Variation Of Functional Groups Research Articles

Molecular Adsorption and Physicochemical Properties at Liquid/Liquid Nanoemulsion Soft Interfaces: Effect of Charge and Hydrophobicity.

Contrary to the popular adage, "Oil and water do not mix", evidence of mixtures comprising the two "immiscible" liquids is universal. In the presence of an emulsifier, oil and water mix to form a colloidal suspension known as emulsion. Their utility in many areas such as food chemistry, biomedical health sectors, catalysis, and the petroleum industry is well recognized. While their application in our society is pervasive, tantalizing fundamental questions regarding the chemistry that takes place at the oil/water soft interface still linger. For instance, do organic compounds show proclivity for this molecularly thin boundary and, if so, what forces, hydrophobic or pure electrostatic among others, drive the molecular interactions? The focus of this Article is on molecular adsorption at the interface of oil-in-water (O/W) nanoemulsion (NE) droplets. The effect of the interfacial surfactant charge (positive, negative, zwitterionic, and neutral) on the affinity of aromatic organic compounds on the O/W NEs has been studied. Using a second harmonic generation (SHG), a nonlinear light scattering technique, we have explored the adsorption equilibrium of charged and neutral organic dyes. By variation of the surfactant functional group and thereby the interfacial charge properties, the source of the adsorption interaction, if any, has been deduced. The population of surfactants containing a charged functional group at the O/W interface is found to be sparse, yet adsorption at some of these interfaces has been observed. A purely electrostatic Coulomb interaction plays a key role, but the presence of a charged interface does not necessitate molecular adsorption. Hydrophobic interactions are not a major driving force of adsorption for the SHG dyes studied. However, a possible pi-interaction is likely in explaining the accumulation of neutral aromatic compounds at the O/W NE interface. These intricate adsorption features are discussed in the context of NE interfacial charge properties and their stability upon molecular adsorption.

How do substrate types affect the seasonal richness and functional feeding groups variation of benthic insects in an arid region (northeastern Algeria)?

How do substrate types affect the seasonal richness and functional feeding groups variation of benthic insects in an arid region (northeastern Algeria)?

Characterization of phytoplankton functional types in the western Bay of Bengal: HPLC- and CHEMTAX-based approach.

This study investigates phytoplankton functional group variations in the western Bay of Bengal (WBoB) during the Spring Intermonsoon. Samples were collected from four cross-shore transects: Mahanadi (MN), Vamsadhara (VD), Godavari (GD), and Krishna (KS). East India Coastal Current and warm gyre influenced the southern transects (KS, GD), VD was experiencing moderate upwelling and MN was characterized by low salinity and oligotrophic conditions due to freshwater input. In response to hydrography, phytoplankton biomass and functional types differed within and between the transects. Chlorophyll-a (Chl-a) was spatially high in VD and low in MN. The subsurface Chlorophyll-a maxima (SSCM) was prominent and shallow in the MN and VD, compared to the southern transects. Total diagnostic pigments concentration was high in VD, followed by GD, KS and MN. Phytoplankton functional groups and each groups contribution to Chl-a was calculated through CHEmical Taxonomy (CHEMTAX). Diatoms and cyanophytes were the dominant functional types in the surface layers. Progressive shift from diatoms in the nearshore region to cyanophytes in the offshore was observed. The low saline and low-nutrient conditions were conducible for the growth of cyanophytes, while nutrient-rich optimum light layer of SSCM and upper layer of VD were favorable for diatoms. Cryptophytes contribution to Chl-a was higher in southern transects compared to the north. Prymnesiophytes and prasinophytes were high in the subsurface and deep layers could be due to their adaptions to light and nutrients. The present study highlights the significance of physical processes associated hydrography in structuring the phytoplankton functional types.

Ionic liquid-mediated removal of naphthenic acids from crude oil: Process modelling and optimization

The present study demonstrated the efficiency of ionic liquid in the removal of naphthenic acids from crude oil. The crude oil sample was obtained from Belema oil field in Southern Nigeria while tetramethyl ammonium hydroxide pentahydrate (TMAH) ionic liquid was commercially obtained. Liquid-liquid extraction was carried out and the reaction conditions were modelled and optimized using Box-Behnken design of the response surface methodology. Ionic liquid concentration (w/v%), reaction temperature (°C), and reaction time (mins) were selected as the factors while extraction efficiency (%) was selected as the response. The results of the study showed that the highest extraction efficiency of 96.67 % was achieved under reaction conditions of 3 w/v% ionic liquid concentration, 50 °C reaction temperature, and 45 mins reaction time. Owing to R2, adjusted R2, and predicted R2 values generally > 0.90, the model accurately described the decarboxylation reaction. Optimization results indicated that removal efficiency can reach over 96 % at 2.82 w/v% ionic liquid concentration, 48 °C reaction temperature, and 45 mins reaction time. The characterization of the original and decarboxylated oils using GC–MS showed reduced concentration of acidic species in the latter. Also, FT-IR of the ionic liquid showed minimal or no variations in functional groups before and after extraction, highlighting a possibility for regeneration of the ionic liquid. The findings of the study showed the use of ionic liquids as green alternatives in the removal of acidic species from crude oil.

Multi-Modal Structure and Distribution Analysis of Functional Groups on Carbon Supports for Polymer-Electrolyte Fuel Cells

Although structures of the functional groups formed on the surface of the carbon supports and their distribution on/inside supports have crucial impacts on determining performance of the catalyst electrodes, understanding of the relationship between them remains unclear, because of limitation of experimental methods for quantitative analysis of them with high spatial resolution. It is well-known that functional groups of the catalyst supports affect chemical properties of the supports, such as, redox- and acid-base properties, hydrophobicity, and electronic interaction. Thus, they should have a great influence on various aspects those related to the performance of polymer electrolyte fuel cell (PEFC), such as the activity, mass transportability, and durability of the catalysts and catalyst layers, and manufacturing process of catalysts and catalyst layer. 1,2). Furthermore, recently, in addition to various conventional high-surface area carbon supports, such as, Vulcan and Ketjen black, accessible carbon supports with mesopores which can host Pt particles protects them from direct ionomer adsorption and allow proton and O2 to have reasonable access to Pt particles, have been attracting great attention for improving catalyst utilization, activity, mass transportability, and suppression of Pt dissolution 3-5). The relationship between structure variation of functional groups on various supports and electrode performances should be of interest. The major difficulty for analyzing the functional groups on carbon supports come from the structure complexity of carbon surface (as well as inner part of the carbon particles), inhomogeneous distribution of various functional groups produced in various chemical processes, and multi-component structure of catalyst electrodes with catalysts and ionomers. Against such background, in this study, we have developed a new experimental approach utilizing multi-modal analysis method with x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), temperature-programmed-desorption mass spectroscopy (TPD-MS), vibrational spectroscopy, electron tomography (3D-TEM), and cryo transmission electron microscopy (cryo-TEM). By combining suitable experimental probes for each structural feature and each component in multi-component structures, and by analyzing in integrated manner, we are able to understand the complex structure of functional groups on and inside carbon supports. Here, we demonstrate an example of the analysis for Vulcan (VULCAN® XC72, Cabot Corporation) and Pt-supported Vulcan (TEC10V30E, Tanaka Kikinnzoku Kogyo K. K. ). Vulcan is a solid carbon support used for polymer electrolyte fuel cell catalysts. The sample was reduced for about 30 minutes in a 100% hydrogen atmosphere at room temperature. Hard x-ray photoelectron spectroscopy (HAXPES) using synchrotron radiation x-rays with x-ray energy of 8 keV (BL46XU at SPring-8) . Also soft X-ray XAS were performed on BL1N2 at Aichi SR . Figure 1 shows the C1s HAXPES spectrum and the C K-edge XANES spectrum acquired by total electron yield (TEY) method. HAXPES was normalized by the signal intensity of the C-C substrate components (sp2, sp3) of the support at 284.5 eV 6), whereas the C K-edge XANES is normalized by the signal intensity of the 2pz (π*) orbital extending perpendicular to the carbon hexagonal network plane of the C–C substrate component of the support at 285.2 eV 7, 8). The functional groups are clearly observed in both spectra and the signal intensity of the functional group of the Pt catalyst increased with respect to the support alone, indicating that the amount of functional group on the support increased due to the Pt loading process. By combining other experimental results and theoretical simulations, the relationship between structure properties and electrode performance can be discussed. Acknowledgement This work was conducted in FC-Platform project supported by the New Energy and Industrial Technology Development Organization (NEDO). References :1) E. Antolini, Applied Catalysis B: Environmental 88, 1 (2009)2) Y.-J. Wang, N. Zhao, B. Fang, H. Li, X. T. Bi, and H. Wang, Chem Rev 115, 3433 (2015)3)V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson, and A. Kongkanand, ACS Energy Letters 3, 618 (2018)4)S. Ott, A. Orfanidi, H. Schmies, B. Anke, H. N. Nong, J. Hübner, U. Gernert, M. Gliech, M. Lerch and P. Strasser , Nature Mater., 19, 77 (2020)5)A. Kobayash, T. Fujii, C. Harada, E. Yasumoto, K. Takeda, K. Kakinuma, and M. Uchida, Acs Appl. Energy Mater. 4 2307 (2021)6) S. Kundu, Y. Wang, W. Xia, and M. Muhler, J. Phys. Chem. C, 112, 16869 (2008)7) Y. Murakami, Y. Ota, and T. Okada, Anal. Sci., 39, 67 (2023)8) C. L. Guillou, S. Bernard. F. de la Pena, and Y. L. Brech, Anal. Chem., 90, 8379 (2018) Figure 1

Effect of Lithium Salts on the Properties of Cassava Starch Solid Biopolymer Electrolytes.

This study evaluates the effect of lithium salts on the structural, electrochemical, and thermal properties of cassava starch solid biopolymer electrolytes (SBPEs). Films of SBPEs were synthesized using plasticizing agents and lithium salts (LiCl, Li2SO4, and CF3LiSO3) via thermochemical method. The SBPEs with lithium salts exhibited characteristic FTIR bands starch, with slight variations in the vibration oxygen-related functional groups compared to salt-free biopolymer spectra. The RCOH/COC index (short-range crystallinity) was higher in the films synthesized without lithium salt and the lowest value was established in the films synthesized with Li2SO4. Thermal degradation involved dehydration between 40 to 110 °C and molecular decomposition between 245 to 335 °C. Degradation temperatures were close when synthesized with salts but differed in films without lithium salt. DSC revealed two endothermic processes: one around 65 °C linked to crystalline structure changes and the second at approximately 271 °C associated with glucose ring decomposition. The electrochemical behavior of the SBPEs varied with the salts used, resulting in differences in the potential and current of peaks from the redox processes and its conductivity, presenting the lowest value (8.42 × 10-5 S cm-1) in the SBPE films without salt and highest value (9.54 × 10-3 S cm-1) in the films with Li2SO4. It was concluded that the type of lithium salt used in SBPEs synthesis affected their properties. SBPEs with lithium triflate showed higher molecular ordering, thermal stability, and lower redox potentials in electrochemical processes.

Study on the variation in key functional groups of coal and the mechanism of CO and CO2 generation under the thermal effect of lean-oxygen conditions

Most closed fire areas in coal mines encounter rapid reignition after unsealing. To prevent the reignition of residual coal, it is necessary to study the impact of the lean oxygen conditions (LOCs) in closed fire areas on the characteristics of coal spontaneous combustion (CSC), evolution of the pore and fissure structures, and generation mechanisms of gases such as CO and CO2. A systematic study was conducted using in situ infrared, synchronous thermal analyzer (STA-DSC), scanning electron microscope (SEM), N2 adsorption, and programmed heating experiments. The results show that during the low-temperature oxidation process (LTOP), the temperature and oxygen concentration had a significant impact on the content variations of functional groups such as –OH, CO, COOH, CH2/CH3, and CC. Moreover, the higher the oxygen concentration, the higher was the effect. The concentration and heat release rate of CO and CO2 generation were positively correlated with the oxygen concentration. As the temperature increased, cracks developed gradually on the coal surface, and micropores transformed into mesopores and macropores. The specific surface area decreased gradually. When the temperature was below 110 ℃, the microstructure of the coal sample did not vary significantly. When the temperature was above 110 ℃, the effect was significant. The higher the oxygen concentration, the more significant was the impact on the pore characteristics of the coal. Two main pathways exist for CO and CO2 generation. CO2 generation requires a higher temperature than that required for CO. The research results provide a theoretical basis for the unsealing of closed fire areas and prevention of reignition.

Fabricating fragmented intramolecular D-A integrated carbon nitride photocatalyts with elevating activity: Performance and mechanism analysis

Carbon nitride (CN) possesses great potential in photocatalytic solar-energy conversion for environmental pollution removal and hydrogen energy generation. However, pristine CN suffers unsatisfactory photocatalytic activity owing to insufficient visible light response, low activity sites exposure, lazy exciton separation and ready carrier recombination. In this work, fragmented intramolecular D-A integrated CN (FBCN) was contracted via a facile m-aminophenylboronic acid doping followed two-step post-processing. The intramolecular D-A integrated structure can strengthen exciton separation and carrier migration driving forces, while the fragmented nanoflakes structure with rich in-plane edges can shorten the migration distance of charge-to-surface in-plane and vertical direction, as well as expose more marginal active sites. The hydrogen evolution rate of optimized 25-FBCN photocatalyst reaches 2545 μmol h−1 g−1, which is 5.2 times higher than that of pristine CN and 1.3 times over the 25-BCN. The 25-FBCN can degrade 87% sulfamethoxazole, and the kinetic rate constant is 3.9 times higher than that of CN. The radical capture and ESR tests reveal stronger radical signals in 25-FBCN degradation system than that of CN. The MS and online FTIR present photodegradation pathway and intermediate, and in-site record functional groups variation during degradation reaction. The SEM/TEM/AFM/XPS/EPR, N2 adsorption-desorption and water contact analysis confirm the generation of smaller-sized nano fragments with rich in-plane edges. The UV–vis DRS/EIS/PCR/PL/TRPL and band structure verify that more effective charge dissociation/migration behavior of 25-FBCN than pure CN. Finally, DFT theoretical calculations and KPFM test further verify the generation of intramolecular D-A integrated structure and clarify the latent propel mechanism of performances.

Strategies for Improving Selectivity and Sensitivity of Schiff Base Fluorescent Chemosensors for Toxic and Heavy Metals.

Toxic cations, including heavy metals, pose significant environmental and health risks, necessitating the development of reliable detection methods. This review investigates the techniques and approaches used to strengthen the sensitivity and selectivity of Schiff base fluorescent chemosensors designed specifically to detect toxic and heavy metal cations. The paper explores a range of strategies, including functional group variations, structural modifications, and the integration of nanomaterials or auxiliary receptors, to amplify the efficiency of these chemosensors. By improving selectivity towards targeted cations and achieving heightened sensitivity and detection limits, consequently, these strategies contribute to the advancement of accurate and efficient detection methods while increasing the range of end-use applications. The findings discussed in this review offer valuable insights into the potential of leveraging Schiff base fluorescent chemosensors for the accurate and reliable detection and monitoring of heavy metal cations in various fields, including environmental monitoring, biomedical research, and industrial safety.

Oxalic acid-modified activated carbons under hydrothermal condition for the adsorption of the 2-butanone.

Growing volatile organic compound (VOC) emission will cause air pollution and further threaten human health. Activated carbon is widely applied to treatment of VOCs in virtue of lower cost and excellent adsorption ability. In this work, the adsorption capacity of polarity VOCs on activated carbon is improved by oxalic acid (H2C2O4) hydrothermal modification. After 2M H2C2O4 modification, the adsorption capacity of 2-butanone rose from 312.60 to 345.98mg/g, and the time reaching saturation adsorption became shorter. BET results showed that both the specific surface area and total pore volume of 2M H2C2O4-modified activated carbon increased by 3.32% and 3.9%, respectively. Both FTIR and XPS characterization confirmed variation of the surface oxygen-containing functional groups (SOFGs), while quantitative analysis via Boehm titration showed the significant increase of total acidity (61.36%), particularly the carboxyl content increased by 96.28%. The results indicated modification process can not only change the pore structure but also the SOFGs of activated carbons. The dynamic adsorption curves conform to the Bangham kinetics model, indicating that the adsorption of 2-butanone on both activated carbon is controlled by the diffusion in the pore channel. The adsorption data was also modeled by the internal particle diffusion model, and the internal diffusion adsorption stage is the rate-controlling step. The stability before and after adsorption and the cycling performance were studied.

Polyethyleneimine-induced in-situ chemical epitaxial growth ultrathin 2D/2D graphene carbon nitride intralayer heterojunction with elevating photocatalytic activity: Performances and mechanism insight

Integrating 2D carbon nitride (CN) photocatalyst with 2D graphene into a lateral heterojunction can decrease energy loss within interlayer space, which is an intriguing strategy for tailoring photocatalyst for energy and environmental applications. Herein, a polyethyleneimine (PEI) induced in-situ chemical epitaxial growth strategy was adopted to tailor graphene-oxide CN (GO-CN) intralayer heterostructure photocatalyst, where PEI was served as chemical inducer and crosslinker to construct polymerization precursor, and a one-pot self-assembly followed in-situ thermal-polymerization and thermal-etching method was conducted. Series characterizations manifest the successful construction of ultrathin 2D-2D GO-CN intralayer heterostructure, which possesses ameliorated specific surface area, visible-light harvest and charge behaviors. Quench tests, ESR and LC-MS explored photodegradation active species, intermediate and route, while online FTIR real-time and in-situ monitor the variation of functional groups. In the end, DFT theoretical analysis further affirm the charge transfer between GO and CN, and unveil conceivable elevated mechanism.

Variation and drivers of soil fungal and functional groups among different forest types in warm temperate secondary forests

Soil fungal communities play a crucial role in maintaining and regulating ecosystem functions. The soil fungal structure of different plant communities in forests has been widely studied. However, the drivers of changes in soil fungal community dynamics in warm temperate secondary forests and the pathways influencing them remain to be explored. The Illumina high-throughput sequencing and FUNGuild platform were used to characterize the soil fungal diversity and community composition of six typical plant communities (JM, Juglans mandshurica; PD, Populus davidiana; QM, Quercus mongolica; MB, mixed broadleaf forest; MC, mixed conifer forest; PT, Pinus tabuliformis) in warm temperate secondary forests. The drivers of structural changes in dominant fungal taxa and functional groups were also explored. The pathways through which forest type, soil properties, altitude, climate, and plant diversity affected fungal community structure were further clarified. The results suggested that Ascomycota, Basidiomycota, and Zygomycota dominated the soil fungal communities in warm temperate secondary forests. Except for symbiotic fungi, there was no significant difference in soil fungal α-diversity among forest types. However, there were significant differences in total fungi and functional group community composition. The drivers of diversity and community composition of different soil fungal taxa in warm temperate secondary forests differed. In addition, the partial least squares path model indicated that the composition of soil fungal community in warm temperate secondary forests was directly influenced by forest type and was less dependent on soil properties. Collectively, our study highlights the importance of forest type, soil properties, and other factors (climate, altitude, plant diversity) in driving changes in soil fungal community structure.

Applying synchrotron radiation-based attenuated total reflection-fourier transform infrared to chemically characterise organic functional groups in terrestrial soils of King George Island, Antarctica

Anthropogenic activities, especially associated with fossil fuel combustion, are raising concerns worldwide, but remote areas with extreme climate conditions, such as Antarctica, are isolated from the adverse influence of human civilisation. Antarctica is considered as the most untouched place on Earth. Such pristine areas, which have extremely low chemical pollutant concentrations owing to restricted anthropogenic impacts, exemplify plausible model environments to test the reliability and sensitivity of advanced analytical techniques employed to chemically characterise and evaluate the spatial distribution of chemical pollutants. Here, synchrotron radiation-based attenuated total reflection-Fourier transform infrared (SR-ATR-FTIR) spectroscopy was employed to evaluate the variations in the organic functional groups (OFGs) of terrestrial soils of King George Island, Antarctica. Second-derivative SR-ATR-FTIR spectroscopy coupled with several multivariate statistical techniques highlighted the influence of anthropogenic activities on the alterations of OFGs in terrestrial soils collected near airports. Moreover, the daily activities of penguins could also have caused fluctuations in some OFGs of the samples the close to the Tombolo area and Ardley Island. The findings proved the effectiveness of SR-ATR-FTIR in evaluating the potential sources of variations in the chemical constituents, especially OFGs, in Antarctic terrestrial soils.

The Synthesis and Base-Induced Breakdown of Triaryl 1,4-Oxathiins-An Experimental and DFT Study.

1,4-Oxathiins are valued for a breadth of bioactivities and are known commercial fungicides. This article explores a novel preparation of 2,3,6-trisubstituted 1,4-oxathiin-S,S-dioxides via the reaction of benzyl 1-alkynyl sulfones and aryl aldehydes under basic conditions. A total of 20 examples possessing exclusively a trans arrangement of the 2,3-diaryl substituents are exhibited; the products demonstrate a variation of functional groups on the aryl ring attached to the heterocyclic ring system. The preparation is hindered by the base sensitivity of the products, and a ring-opened by-product typically contaminates the reaction mixture. A DFT assessment of the overall system includes a lithium counterion and offers possible pathways for the incorporation of the aldehyde, the cyclization step and the requisite proton transfers. In addition, the DFT work reveals options for the ring opening chemistry. It appears the trans 2,3-diaryl selectivity is set during the cyclization stage of the reaction sequence. The practical work uncovers a new reaction pathway to create a family of novel 1,4-oxathiin-S,S-dioxides whereas the computational work offers an understanding of the structures and possible mechanisms involved.

DoE-Assisted Development of a 2H-MoS2 -Catalyzed Approach for the Production of Indole Derivatives.

2H-MoS2 is an appealing semiconductor because of its Earth-abundant nature, cheapness, and low toxicity. This material has shown promising catalytic activity for various energy-related processes, but its use in catalysis for C-C bond forming reactions towards useful organic compounds is still largely unexplored. The lack of examples in organic synthesis is mainly due to the intrinsic difficulties of using bulk 2H-MoS2 (e. g., low surface area), which implies the reliance on high catalytic loadings for obtaining acceptable yields. This makes the optimization process more expensive and tedious. Here, we report the development of a 2H-MoS2 -mediated synthesis of valuable bis(indolyl)methane derivatives, using indoles and benzaldehydes as starting materials. Exploiting the Design of Experiments (DoE) method, we identified the critical parameters affecting the catalytic performance of commercial 2H-MoS2 powder and optimized the reaction conditions. Lastly, we demonstrated that the catalytic system has versatility and good tolerance towards functional group variations of the reagents.

Retarding thermal-oxidative aging of anhydride-cured epoxy asphalt binder and mixture by incorporating antioxidant Irganox 1010

ABSTRACT This research focused on the stabilisation of anhydride-cured epoxy asphalt (EA) over thermal-oxidative aging. EA binders with graduated Irganox 1010 antioxidant contents at 0, 0.3, 0.6, 0.9, and 1.2 wt% were prepared and then subjected to accelerated oven-conditioning aging at 85 and 100°C. The thermal stability, viscosity, mechanical parameters, and chemical structure of EA containing Irganox 1010 were evaluated during aging. The results showed that Irganox 1010 contributed to enhanced thermal stability, higher initial viscosity, and longer allowable construction time for EA. The 0.3–0.9 wt% Irganox 1010 had good compatibility with EA without weakening performance. During aging, Irganox 1010 effectively restrained degradation of the EA binder’s mechanical properties and the EA mixture’s low-temperature deformation. The variations of functional groups indicate that Irganox 1010 prominently restrained the oxidation of the asphalt phase and lightly affected the post-curing of the resin phase. There was a strong correlation between decreasing rate of bending strain of the mixture and increasing rate of sulfoxide in the binder. The mutual synergistic effect of resin and antioxidant improves the oxidation resistance of asphalt. Considering the aging improvement and economic cost, it is recommended to use 0.6 wt% Irganox 1010 as an antioxidant for anhydride-cured EA. Highlights Epoxy asphalt (EA) binder and mixtures incorporating antioxidant Irganox 1010 were analysed. Irganox 1010 plays a crucial role in aging protection effect of EA binder and mixture. Irganox 1010 antioxidant prominently restrains the oxidation of the asphalt phase and lightly affects the post-curing of the resin phase. There was a strong correlation between the bending strain of mixture and sulfoxide of binder. Addition of 0.6 wt% Irganox 1010 is recommended as an antioxidant for EA materials.

Systematic investigation of simultaneous copper biosorption and nitrogen removal from wastewater by an aerobic denitrifying bacterium of auto-aggregation

Finding effective methods for simultaneous removal of eutrophic nutrients and heavy metals has attracted increasing concerns for the environmental remediation. Herein, a novel auto-aggregating aerobic denitrifying strain (Aeromonas veronii YL-41) was isolated with capacities for copper tolerance and biosorption. The denitrification efficiency and nitrogen removal pathway of the strain were investigated by nitrogen balance analysis and amplification of key denitrification functional genes. Moreover, the changes in the auto-aggregation properties of the strain caused by extracellular polymeric substances (EPS) production were focused on. The biosorption capacity and mechanisms of copper tolerance during denitrification were further explored by measuring changes in copper tolerance and adsorption indices, as well as by variations in extracellular functional groups. The strain showed extremely strong total nitrogen removal ability, with 67.5%, 82.08% and 78.48% of total nitrogen removal when NH4+-N, NO2−-N, and NO3−-N were used as the only initial nitrogen source, respectively. The successful amplification of napA, nirK, norR, and nosZ genes further demonstrated that the strain accomplished nitrate removal through a complete aerobic denitrification pathway. The production of protein-rich EPS of up to 23.31 mg/g and an auto-aggregation index of up to 76.42% may confer a strong biofilm-forming potential to the strain. Under the stress of 20 mg/L copper ions, the removal of nitrate-nitrogen was still as high as 71.4%. In addition, the strain could achieve an efficient removal of 96.9% of copper ions at an initial concentration of 80 mg/L. Scanning electron microscopy and deconvolution analysis of characteristic peaks confirmed that the strains encapsulate heavy metals by secreting EPS and, meanwhile, form strong hydrogen bonding structures to enhance intermolecular forces to resist copper ion stress. This study provides an innovative and effective biological approach for the synergistic bioaugmentation removal of eutrophic substances and heavy metals from aquatic environments.

Sewer sediment adhesion reduction and hydraulic floating promotion by alkaline treatment

Deposition of sediment in sewers decreased flow capacity, with harmful gases and pipe erosion. Sediment floating and removal remained challenges due to its gelatinous structure, which induced strong erosion resistance. This study proposed an innovative alkaline treatment for destructuring gelatinous organic matters and improving hydraulic flushing capacity of sediments. At the optimal pH 11.0 condition, the gelatinous extracellular polymeric substance (EPS) and microbial cells were disrupted, with numerous outward migration and solubilization of proteins, polysaccharides and humus. The aromatic protein solubilization (tryptophan-like and tyrosine-like proteins) and humic acid-like substance deconstruction were the major driving factors for sediment cohesion reduction, which disintegrated the bio-aggregation and increased the surface electronegativity. Meanwhile, the variations of functional groups (CC, CO, COO-, CN, NH, C-O-C, C-OH, OH) also contributed to the interaction breakage and glutinous structure disruption of sediment particles. It was found that the rising pH conditions reduced sediment adhesion and promoted particle floating. Solubilizations of total suspended solids and volatile suspended solids were increased by 12.8 and 9.4 times, respectively, while the sediment adhesion was reduced by 3.8 fold. The alkaline treatment greatly improved sediment erosion and flushing capacities under shear stress of gravity sewage flow. Such sustainable strategy only cost 36.4 CNY per sewer meter length, which was 29.5–55.0 % of the high-pressure water jet flushing and perforated tube flushing approaches.

Effect of molecular structure change on the properties of persistent free radicals during coal oxidation

This study is aimed at exploring the effect of molecular structure changes on the properties of persistent free radicals in coal during the heating process of coal spontaneous combustion (CSC). Therefore, the persistent free radicals and main functional groups variation characteristics in the process of coal oxidation were analyzed by means of in situ electron spin resonance and in situ infrared spectroscopy, and the change relationship between the molecular structure of coal and the persistent free radicals in coal during the reaction was further discussed by correlation analysis. The results showed that the concentration of persistent free radicals showed a stage change of “first decreasing, then increasing and then decreasing”. The g-factor decreases gradually and the heteroatom free radicals are consumed continuously. Dehydrogenation oxidation reaction causes the weakening of the “electron-proton” interaction, which narrows the line-width (ΔH) of free radicals. The phenolic hydroxyl as the electron donating group is converted into -CO functional group through dehydrogenation and oxidation reaction, which promotes the formation and accumulation of persistent free radicals in coal. Under the influence of phenolic hydroxyl, the relationship between the stretching vibration strength of aromatic ring CH and the properties of persistent free radicals in coal shows a similar change law with phenolic hydroxyl. In addition, the chain structure represented by –CH2-, –CH3/–CH2- is continuously consumed in the oxidative dehydrogenation reaction, triggering a series of free radical reactions. The free radicals formed in this process are affected by the steric hindrance of polymer networks and the electron delocalization of aromatic group in coal, so the persistent free radicals can be formed and accumulated. The dehydrogenation and oxidation reaction of the active group led to the reduction of g-factor and ΔH. Persistent free radicals play an important role in the free radical chain reaction that triggers CSC, so preventing the dehydrogenation and oxidation reaction of hydroxyl (especially phenolic hydroxyl) and aliphatic hydrocarbons (especially –CH2- and –CH3/–CH2-) is the key to prevent CSC.

Alkalization-induced disintegration increased redox activity of solid humic acids and its soil biogeochemical implications

Solid humic acids (HAsolid) plays a significant role in maintaining soil ecosystem services, especially in alkaline soil. The unique chemical structures and electrochemical properties are the cores that HAsolid works. In this study, the alkalization-induced variations of particle morphology, functional groups and redox activity of HAsolid were investigated and its soil biogeochemical implications were discussed. Atomic force microscopy (AFM) deflection images and zeta potential results showed that alkalization induced disintegration of HAsolid, with particle size reducing to 200 nm when pH value reached 10.0. This result suggested that HAsolid could exist in alkaline soil. AFM-IR along with fluorescence intensity of HAsolid at different pH further proved that the supramolecular aggregation of HAsolid became loose and dispersive with more redox-active functional groups exposure after alkalization, which could lead to HAsolid susceptible to degradation in alkaline soil. Conductivity of HAsolid decreased 42.86 % when pH increased from 5.0 to 10.0, while electron exchange capacity (EEC) of HAsolid increased 45.30 %, indicating the increase of redox activity of HAsolid. Increase of redox activity of HAsolid by alkalization-induced disintegration not only can accelerate organic pollutant degradation via enhancing microbial co-metabolism, but also speed up the organic carbon loss. This study contributes to a better understanding of the role of HAsolid in organic carbon stocks and fluxes of alkaline soils and has great implications for soil biogeochemical process.