Concentration Of Functional Groups Research Articles

Experimental research on spontaneous oxidization combustion characteristics of coal after pre-adsorption CO2

ABSTRACT CO2 is injected into coal bodies in advance so that CO2 is fully adsorbed in the crack pores of the coal. It can inhibit the combination of coal and oxygen, so as to prevent and control the natural combustion of coal left in goaf. However, domestic and foreign scholars have little research on the low temperature oxidation characteristics and functional group changes of coal after CO2 pre-injection. In this article, a temperature programmed experimental device is used to analyze the formation of the macro-combustion index gas; a Fourier transform infrared spectroscopy experimental analyzer was determined the content of active functional groups of each component. The results showed that when the coal-sample pre-adsorbed CO2, the generation trend of CO2 formed an approximate “V” shape, the oxygen consumption decreased by about 4%. The initial generation temperature of CO and alkane gases is lagged, and the lag temperature is 20 ~ 30°C. CO2 occupied the surface of the coal surface, and inhibiting the oxidation response of oxygen-containing functional groups. The content of hydroxyl group increases, the oxidative decomposition rate of aliphatic hydrocarbon slows down, and the content of aromatic hydrocarbon increases, which can effectively slow down the course of coal oxidation and spontaneous combustion.

Co-production of spirosiloxane and biochar adsorbent from wheat straw by a low-cost and environment-friendly method

To enhance the value of wheat straw derivatives, wheat straw ash (WSA) was used as a reactant for the first time to synthesize spirocyclic alkoxysilane, an important organosilicon raw material, using an energy-saving and environmentally friendly non-carbon thermal reduction method. After spirocyclic alkoxysilane extraction, the biochar in the wheat straw ash prepared an adsorbent for Cu2+. The maximum copper ion adsorption capacity (Qm) of silica-depleted wheat straw ash (SDWSA) was 31.431nullmg/g, far exceeding those of WSA and similar biomass adsorbents. The effects of the pH, adsorbent dose, and contact time on the adsorption behaviour of the SDWSA for Cu2+ adsorption were systematically investigated. The adsorption mechanism of Cu2+ by the SDWSA was investigated using the Langmuir, Freundlich, pseudo-first-order kinetic, pseudo-second-order kinetic, and Weber and Morris models by combining the preliminary experimental data and characterization results. The adsorption isotherm and Langmuir equation matched perfectly. The Weber and Morris model can describe the mass-transfer mechanism of Cu2+ adsorption by SDWSA. Both film and intraparticle diffusion are rapid control steps. Compared to WSA, SDWSA has a larger specific surface area and a higher content of oxygen-containing functional groups. A large specific surface area provides more adsorption sites. Oxygen-containing functional groups react with Cu2+ through electrostatic interactions, surface complexation, and ion exchange, which are the possible adsorption mechanisms for SDWSA. These methods improve the added value of wheat straw derivatives and promote wheat straw ash recovery and centralized treatment. This makes it possible to use the thermal energy of wheat straw and facilitates the treatment of exhaust gases and carbon capture.

Single versus dual microgel species for forming guest-host microporous annealed particle PEG-MAL hydrogel.

Inter-particle secondary crosslinks allow microporous annealed particle (MAP) hydrogels to be formed. Methods to introduce secondary crosslinking networksin MAP hydrogels include particle jamming, annealing with covalent bonds, and reversible noncovalent interactions. Here, we investigate the effect of two different approaches to secondary crosslinking of polyethylene glycol (PEG) microgels via reversible guest-host interactions. We generated a dual-particle MAP-PEG hydrogel using two species of PEG microgels, one functionalized with the guest molecule, adamantane, and the other with the host molecule, β-cyclodextrin (Inter-MAP-PEG). In a different approach, a mono-particle MAP-PEG hydrogel was generated using one species of microgel functionalized with both guest and host molecules (Intra-MAP-PEG). The Intra-MAP-PEG formed a homogenous distribution due to the single type of microgels used. We then compared the mechanical properties of these two types of MAP-PEG hydrogels and found that Intra-MAP-PEG resulted in significantly softer gels with lower yield stress. We investigated the effect of intra-particle guest-host interactions through titrated weight percentage and the concentration of functional groups added to the hydrogel. We found that there was an ideal concentration of guest-host molecules that enables intra- and inter-particle guest-host interactions with sufficient covalent crosslinking. Based on these studies, Intra-MAP-PEG provides a homogeneous guest-host hydrogel that is shear-thinning with reversible secondary crosslinking.

The oxygen reduction reaction activity and selectivity of porous-carbon supported transition metals (M-C: M Mn, Fe, Co, Ni, Cu) electrocatalysts

In general, both transition metal addition and nitrogen doping are important to the four-electron (4e−) oxygen reduction reaction (ORR) activity of carbon-based catalysts, in which nitrogen-containing species, such as M-Nx, pyridinic N and graphitic N, are believed to be the active sites. On the other hand, nitrogen-free carbon supported transition metals often show their excellent electroactivity toward two-electron (2e−) ORR. Herein, carbon supported transition metal catalysts (M-C: MMn, Fe, Co, Ni, Cu) with high specific surface areas were prepared by a simple zinc-mediated pyrolysis method and their ORR activity and selectivity were systematically studied. It is found that various transition metals result in a large difference in the content and type of oxygen-containing functional groups of the M-C catalysts. The results show that CuC and CoC exhibit promising ORR activity close to the 4e− transfer mechanism in 0.1 M KOH electrolyte. FeC and MnC show a mixture of 2e− and 4e− transfer pathways. NiC is an efficient catalyst for efficient H2O2 generation through a primary 2e− ORR. It is found that the ORR selectivity of M-C is correlated to the content and type of oxygen-containing functional groups in the catalysts, and C-O-C is likely an effective active site for 4e− ORR based on both experimental results and theoretical calculations.

Effects of surfactant adsorption on the surface functional group contents and polymerization properties of coal dust

In order to better explain the wetting and polymerization mechanism between surfactant and coal dust, the effects of surfactant adsorption on the surface physicochemical properties of coal dust were investigated based on the infrared spectroscopy, zeta and dust control efficiency experiments. The results showed that compared with nonionic surfactant, anionic surfactant was more easily adsorbed on coal dust surface, while the combination of anionic-nonionic surfactants made surfactant molecules more easily adsorbed on the surface of coal dust, especially compound surfactant (B+D). With the surfactant adsorption increased, the hydrophobic functional group content and absolute potential value of coal dust decreased. For example, the surface potential and hydrophilic functional group content of coal dust adsorbing the compound surfactant (B+D) was enhanced by 43.92%, 165.7% than that of single surfactant (B). Additionally, it was verified that surfactant adsorption capacity could not be used as a critical factor to optimize surfactants applied to enhance the solution wettability. In field tests, the developed compound surfactant (B+D) enhanced respirable dust and total dust control efficiencies by 41.86% and 40.16%, respectively, compared to that of water spray. This study was conducive to choose surfactants to improve coal dust control performance of the aqueous solution.

Tannin-Based Microbicidal Coatings for Hospital Privacy Curtains.

The goal of this study was to develop a sustainable, tannin-based option for silver-based and other current antimicrobial solutions for hospital privacy curtains. Commercial tree-derived tannins were characterized and their in vitro antibacterial properties against Staphylococcus aureus and Escherichia coli were determined. Hydrolysable tannins showed greater antibacterial efficacy than condensed tannins but differences in antibacterial efficacy between any of the tannins could not be attributed to their functional group content or molar mass. Outer membrane disruption was not a significant factor in antibacterial efficacy of tannins against E. coli. In a hospital field study, draw patches coated with hydrolysable tannins and affixed to privacy curtains reduced total bacteria count by 60% over eight weeks compared to their matching uncoated reference sides. In a follow-up laboratory study with S. aureus, very light spraying with water improved contact between bacteria and coating, enhancing the antibacterial effect by several orders of magnitude.

Characterization, Antioxidant Activity, and In Silico Molecular Docking of Chitosan from Snail Shell Waste by Ultrasonic Technique

Snails are often found in Indonesia, especially at Kediri, but the snail shell has no commercial value. This research report describes the characterization and antioxidant activity of chitosan from snail shell waste (chitosan-SSW) by ultrasonic technique and analyzes the potential of chitosan as an inhibitor of receptors of free radicals using an in silico molecular docking method. Characterization of chitosan-SSW was performed to analyze the content of water, protein, and functional groups as well as molecular weight, particle size, mor-phology, antioxidant activity, and in silico molecular docking. We found that chitosan-SSW with ultrasonic treatment had a high degree of deacetylation (DD) and high molecular weight (MW). The characteristic of chitosan-SSW was found to be as follows: water content of 0.43 %, protein content of 1.59 %, molecular weight of 2.198 kDa, and deacetylation degree value of 79.50 %. Importantly, chitosan-SSW had high antioxidant activity to potentially reduce free radical of DPPH with IC50 value of 2.44 µg/mL. Chitosan is predicted to have the potential as an inhibitor of lipoxygenase, CYP2C9, and NADPH-oxidase.

Lignin decolorization in organic solvents and their application in natural sunscreen

In order to improve the utilization of industrial lignin as an effective component for ultraviolet (UV) shielding, organic solvent (methanol, ethanol, and acetone) fractionation was applied to improve its UV absorption performance and reduce its apparent color. Physicochemical properties of lignin and lignin-based sunscreens, such as molar mass fraction, functional group content, color change and UV shielding properties, were characterized in detail by GPC, UV spectroscopy, 31P NMR and HSQC-NMR spectroscopy. The results showed that the color and UV-shielding properties of the soluble fraction were significantly superior to those of the original and insoluble fractions. Different lignin fractions were acted as the only active substance in the pure cream and its UV-shielding properties were compared. Among them, the composite sunscreen by adding 5 wt% acetone fractionated lignin had highest sun protection factor (SPF) value of 6.6, approximately 4.5 times higher than those sunscreens mixed with pristine lignin. Overall, this work offers the potential of industrial lignin in value-added applications such as UV protection and cosmetics.

Effect of amino acids on growth, elemental content, functional groups, and essential oils composition on hydroponically cultivated coriander under different conditions

Amino acids act as crucial growth promoters by improving plant metabolism. Coriander is an herbaceous plant mainly cultivated from fruits. The present study objective was to analyze the effect of amino acids solution on growth, elemental content, chlorophyll, carotenoid, amino acids, and essential oils profile of coriander cultivated hydroponically under board range red & blue (BRB) and white light. The experiments were done in three sets, with three different concentrations (0, 100, & 200 ppm) of amino acid solution. The incorporation of amino acids into the nutrient solutions stimulates the nearly 20% morphological changes in the coriander plant, especially at 100 ppm in an aqueous medium in BRB light condition. The quantitative values of the 23% nitrogen, 18% phosphorous, 31% potassium, 44% magnesium, 16% iron, 76% sodium, 16% nickel, and 143% zinc in hydroponically cultivated coriander were higher at 100 ppm of amino acids solution. The use of 100 ppm amino acids solution in the nutrients used for hydroponics witnessed radical enhancement in the chlorophyll and carotenoid content and diversity of functional groups in coriander. The hydroponically cultivated coriander at 100 ppm of amino acid solution under BRB light allowed the synthesis of a higher amount of many amino acid accumulations. Plants cultivated at 100 ppm amino acids solutions contained more aromatic monoterpenes and higher linalool content (59.71%). Our study concluded that coriander cultivated at 100 ppm of an amino acid solution under BRB light condition had a positive impact on plant growth, primary and secondary metabolic accumulation Amino acids increase the plant growth, elemental content, chlorophyll, carotenoid, amino acids, and essential oils profile of coriander.

Cichorium intybus L. is a potential Cd-accumulator for phytoremediation of agricultural soil with strong tolerance and detoxification to Cd

Identifying suitable plants for phytoremediation of Cd (cadmium) contaminated agricultural soil is critical. In this study, whether chicory (Cichorium intybus L.) qualified as an ideal accumulator for phytoremediation was investigated. The hydroponic and pot experiments showed that Cd concentration in chicory leaves exceeded 100 mg kg−1 (BCF >1, TF >1) with 40 mg kg−1 Cd in pot; No significant effects on chicory growth, leaf protein and physiological and biochemical aspects when treated with ≤ 20 μM or 40 mg kg−1 Cd, because chicory could relieve Cd toxicity by increasing activities of photoprotection mechanisms, the reactive oxygen species scavenging system and concentrations of functional groups in plant tissues. In field experiment, 16.2 and 26.6 t ha−1 of chicory leaves was harvested in winter and summer, respectively. The highest Cd concentration in leaves was close to 25.0 mg kg−1 (BCF >1, TF >1) from the acid soil with 0.980 mg kg−1 Cd. Over 320 g ha−1 Cd was extracted from soil by harvesting chicory leaves both in winter and summer, with 9.24% and 12.9% of theoretical phytoremediation efficiency. Therefore, chicory can be as an ideal Cd-accumulator for phytoremediation of slight-to-moderate Cd-contaminated agricultural soil in any season.

Use of a new ZnFe2O4/biochar composite for degradation and ecotoxicity assessment of effluent containing methylene blue dye

In this study, biochar from coffee grounds was used for the first time as a support for ZnFe2O4 and its application and evaluation as a photocatalyst in methylene blue dye degradation reactions. The new composites were verified by different characterization techniques: XRD, FT-IR, SEM, EDS and band gap. The effect of different proportions of ZnFe2O4 and biochar was investigated on the dye degradation efficiency. The composites ZFO1HC3, ZFO1HC1 and ZFO3HC1 showed 93, 100 and 100% degradation in 60 min of reaction, respectively. The composites were more efficient than pure ZnFe2O4 (∼37% degradation), and this may be related to the fact that the biochar has a high concentration of phenolic, hydroxyl and carboxylic functional groups on its surface. Furthermore, this may be associated with a decrease in band gap energy and in the recombination rate of e¯/h+ pairs. Radical identification tests indicated that h+, O2− and OH were the reactive species involved in the degradation. In addition, to assess the potential toxicity of the effluent containing methylene blue, Danio rerio fish were exposed for 96 h to the crude and treated dye solution. Results showed changes in biomarkers in the gills, such as an increase in catalase activity in the group exposed to untreated methylene blue, and a reduction in glutathione S-transferase activity in this same group. Thus, the set of biomarkers evaluated in fish exposed to effluent containing methylene blue treated with a new ZnFe2O4/biochar composite showed better results when compared to those exposed to raw effluent.

Study on the influence of key active groups on gas products in spontaneous combustion of coal

In order to reveal the internal relationship between the active groups and gas products in spontaneous combustion of coal, the correlation between the content of active functional groups and the production of gas products was studied by temperature programmed experiment and in situ infrared spectroscopy analysis experiment. The results show that there are three characteristic temperature points in the gas release curve of Jurassic coal spontaneous combustion in northern Shaanxi, which can be divided into slow oxidation stage, critical temperature stage, rapid oxidation reaction stage and combustion stage. CH3, CH2, C–H and OH are actively consumed in the spontaneous combustion of coal. CO gradually increased, which is an important oxidation product during Jurassic coal oxidation in northern Shaanxi. The chain length CH2/CH3 is attacked and the fracture shortened, while the oxygen enrichment degree of CO/CC in coal increases gradually. The correlation values of key active groups of CH3, CH2, C–H, OH, CO, CH2/CH3, and CO/CC with oxygen, carbon and oxygen gases and alkane and olefin gases in the process of coal oxidation heating in different coal seams in northern Shaanxi during Jurassic period are obtained. The results show that CH3, CH2 and CH2/CH3, are the main parts of oxygen molecules attacking and binding in the Jurassic coal oxidation process in northern Shaanxi, and the oxygen-rich products of coal decompose into carbon oxygen gas and alkane alkene gas. Due to the different activation energies of various active groups, the spontaneous combustion of coal shows different reaction degrees in each stage. The research results can be used to understand the occurrence and development degree of spontaneous coal combustion, and have important guiding significance for the monitoring and warning of spontaneous coal combustion and the targeted prevention and control of spontaneous coal combustion disasters.

Effect of microwave pretreatment on oxidization behaviors of bituminous coal: Experimental measurement and quantum chemistry calculation

The poor heat conduction and mass transfer of coal seam causes unsatisfying performance of gas production for in situ combustion, while microwave pretreatment is a promising technology to solve this problem. In this work, microwave heating is adopted as pretreatment method to prepare coal samples at different microwave time. The low temperature oxidization and high temperature combustion behaviors of raw coal and modified coal samples were studied with programmed temperature rising method. The functional group content in coal samples were measured with Fourier transform infrared spectrometer, while the relationship between microstructure and reactivity was studied with quantum chemistry calculation. As microwave heating time extends from 0 s to 180 s, the crossing point temperature decreases, while the combustion reaction rate increases. As microwave time prolongs from 180 s to 240 s, the crossing point temperature becomes larger, while the combustion reaction rate becomes smaller. As microwave time increases from 0 s to 240 s, hydroxyl content and carbonyl content in coal samples reduce while ether content rises. The reduction of hydroxyl and increase of ether result in an enhancement of oxidization reactivity. The decrease of carbonyl is unfavorable for oxidization reactivity. Therefore, the effect of microwave heating on coal reactivity has two sides. This explains why the microwave pretreatment time has a non-monotonic effect on the coal reactivity in both low temperature and high temperature range.

Effect of carbon to nitrogen ratios of municipal sludge on its dehydration property

ABSTRACT Municipal sludge is the main by-product in the process of sewage treatment, and the primary problem to be solved for its harmless disposal or energy utilization is its poor dehydration property. In this paper, biological conditioning technology was used to ferment municipal sludge with methanogens under different carbon to nitrogen ratios (C/N) through an anaerobic fermentation system. The mechanism of improving sludge dewatering performance under fermentation and the effect of C/N of sludge on its dehydration property were investigated. The results showed that the flocculent structure of the sludge was destroyed by the fermentation of methanogens, the sludge’s inherent moisture was released, and the dehydration property was promoted. With the change of C/N from 8 to 20, the hydrophilic oxygen-containing functional group content of the sludge decreased first and then increased. When C/N was 16, the content of hydrophilic oxygen-containing functional groups diminished to the lowest level. Meanwhile, the surface of the sludge showed dense microscopic cavities and small holes, indicating that the sludge flocs had been cracked to a large extent, and thus the ability of the sludge to bind water was weakened. The bound water content of the fermented sludge from low to high was 48.9, 59.0, 64.3, and 71.7% respectively, with C/N of 16, 12, 20, and 8. Therefore, within the scope of this experiment, the optimal C/N for the sludge dehydration property could be identified as around 16, which could reduce the bound water content of the sludge from 87% to 48.9%.

Enhancement of excess sludge dewatering by three-dimensional electro-Fenton process based on sludge biochar.

Deep dewatering of waste activated sludge (WAS) is still a challenge due to high content of bound water and non-Newton fluid properties of sludge flocs. Electro-Fenton (EF) can enhance sludge dewaterability, however, low pH needed in homogeneous EF and fine flocs after EF conditioning influenced deep dewatering of sludge and the subsequent resource recovery disposal. In this study, a three dimension electro-Fenton (3D-EF) using Fe modified sludge biochar (Fe@SBC) as particle electrode, heterogeneous Fenton catalyst and skeleton builder for deep dewatering of sludge under neutral pH was proposed. Fe@SBC obtained at 800°C exhibited high capacity of H2O2 electrogeneration and activation due to high conductivity and content of 2e-ORR selectivity functional groups. With promoted generation of H2O2 and hydroxyl radical (•OH), 3D-EF with Fe@SBC showed higher decomposition of bound extracellular polymeric substances (EPS) and disintegration of cells in sludge flocs, resulting in releasing bound and intracellular water into free water. Compared with EF, 3D-EF with Fe@SBC800 had higher ability in breaking macromolecules of protein and polysaccharide, as well as removing -COOH and -NH2 groups in EPS, which could facilitate release of bound water trapped in EPS and self-coagulation of fine flocs. During subsequent filtering process, Fe@SBC could enhance sludge filterability as skeleton builder. A synergetic effect of strong oxidation and physical conditioning were proposed in 3D-EF sludge dewaterability with Fe@SBC, and the improved oxidation by Fe@SBC was supposed to play the major role.

Study on the Occurrence Difference of Functional Groups in Coals with Different Metamorphic Degrees.

In order to quantitatively study the difference in occurrence content of functional groups in coals with different metamorphic degrees, the samples of long flame coal, coking coal, and anthracite of three different coal ranks were characterized by FTIR and the relative content of various functional groups in different coal ranks was obtained. The semi-quantitative structural parameters were calculated, and the evolution law of the chemical structure of the coal body was given. The results show that with the increase in the metamorphic degree, the substitution degree of hydrogen atoms on the benzene ring in the aromatic group increases with the increase in the vitrinite reflectance. With the increase in coal rank, the content of phenolic hydroxyl, carboxyl, carbonyl, and other active oxygen-containing groups gradually decreased, and the content of ether bonds gradually increased. Methyl content increased rapidly first and then increased slowly, methylene content increased slowly first and then decreased rapidly, and methylene content decreased first and then increased. With the increase in vitrinite reflectance, the OH-π hydrogen bond gradually increases, the content of hydroxyl self-association hydrogen bond first increases and then decreases, the oxygen-hydrogen bond of hydroxyl ether gradually increases, and the ring hydrogen bond first significantly decreases and then slowly increases. The content of the OH-N hydrogen bond is in direct proportion to the content of nitrogen in coal molecules. It can be seen from the semi-quantitative structural parameters that with the increase in coal rank, the aromatic carbon ratio fa, aromatic degree AR and condensation degree DOC increase gradually. With the increase in coal rank, A(CH2)/A(CH3) first decreases and then increases, hydrocarbon generation potential 'A' first increases and then decreases, maturity 'C' first decreases rapidly and then decreases slowly, and factor D gradually decreases. This paper is valuable for analyzing the occurrence form of functional groups in different coal ranks and clarifying the evolution process of structure in China.

Ultrasound-assisted H2O2 directional-modification of powdered activated carbon for the enhanced adsorption of secondary effluent organic matter from printing and dyeing processes

The physicochemical properties of powdered activated carbon (PAC) are important factors affecting its adsorption performance, which is also related to the characteristics of target organic pollutants. In this study, the key indicators affecting the adsorption performance of PAC were identified, and the physicochemical properties of PACs were modified by hydrogen peroxide and/or ultrasound in a targeted manner to improve the adsorption performance. The results indicated the adsorption properties of printing and dyeing secondary effluent organic matter (EfOM) in terms of CODcr and UV absorbance at 254 nm (UV254) positively correlated with mesoporous volume, average pore size and acid group content of PAC. After modification, the mesoporous volume and average pore size of PAC increased, and the number of acidic groups increased, thus enhancing the adsorption efficiency. EfOM removal characteristics showed that PAC preferentially adsorbed unsaturated bonds or aromatic compounds, tryptophan-like proteins, soluble microbial metabolites and low molecular weight fractions below 1 kDa. In addition, the relative contents of specific surface area, pore volume and oxygen-containing functional groups (O-CO, C-OH, CO/O-C-O) of PAC decreased after adsorption, indicating that EfOM adsorption was a physical and chemical process, including pore filling, hydrophobic interaction and chemical bond force interaction. In general, PACs with larger mesoporous volume, average pore size and abundant acid groups possessed good adsorption performance towards EfOM.

Elucidating the effect of the physicochemical properties of organosolv lignins on its solubility and reductive catalytic depolymerization

Unsatisfactory solubility and recalcitrant condensed structures of isolated lignins (technical lignins) severely limit their processability into renewable materials, fuels, and chemicals. Therefore, a comprehensive understanding of the structural and physicochemical properties of isolated lignins is of great value in explaining their performance in the solubilization and further depolymerization to high-value applications. In this work, we investigated the solubilization and depolymerization performance of organosolv lignins from three different sources (beech (L01), birch (L02), and wheat straw (L03)). We applied sequential solvent fractionation as a tool to subdivide parent lignins into four more homogeneous subfractions (SF1, SF2, SF3, and IF), with a gradual increase in molecular weight and interunit linkages and a decrease in phenolic –OH group from SF1 to IF. The solubility tests of the parent lignins and their subfractions at ambient conditions were carried out in six organic solvents (n-hexane, diisopropyl ether, ethyl acetate, ethanol, methanol, and acetone) with large differences in Hansen solubility parameters. Among the solvents studied, the solvents with δp > 8 MPa1/2 demonstrated a high solubilization yield of organosolv parent lignins and their subfractions. The solubilization behavior of parent lignins and subfractions was further described based on their inherent structural properties, such as molecular weight and functional group content (phenolic –OH and –COOH). The structure–reactivity characteristics of parent organosolv lignin and their subfractions were also investigated under different conditions in the presence of catalyst-containing transition (NiHTC-500) and noble (Pd/C) metals as active centers. Strong structural correlations between parent lignin/subfractions and depolymerized lignin oils were derived using GC-FID/MS, GPC, 1H–13C HSQC NMR, and 31P NMR.

Oxygen-terminated vanadium carbide with graphitic carbon nitride nanosheets modified electrode: A robust electrochemical platform for the sensitive detection of antibiotic drug clioquinol

Engineering the electrocatalyst's nanostructure is key-factor in constructing a high-performance electrochemical sensor. The MXene vanadium carbide (V8C7Tx; VC) nanosheets encapsulating graphitic carbon nanosheets nanocomposite (VC/g-CN NSs NC) as an effective electrocatalyst for detecting clioquinol (CQL) is reported here. The interconnected VC and g-CN nanosheets form a very effective conductive network. The high concentration of O-terminated functional groups in the oxidized VC and the abundant surface area of g-CN contribute to the enhanced electrocatalytic effectiveness of the nanocomposite. The synergistic interaction between the VC NSs and g-CN NSs creates a nanocomposite ideal for CQL detection because it offers many active sites with a fast electron transfer rate. A lower oxidation potential and higher peak current responsiveness distinguish the proposed drug sensor from previously described CQL sensors. Under optimal conditions, the constructed sensors showed strong analytical performance, as shown by a low detection limit of 2.2 nM, high sensitivity of 15.6 µA µM−1 cm−2, a broad linear range of 0.3–220 µM, and significant recovery outcomes in the analysis of real samples. Thus, the VC/g-CN NSs NC material has promise for use in high-performance electrochemical applications.

A double-edged sword: Reductive soil disinfestation changes the fates of trace metal elements in soil

Although the effects of reductive soil disinfestation (RSD) in soil sterilization have been proven in several countries, the potential risks of trace metal elements (TMEs) caused by RSD require further assessment. Here, freshly Cd-spiked soil and historically contaminated greenhouse soil were exposed to RSD and the fates of TMEs, Cd, Co, Cu, Ni, Pb, and Zn, were investigated. All RSD treatments lasted for 21 days and subsamples were collected at different time intervals. Samples were open-air incubated for another 7 days until day 28 to simulate the situation after drainage. The bioavailability and geochemical fractionation of TMEs were investigated based on single and sequential extraction procedures and the environmental risks were assessed. The results showed that RSD increased the relative abundance of Firmicutes and Bacteroidetes, and the content of functional groups, including Fe, Mn, and S compounds respirations increased after RSD, highlighting the possible reductive dissolution of FeMn oxides and precipitation of TMEs. The dissolution decreased the reducible fractions of TMEs and increased the acid-soluble fractions of Co, Ni, Pb, and Zn, in the European Community Bureau of Reference results, reflecting the activation of TMEs in soils. However, the precipitation of sulfate resulted in the stabilization of Cd and Cu in two types of soils, increased their residual fractions, and decreased their acid-soluble fractions and bioavailabilities. After drainage, because the influence caused by precipitation rapidly disappeared and the impact of FeMn oxides dissolution remained, the acid-solubility of TMEs was greater than their initial status in the two soils. Furthermore, as a highly toxic metal, the activation of Cd at 28 days caused the rapid increase of ecological risks, which is particularly concerning. The results suggest that RSD temporarily increases the potential risks of TMEs and that certain measures must be taken.