Structure Of Fulvic Acid Research Articles

Evolution from basic to advanced structure of fulvic acid and humic acid prepared by food waste

Fulvic acid (FA) and humic acid (HA) are common polyacids in nature. However, the evolutionary process of their basic and advanced structures is still unclear. FA and HA were separated into five molecular weight components to investigate the process of evolution from small to large molecules. The primary structure analysis showed that FA were rich in CN, COOH and OH content, while HA were rich in (CH2)n, NH2 and CC. Moreover, with the molecular weight increasing, the structures could complement each other to maintain the hydrophilic or hydrophobic balance. The 2D-COS spectroscopy demonstrated that during the growth of FA, COOH, NH2 and OH firstly respond. On the other hand, during the growth of HA, NH2 and (CH2)n firstly respond. In addition, advanced structure of FA was affected by intramolecular hydrogen bonds and π − π interaction. HA was affected by hydrophobic interactions due to the abundance of hydrophobic groups, primarily (CH2)n and benzene rings. 3D conformational fitting and particle size characterization confirmed that the interaction forces determine that FA and HA become tightly and loosely molecules respectively. This study is to further explore the geochemical formation and evolution process of FA and HA molecules.

Preparation and Molecular Structural Characterization of Fulvic Acid Extracted from Different Types of Peat.

Humic acid is a type of polymeric, organic weak acid mixture with a core aromatic structure and main-component oxygen-containing functional group. Fulvic acid is a type of humic substance that can be dissolved in acid, alkali, or water. This study discusses the influence of different peptides on the molecular structure of fulvic acid, which was extracted from herbaceous, woody, and mossy peats using alkaline dissolution and acid precipitation methods. Analyses using infrared, UV-Vis, 13C-NMR, and X-ray photoelectron spectroscopies, as well as X-ray diffraction (XRD), were conducted to compare the effects of different peat types on the content and molecular structure of fulvic acid. The woody peat fulvic acid content was the highest among all peat fulvic acids (0.38%). However, the yield of fulvic acid from herbaceous peat was the highest (2.53%). Herbaceous peat fulvic acid contains significant quantities of carbonyl, amino, methylene, carboxyl, and phenolic hydroxyl groups and ether bonds. Woody peat fulvic acid contains carbonyl and methoxy groups, benzenes, aromatic carbons, aromatic ethers, and phenols. The degree of aromatization of woody peat fulvic acid was the highest. Mossy peat fulvic acid contains high levels of hydroxy, methyl, methylene, and phenol groups and aromatic ethers. The structural differences in fulvic acids in the different types of peat were primarily manifested in the content of functional groups, with little influence from the types of functional groups. XRD analysis of the different peats revealed that their structures all comprised benzene rings. However, mossy peat contained more C=O and -COOH groups, whereas herbaceous peat contained more C-O groups.

Effect of microbial pretreatment on degradation of food waste and humus structure

The study aimed to investigate the pretreatment characteristics of food waste (FW) by Bacillus licheniformis and Bacillus oryzaecorticis, and to determine the contribution of microbial hydrolysis in the structure of fulvic acid (FA) and humic acid (HA). FW was pretreated with Bacillus oryzaecorticis (FO) and Bacillus licheniformis (FL), and the resulting solution was heated to synthesize humus. The results showed that the acidic substances produced by microbial treatments led to a decrease in pH. In addition, Bacillus oryzaecorticis degraded starch and released a large amount of reducing sugar, providing OH and COOH to FA molecules. Bacillus licheniformis showed a positive effect on the HA structure, which had higher OH, CH3 and aliphatics. FO is more beneficial to retain OH and COOH, while FL is more beneficial to retain amino and aliphatics. This study provided evidence for the application of Bacillus licheniformis and Bacillus oryzaecorticis in waste management.

A Sandwich Structure of Fulvic Acid and PMIDA-Modified LDHs for the Simultaneous Removal of Cu2+ and Aniline in Multicomponent Solutions

The coexistence of organic and inorganic pollutants in industrial wastewater has emerged as a concerning environmental issue worldwide due to the critical levels of biological toxicity of these pollutants. In this context, the present study proposes a sandwich structure of fulvic acid and PMIDA-modified LDHs (FA/PMIDA-LDHs) for the simultaneous removal of Cu2+ and aniline from wastewater. The specific structure was synthesized using a combination of coprecipitation and impregnation methods. Abundant benzene rings and oxygen-containing functional groups greatly increased the number of sites for the adsorption of both Cu2+ and aniline. The maximum adsorption capacity of Cu2+ and aniline in solution with initial pH 5.0 at 25 °C could reach 221.24 and 132.28 mg/g, respectively. Cu2+ could be chelated by the functional groups in the FA/PMIDA-LDHs structure, and a coupled reduction-complexation mechanism was proposed for this process. The uptake of aniline on FA/PMIDA-LDHs was demonstrated to be a result of the combination of coordination forces, hydrophobic effects, π-π interactions, and hydrogen bonds. In a multicomponent solution, FA/PMIDA-LDHs exhibited excellent salt tolerance of up to 1000 mg/L of Na+ or Ca2+. The effects of Fe3+, Ni2+, Cl-, Cr2O72-, SO42-, and H2PO4- on the uptakes of Cu2+ and aniline were also investigated.

Peran Senyawa Asam Fulvat dari Air Gambut terhadap Produktivitas Gas Hidrogen dengan Metode Elektrolisis

Wetlands water is water formed from the breakdown of organic substances found in peatlands. In general, wetlands water has acidic properties (pH<7), besides that the constituent compounds are humic substances, which consist of humic acid, fulvic acid and humin. Of the three acids that can react with air, namely fulvic acid, because this acid can react with all conditions, whether acidic, neutral or alkaline. Meanwhile, humic acid can only react with air in alkaline conditions. So, this research discusses the role of fulvic acid in H2O bonds to produce hydrogen by electrolysis. In the structure of fulvic acid which has an aromatic ring, where the aromatic ring can produce a magnetic field, so that the aromatic ring on the fulvic acid can resonate. The resonance reaction of deep fulvic acid can induce and weaken the H2O bond by attracting oxygen atoms in the H2O bond, because atoms have paramagnetic properties where these atoms can be weakly attracted by magnets, so that the H2O bonds become weak and can be easily reduced to hydrogen gas. fulvic acid, there are several other compounds contained in peat water and also help in the attenuation of H2O, namely K, Ca, Na, Fe, Mg, and Al compounds, where these compounds can react with H2O and produce H2. From the results of research conducted, the volume of hydrogen gas produced was 62.7 mL with a power consumption of 7.7-6.0 watts and the resulting current reached 0.64-0.5 amperes for 11 minutes of electrolysis time.

Effects of sulfuric acid pretreatment and liquid acids precipitation on the structure of fulvic acid extracted from peat

To achieve high-value utilization of peat, the process of coupling methane fermentation and extraction of fulvic acid was explored and the effects of sulfuric acid pretreatment before methane fermentation and different liquid acid precipitation on the spectral characteristic of fulvic acid was studied. The fulvic acid precipitated by nitric acid has a high content and a high degree of aromatization. The highest yield of fulvic acid samples is precipitated by phosphoric acid. The fulvic acid extracted from the residues after sulfuric acid pretreatment methane fermentation descends of yield while content increase. Meanwhile, methane fermentation would consume methyl, hydroxyl, and carboxyl groups without benzene rings consumed. In addition, sulfuric acid pretreatment would promote this process and consume more functional groups to produce more methane. The research results show that coupling methane fermentation of peat and extraction of fulvic acid is feasible, and the sulfuric acid pretreatment has a significant effect to fulvic acid. To sum up, sulfuric acid pretreatment would promote methane fermentation process and degrade more fulvic acid.

Degradation of refractory organic contaminants in membrane concentrates from landfill leachate by a combined coagulation-ozonation process

Landfill leachate is a typical refractory wastewater for which research into rapid and efficient treatment methods has become very topical. In this study, a coagulation-ozonation process was developed to treat the concentrate arising from membrane treatment of landfill leachate. The effect of coagulant type and initial pH on treatment efficiencies was investigated. Results showed that many of organics were effectively removed in the coagulation process. Thereafter, ozone was applied to further treat the coagulation-resistant organic substances. Our results revealed that the degradation rate of these coagulation-resistant substances followed the trend (color number) CN > (light absorbance at 254 nm) UV254 > (chemical oxygen demand) COD, and the residual coagulation-resistant substances were oxidized rapidly in the ozone process. Ozone first destroyed the molecular structure of fulvic acid and the by-products generated, such as protein-like substances. In addition, the molecular weight, organic condensation degree, and concentration of benzene ring compounds were considerably decreased. Moreover, the macro molecular organics (i.e., humic acid and fulvic acid) within the size range 1–100 kDa were effectively degraded and partially transformed into bicarbonate. Overall, the combined coagulation-ozonation process reduced COD, UV254, and CN in the landfill leachate concentrate by 88.32%, 94.37%, and 98.83%, respectively, and thus the biodegradability of the treated leachate also was significantly improved. This excellent performance proved the feasibility of the combined coagulation-ozonation process for the removal of recalcitrant organic substances contained in landfill leachate concentrate, benefiting subsequent biological treatment.

Paramagnetic Properties of Humic Substances in Taiga and Tundra Soils of the European Northeast of Russia

The study of paramagnetic activity of humic substances in taiga and tundra soils of the Komi Republic and the assessment of the influence of soil hydromorphism on concentrations of free radicals in the structure of humic acids (HAs) and fulvic acids (FAs) have been performed. The concentration of free radicals in HA specimens was up to 11 times higher than that in FA specimens due to a higher content of aromatic and other condensed structures in HA molecules. This fact attests to the high capacity of HAs to polymerization and complexation reactions with participation of radicals. The average value of g-factor is higher for FA specimens than for HA specimens, which attests to a greater electron density shift of unpaired electron to oxygen atom in the structure of FAs because of its spin-orbital interaction with oxygen-containing functional groups, the concentrations of which are significantly higher in FAs than in HAs. An increase in the concentration of free radicals in the molecular structure of HAs is observed in taiga soils with an increase in the degree of their hydromorphism (from automorphic to semihydromorphic soils), which is related to the biohydrothermal conditions of humus formation in bog-podzolic soils with retarded biochemical processes and low degree of plant litter humification. As a result, HAs with the high content of free radicals in their structure are formed. An opposite situation is observed for HAs in tundra soils with a decrease in the content of unpaired electrons under conditions of the increased hydromorphism. The difference in the character of changes in the paramagnetic activity of HAs in taiga and tundra soils with different degrees of hydromorphism may be related to different natures of plant residues participating in humification processes. A tendency for a decrease in the paramagnetic activity in both HAs and FAs from the south to the north is observed, which may be related to a general decrease in the content of poly-conjugated systems in the structure of humic substances in tundra soils.

The content of fulvic acids in the primary effluent at the Płaszów WWTP in Kraków

Municipal wastewater contains significant amounts of organic substances of both natural and anthropogenic origin. Wastewater treatment removes most of contaminants, however new substances are formed as a result of biochemical changes taking part during the treatment process; some of them remain in the final effluent and may pose a threat to life and health of living organisms. Humic substances (HS), which include soluble fulvic acids (FA) are contaminants commonly found in wastewater. This is why the research attempted to examine the content of fulvic acids in mechanically treated wastewater at the Płaszów Wastewater Treatment Plant (WWTP) in Kraków. The study was conducted to assess the quantities of the pollution load coming to the plant. FA were separated (isolated) at a hydrophobic ion exchanger, and then subjected to qualitative analysis to determine their elemental composition and degree of contamination with metals and other substances. Studies were also conducted in the infrared spectrum to determine the effects of internal structure of fulvic acids. Humic acids (HA) are precursors of chloroorganic compounds and other carcinogenic, mutagenic and teratogenic substances in oxidation and disinfection processes. Therefore the problem of FA in the final effluent is important, because of their amount and location of a wastewater discharge point.

ОЦЕНКА ИЗМЕНЕНИЙ В СОСТАВЕ ФУЛЬВОКИСЛОТ ПОСЛЕ МЕХАНОАКТИВАЦИИ ТОРФА С ПОМОЩЬЮ МЕТОДОВ ИК- И ПМР-СПЕКТРОСКОПИИ

By methods of IR- and PMR-spectroscopy has showed that a reconstruction in the structure of fulvic acid after the mechanoactivation of peat associated with the change of functional groups in their composition – increases the number of oxygen-containing groups and unsubstituted aliphatic structures. Besides, an extractive yield of fulvic acids increases in 40–60% as a result of mechanoactivation of peat.

QSPR for predicting chloroform formation in drinking water disinfection

Chlorination is the most widely used technique for water disinfection, but may lead to the formation of chloroform (trichloromethane; TCM) and other by-products. This article reports the first quantitative structure–property relationship (QSPR) for predicting the formation of TCM in chlorinated drinking water. Model compounds (n = 117) drawn from 10 literature sources were divided into training data (n = 90, analysed by five-way leave-many-out internal cross-validation) and external validation data (n = 27). QSPR internal cross-validation had Q 2 = 0.94 and root mean square error (RMSE) of 0.09 moles TCM per mole compound, consistent with external validation Q2 of 0.94 and RMSE of 0.08 moles TCM per mole compound, and met criteria for high predictive power and robustness. In contrast, log TCM QSPR performed poorly and did not meet the criteria for predictive power. The QSPR predictions were consistent with experimental values for TCM formation from tannic acid and for model fulvic acid structures. The descriptors used are consistent with a relatively small number of important TCM precursor structures based upon 1,3-dicarbonyls or 1,3-diphenols.

Structural characterization of fulvic acids, extracted from sewage sludge during composting, by thermochemolysis–gas chromatography–mass spectrometry

Thermochemolysis coupled with gas chromatography and mass spectrometry were applied to determine the chemical structure of fulvic acids (FA) extracted from a sewage sludge and straw mixture at different steps of composting. The FA starting structures were composed mainly of mono-, di- and tri-methoxy (alkyl) benzoic acids representing lignin derivatives in an advanced stage of oxidation, as well as of methylated polyphenols and a series of fatty acids saturated C15, C16, C18, unsaturated and branched C18:1. Besides, there are many unidentified structures suspected to be N-containing compounds. During the composting process, the fate of the three structural typical monomer units of lignin was followed. The p-hydroxyphenyl units showed a strong relative decrease especially at the beginning of composting. The guiaicyl units showed a steady increase in course of composting. A relative decrease of syringyl units was noted at the beginning of composting, but they then relatively increased towards the end of composting. These changes support the formation during composting of more oxidized units. All subunits composing the fulvic acid structures have been subdivided into main five groups of similar chemical structure. The lignin-like C6–C3 subunits showed a relative decrease during composting attributed to microbial oxidation, but there was a relative increase during the intermediate step of composting related probably of an enhancing of lignin solubility. The C6–C1 subunits were reduced at the beginning of composting, which mainly attributed to the oxidation of 4-methoxybenzaldehyde to hydroquinones derivatives under the composting conditions. Although, the relative increase of these subunits (C6–C1) at the end of composting originates from oxidation of C6–C3 lignin side-chains or could be partly attributed to microbial neosynthesis. The unidentified N-containing compounds increased strongly during course of composting. The rise in the level of fatty acids at the beginning of composting is attributed to an increase of branched-chain fatty acids such as C18:1 commonly used as bacterial biomarkers. Their amounts were greatly reduced at the end of composting. Both the Shannon–Weaver and similitude indices show a relative increase in structural diversity at the start of composting conditions following the appearance of hydroquinone derivatives and unidentified nitrogen compounds in the FA network. But, the produced FA structure reaches a certain level of homogeneity at the end of composting through self-polycondensation or recombination of C6–C1 subunits and hydroquinones derivatives with N-containing compounds.

Theoretical study on fulvic acid structure, conformation and aggregation: A molecular modelling approach

The ubiquitous presence of humic substances (HS), combined with their ability to provide multiple sites for chemical reaction, makes them relevant to numerous biogeochemical processes such as mineral weathering, nutrient bioavailability, and contaminant transport. The reactivity of HS depends on their functional group chemistry and microstructure, which are in turn influenced by the composition of the surrounding media. In order to help towards an understanding of structure conformations and aggregation process of HS in soils and waters and to get a better knowledge of these kinds of materials, a fulvic acid (FA) has been modelled as a function of its ionic state under different conditions. Our proposed theoretical model based on the Temple-Northeastern-Birmingham (TNB) monomer fits well with experimental observations on the solubility (dipolar moment) and electronic and vibrational spectra of FAs. The presence of water molecules has a great stabilization effect on the electrostatic energy; this effect is greater as ionized rate increases. In vacuum, the non-ionized aggregated species are more stable than monomers because of the increase in their interaction due to H-bonding and non-bonding forces. When the molecules are ionized, no aggregation process takes place. In solution, the FA concentration is a critical factor for the aggregation. The system containing two FA molecules probably did not form aggregates because its equivalent concentration was too low. When the concentration was increased, the system gave rise to the formation of aggregates. The ionic state is another critical factor in the aggregation process. The ionized FA has a higher electric negative charge, which increases the energetic barriers and inhibits the approximation of FA caused by the Brownian movement.

Structural characterization of fulvic acids during composting of sewage sludge

Changes occurring in the chemical structure of fulvic acids extracted from composted sewage sludge at different times of treatment were investigated by various chemical methods (elemental analysis, Fourier transform infrared and carbon-13 nuclear magnetic resonance). The starting material was composed of aromatic structures, carbohydrates, polyalcohol or polyacid alkyl side-chains. During the stabilisation phase of composting, microbial metabolism seems to begin by the decomposition of aliphatic alcohols or acids shown by a decrease of absorbance around 1136 cm −1, a resonance in C-alkyl and carboxyl areas. In parallel, structures with anomeric, cetal or ketal carbons and aromatic compounds around 102, 130–160 ppm respectively, were preserved or yielded from microbial decomposition. At the end of composting, the increase of resonance around 32 and 174 ppm in the NMR spectra and the increase of absorbance around 1142 cm −1 in the FTIR spectra suggest the presence of ester/ether linkages and neoformation of alkyl ethers/esters. The latter structures could be considered as new constituent moieties incorporated during humification, rather than compounds somehow trapped in the fulvic acid structures. The end product exhibits more aromatic and polycondensed structures, which are chemically and biologically more stable and less reactive than the starting material.

Fulvic acid enrichment in the microlayer of the Gerlache Inlet Sea (Antarctica): preliminary results

The aim of this work was to study the presence of fulvic acids in Antarctic waters, as they appear to be principal film-forming components in the surface microlayer. We obtained a series of samples during two Antarctic Italian Expeditions in 1998/99 and 2000/01 and studied the distribution and the structural differences between fulvic acids extracted from both microlayer and subsurface waters. Fulvic acids are concentrated in the microlayer and the enrichment factor between microlayer and subsurface water differs between samples. The enrichment factor values for fulvic acids lie between those found for dissolved organic carbon (DOC) and particulate organic carbon (POC) in the literature. Fulvic acids extracted from the microlayer were found to be different in structure from those present in the subsurface layer and enriched in sulphur content. We hypothesised that sulphur-containing compounds are slightly bound and/or occluded in fulvic acid structures. The sulphur-containing compounds analysed in the microlayer could be dimethylsulfide (DMS) and/or its products stemming from photochemical and biological oxidation reactions.

Molecular structure of fulvic acids by electrospray with quadrupole time-of-flight mass spectrometry.

Characterisation of the molecular structure of aquatic fulvic acids (FA) has been performed using a quadrupole time-of-flight (Q-TOF) mass spectrometer equipped with an electrospray ionisation interface. Molecular masses centred around 450 Da and sinusoidal spectral distributions have been obtained for all fulvic acids. Tandem mass spectrometry (MS/MS) experiments showed losses of 18 Da (H(2)O) and 44 Da (CO(2)), and possible molecular structures were determined for the first time to our knowledge. A methodology is reported for evaluating the average elemental composition of FA from high-resolution mass spectra by processing post-acquisition data calculations using molecular size distributions and atomic compositions of ions. The results are found to be consistent with elemental analysis data.

Mechanism study of the coagulant impact on mutagenic activity in water

Both gas chromatography/mass spectrometer (GC/MS) and Ames test results were used to study the Al 2(SO 4) 3 and FeCl 3 coagulation and sedimentation effluents in a pilot plant. Based upon the molecular structure of fulvic acid and the mechanism of organics coagulation, the authors propose a mechanism for fulvic acid adsorbing mutagenic organics in water. When the coagulant is fed into water, the metal ions will combine with fulvic acid to form complexes, this releases the organics and mutagen which are adsorbed and complexed by fulvic acid and results in an increase of mutagenic activity in the effluent. In addition, according to the principle of fulvic acid to generate free radicals and the chemistry of Fe 3+, the authors discuss the impact of two coagulants on the generation of mutagenic activity. It is indicated that Fe 3+ catalysing the reaction for fulvic acid to produce free radicals is the reason that the mutagenic activity in FeCl 3 coagulation and sedimentation effluent is higher than in Al 2(SO 4) 3 effluent.

95/05594 Peat humic and fulvic acid structure analysis by 13C-NMR-spectroscopy method

95/05594 Peat humic and fulvic acid structure analysis by 13C-NMR-spectroscopy method

Study on the structure of fulvic acid from weathered coal using modified sodium dichromate oxidation and GC-MS

Study on the structure of fulvic acid from weathered coal using modified sodium dichromate oxidation and GC-MS

A Multi Method Approach to Study Humic Compounds and Metal Speciation in Marine Sediment Samples

Abstract A multi-method experiment was carried out to study humic compounds and metal speciation in a marine sediment sample. The humic and fulvic acid structures were investigated by infrared spectrometry,13 C NMR, thermogravimetry, and elemental analyses. Trace metals (Cu, Pb, Cd, Zn, Fe, Cr, Ni, Co, Mn and Al) were determined in digests of the sample and in solutions obtained by selective extraction procedures. The distribution of metals associated with humic substances has also been investigated by high pressure liquid chromatography using inductively coupled plasma atomic emission spectrometer as detector. The results show that manganese, iron and aluminum are present in inorganic form, whereas 37% of nickel and 8.8% of copper are present in the metal-humic compound form.