content and properties of humic acids (HAs) in lignites, the experimental conditions including oxidation time, H2O2 concentration, and the solid-liquid ratio were investigated. Under the optimum oxidation conditions, the contents of HAs of YL and HB lignite were 45.4 and 40.9%, respectively. The HAs extracted from oxidized and raw lignites were characterized and compared. The results showed that the HAs extracted from oxidized lignites contain more total acidic groups, carboxyl groups, and aliphatic carbon than that in HAs extracted from raw lignites, and their hydrophilic-hydrophobic index value is higher and thermooxidative stability is better than those in HAs extracted from raw lignites. In addition, the composition of polycyclic aromatic hydrocarbons and fluorophore types in HAs extracted from oxidized lignites are similar to the HAs extracted from raw lignites. The results indicated that the oxidation operation can increase the content of HAs in lignites, and simultaneously increase the content of oxygen-containing functional groups and biological activity of HAs, which provided a reference for the subsequent application of HAs.

Research of New Cross-Flow Technology with a Gas Heat Carrier for Lignite Pyrolysis

The adaptability of the gas heat carrier cross-flow pyrolysis process to Huolinhe lignite (0-80 mm) and the influence of the temperature of the heat carrier and moisture of the raw materials on the yield and properties of the pyrolysis products were studied using a 30 t/d cross-flow pyrolysis pilot plant with a gas heat carrier. When the temperature of the gas heat carrier was increased from 750 to 850 °C, the volatiles (V daf) produced from the char decreased from 16.81 to 10.57%, the yield of tar (Tar d) increased from 73.81 to 81.1% of the Gray-King (G-K) tar yield, and the yield of gas decreased from 1312 to 1205 Nm3/t. When the temperature of the gas heat carrier was constant at 850 °C and the moisture content (M t) of lignite was reduced from 12.49 to 7.14%, the V daf of char declined from 10.57 to 6.59%, the yield of gas was reduced from 1205 to 805 Nm3/t, the calorific value of gas increased from 3.88 to 4.68 MJ/m3, and the Tar d increased to 81.56% of the G-K tar yield. The light tar content (boiling point below 360 °C) was more than 60%, and the ash content was less than 0.04%. The cross-flow pyrolysis moving bed could effectively treat full-size lignite, afforded continuous and stable operation, and provided a high oil and gas yield, which provides basic data for further industrial design.

Effects of fulvic acid on the photosynthetic and physiological characteristics of Paeonia ostii under drought stress

PAEONIA OST II

has become an economically important oil crop in recent years, but its growth is seriously affected by drought stress in dry areas. In this study, the alleviating effect of fulvic acid (FA) on potted P. ostii under natural drought stress was investigated. The natural drought stress adopted in this experiment was mainly characterized by the low soil water content, and the roots of plants cannot absorb enough water to compensate for the consumption of transpiration, which affects the normal physiological activities and causes damage. The results showed that FA treatment significantly increased the leaf water content and antioxidant enzyme activities and decreased reactive oxygen species (ROS) accumulation, the proline (Pro) content, and the relative electrical conductivity (REC). Moreover, FA treatment improved photosynthetic parameters and chlorophyll (Chl) fluorescence parameters, maintained the integrity of chloroplasts and mesophyll cells, and increased the expression level of drought-tolerant genes. These results indicated that FA treatment could induce antioxidant enzymes to eliminate ROS, reduce membrane lipid peroxidation and decrease damage to photosynthesis in P. ostii under drought stress, which would provide a measure for alleviating the damage of P. ostii caused by drought stress.

Synergistic Extraction and Characterization of Fulvic Acid by Microwave and Hydrogen Peroxide-Glacial Acetic Acid to Oxidize Low-Rank Lignite

Fulvic acid (FA) has important properties and is used widely in agriculture, industry, medicine, and other fields. However, there is a lack of environmentally friendly and efficient extraction methods for coal-based FA and its molecular structural characterization. In this study, FA was extracted cleanly and efficiently from low-rank lignite via the innovative method of microwave combined with hydrogen peroxide and glacial acetic acid, followed by purification by the sulfuric acid-acetone method. The molecular structures of FA were precisely characterized by UV-vis spectroscopy, infrared (IR) spectroscopy, 1H nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS). The results showed that the microwave combined with hydrogen peroxide-glacial acetic acid method had stronger oxidative degradation ability compared with the conventional method. Under optimized conditions, the yield of FA reached 60.97%. During the oxidation process, the macromolecular network structure of coal was destroyed, resulting in the production of many oxygen-containing functional groups. According to the IR and UV-vis spectra, there were abundant oxygen-containing functional groups such as hydroxyl, carboxyl, carbonyl, and quinone groups in the molecular structure of FA. Determination of the total acid group content in the oxygen-containing functional groups of FA showed that the content of carboxyl groups was much higher than that of phenolic hydroxyl groups. The 1H NMR showed that there were hydrogen atoms present as part of carboxyl, aromatic, phenolic hydroxyl, and aliphatic groups in FA. The (GC-MS) results suggested that FA is a mixture of dozens of complex compounds, including alkanes, alcohols, esters, etc.