Aromatic Carboxyl Research Articles

Applying synchronous fluorescence and UV-vis spectra combined with two-dimensional correlation to characterize structural composition of DOM from urban black and stinky rivers.

UV-visible spectroscopy and synchronous fluorescence spectroscopy (SFS) combined with two-dimensional correlation spectroscopy (2D-COS) were applied for extracting fluorescence components, tracing organic functional groups, and revealing variations of dissolved organic matter (DOM) in Puhe River. Water samples were collected from the mainstream and two tributaries (Nanxiaohe River and Huangnihe River). DOM in three rivers was composed of protein-like fluorescent (PLF), microbial humus-like fluorescent (MHLF), fulvic-like fluorescent (FLF), and humic-like fluorescent components, which were relative to aromatic groups, phenolic groups, carboxylic groups, and microbial products. The PLF and MHLF were dominated in DOM fractions in the rivers, and the average content of the PLF was the highest in Nanxiaohe River. Humification degree of DOM was the highest in Puhe River, followed by Huangnihe River and Nanxiaohe River. However, molecular mass of DOM in Puhe River was the lowest, followed by Huangnihe River and Nanxiaohe River. Based on the 2D-COS of the SFS and UV-visible spectra, the variation order of DOM fractions in Puhe River was PLF → MHLF → FLF, and the PLF was consistent with the phenolic groups, aromatic groups, and carboxylic groups, but the adverse trend with the microbial products. The variation order in Nanxiaohe River was MHLF → PLF → FLF, and the MHLF was consistent with the aromatic groups, phenolic groups, carboxylic groups, and microbial products. The variation order in Huangnihe River was MHLF → PLF → FLF too, and the PLF was consistent with the carboxylic groups and aromatic groups. The results of the present study demonstrate that UV-visible spectroscopy and SFS combined with 2D-COS are useful methods to characterize structural composition of DOM from urban black and stinky rivers so as to investigate their pollution status.

SYNTHESIS OF PROBE MOLECULES, 6-(DIMETHYLAMINO)-2-PHENYLISOINDOLIN-1-ONES, FOR MECHANISTIC STUDIES OF FIREFLY LUCIFERASE INHIBITION.

Firefly luciferase is used in high-throughput screening based on the detection of chemiluminescence. It catalyzes an esterification reaction of luciferin with adenosine 5'-triphosphate (ATP) followed by decarbonylation with oxygen and concomitance of light. Previously, we reported that firefly luciferase also possesses acyl-CoA synthetase activity and catalyzes an aromatic carboxylic acid group of F-53, using ATP, Mg2+ and coenzyme A (CoA), to produce F-53 covalently attached to active-site lysine-529 residue of firefly luciferase through the formation of an amide group. The amidation of lysine-529 resulted in a deactivation of luciferase. In order to probe firefly luciferase inhibition's mechanism, we synthesized two probe molecules 1 and 2, mimicking F-53. Molecule 1 contains an azido-appended side chain in the aromatic ring of F-53, while 2 possesses an azido and a carboxylic acid group appended side chains. Both synthetic schemes are readily amenable to large-scale syntheses. Molecule 1 was made from 2-allylaniline, which was derived from a thermal-induced aromatic-Claisen rearrangement of N-allylaniline. The azido-appended side chain of 2 was installed from a Horner-Wadsworth-Emmons reaction and the carboxylic acid side chain from a Sonogashira reaction.

The quality of dissolved organic matter extracted at different times from pig compost and its copper binding capacity based on EEM-PARAFAC

Dissolved organic matter extracted from compost tea, can be regarded as alternatives to inorganic fertilizers as well to be used as a washing agent for heavy metal polluted soil. However, the composition and quality of compost tea produced under different extraction time are still unknown. The objective of the current study was set to explore the influence of different extraction time (i.e., 6, 12, and 24 h) on the composition, quality, and copper binding capacity of compost tea originated from pig manure compost. The results indicated that the extraction time obviously influenced the phenolic, aromatic carboxylic, and polycyclic aromatic groups of compost tea. In addition, the compost tea undergo the shorter extraction time (i.e., 6 and 12 h) contained more protein and humic-like compositions. Among the all treatments tested herein, the compost tea produced from 12 h extraction time obviously exhibited higher aromaticity, molecular weight, and humification degree than other two treatments. The highest stability constant value (log KM) was observed for the shortest extraction time, i.e., 6.08. According to the quality measures and copper binding capability, shorter extraction times (i.e., 6 and 12 h) would be suggested for compost tea production from pig manure compost.

Chemical characterization of mountain forest soils: impact of long-term atmospheric deposition loadings (Czech-Polish-German border region).

The composition of lipids in soil offers clues to soil degradation processes due their persistency and selectivity in soil, and close relation to long-term processes in the ecosystem, thanks to their role in cell membranes of organisms. Organic solvent-extractable compounds were recovered from soils collected at two sites differing in the degree of forest damage. Gas chromatography/mass spectroscopy and Fourier transform infrared spectroscopy were applied in order to characterize solvent-extractable lipids. Raman spectroscopy was also applied as it provides distinct advantages for determining the structural order of carbonaceous materials. The organic matter measurement techniques were combined with an established simultaneous multi-element measurement technique. Variations in individual soil horizons from the sites were reflected in the crystallinity of epicuticular waxes, presence of long-chain aliphatic hydrocarbons, concentrations of n-alkanes, saturated and unsaturated fatty acids, dicarboxylic acids, and in the content of aromatic structures, hydroxyl, ester, and carboxylic acid groups. The results are explained by differently transformed organic matter. The concentrations of elements in the soils were also affected by atmospheric depositions, including higher accumulations of arsenic and antimony, and lower contents of natural nutrients. These data have potential to be used as sensitive biogenic indicators of ecosystem damage by long-term atmospheric depositions.

Bio-reduction of ferrihydrite-montmorillonite-organic matter complexes: Effect of montmorillonite and fate of organic matter

Organic matter (OM) is often associated with Fe (hydr)oxides such as ferrihydrite (Fh) in soils and sediments, forming binary Fh-OM complexes. Microbial reduction of Fh results in destabilization of the complexes and mineral/OM transformation. However, little is known about the role of clay minerals in such processes, despite their common co-existence with Fh and OM in natural environments. Here Fh-OM complexes were synthesized in the presence of montmorillonite (SWy-2), forming ternary Fh-(SWy-2)-OM complexes. A metal-reducing bacterium Geobacter sulfurreducens was used to reduce Fh in the complexes under circumneutral pH and anoxic conditions with or without H2 as extra electron donor. Various spectroscopy and mass spectrometry methods were used to monitor the progress of Fh bio-reduction and mineral/OM transformation. Results showed that G. sulfurreducens utilized mineral-bound OM as electron donor and/or carbon source to couple with Fh reduction. Relative to Fh-OM complex, addition of SWy-2 to Fh-OM complex enhanced the bio-reduction extent of Fh by increasing the proportion of bioavailable OM that was weakly bound to SWy-2. However, its effect on the bio-reduction rate was variable. SWy-2 initially decreased the rate, because it spatially separated OM (electron donor) from Fh (electron acceptor). During later incubation, SWy-2 increased the reduction rate by sorbing biogenic Fe2+ that would otherwise passivate the Fh and cell surfaces. Bio-reduction transformed mineral-bound OM to microbial products (e.g. necromass, extracellular polymeric substances), but organic compounds with aromatic structures, carboxyl groups and large molecular weight were more resistant to desorption and oxidation. The persistence of these compounds against bio-reduction induced transformation is likely due to their stronger binding with minerals and/or lower nominal oxidation states of carbon relative to other compounds. Our results provide new insights into the role of clay minerals in regulating biogeochemical cycling of solid-phase Fe and transformation of mineral-associated OM in anoxic soil environments.

The influence of iodide in corrosion inhibition by organic compounds on carbon steel: Theoretical and experimental studies

The corrosion inhibition by cinnamic, p-coumaric and caffeic acid on carbon steel in 1.0 M HCl and its synergistic combination with KI was investigated using electrochemical and quantum chemical methods. A synergistic effect was observed when 2 mM potassium iodide was added to 0.1 mM inhibitor, where the corrosion inhibition efficiency (IE%) increased from 70% to 80%. In addition, the participation of iodide in the Fe surface was investigated during the adsorption of corrosion inhibitors such as cinnamic, p-coumaric and caffeic acids on Fe(1 1 0). The formation of an iodide monolayer on the Fe(1 1 0) surface was studied by density functional theory (DFT) periodic slab calculations. The DFT results revealed that cinnamic, p-coumaric and caffeic acids were adsorbed effectively on the metal surface through aromatic rings and carboxylic acid groups, as the bond distances with the Fe surface were 2.09 Å for FeC and 1.97 Å for FeO. Low adsorption energies were obtained; −52.90, −44.29 and −33.39 kcal/mol for cinnamic, p-coumaric and caffeic acids, respectively. Additionally, the magnetic moment of the Fe plane was changed significantly if the aromatic carboxylic acid adsorbed onto the metal surface had coating strengths as follows: cinnamic > p-coumaric > caffeic. The present study therefore provides a mechanistic understanding of the role of iodide in the corrosion inhibition process.

Kinetic, Thermodynamic, and Crystallographic Studies of 2-Triazolylthioacetamides as Verona Integron-Encoded Metallo-β-Lactamase 2 (VIM-2) Inhibitor.

Inhibition of β-lactamases presents a promising strategy to restore the β-lactams antibacterial activity to resistant bacteria. In this work, we found that aromatic carboxyl substituted 2-triazolylthioacetamides 1a–j inhibited VIM-2, exhibiting an IC50 value in the range of 20.6–58.6 μM. The structure-activity relationship study revealed that replacing the aliphatic carboxylic acid with aromatic carboxyl improved the inhibitory activity of 2-triazolylthioacetamides against VIM-2. 1a–j (16 mg/mL) restored the antibacterial activity of cefazolin against E. coli cell expressing VIM-2, resulting in a 4–8-fold reduction in MICs. The isothermal titration calorimetry (ITC) characterization suggested that the primary binding 2-triazolylthioacetamide (1b, 1c, or 1h) to VIM-2 was a combination of entropy and enthalpy contributions. Further, the crystal structure of VIM-2 in complex with 1b was obtained by co-crystallization with a hanging-drop vapour-diffusion method. The crystal structure analysis revealed that 1b bound to two Zn(II) ions of the enzyme active sites, formed H-bound with Asn233 and structure water molecule, and interacted with the hydrophobic pocket of enzyme activity center utilizing hydrophobic moieties; especially for the phenyl of aromatic carboxyl which formed π-π stacking with active residue His263. These studies confirmed that aromatic carboxyl substituted 2-triazolylthioacetamides are the potent VIM-2 inhibitors scaffold and provided help to further optimize 2-triazolylthioacetamides as VIM-2 even or broad-spectrum MβLs inhibitors.

Transformation of Corn Stalk Residue to Humus-Like Substances during Solid-State Fermentation

Lignocellulase production from straw fermentation has been widely investigated but the research has neglected to quantify fermentation-derived residue transformation to the humus-like substance (HULIS). To investigate the conversion efficacy of corn stalk residue to HULIS, the amount of HULIS associated with chemical composition and structural changes of humic acid-like substances (HAL) was investigated in a 30 L solid-state fermentation tank during a short period of eight days. The results show that the highest decomposition rate of corn stalk and the highest activity of cellulase, xylanase, and β-glucosidase appeared at the fourth day. At the end of fermenting process, the amount of humic acid-like substances (HAL) and the percentage of HAL in humus acid (PQ value) increased 17.5% and 8.9%, respectively, indicating Trichoderma reesei facilitates the transformation of corn stalk residue to HAL. Fatty acids decreased while aromatic carbon and carboxyl content significantly increased during the ongoing fermentation, which had a positive impact on the HAL thermal stability. The FTIR spectral and thermal analysis revealed an improvement in HAL degrees of condensation, oxidation, and aromatization. The present study suggests that the residue of corn stalks fermented with T. reesei might be a good fertilizer to improve soil characteristics.

Pyrolysis characteristics of soil humic substances using TG-FTIR-MS combined with kinetic models

The incorporation and cycling of pyrogenic organic matter in soil is a potential carbon sink, while the pyrolysis behaviors of soil organic matter are still lacking. Pyrolysis characteristics of soil fulvic acid (FA) and humic acid (HA) were investigated using thermogravimetry combined with Fourier transform infrared spectrometer-mass spectrometer (TG-FTIR-MS) and kinetic models. Four reaction stages corresponding to four pseudo-components were distinguished for both FA and HA. FA exhibited greater transformation contributions of hemicellulose-like and cellulose-like pseudo-components, while HA exhibited greater transformation contributions of lignin-like pseudo-components. Compared to HA, higher levels of heat-resistant aromatic compounds, phenolic groups, and carboxylic groups were recognized in FA. Values of both activation energy (Ea, 246.13–661.40 kJ·mol−1) and pre-exponential factor (lnA, 53.49–107.16 min−1) of FA were greater than corresponding Ea (241.74–466.70 kJ·mol−1) and lnA (51.99–74.36 min−1) values of HA determined by Flynn-Wall-Ozawa method and Distributed Activation Energy Model. The main pyrolysis reaction mechanisms of both FA and HA closely matched with the order-based model corresponding to 2nd and 3rd order random nucleation on an individual particle. The evolved gas species of H2, CH4, H2O, and CO2 were dominant for FA and HA pyrolysis. Generally, the total H2/CO2 and CH4/H2O releases were relatively larger for FA and HA pyrolysis, respectively. TG-FTIR-MS is shown to be an effective method to provide valuable and qualitative analysis of the gaseous volatile species evolved during HS pyrolysis. Findings from this systematic study of soil organic matter responding to pyrolysis will be critical for predicting the changes of soil systems or carbon cycle affected by future climate and fire regimes.

Chemical analysis of Ricinus communis L. (Euphorbiaceace) seed kernel extract and its in-vitro toxicity in two Podagrica Species (Coleoptera: Chrysomelidae)

Since synthetic pesticides are associated with many toxicological problems against untargeted subjects, pesticides from botanical sources become a better option. This study obtained R. communis seed kernel extract (RCSKE) through acidified aqueous extraction. The extract was screened using Infra red (IR) and Ultraviolet (UV) spectroscopy, High-Performance Liquid Chromatography (HPLC) and Cass Chromatography (GC) for bioactive agents. In-vitro effects of RCSKE, chlorpyrifos (CPF) and cypermethrin (CYPER-M) on superoxide dismutase (SOD), Catalase (CAT), acetylcholinesterase (AChE) and Carboxylesterase (CE) activities in Podagrica sjosdteti and Podagrica uniforma were determined spectrophotometrically. The IR and UV of RCSKE majorly depict the presence of aromatic ring, ethylenic bond, carbonyl bond, hydroxyl and carboxylic groups. The HPLC and GC majorly show the presence of ricinoleic acid, ricinine and ricin. The RCSKE, CYPER-M and CPF increased CAT activity in P. sjosdteti , but reduced it in P. uniforma . The RCSKE and CYPER-M significantly reduced SOD, and elevated AChE activities in P. sjosdteti . The IC 50 values of RCSKE, CYPER-M and CPF against CE activity in P. sjosdteti were IC 50 = 2.66 µg/ml, IC 50 = 2.37µg/ml and IC 50 = 2.65 µg/ml), respectively, while that of RCSKE against P. uniforma was IC 50 = 2.49 µg/ml. This study suggests that the extract of Ricinus communis seed kernel contains bioactive substances, capable to inhibit the antioxidant, acetylcholinesterase and carboxylesterase enzymes in Podagrica species flea beetles, comparable to commercial pesticides, Cypermethrin and Chlorpyrifos. Key words: Ricinus communis , Chemical screening, Podagrica sjosdteti , Podagrica uniforma , antioxidant enzymes, hydrolytic enzymes DOI : 10.7176/ALST/75-05 Publication date :June 30 th 2019

Microbiological Properties of Microwave-Activated Carbons Impregnated with Enoxil and Nanoparticles of Ag and Se

Microwave-activated carbons from walnut shells (ACMW) were impregnated with Ag and Se nanoparticles and with the Enoxil biologically active preparation, and the microbiological properties of the obtained composites were studied. To increase the functionality of the adsorbent, the activated carbon was oxidized with ozone, resulting in ACMWO containing aliphatic and aromatic carboxylic groups. There was a considerable decrease in the specific surface of the activated carbon after the oxidation process. Nitrogen adsorption was used to determine the structural parameters of the activated carbons. A simultaneous thermal analysis was used to study the thermal behavior of intact and oxidized activated carbons. Infrared spectroscopy was applied to analyze the surface chemistry of the adsorbents. The microbiological activity of the activated carbons was studied using Escherichia coli bacteria and Candida albicans fungi. The kinetic study of the microbiological activity allowed the estimation of the bactericidal/fungicidal action time of the activated carbons.

Nonhydrolyzable Part of Soil Organic Matter in Buried and Modern Soils

Results of the study of humus composition in about 200 modern soils of different genesis and more than 100 buried Pleistocene and Holocene paleosols have been collected and analyzed. The content of the nonhydrolyzable part of soil organic matter (NH OM) in the paleosols is comparable with that in the modern soils (50 ± 15% and 54 ± 21%, respectively). Thus, NH OM does not accumulate in the buried soils during their diagenesis and is not the inert fraction of the soil organic matter (SOM). The NH OM content in the natural organomineral soil complexes–clay fractions of the soils—is lower than that in the whole soil mass. Data on the solid-state 13C NMR spectroscopy of the whole soil samples and the NH OM indicate that the latter are enriched in O-alkyls, including C of acetal groups. The whole soil mass is richer in C of aromatic structures and carboxyl groups. The degree of organic matter humification estimated from the alkyls/O-alkyls ratio for the NH OM is considerably lower than that for the whole SOM. The existence of negative correlation between the contents of NH OM and humic acids in the modern soils (R = –0.86) and in the buried paleosols (R = –0.83) has been shown. The NH OM content in the clay fraction in comparison with the whole soil mass is lower (36 ± 21% and 60 ± 15%, respectively). This reflects the accumulation of weakly decomposed plant residues in this part of the SOM. It is argued that the NH OM is heterogeneous and includes at least two groups of substances: clay-bound organic matter of organomineral complexes (nonhydrolyzable because of strong chemical bonds) and weakly decomposed plant residues resistant to acid and alkaline hydrolysis. The absence of definite relationships between the contents of NH OM and fulvic acids indicates that genetic links between the NH OM and humic acids are stronger than those between the NH OM and fulvic acids. 13C NMR spectroscopy of kerogen from the Carboniferous shale attests to the principal difference between the NH OM of soils and kerogen, in which C of alkyl groups predominates.

Developing surrogate indicators for predicting suppression of halophenols formation potential and abatement of estrogenic activity during ozonation of water and wastewater

This study focused on developing surrogate indicators for predicting oxidation of phenolic groups in dissolved organic matter (DOM), suppression of halophenols' formation potential and abatement of estrogenic activity during ozonation of water and wastewater. The evolution of pH-dependent differential absorbance spectra suggests that O3 preferentially reacts with the DOM phenolic moieties and less so with the aromatic carboxylic groups with increasing O3/DOC (dissolved organic carbon) ratios and changes of UV absorbance and fluorescence. When ozonation used as pretreatment, the formation of halophenols in subsequent chlorination decreased linearly with increasing O3 doses or changes of UV absorbance until it reached 85% suppression of the halophenols' formation from unaltered DOM. The thresholds of decreases of UVA254, UVA280 and humic-like fluorescence corresponding to 85% suppression of halophenols’ formation were in the range of 25%–30%, 30%–35% and 30%–45%, respectively. Pre-ozonation also showed a moderate suppression of haloacetic acids (HAAs) formation potentials, ≤26.5% for reverse osmosis isolate of Suwannee River natural organic matter and ≤31.5% for Yangtze River at applied O3 doses. Measurement of changes of estrogenic activity during ozonation of water and wastewater showed that to attain a >90% abatement of estrogenic activity, the corresponding thresholds of decreases of UVA254, UVA280 and humic-like fluorescence were ∼30%, ∼40%, and ∼70%, respectively. Bromate formation was also suppressed to below 10 μg/L before these thresholds. This study suggests that optimal ozonation conditions and a balance between control of disinfection byproducts (halophenols, HAAs and bromate) and elimination of estrogenic activity can be reached based on online data.

Enantioselective Synthesis of Axially Chiral Biaryls via Cu-Catalyzed Acyloxylation of Cyclic Diaryliodonium Salts

We report here a Cu-catalyzed enantioselective acyloxylation of cyclic diaryliodonium salts. With readily available cyclic diaryliodonium salts and ubiquitous aliphatic or (hetero)aromatic carboxyl...

The grafting of phthalic acid onto polyurethane copolymer and its impact on the surface hydrophilicity, tensile stress, and shape recovery properties

Phthalic acid (PA) was grafted onto polyurethane (PU) in the PA series due to its rigid aromatic structure and carboxyl groups, but PA was simply blended with PU in the control CPA series. The cross-link density and solution viscosity of the PA series notably increased with increasing PA content, and the same parameters of the CPA series did not increase. The maximum tensile stress of the PA series sharply increased due to the chemical cross-linking of the grafted PA, and the tensile strain at break slowly decreased with increasing PA content. The shape recovery of the PA series at 10 °C rapidly increased upon the grafting of PA; however, that of the CPA series decreased with increasing PA content. The hydrophilicity of PU was enhanced by the grafting of PA based on the water contact angle and water vapor permeation results. The low temperature flexibility of the PA series improved more than that of the CPA series under freezing conditions with increasing PA content due to the chemical cross-linking and steric and electrostatic repulsion between PU moieties. Overall, the grafted PA definitely increased the maximum tensile stress, shape recovery, and low temperature flexibility of PU.

Synthesis, characterization, and mechanical performance of various functionalized carbon nanotubes‐polyurethanes nanocomposites

ABSTRACTNanocomposites of functionalized carbon nanotubes (CNTsf) used as a reinforcement agent, and a polyurethane (PU), as a polymeric matrix were synthesized via in situ polymerization. Carbon nanotubes (CNTs) were chemically functionalized using four different chemical treatments to obtain (1) oxidized CNTs (CNTsOH, COOH), (2) CNTs containing aliphatic amine groups (CNTset diam), (3) CNTs attached to an aromatic amine group (CNTs4AB), and (4) CNTs containing a combination of aromatic amine, hydroxyl, and carboxyl functional groups (CNTs4AB, OH, COOH). The nanocomposites (prepared using 0.25, 0.5 or 1.0 wt % CNTsf) were synthesized by two processes: (1) one‐step using a PU made from PCL‐diol (α‐ω‐telechelic polyester diol) obtained by biocatalysis from ε‐caprolactone (ε‐CL) and diethylene glycol (DEG) and 4,4′‐methylenebis (cyclohexyl isocyanate) (H12MDI) in stoichiometric amounts, (2) two‐step process (chain extended PU) using hexamethylene diamine (HMDA). Depending on the chemical route used to synthesized the nanocomposites, CNTsf form, in some cases, covalent bonds and hydrogen bonding with the soft and/or hard segments of the PU matrix. Also, the presence of CNTsf improves the thermal stability of the nanocomposites and some of their mechanical properties, compared to the pure PU properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47319.

The influence of particle size on the intensity and reproducibility of Raman spectra of compacted samples

Given the growing interest in the application of Raman spectroscopy for quantitative purposes in solid pharmaceutical preparations, a revision of the effect of particle size on Raman spectra of compacted samples is presented. For this purpose, a set of tablets of potassium hydrogen phthalate (KHP) of different particle size were prepared. KHP was used because of its purity and stability, which allow to consider that samples will not be altered during measurements; but also because of its chemical structure (aromatic ring and carboxylic groups), that are present in many active pharmaceutical ingredients (API). The latter makes possible to consider KHP as a model pseudo-API. As KHP tablets only contain a pure compound, the mapping strategy that was considered for measuring our samples will not be affected by subsampling issues. The spectra variance can be attributed to the intrinsically reproducibility in recording the spectra (which mainly depends on the instrument set-up) and the site-to-site differences in elastic scattering properties. Two different instrumental optics have been studied: a macro-Raman system and a Raman microscope (500 μm and 50 μm laser spot size, respectively). The effect of the spectra preprocessing is also evaluated.The overall results demonstrate raw Raman intensity increases with particle size up to a value that depends on tablet width and that the applied spectral preprocessing (baseline correction and a unit vector normalization), reduces the differences in Raman intensities due to the particle size, but does not completely eliminate it for the lower particle sizes (< 20 μm). For tablets containing particles with predefined sizes, it corrects the mapping site-to-site differences in elastic scattering.

Separation of Benzoic and Unconjugated Acidic Components of Leonardite Humic Material Using Sequential Solid-Phase Extraction at Different pH Values as Revealed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry and Correlation Nuclear Magnetic Resonance Spectroscopy.

Here, we report on sequential solid-phase extraction of leonardite hymatomelanic acid (CHM) on a non-ionic sorbent at four steadily lowered pH values: 7, 5, 3, and 2, yielding fractions with different acidic properties. Using nuclear magnetic resonance (NMR) spectroscopy and ultrahigh-resolution mass spectrometry, we revealed a gradual shift of dominating scaffolds in the fractions of CHM from reduced saturated to oxidized aromatic compounds. An increase on the average aromaticity of the CHM fractions was accompanied by a red shift in fluorescence spectra. These results were supported by heteronuclear single quantum coherence and heteronuclear multiple bond correlation NMR experiments. We have demonstrated that the CHM fraction isolated at pH 5 was dominated by aliphatic carboxyl carriers, while the pH 3 fraction was dominated by aromatic carboxyl acids. The developed fractionation technique will enable deeper insight on structure-property relationships and the design of the humic-based materials with tailored reactive properties.

Composting enhances the removal of lead ions in aqueous solution by spent mushroom substrate: Biosorption and precipitation

This study aims to elucidate the effects of composting on spent mushroom substrate (SMS) in lead ions removal by comparing the physicochemical properties of composted spent mushroom substrate (CSMS) with composted cow dung (CCD) and SMS. The effect of experimental factors (pH, contact time, dosage and initial concentration) on lead ions removal was determined by batch experiments. Composting elevated the pH value (7.80), cation exchange capacity (CEC, 77.02 cmol/kg) and hydrophilicity, resulting in a higher removal efficiency for lead ions of CSMS than that of SMS. The increased proportion of aromatic hydrocarbon and carboxyl was propitious to lead ions removal via their response to pH variation. Biosorption and precipitation were the overriding mechanisms involved in the lead ions removal by CSMS. Our results present a simple and energy-efficient method to enhance the ability of SMS to remove heavy metals.

Wet peroxidation of resorcinol catalyzed by copper impregnated granular activated carbon

The present article reports the treatment of resorcinol using a catalytic wet peroxidation (CWPO) process in the presence of copper impregnated granular activated carbon (Cu/GAC) with a bench-scale batch reactor. The typical physico-chemical properties of synthesized catalyst were characterized with different equipment and methods. 90% resorcinol removal and 81% of TOC removal was achieved at optimum conditions (pH = 6, the stoichiometric ratio of H2O2/resorcinol = 1.2, catalyst dose = 0.5 g/L, initial concentration of resorcinol = 100 mg/L, temperature = 70 °C and time t = 4 h). Fourier-transform infrared spectroscopy (FTIR) measurements revealed that GAC posses various conjugated hydrocarbon groups including aromatic hydrocarbons, carboxylic groups, carboxyl and carbonate. Cu/GAC catalyst has a surface smoother than that of pristine GAC. At neutral or natural pH (∼6.4) of resorcinol, CWPO of resorcinol is favorable by Cu/GAC catalyst. Catalyst stability study revealed that Cu/GAC sustain its catalytic reactivity to over 76% in the five cycles without any regeneration. The thermogravimetric analysis confirmed that 350 °C temperature found to be optimum for calcination of Cu/GAC without any major losses. The mineralization mechanism was proposed based on intermediates identified during CWPO reaction.