Characterization Of Fulvic Acids Research Articles

Characterization of fulvic acids contained in municipal sewage purified with activated sludge

Characterization of fulvic acids contained in municipal sewage purified with activated sludge

Extraction and characterization of fulvic acid from corn straw compost by alkali solution acid precipitation

The effective utilization of corn straw is a challenge. Extracting fulvic acid from corn straw compost improves the utilization rate of corn straw, reduces the use of chemical fertilizers, and supports sustainable agricultural development. By the response surface, the best alkali solution acid precipitation extraction conditions were obtained, which involved a KOH concentration of 9.67%, a reaction temperature of 100.32 °C, a reaction time of 9.91 h. Through the Fourier transform infrared spectroscopy (FTIR), it found that BFA contained more oxygen-containing functional groups than MFA, such as those in aliphatic, hydroxyl, ketone and carbonyl groups. Compared to the MFA, the BFA included more types of hydrogen and showed a looser superficial structure. The average molecular model of BFA was constructed with the formula C17H16O7 (M=332). BFA has a lower molecular weight than MFA, which should ensure that BFA is readily absorbed and used by crops. BFA promoted the growth of rice seeds effectively, and the optimal BFA concentration for seed germination was 0.4%. In this study, corn straw composting was used as the main object. The molecular structure of BFA extracted from corn straw compost was established by the alkali solution acid precipitation method. It confirmed that BFA could replace MFA as a biorenewable, environmentally friendly agricultural product.

Deciphering the Composition of Fulvic Acids from Recirculating Aquaculture Systems by Quadrupole Time-of-Flight Mass Spectrometry

The constant reuse of waters in recirculating aquaculture systems (RAS) together with the continuous addition of organic matter from fish degradation components, faeces and non-consumed feed promote the accumulation of dissolved organic matter (DOM), particularly of fulvic acids (FA), leading to the yellow discoloration of their waters. The accumulation of these acids in RAS can have potential effects on its water quality, and consequently fish health and welfare. Thus, the characterization of FA is paramount for improving water quality, and subsequently fish productivity in RAS. In this study, a non-targeted analysis by quadrupole time-of-flight mass spectrometry (QTOF-MS) was used to characterize the recirculating aquaculture systems fulvic acids (RASFA) and then compare their molecular fingerprints with actual reference standards of fulvic acids (FA) (Suwannee River; SRFA, Elliott soil; ESFA and Pahokee Peat; PPFA) purchased from the International Humic Substance Society (IHSS). The results of this study demonstrated the applicability of QTOF-MS as a rapid and comprehensive screening technique to characterize the FA fraction of DOM from RAS and to monitor differences in their molecular fingerprints when compared with other FA samples (SRFA, ESFA and PPFA). The QTOF-MS data from SRFA and ESFA standards matched the list of formulas obtained by 17 high-resolution mass spectrometry (HRMS) instruments with 90 and 76% accuracy, respectively, which guaranteed the power of QTOF-MS without the need for further coupling to liquid chromatography (LC). RASFA was found to be rich in low- and high-oxygen unsaturated classes of compounds (lowOC: 61.73% and highOC: 19.28%) and was similar in composition to SRFA. On the contrary, the ESFA and PPFA soil standards consisted mainly of aliphatic compounds (36.77 and 55.74%, respectively) and differed significantly in composition from the RASFA and SRFA water samples. RASFA matched with 66% of the elemental compositions obtained from the DOM of makeup waters analyzed in a previous experiment, indicating freshwater and seawater origins with a high fraction of terrestrial-derived organic matter (Tanimoto score: 0.53 between RASFA and SRFA). The unique information obtained from the molecular-level analysis of FA samples by QTOF-MS highlights the importance of this technique to characterize and compare FA from different origins rendering it possible to track the FA compositional changes along the water treatment processes of RAS. To our knowledge, this is the first study that characterizes the molecular fingerprints of the RASFA by QTOF-MS and compares them with the available FA reference standards from IHSS.

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.

Evident variations of fungal and actinobacterial cellulolytic communities associated with different humified particle-size fractions in a long-term fertilizer experiment

Cellulose is the dominant form of carbon (C) existing in arable soils, however the ecology of its degradation in soil is still relatively poorly understood. Here, community abundance and composition of fungal and actinobacterial cellulolytic genes (cbhI and GH48) from glycoside hydrolase family 7 and 48 together with characterization of fulvic acid (FA) and humic acid (HA) determined by cross polarization magic angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy were explored in five soil particle-size fractions (large macroaggregate, coarse sand, fine sand, silt and clay), collected from a 33-yr mineral and organic fertilizer experiment. The results revealed the significant effects of particle-size fraction and fertilization on the distribution of soil humus and cellulolytic microbial community abundance. Strong correlations were detected between C content and structure of soil humus with cellulolytic microbial abundance. Generally, larger fractions (>63 μm) especially fine sand, which showed a lower degree of humification with higher aromaticity, lower HA/FA ratio, aliphaticity and alkyl/O-alkyl ratio of HA, were associated with greater abundance of cellulolytic microbes. However, smaller fractions (<63 μm), especially the clay fraction, showed lower cbhI and GH48 gene abundances with a greater degree of humification indicated by 13C NMR spectra. Phylogenetic analysis of the obtained nucleotide sequences revealed undiscovered sequences of both fungal and actinobacterial cellulolytic microbes. However, no clear clustering of sequences from particular particle-size fraction or fertilizer treatment was observed, even though combined application of chemical fertilizer and manure significantly increased cellulolytic gene abundances.

Synthesis, Characterization of Fulvic Acid–Poly(Methylmethacrylate) Graft Copolymers Based on Surface-Initiated Atom Transfer Radical Polymerization and its Effect on Performance of Poly(Lactic Acid)

ABSTRACTFulvic acid–poly(methylmethacrylate) graft copolymers were synthesized by surface-initiated atom transfer radical polymerization with fulvic acid. The result demonstrated that the hydrophobicity of fulvic acid–poly(methylmethacrylate) was improved after modification by surface-initiated atom transfer radical polymerization. Furthermore, poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites were prepared to improve the performances of poly(lactic acid) by blend melting. Compared to poly(lactic acid) with Xc of 5.38%, the Xc of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was 19.94%. Moreover, the impact strength of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was increased by 5.19% compared to poly(lactic acid). In all, this study provided an effective and feasible method for optimizing interface performance and enhancing the thermal stability of poly(lactic acid).

Characterization of fulvic acids by liquid chromatography-quadrupole time-of-flight mass spectrometry

Fulvic acid standards from Suwannee River, Pony Lake, Elliot Soil, Waskish Peat, and Nordic Reservoir were characterized by liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) operating in negative electrospray ionization mode. The method employed a commercially available stationary phase that resulted in a distinctive chromatographic peak for each of the fulvic acid samples that differed in width and retention time at peak maximum. The QTOF-MS, operating in TOF mode, revealed that the unique chromatographic peak shapes were the result of the relative fraction of hydrogen and oxygen contained in various fulvic acid components. Those species that contained larger amount of hydrogen displayed a larger mass defect and were retained longer on the LC column, indicating reduced polarity. This is supported by a reduction in the degree of fragmentation related to polar functional groups as the mass defect and retention time increased. Lastly, the analysis of even and odd mass (at m/z 1 greater) ion intensity ratios revealed a correlation to the percent nitrogen of the various standards.

Plant Uptake of Iron Chelated by Humic Acids of Different Molecular Weights

Mobilization of iron (Fe) chelated by humic acids (HA) of low (HA10,000) and high molecular weight (HA100,000) fractions and its uptake by plants were investigated in growth experiments with sunflower seedlings. The iron chelates (labeled with 59Fe) contained in dialysis bags (mw. cutoff=3500) were placed in minus iron Hoagland solutions as the Fe source and at the same time fulvic acid (FA), EDTA, and low and high molecular weight HA fractions were added in the solutions as mobilizators. Characterization of FA, HA10,000, and HA100,000 were performed by infrared spectroscopy and chemical analysis, e.g., total acidity, COOH, and phenolic‐OH content. Roots and leaves were harvested, dried, and ground for Fe activity determination. Iron contents and pH in the nutrient solutions were measured before and after treatments. The supply of Fe to the plants was apparently sufficient, because no Fe deficiency has been detected in the test plants but during the whole absorption period, the pH of the nutrient solution was about 4.5. The Fe contents in leaves indicated that part of the Fe was rapidly transported from roots to leaves. Judging from the Fe contents in leaves, it was assumed that the small size HA10,000 and EDTA were the most efficient in affecting transport of Fe from root to leaf tissue. FA, HA10,000, and especially HA100,000 were unable to penetrate the dialysis bags and, hence, were effective in Fe mobilization only after the Fe, dissociated from the Fe‐HA chelate, has passed the dialysis membrane into the nutrient solutions. In contrast, the small size EDTA was expected to have penetrated the dialysis bags, permitting mobilization of chelated Fe by ligand exchange inside the bags, and transporting the Fe to the roots. The results suggested that the humic substances used in this study were able to form with the Fe3+ ion complexes that maintained the iron available to the sunflower plants. In the chemical form of Fe.L, where L was FA o HA, the iron within the bags or in solution or in the roots free space, was available for exchange reactions with the natural sunflower plant chelators for its transport to the leaves.

Spectroscopic Characterization of Fulvic Acid Under Different Cover Crop Systems

Fulvic acids (FAs) are an important dynamic component of soils that may be affected by soil management. Carbon‐13 cross‐polarization total sideband suppression nuclear magnetic resonance (CP‐TOSS 13C NMR) was used to examine the effect of cover crop systems on the characteristics of fulvic acid fractions. FA was isolated from soils with the following treatments: 1) vetch/rye, 2) rye alone, and 3) check (no cover crops) with varying nitrogen fertilizers. Preliminary NMR results indicate that FA from the rye alone system both with and without nitrogen fertilizers contains less aliphatic carbon (0–108 ppm) than that from the other two treatments. Based on the elemental composition analysis result, C∶N ratio of FA from rye alone cover with or without nitrogen fertilizer is lower than FA from vetch/rye cover system. These data suggest that farming systems affect the FA compositions.

Characterization of fulvic acids during olive mill waste composting (Elemental, Thermal and fluorescence analyses)

Elemental analysis, fluorescence spectroscopy and differential scanning calorimetry (DSC) were applied to the study of fulvic acids isolated from different stages during olive mill waste composting. The fulvic extracted acids are characterized by a high nitrogen content and O/C ratio values that may result from the high degree of humification and the synthesis of more condensed humic complexes. This was confirmed by fluorescence spectroscopy in the synchronous-scan mode by the decrease of shoulder intensities at intermediate wavelengths indicating the increase of polycondensation and conjugation of unsaturated structures and the greater uniformity of fluorophores. Fluorescence spectra in the emission, excitation and synchronous modes became simpler with compost maturation. This was confirmed by DSC results which proved the high degree of polycondensation of aromatic nuclei of fulvic acid molecules during olive mill waste composting.

Characterization of fulvic acids by elemental and spectroscopic (FTIR and 13C-NMR) analyses during composting of olive mill wastes plus straw

Elemental, functional and spectroscopic analyses (FTIR, 13C-NMR) were performed to study fulvic acids of composted olive mill wastes plus cereal straw, in order to follow the maturity of the final product during composting. The extracted fulvic acids were characterized by high nitrogen, acidic functional group and phenolic hydroxyl contents that might have resulted from the high degree of humification and the synthesis of more condensed humic complexes. This was confirmed by a decrease of alcoholic and aliphatic structures and an increase of aromatic structures, as shown by the FTIR and 13C-NMR analyses. The results showed that stability of the final product was reached after 12 months of composting and that fulvic acid levels could constitute an additional tool to assess final product maturity and its agronomic value.

High-performance liquid chromatographic fractionation and characterization of fulvic acid

High-performance immobilized metal ion affinity chromatography (HP-IMAC) was used to fractionate humic substances (HS) based on their affinity for the immobilized copper(II) ion using acidic and glycine eluents. The work was carried out with two naturally occurring aqueous fulvic acids and commercially available Suwannee River fulvic acid. The IMAC-fractionated HS were then characterized by reversed-phase high-performance liquid chromatography (RP-HPLC) and size exclusion chromatography. The results showed that the affinity HS fraction eluted first using an acidic pH=2 eluent exhibited a relatively high hydrophilic character, whereas the fraction eluted later using a glycine eluent exhibited both a higher hydrophobic character and larger molecular size. On the other hand, the HS fraction with no affinity for the immobilized copper had low molecular size. The affinity of the HS fraction for copper(II) increased with increasing molecular weight. Based on the composite results of three different HS, it is evident that strong relationships exist between affinity, molecular weight, and hydrophilic/hydrophobic properties during the HP-IMAC fractionation. The results presented here have significance for understanding the nature of chemical interactions at the molecular level between dissolved organic matter and trace metals. IMAC, coupled with other liquid chromatographic strategies, is a promising tool for chemical fractionation and characterization of HS.

Fractionation and characterization of fulvic acid by immobilized metal ion affinity chromatography

Immobilized metal ion affinity chromatography (IMAC) has been used to separate humic substances (HS) based on their affinity for metal ions. The work was carried out with a stream fulvic acid (FA) as a representative HS. The effect of pH and ionic strength on the retention of HS was investigated, and comparison of different metal ions (Cu 2+, Ni 2+, Co 2+ and Cd 2+) for IMAC of HS was examined. pH dependence of retained HS and retention volume, and salt-promoted complexation were found; these results are similar to those reported for some proteins using IMAC in previous studies. The HS binding capacity and retention volume in four metal ions studied for IMAC were in the order: Cu 2+>Ni 2+>Co 2+>Cd 2+, which agrees with the Irving–Williams series. The HS retained on the Cu 2+-IMAC was eluted with eluent of decreasing pH value, and the fractions collected were characterized by UV–VIS and fluorescence spectra, and fluorescence quenching titration. The results show that HS fractions eluted with lower pH eluent have a higher conditional stability constant ( log K Cu– HS ′ ) for copper(II), red-shifted maximum excitation (Ex) and emission (Em) fluorescence wavelengths (shifted towards longer wavelengths), lower fluorescence (Flu)/absorbance (Abs) ratios, spectral slope and E 265 nm /E 365 nm , indicating that the stronger affinity HS fractions may have relatively higher molecular size and a higher proportion of compounds absorbing and fluorescing at longer wavelength. Based on the results obtained, IMAC appears to be a promising tool for chemical separation of HS. The results will help in the understanding of the nature of HS and their metal binding characterization, and in modelling natural environments.

Characterization of Fulvic Acid by Laser-Desorption Mass Spectrometry

Characterization of Fulvic Acid by Laser-Desorption Mass Spectrometry

The isolation and characterization of fulvic acid and humic acid from river water

Many rivers in New Hampshire are rich in dark brown organic matter from natural sources. Because the interactions between metal ions like Fe 3+ and the organic fulvic and humic acids makes water treatment difficult, we are studying the nature of the organic acids. Fulvic acid was isolated from the B 2 horizon of a Podzol soil obtained at Conway, NH, and fulvic and humic acids were isolated from the Oyster River (Lee, NH) and Jewel Pond (Stratham, NH). The method of isolating the organic matter from water involves new techniques. The oxygen-containg functional groups, carbon, hydrogen, and nitrogen were analyzed for all samples. The fulvic acid and humic acid samples isolated from water are different from each other, but similar to analogous soil samples.