Efficient oxidative depolymerization of lignite through selective cleavage of cross-linked structures for producing oxygen-containing chemicals

Investigation of hydrothermal depolymerization of lignite under different conditions by 13C NMR spectroscopy

Synergistic effects of Paenibacillus mucilaginosus and Penicillium pimiteouiense on the extraction of humic substances from lignite

Intensive use of inorganic fertilizers has led to soil degradation, decreased productivity, and increased greenhouse gas emissions. Humic acid (HA) offers a sustainable solution by improving soil health and nutrient uptake while reducing dependence on chemical inputs. However, commercial HA from leonardite is expensive and rarely available in Indonesia. This study aimed to develop a high-quality and cost-effective HA product from low-rank coal (LRC) mined in South Sumatra. Given LRC’s low calorific value and high organic content, it presents an underutilized but promising HA source. A descriptive quantitative approach was used, starting with LRC selection and modified extraction to obtain HA. Laboratory-scale characterization revealed that locally sourced HA shares many functional groups with commercial leonardite-based HA. Hydrofluoric acid pretreatment significantly increased HA yield from 26.3% to 44%. A field trial was conducted on degraded soil overused with inorganic fertilizers, using a completely randomized block design with five treatments and five replications. Red chili (Capsicum annuum L.) was selected because of its high economic value. Data were analyzed using ANOVA at a significance level of 5%. The results showed that the combination of HA derived from LRC with low phosphate fertilizer (150 kg ha-1 SP-36 + 27 kg ha-1 HA) significantly increased plant height, fruit yield, and soil P availability, resulting in a yield of more than 28 t ha-1. These findings demonstrate the potential of LRC as a sustainable HA source to restore degraded soils and increase crop productivity in Indonesia.

The process of isolating humic substances especially humic acid consumes a lot of time. The isolation (extraction, fractionation and purification) processes of humic acid from different sources such as soils, organic fertilizers and so on vary from 12 hours to 7 days. Based on the previous findings reported by other researchers, the standard extractant ratio used for humic acid extraction is 1:10 because it gives the highest yield of humic acid isolated. Previous studies tend to focus on the isolation duration of humic acid but not extractant ratio. To date, there is also lack of information about the extraction period and extractant ratio required to extract humic acid from rice straw compost. This study aimed to assess the minimum duration and extractant ratio for extracting humic acid from rice straw compost. A ratio of 1: 5 and 1: 10 of rice straw compost sample to chemical used were performed in humic acid extraction. A 5 g of rice straw compost sample was mixed with 25 mL and 50 mL of 0.5 M sodium hydroxide, respectively, and were extracted under different extraction periods (1, 3, 5, 7, 9, 12, and 24 hours). There was significant difference in the extraction periods and extractant ratio on the yield of humic acid. This study revealed that an extractant ratio of 1:10 and 12 hours of extraction period are required to extract humic acid from rice straw compost and can be purified within 1 hour using distilled water. Humic acid yield was significantly lower when the extraction period was less than 12 hours because the time was not sufficient for the H+ ions to displace Na+ ions and other cations. Furthermore, the difficulty of HA extraction period of less than 12 hours was probably due to difficulty of wetting the air-dried compost. The significance of this study is humic acid from rice straw compost can be isolated within 12 hour of extraction period, 24 hours of fractionation period and 1 hour of purification period under extractant ratio of 1:10. Thus, this may help in reducing time and costs needed to produce the humate product from this compost. The extractant ratio of 1:10 is more preferred because of the higher humic acid yield obtained.

The study was carried out with the following objectives: (i) to quantify the amount of humic acid (HA) that could be extracted from composted pineapple leaf residue using potassium hydroxide (KOH) produced from pineapple leaf residue, and (ii) to compare the elemental composition, functional groups, and spectral characteristics of HA extracted from composted pineapple leaf using 0.1 M KOH from pineapple leaf and that of analytical grade (0.1 M KOH). The 0.1 M KOH from pineapple leaf residue extracted 20% HA from composted pineapple leaf residue while that of the analytical grade (0.1 M KOH) extracted 30%. The elemental composition (C, H, N, O, and S), functional groups (carboxylic, phenolic OH, and total acidity), and spectral characteristics of the HA extracted using the 2 extractants were generally similar. Potassium hydroxide from pineapple leaves can be used to extract some reasonable amount of HA without appreciably altering the elemental and functional groups constitution as well as the spectral characteristics. The potential of using KOH from pineapple leaf residue in HA studies appears promising.

High resolution PCR-SSP

Production of artificial humic acid from corn straw acid hydrolysis residue with biogas slurry impregnation for fertilizer application

Large lignite reserves are concentrated in the Dnipro lignite basin of Ukraine. It is profitable to extract it by open-pit mining, as the seams are shallow. Ukrainian lignite is predominantly earthy, subbituminous, which in turn is characterized by a high content of free humic acids. Despite the significant lignite reserves in Ukraine and favourable conditions, its production is insignificant. Most of the lignite is used as fuel, and a small part of it is used as raw material. We have studied the lignite of the Oleksandriya deposit of Ukraine, which contains a large amount (about 80 %) of humic acid, which is the basis to produce effective water-soluble sorbents. The article investigates and determines the efficiency of using lignite from the Oleksandriya deposit to produce humic substances, their elemental composition, and the yield of humic acids from them. The efficiency of the use of humic substances obtained from lignite of the Alexandria deposit in the binding of heavy metal ions (Pb2+, Cd2+) using the method of complexation - ultrafiltration - was determined. The performance of ultrafiltration membranes with a humate solution was determined. The retention coefficient of metal ions, which depends on the concentration of humic substances, was calculated. The conducted studies allow us to assert that the application of the ultrafiltration-complexation method using complexing agents based on humic substances of lignite from the Alexandria deposit can significantly increase the degree of purification of aqueous solutions from heavy metal ions. These studies are relevant and expand the possibilities of using lignite. It has been shown that Ukrainian lignite can be used to produce an environmentally friendly and cheap complexing agent. An important priority for the use of water-soluble humic substances is the large lignite reserves in Ukraine, which can also contribute to improving economic performance. Also, the studies conducted suggest that the application of a combined method that combines ultrafiltration with complexation when using complexing agents based on lignite humic substances can significantly increase the degree of purification from heavy metal ions.

Extraction and purification of humic acids from lignite wastes using alkaline treatment and membrane ultrafiltration

Environmental context Analysis of soil organic matter is important for understanding turnover and stabilisation processes of organic carbon in soils. Capillary electrophoresis is used here to investigate humic acids from soils of diverse forest sites, and show that the patterns of signals are indicative of soil characteristics. The method provides useful information of soil types and complements the existing set of methods for humic acid characterisation. Abstract Analyses of humic substances provide very useful information about turnover characteristics and stabilisation processes of soil organic matter in environmental soil samples. The present study investigates 113 samples of forest soils from three different layers (undecomposed litter (L), if present, mixed samples of F (intermediate decomposed) and H (highly decomposed) organic matter (FH) and upper mineral soil layers (Ah horizon) from 0 to 5 cm) by extracting humic acids (HAs) and recording electropherograms. Five signals of these electropherograms were evaluated and correlated with basic parameters from soil (organic carbon, Corg, and total nitrogen, Nt, and extraction yields of HAs) and HAs (total carbon, Ct, and Nt), and with signals from photometry, mid-infrared and fluorescence spectroscopy. The developed method was able to separate HAs from different soil layers by calculating a discriminant function based on the five evaluated electrophoretic signals. The dataset of this work opened the opportunity to correlate the observed electrophoretic signals with the other determined soil parameters and spectroscopic signals. This can be seen as a very important step in the direction to assignments of the obtained electrophoretic signals. Soil characteristics were reflected quite well by this method and, combined with the other approaches, it is suitable for applications in further studies.

Lignocellulose hydrothermal artificial humic acid production: Reaction parameters screening and investigation of model/real feedstock

A clean and efficient conversion process is essential for the utilization of low-rank coals. Lignite, a typical representative of the low-rank coal family, has huge potential for the production of valuable chemicals via the oxidative depolymerization reaction. Ruthenium ion-catalyzed oxidation (RICO) is an effective route for lignite depolymerization under mild conditions, but the high cost of precious Ru limits the potential large-scale application of RICO. How to recycle and reuse Ru is critical to promote the application of RICO. In this work, a novel and efficient approach for reusing Ru through recycling the solvent mixture containing Ru was established for RICO. First, the influence of different reaction parameters on the depolymerization degree of lignite and benzene polycarboxylic acid (BPCA) yields was investigated. Second, the distribution of Ru in the organic phase (OP), aqueous phase (AP), and residual solid phase (RSP) was analyzed after the RICO reaction. Finally, based on the distribution of Ru in different phases, a novel route of recycling Ru by reusing the Ru-containing solvents was proposed. The results showed that the dosage of RuCl3 and NaIO4 had a significant influence on both the depolymerization degree of lignite and BPCA yields. The distribution of Ru had a close relationship with the depolymerization degree of lignite and the dosage of NaIO4. After the depolymerization reaction, the CCl4 phase containing Ru was reused directly as the solvent for the next run, which could fulfill the reuse of both CCl4 and Ru. The results proved that the Ru-containing CCl4 phase could maintain catalytic performance for 5 runs. This work provides an efficient route to reuse Ru for the RICO depolymerization of lignite into valuable organic acids. As far as we know, this is the first report concerning the recycling and reuse of Ru during the RICO of lignite. This work is important for the application of RICO in lignite depolymerization.

Biochar (BC) and humic acid product (HAP) soil amendments may improve plant performance under water-limited conditions. Our aim was to investigate if BC and HAP amendments, alone or in combination, will have positive and synergistic effects. A three-factorial fully randomized study was carried out in the greenhouse for 66 days, including the factors ‘BC’, ‘HAP’ and ‘water regime’. Maize (Zea mays var. ‘Amadeo’ DKC-3399) was grown in pots (6 kg sandy soil pot−1) amended with/without BC (0, 1.5 and 3 %; w/w) and with/without HAP (0 or an equivalent of 8 kg ha−1). Two water regimes, limited and frequent (H2O limit , H2O frequ ), were applied after day 28 following seedling establishment at 60 % water holding capacity (WHC). In the H2O limit treatment, the soil water content was allowed to drop until wilting symptoms became visible (25–30 % WHC) while in H2O frequ the WHC was brought to 60 % of the maximum on a daily basis BC but not HAP, added alone or in combination with BC, significantly increased the biomass yield and the water and N use efficiency of plants at both water regimes. The BC-mediated relative increase in the yield was equal with both watering regimes, refuting initial hypotheses. BC had generally a stimulating effect on water relations and photosynthesis, it increased the relative water content and the leaf osmotic potential, decreased the stomatal resistance and stimulated the leaf gas exchange (transpiration). Both, BC and pure HAP addition, stimulated photosynthesis by increasing the electron transport rate (ETR) of photosystem II (PSII) and of the ratio between effective photochemical quantum yield to non-photochemical quenching (Y(II)/Y(NPQ), revealing reduced heat dissipation. Biochar use in poor sandy soils can improve plant growth by improving soil-plant water relations and photosynthesis under both H2O frequ and H2O limit conditions. HAP loading, however, did not improve the effect of biochar or vice versa.

In order to obtain regenerated humic acids from bituminous coals, six kinds of coals-Takamatsu (C: 75.7%), Onoura (C: 80.1%), Miike (C: 82.3%), Hashima (C: 85.0%), Shin-omine (C: 87.1%) and Nishikawachi (C: 89.5%) were oxidized with nitric acid under various conditions. In the case of Miike coal, a maximal yield of humic acid (based on original coal) was obtained at the oxidation time about 14 hours with 1 normal nitric acid and about 6 hours with 2 normal nitric acid at 100°C. On the oxidation of bituminous coals with 2 normal nitric acid in 5 hours at 100°C, the yield of humic acids depended upon the rank of coals. Under these conditions coal containing about 84% carbon gave a maximal yield of humic acid. To prepare humic acids in good yiels from coals of the higher rank, it was necessary to employ the more drastic oxidation conditions.Carbon, hydrogen and nitrogen contents, neutralization equivalent weights and cadmium ion uptakes of humic acids that regenerated from bituminous coals were determined.

Humic substances (HS) are organic matters formed during the physical, chemical and microbiological transformation process of dead tissue of animal and plant. It is present ubiquitously in soil, sediments and aquatic environment. HS contain carbon, hydrogen, oxygen and nitrogen with small amount of sulfur. These elements are always present regardless of their origin and country. The macromolecular structures of HS are highly sensitive to different chemical conditions of solution. Their reactivity in an environment depends on the functional groups, macromolecular structure and concentration. HS exhibit dual aspects. The presence of Humic Acid (HA) in a water supply is undesirable as they raise total organic pollution level, colour intensity, distinct absorbing capacity and chemical activities. They have capability to induce cytotoxicity for many mammalian cells and are cause factor of many diseases. On the other hand specific properties of HA products enable their application in agriculture, industry, environment and biomedicine.