Concentration Of Functional Groups Research Articles

Rational design, synthesis, and characterization of facilitated transport membranes exhibiting enhanced permeability, selectivity and stability

Despite outperforming conventional polymer membranes in the short time frame, facilitated transport membranes (FTMs) are prone to photo/chemical aging, which causes a rapid decay of their performance. Moreover, when embedded in polymer materials to fabricate mixed matrix membranes, structural defects may form at the metal-polymer interface, causing a selectivity loss. To overcome these issues, a series of poly(amic acid)s (PAAs) have been synthesized using 4,4’-oxydiphathalic anhydride (ODPA) and Jeffamine monomers of varying molecular weight, and used to fabricate silver nanoparticles via the chelating reaction with silver ions, in attempts to simultaneously i) achieve defect-free mixed matrix membranes (MMMs), ii) target CO2 selective transport, and iii) enhance long-term stability. The occurrence of the chelating reaction between silver and the PAA was confirmed, and as a result, individual and un-aggregated PAA-coated silver nanoparticles were obtained and incorporated into a commercial polymer, Pebax 1657, to fabricate defect-free mixed matrix membranes. The effect of the PAA length and ether functional group concentration on the structure and performance of the resulting mixed matrix membranes was systematically investigated. Remarkably, inclusion of only 2 wt% nanoparticles in Pebax enhances the CO2 permeability by 50% and CO2 selectivity by 100% relative to neat polymer. A detailed analysis of the sorption and diffusion coefficients was performed to elucidate the molecular origin of the observed membrane performance. Finally, preliminary data show that the newly synthesized materials exhibit high chemical stability upon exposure to pure H2.

The Influence of Carboxyl-Functionalized Carbon Dots on Ethanol Selectivity in Gas Sensing

For semiconductor tin dioxide (SnO2) materials, the oxygen adsorption theory often struggles to explain their selectivity towards specific gases. Therefore, it is worth considering altering the surface functional groups of SnO2 to modify its surface state and enhance its selectivity towards specific gases. Due to the rich functional groups on the surfaces of carbon dots, this study employed a hydrothermal method to prepare three types of carbon dots with varying carboxyl functional group contents by adjusting the hydrothermal time. These carbon dots were then used as dopants and combined with SnO2 to create composite gas-sensitive devices. The gas-sensing test results indicate that the introduction of carboxyl functional groups can enhance the selectivity of SnO2 towards ethanol. Furthermore, at any operating temperature within the range of 150–300 °C, the higher the carboxyl functional group content on the surface of carbon dot-doped SnO2, the higher the sensitivity towards ethanol. By employing density functional theory (DFT), the interaction energies between the surfaces of carbon dots and surface carboxyl groups with the target gas were calculated. These calculations validated the gas-sensing test results, confirming that the presence of carboxyl functional groups enhances the selectivity towards ethanol. The results of this study can provide new insights into the research on the selective mechanism of gas-sensitive materials.

Extraction of humic acid from peat and lignite and the thermal behavior of their mixtures with ammonium nitrate

Due to the positive effect on soil structure and the influence on improving the efficiency of plant roots nutrient uptake, humic acids (HA) are widely considered for fertilizer production. Especially, it seems to be particularly promising to use them as additives in technologies of mineral fertilizer production. One of the common mineral fertilizer components, due to its good water solubility and the presence of nitrogen in two forms, is ammonium nitrate (AN). The aim of this study was to determine the influence of the humic acids extracted from peat and lignite on the thermal decomposition of HA and the thermal decomposition of ammonium nitrate and humic acids mixtures. For the quality assessment of HA, spectroscopic methods (FTIR/ATR and CP/MAS 13C NMR) and analysis of elemental composition were used. The analysis of the spectra showed differences in the degree of humification of humic acids extracted from various raw materials. HA isolated from peat were distinguished by the presence of peptides, polysaccharides, and lignin residues. Elemental analysis showed the higher carbon and sulfur content in the extracted HA compared to the reference samples. The results of the TG-DTA-MS analysis confirmed the influence of differences in the molecular structure of humic acids, especially in the aliphatic and aromatic carbon content, on the thermal decomposition process. Total content of carboxylic and/or hydroxylic functional groups had a significant impact on the start of the decomposition temperature. Their increase visibly influenced the acceleration of the exothermic decomposition of AN.

The presence of copper ions alters tetracycline removal pathway in aerobic granular sludge: Performance and mechanism

This study investigated the removal characteristics of tetracycline (TC) in the presence of copper ions (Cu2+) in aerobic granular sludge by analyzing the TC removal pathway, composition and functional group changes of extracellular polymeric substances (EPS), and microbial community structure. The TC removal pathway changed from cell biosorption to EPS biosorption, and the microbial degradation rate of TC was reduced by 21.37% in the presence of Cu2+. Cu2+ and TC induced enrichment of denitrifying bacteria and EPS-producing bacteria by regulating the expression of signaling molecules and amino acid synthesis genes to increase the content of EPS and –NH2 groups in EPS. Although Cu2+ reduced the content of acidic hydroxyl functional groups (AHFG) in EPS, an increase in TC concentration stimulated the secretion of more AHFG and –NH2 groups in EPS. The long-term presence of TC presence of the relative abundances of Thauera, Flavobacterium and Rhodobacter and improved the removal efficiency.

Effects of ultrasonic and surfactant coupling treatment on the wettability of coal

Coal wettability has an important influence on the permeability of water-injected coal seam. The coal seam water injection effectively improves the ultrasonic excitation effect, and the surfactant can mitigate the water lock effect produced during water injection. To study the effect of ultrasonic and surfactant coupling treatment on the wettability of coal, the ultrasonic excitation fracturing system was used to perform excitation experiments on different coal samples. The coal microscopic properties were determined, and the coal wettability was characterized based on the contact angles. The experimental results demonstrate that the general decrease in the content of hydrophilic groups after the coal was coupled with ultrasonic and surfactant compared to the alkyl polyglycoside (APG) treatment, and the decrease in the content of oxygen-containing functional groups was more obvious; the pore size, pore volume and specific surface area (SSA) of coal all increased to different degrees, especially for pore size and pore volume; under the treatment of ultrasonic or surfactant, the coal wettability was enhanced, while the wettability was further enhanced by the coupling treatment; when ultrasonic was coupled with the surfactant, an advantageous complementary effect could be formed, which improved the final effect of the coupling treatment.

Revealing the Chemical Nature of Functional Groups on Graphene Oxide by Integrating Potentiometric Titration and Ab Initio Calculations.

A new graphene oxide (GO) model with reasonable functional group types and distribution modes was proposed by integrating potentiometric titrations and ab initio calculations. Due to the complex synthesis mechanism, the atomic structure of GO has been controversial for a long time. Here, we use density functional theory calculations to mimic the oxidation process, and a series of GO fragments (GOFs) were deduced. A new pKa calculation method (RCDPKA) developed specifically in this work was further used to predict pKa values of the fragments. Then, we performed potentiometric titrations on four different GO samples to confirm the existence of these GOFs and determine the content of functional groups. Interestingly, different GO samples present the same pKa values in titration, and the results are consistent with the predicted ones. Based on the evidence from titration and calculation, prominent correlations between functional groups could be found. Groups at the edges are mainly double-interactive carboxyls (pKa1 ≈ 3.4, pKa2 ≈ 5.7) and double-adjacent phenolic hydroxyls (pKa1 ≈ 8.8, pKa2 ≈ 12.1), while groups on the plane are mainly collocated epoxies and hydroxyls (pKa1 ≈ 11.1, pKa2 ≈ 13.8) on both sides of the plane with a meta-positional hydrogen bond interaction. These findings were further validated by multiple characterizations and GO modifications. These results not only stimulate a fundamental understanding of the GO structure but also provide a quantitative analysis method for functional groups on GO.

Controllable synthesis of lignin nanoparticles with antibacterial activity and analysis of its antibacterial mechanism

As a kind of polyphenol substance, lignin is considered to have good biological activity and certain antibacterial properties. However, it is difficult to be applied because of its uneven molecular weight and difficulty in separation. In this study, by way of fractionation and antisolvent, we obtained lignin fractions with different molecular weight. Moreover, we increased the content of active functional groups and regulated microstructure of lignin, thereby increased lignin's antibacterial property. The classification of chemical components and the control of particle morphology also provided convenience for the exploration of lignin's antibacterial mechanism. The results showed that acetone with high hydrogen bonding ability could collect lignin with different molecular weights and increase the content of phenolic hydroxyl groups, up to 31.2 %. By adjusting the ratio of water/solvent (v/v) and stirring rate during the process of antisolvent, lignin nanoparticles (sphere 40–300 nm) with regular shape and uniform size can be obtained. Through observing the distribution of lignin nanoparticles in vivo and in vitro after co-incubation for different time, it could be found that lignin nanoparticles firstly damage structural integrity of bacterial cells externally, and then are swallowed into cells to affect their protein synthesis, which constitutes a dynamic antibacterial process.

Amorphous Fluorinated Acrylate Polymer Dielectrics for Flexible Transistors and Logic Gates with High Operational Stability.

Fluorinated amorphous polymeric gate-insulating materials for organic thin-film transistors (OTFTs) not only form hydrophobic surfaces but also significantly reduce traps at the interface between the organic semiconductor and gate insulator. Therefore, these polymeric materials can enhance the OTFT's operation stability. In this study, we synthesized a new polymeric insulating material series composed of acrylate and fluorinated functional groups (with different ratios) named MBHCa-F and used them as gate insulators for OTFTs and in other applications. The insulating features of the MBHCa-F polymers, including surface energy, surface atomic content properties, dielectric constant, and leakage current, were clearly analyzed with respect to the content of the fluorinated functional groups. At higher fluorine-based functional group content, the polymeric series exhibited higher fluorine-based contents at the surface and superior electrical properties, such as field-effect mobility and driving stability, at OTFTs. Therefore, we believe that this study provides a substantial method for synthesizing polymeric insulating materials to enhance the operational stability and electrical performance of OTFTs.

Characteristics and mechanism of Glutathione in inhibiting coal spontaneous combustion

Inhibitors play an important role in preventing and controlling coal spontaneous combustion (CSC). In this study, the inhibitory effects of antioxidant-reduced glutathione (G-SH) on CSC were examined. Thermogravimetric-differential scanning calorimetry (TG-DSC), cross-point temperature (CPT), and oxidation product tests were used to examine the effect of G-SH on the tendency of CSC and compare the discrepancy in the inhibition effect of G-SH and the halogen inhibitor. The changes in the free radical type, concentration, and surface functional groups in coal before and after the addition of G-SH were analyzed using electron spin resonance spectroscopy (ESR) and Fourier transform infrared spectroscopy (FT-IR). Six common active radical models were constructed, and the thermodynamic parameters of the reaction were calculated using density functional theory (DFT). The results revealed that G-SH inhibits the spontaneous combustion of coal. The inhibitory effect of G-SH was significantly stronger than that of the halogen salt inhibitors CaCl2 and MgCl2, and the higher the concentration of G-SH, the stronger is the inhibitory effect. The characteristic temperature points in the thermogravimetric experiment of coal samples with G-SH shifted to a higher temperature zone, and the CO concentration and oxygen consumption were lower than those of raw coal. After G-SH treatment, the type and relative concentration of free radicals in coal were lower than those in raw coal, the content of aliphatic hydrocarbon functional groups and oxygen-containing functional groups decreased, and the content of sulfur-containing functional groups increased. According to the calculation of Gibbs free energy and reaction enthalpy, G-SH can effectively neutralize the active free radicals in the process of coal oxidation, and the reaction activity with the free radicals in the process of coal oxidation is ·OOH > ·OH > ·CH3 > RO· > R· > ROO·. According to the experimental results, it is inferred that G-SH continuously supplies a large number of hydrogen donors (·H) for the reaction during the oxidation process and simultaneously neutralizes carbon free radicals and carbon oxygen free radicals, thereby reducing the concentration and reactivity of free radicals in the whole chain reaction process and blocking the occurrence of coal-oxygen composite reaction.

A novel micro-sphere activated carbon synthesized from waste cigarette butts for ammonia adsorption

Waste cigarette filters mainly contain hardly degradable cellulose acetate, toxic nicotine, and traces of heavy metals, and therefore cause environmental pollution hazards when discarded. In order to convert cigarette butt waste into a valuable product, this article investigates the preparation of activated carbon from cigarette butts via a two-step process of hydrothermal reaction and a subsequent chemical activation with phosphoric acid as an activator. During hydrothermal reaction, it was found that a process of decarboxylation and dehydration cleavage of acetate occurs, leading to micron fragments and subsequent agglomeration into carbonaceous micro-spheres. The cigarette-butts-derived activated carbon micro-spheres have a high BET surface area of ∼ 1406 m2/g and NH3 adsorption capacity of ∼ 35.9 mg/g. It was revealed that the ammonia adsorption capacity tends to be positively and linearly correlated with the acidic functional group content of the activated carbon surface while negatively with BET surface area.

The variations and mechanisms of coal wettability affected by fracturing fluids with different concentrations of Ca2+ during fracturing

In low-porosity, low-permeability, and high-adsorption coalbed methane (CBM) reservoirs, the flow of fracturing fluid and methane gas is strongly affected by the wettability of coal. Ca2+ in mine water can affect the wettability of coal by changing the properties of the fracturing fluid, thus affecting the recovery efficiency of CBM. To investigate the mechanism of the wetting properties of bituminous coal by fracturing fluid with different concentrations of Ca2+, contact angle and T2 distribution curves were tested using an interfacial rheometer and low-field nuclear magnetic resonance (LF-NMR), and changes in water absorption and functional groups of coal soaked by fracturing fluid with different concentrations of Ca2+ were described using a precision electronic balance, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to evaluate the wetting properties of coal. Molecular dynamics simulation was used to characterize the microscopic wetting properties of water molecules on the coal surface. Results show that when the concentration of Ca2+ is lower than 50 mg/L, the surface tension of the fracturing fluid gradually decreases, and the lowest value is 27.66 mN/m at 50 mg/L. The overall change in the contact angle and T2g value was lower than that of the control group (no Ca2+). The content of oxygen-containing functional groups on the surface of coal increased by 22.30%, and the content of C-O functional groups inside coal increased by 3.55%. The relative concentration and density of water molecules on the coal surface increase with increasing molecular diffusion ability. These results indicate that when the Ca2+ concentration is lower than 50 mg/L, the wettability of coal is enhanced, and thus, the fracturing fluid and methane gas flow capacity is improved. However, with increasing Ca2+ concentration, this phenomenon is reversed, and the water absorption of coal decreases, indicating that the wetting ability of coal decreases. The results of this study provide theoretical guidance that can be used to improve the recovery of CBM by fracturing and permeability enhancement measures, and preparing fracturing fluid in mine water to strengthen the protection of freshwater resources.

Rapid extraction of gold from complex solutions by metal sulfides

The industrial application potential of current adsorbents for Au(III) recovery is limited due to their high costs, poor adsorption capacity, and complicated preparation processes. This study introduces a novel approach to address these challenges by synthesizing metal sulfides through a one-step hydrothermal method. The synthesized metal sulfides exhibit exceptional adsorption capacities, exceeding 1500 mg/g. Particularly, petal-shaped CuS demonstrates outstanding performance in extracting gold from complex solutions, including fresh water and simulated leaching liquid of electronic circuit boards. With an impressive adsorption capacity of 2536 mg/g in a 700 mg/L Au (III) spiked solution, CuS achieves a remarkable 90.6% removal efficiency. The adsorption process of CuS on gold can be well described by a pseudo-second-order kinetic model and the Langmuir model. Furthermore, CuS is successfully loaded onto sodium alginate (SA) aerogel for large-scale applications. The layered structure of SA overcomes the challenge of solution retrieval, making it a promising material with outstanding removal performance for industrial use. In cases where a high specific surface area does not confer advantages, CuS demonstrates superior performance compared to numerous gold ion adsorbents. This observation motivates us to emphasize the content of active functional groups during the design of gold ion adsorbents. This research significantly advances the field of Au(III) recovery by providing cost-effective and efficient adsorbents with simplified synthesis processes and strong adsorption capabilities.

Investigation on the effect of functional groups on the wettability of coal dust: Experiments and theoretical validation

The interaction between the functional groups of pulverized coal and water molecules is essential to study the wettability of pulverized coal surfaces. Coal dust samples with the same degree of deterioration were modified in this study using appropriate concentrations of nitric acid and hydrogen peroxide. Based on macroscopic experiments such as Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), the functional group content and surface wettability changes of coal dust before and after modification were investigated, respectively. Experiments demonstrated that the increase in the percentage of oxygen-containing functional groups (OFGs) before and after the modification of coal samples improved the hydrophilicity of the coal surface, which was mainly dominated by the effect of O = C-O. Eight simulation systems were also constructed by grafting different functional groups with flaky graphene as the substrate in combination with molecular dynamics (MD) theory. The results of simulated contact angle, interaction energy, and radial distribution function were used to analyze the influence law of these groups on the wettability of pulverized coal in detail. Simulations indicate that the diffusion of water molecules on the coal surface is related to the number of hydrogen bonds formed between water and coal. In the simulated system of polar groups, the hydrophilicity of the interface is enhanced due to the strong hydrogen bonding between water molecules and functional groups. However, for the analysis of non-polar groups, the hydrophobic nature is improved due to the increase of carbon chains. The results of the experiments and the simulations correspond to each other, revealing the reasonableness of the simulations. It was finally confirmed that the wetting ability of water molecules for the eight functional groups was in the order of: –COOH > –OH > –CHO > –NH2 > –COC > –CH3 > -C2H5 > -C3H7.

Sustainable eutectic mixture strategy of molten salts for preparing biochar with interconnected pore structure from algal residue and its performance in aqueous supercapacitor

A green ternary (NaCl/KCl/ZnCl2) mixed salt-assisted carbonization of spirulina residues was proposed to produce the nitrogen-doped biochar (NBC) with a hierarchical porous structure for the application of supercapacitors. Modifying the ratio of mixed salt to residues and the carbonization temperature allows it to control the specific surface area (SSA) of biochars, the type and content of functional groups, and the graphitization of the carbon skeleton. Here, the eco-friendly mixed salt functioned for a multifunctional purpose by acting as both a pore regulating agent and the reaction medium. The optimal 650–5 sample, produced by a reaction temperature of 650 °C and ratio of 5, exhibited remarkable specific capacitance of 215 F/g and 207 F/g at 0.2 A/g in 1 M H2SO4 and 6 M KOH electrolytes, respectively, and the composed symmetrical capacitors showed excellent cycling stability in the four aqueous electrolytes (plus 1 M Na2SO4 and 15 mol/kg LiTFSI), with capacitance retention rate all ≥90 % after 10,000 cycles. In the LiTFSI system, the energy density was 25.28 Wh/kg at 375.04 W/kg. Furthermore, experiments using recycled salt confirmed the sustainability of this approach.

Ultrasonic–Thermal Regeneration of Spent Powdered Activated Carbon

This study investigated the ultrasonic–thermal regeneration of powdered activated carbon (PAC) spent using 4-chlorophenol (4-CP). Similarly, a thermal regeneration process was also studied and the reaction conditions (i.e., regeneration temperature, heating rate, regeneration time) were tested. Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis were applied to characterize the regenerated PACs under different treatments (thermal, ultrasonic and ultrasonic–thermal) and also compare them with the fresh and exhausted PACs. According to our regeneration observations, the ideal regeneration parameters were determined to be a 40 kHz frequency, 0.18 W/mL sonication power, 0.1 M NaOH and 50% (v/v) ethyl alcohol as the regeneration solution, and 1 g/L of saturated PAC mass with thermal regeneration as the second stage at 500 °C, desorbed for 30 min with a heating rate of 20 °C min−1. Under these conditions, the RE value achieved 90.99% and the η value reached 5.6%. The results of FTIR, XPS and XRD revealed that the oxygen functional group content of ultrasonic–thermal regenerated PAC significantly increased. These oxygenous groups exerted a positive effect on the adsorption process of the regenerated PAC and the subsequent adsorption–regeneration process.

The effect of short-chain fluorocarbon and electrolyte on simultaneous dedusting and explosion prevention performance when applied to coal particle with high oil-content

The fully mechanized mining faces in underground oil-rich coal mines are exposed to the serious dust pollution and the high risk of dust explosion. Traditional materials cannot effectively realize the removal and inerting of coal particles with high oil content. Thus, this paper innovated new materials to eliminate the occupational disasters and explosion accident in underground coal mines by achieving simultaneous dedusting and explosion prevention of coal particles with high oil content. Compare with traditional materials, the presence of short-chain fluorocarbon surfactants and electrolytes achieved 76.30–84.92% improvement on dedusting rate, a maximum 22 times improvement on MIE, 4.20–8.90% improvement on MIT, and 50% improvement of MEC. Mechanism analysis revealed the better performance is attributed to the optimized wetting and agglomerating behaviour. Kinetic analysis showed that the new materials reduced the heat release and inhibit combustion process. The NaCl outperforms NaHCO3 in achieving better dedusting and explosion suppression performance in most cases for its higher TSI and more efficient explosion prevention mechanisms. Studies also demonstrated that the oil content could moderate the dedusting and explosion prevention performance due to the reduction of static liquid bridge force in terms of the increased proportion of saturated hydrocarbons and aromatic hydrocarbons, the reduced concentration of polar functional group, and the corresponding increased contact angle “θ”. The Findings of this paper provide an efficient and environmental-friendly choice for ensuring occupational health and safe production in underground oil-rich coal mines by achieving simultaneous dedusting and explosion prevention. It will also guide the innovation and development of multiple protective materials for coal mine safety protection.

Porous Chitosan Composite Membrane Tandem Laser-Induced Breakdown Spectroscopy for Detection of Metal Elements in Liquid Samples

Laser-induced breakdown spectroscopy (LIBS) is currently one of the most popular techniques for direct element analysis of solid samples. However, when directly used for liquid sample analysis, there are disadvantages, including sample splashing, plasma quenching, and poor signal stability. These problems can be overcome through liquid-solid matrix conversion; at the same time, LIBS signal enhancement can be realized, and the sensitivity of detection of liquid samples can be improved. For this research, the authors used chitosan (CS) as a raw material, and introduced poly(vinyl alcohol) (PVA) and polyethyleneimine (PEI) to finally synthesize a new type of porous membrane material with better stability and more functional group content. The membrane was used as a liquid-solid conversion matrix material combined with LIBS technology to successfully achieve rapid separation and detection of Cu, Ag, Pb, and Cr, and the corresponding detection limits can reach 0.038, 0.069, 0.012, and 0.009 mg/L, respectively. This method further improves the sensitivity of the LIBS method. Combining it with membrane materials will replace inactive membranes and open up a new way for the rapid analysis of solution samples using LIBS technology.

Oxidative combustion law of water-soaked coal under oxygen-lean condition

ABSTRACT Residual coal is easily submerged and damaged by groundwater. In the course of mining underlying coal seam, coal belonging to the overlying gob area tends to spontaneously combust during draining water. To explore the effect of micro-functional group transformation in immersed coal on the coal spontaneous combustion (CSC) traits during the low-temperature oxidation process (LTO), the migrant law of special functional groups under varying oxygen concentration (Co) of immersed coal was discussed by infrared spectroscopy. The endothermal and exothermal properties of the function group inside of coal were studied via thermal analysis. It is shown that the higher Co, the more oxygenic function groups on the soaked, and by contrasted with the Co of 18% the 14% has a small increase and the chain length is shortened. The temperature increment together with the Co content determines the functional group content, the pyrolysis process produces some function group. The lower the Co, endothermic coefficient decreases and endothermic temperature increases, the higher the ignition temperature of coal oxy-combustion, the lower the total heat release. And the speed of the oxygen-absorbing weight gain and the conversion of the functional group would be improved followed by the burnout temperature rising. Below 14% Co, the oxidative combustion process will be greatly inhibited. Those findings complement a theoretical basis for preventing long-term water-soaked coal oxidative spontaneous combusting in shallow buried coal seams.

ANTIMICROBIAL ACTIVITY OF BACTERIAL CELLULOSE MODIFIED WITH PLANT EXTRACTS

Bacterial cellulose (BC) is utilized in numerous industries, including the cosmetic, biomedical, and packaging industries. Nonetheless, BC lacks antibacterial activity and must be combined with antimicrobial agents, including plant extracts. This review aims to give information on the antibacterial activity of BC that has been modified by the addition of plant extracts. The method used in this study is article review. Articles were selected from Q1-Q3 category international journals published within the recent decade. Based on the results, extracts of rhizomes, ethanol extracts of gwarri stems and leaves, oregano leaves, rosemary leaves, lovage leaves, parsley leaves, green tea leaves, rosella petals, and red and pink variants of hibiscus flowers, bitter melon seeds, gletang leaves, arabica coffee, and andaliman fruit, temu Kunci dimethyl sulfoxide extract, mulberry leaf NaOH extract, pomegranate skin water extract, and rosemary leaves have been used to modify BC. Antimicrobial activity showed the most significant increase in BC-modified ethanol extract of rosella petals at a concentration of 500 ppm with an OD600 of 0% against Pseudomonas aeruginosa. FTIR and SEM investigations of pure BC and BC modified with plant extracts revealed variations in functional group content and three-dimensional fibrillar network structure.

Effect of Soaking Time on the Spontaneous Combustion Characteristics of Lignite

ABSTRACT When mining deep coal seams, the overlying mined-out area must be pumped and drained, and the remnant coal in the mining void area is vulnerable to spontaneous combustion via water immersion and air drying. To investigate the effect of soaking time on the spontaneous combustion characteristics of lignite, low-temperature N2 adsorption experiments and Fourier transform infrared spectroscopy (FTIR) experiments were used in this study to investigate the changes in pore structure and functional group content of coal samples by increasing the soaking time. Based on programmed warming experiments, macroscopic characteristic indicators of coal spontaneous combustion (CSC) oxidizability, such as the oxygen consumption rate and index gas, were derived. Results showed that the effect of soaking caused the total pore volume and specific surface area of lignite to increase to different degrees, which enhanced the adsorption capacity of coal to oxygen and improved the effective contact of oxygen with the active sites on the coal surface. However, there was no consistency in the effect of different soaking times on the content of reactive functional groups of the coal, with higher methyl and methine contents after 60 days of soaking (S60) and 120 days of soaking (S120) than in the raw coal (RC), and less in 90 days of soaking (S90). The propensity of coal to spontaneously combust is determined by both the pore structure and reactive functional groups, which shows the propensity of spontaneous combustion S60>S120>RC>S90. Results from this study are important in understanding the mechanism of CSC of water-soaked lignite in mined-out areas and can provide theoretical guidance to prevent CSC in mining areas.