Concentration Of Functional Groups Research Articles

Effect of temperature on interface debonding behavior of graphene/graphene-oxide on cement-based composites

Temperature effect easily affect the adhesion of graphene/graphene oxide (GO) on the cement-based composites originating from the weaker non-covalent bonding at the interface, leading to weakening of the cementitious composite properties. In this study, the interfacial debonding behavior of graphene/GO and cement-based composites was investigated for low to high temperatures (250∼550 K) using controlled molecular dynamics simulations. The maximum tensile force and work of adhesion both decrease with increasing temperature, and the value of GO is 5∼6 times that of graphene. Especially at the high temperature end, GO is still difficult to peel off (Fmax: 7.93×103 pN, Wmax:2129.60 Kcal/mol). Meanwhile, the insights into the distribution and concentration of functional groups have shown that high concentrations and edge functional groups can improve interface adhesion. Energy decomposition demonstrated that, compared to the Coulomb effect of charge and the prestress of surface wrinkles, the van der Waals effect plays a major role in interface adhesion. Entropy analysis further reveals the high temperature sensitivity of graphene and the low sensitivity of GO due to edge functional groups. We believe that the insight into the temperature effect of interface debonding behavior at nanoscale can provide theoretical support for the effective temperature working conditions of graphene/graphene-oxide on cement-based composites.

Sewage Sludge-Derived Biochar and Its Potential for Removal of Ammonium Nitrogen and Phosphorus from Filtrate Generated during Dewatering of Digested Sludge

Utilizing waste, such as sewage sludge, into biochar fits the circular economy concept. It maximizes the reuse and recycling of waste materials in the wastewater treatment plant. The experiments were conducted to assess: (1) the impact of the temperature on the properties of biochar from sewage sludge (400 °C, 500 °C, 600 °C, 700 °C); (2) how the physical activation (CO2, hot water) or chemical modification using (MgCl2, KOH) could affect the removal of ammonia nitrogen and phosphorus from filtrate collected from sludge dewatering filter belts or synthetic solution, wherein the concentration of ammonium nitrogen and phosphorus were similar to the filtrate. Based on the Brunner–Emmett–Teller (BET) surface and the type and concentration of surface functional groups for the second stage, biochar was selected and produced at 500 °C. The modification of biochar had a statistically significant effect on removing nitrogen and phosphorus from the media. The best results were obtained for biochar modified with potassium hydroxide. For this trial, 15%/17% (filtrate/synthetic model solution) and 72%/86% nitrogen and phosphorus removal, respectively, were achieved.

Effect of Gemini surfactant on wettability of Lignite: An experimental and molecular dynamics simulation study

In this study, the nonionic Gemini surfactant S465 was used for regulating the wettability of the lignite surface. The adsorption characteristics of the surfactant on the lignite surface are discussed, and the mechanism of adsorption is explained from a microscopic viewpoint. The adsorption experiments show that the adsorption of S465 on the lignite surface is consistent with predictions made by the Langmuir adsorption isotherm. Furthermore, it indicates that the adsorption process is spontaneous and exothermic. X-ray photoelectron spectroscopy (XPS) analysis shows that the oxygen-containing functional groups content (CO, C = O, and O = C-O) on the lignite surface decreases after the adsorption of the surfactant, which enhances the hydrophobicity of the lignite surface. It is found from molecular dynamics (MD) simulation that the polar ethoxy groups of the surfactant touch the lignite surface, and the nonpolar groups (alkyl chains) entwine closely with each other, forming a protective layer, which keeps water away from the surface of the lignite. The mobility of water molecules is higher in the lignite/surfactant/water system compared to the system without surfactants, and the adsorption of surfactants results in the lignite interaction with water being weaker, therefore, the hydrophobicity of lignite is improved after the adsorption of the surfactant.

Catalytic cycloaddition of CO2 to epoxidized methyl oleate over a HBimCl-NbCl5/HCMC: Physicochemical, mass transfer and kinetic investigation

The cycloaddition of CO2 to epoxidized molecules is an ecofriendly strategy for synthesizing aliphatic carbonates. In this study, heterogeneous catalytic synthesis of carbonated methyl oleate was performed. Influences of reaction parameters such as reaction temperature (403.15–443.15 K), pressure (1–3 MPa), concentration of functional groups (1.22–2.88 mol·L−1) and catalyst loading (0.025–0.042 g·mL−1) on the kinetics were evaluated. Gas-liquid mass transfer of CO2 in the methylated oleic acid system was investigated, and a mathematical model was developed. The dissolution of CO2 was found to be exothermic, and the dissolution capacity decreases with increasing temperature and decreasing pressure. The solubility of CO2 follows an order of methylated form > epoxidized form > carbonated form. A high conversion rate (68.45 %) of epoxides was achieved in 6 h at 443.15 K and 3 MPa with a catalyst loading of 0.042 g·mL−1. These results show a potential route for synthesizing aliphatic carbonates by combining methyl oleate with CO2.

Surface modification by CO2 plasma boosting core shells structural Fe/Fe3C/FeN @ graphite carbon nanoparticles toward high performance microwave absorber

The surface modification of three-dimensional (3D) materials is an efficient method for adjusting their interfacial defect concentration, electronic conductivity and content of functional groups with extensive applications in catalysis, electrode materials and bioengineering. In this work, a multiphase iron nanocrystals consisting of Fe3C, Fe and FeN nanoparticles encapsulated in hierarchical structure of graphite carbon (denoted as Fe/Fe3C/FeN@GC) is synthesized for the first time by a novel high temperature plasma method. Meanwhile, more defects and functional groups are introduced by surface modification of graphite carbon layer of Fe/Fe3C/FeN@GC with controllable CO2 (low temperature) plasma. Benefiting from the advantages of multiple heterogenous interface and the abundant interfacial polarization relaxation that represent strong electromagnetic (EM) wave dissipation as well as an applicable impedance matching, the optimized Fe/Fe3C/FeN@GC demonstrate superior microwave absorption (MA) properties. The minimum reflection loss (RL) achieves −54.4 dB (more than 99.9% MA) at 17.6 GHz with a thin thickness of 1.8 mm, and the maximum effective absorption bandwidth (EAB, RL < −10 dB) is up to 6.2 GHz (11.8–18.0 GHz) at 2.0 mm. The above results reveal that the optimized Fe/Fe3C/FeN@GC composites with strong absorption, broad EAB, light mass (only filling content of 30 wt%) and ultrathin thickness are prospective candidate for high performance EM wave absorbers.

Removal of Cr(VI) from aqueous solution using ball mill modified biochar: multivariate modeling, optimization and experimental study

Chromium (Cr(VI)) pollution has attracted wide attention due to its high toxicity and carcinogenicity. Modified biochar has been widely used in the removal of Cr(VI) in water as an efficient and green adsorbent. However, the existing biochar prepared by chemical modification is usually complicated in process, high in cost, and has secondary pollution, which limits its application. It is urgent to explore modified biochar with simple process, low cost and environmental friendliness. Therefore, ball milling wheat straw biochar (BM-WB) was prepared by ball milling technology in this paper. The adsorption characteristics and mechanism of Cr(VI) removal by BM-WB were analyzed by functional group characterization, adsorption model and response surface method. The results showed that ball milling effectively reduced the particle size of biochar, increased the specific surface area, and more importantly, enhanced the content of oxygen-containing functional groups on the surface of biochar. After ball milling, the adsorption capacity of Cr(VI) increased by 3.5–9.1 times, and the adsorption capacity reached 52.21 mg/g. The adsorption behavior of Cr(VI) follows the pseudo-second-order kinetics and Langmuir isotherm adsorption model rate. Moreover, the Cr(VI) adsorption process of BM-WB is endothermic and spontaneous. Under the optimized conditions of pH 2, temperature 45 °C, and adsorbent dosage 0.1 g, the removal rate of Cr(VI) in the solution can reach 100%. The mechanism of Cr(VI) adsorption by BM-WB is mainly based on electrostatic attraction, redox and complexation. Therefore, ball milled biochar is a cheap, simple and efficient Cr(VI) removal material, which has a good application prospect in the field of remediation of Cr(VI) pollution in water.

Experimental Study on the Inhibition Effect of the Inhibitor on Coal Spontaneous Combustion Under Critical Temperature.

At present, related research on inhibitors has been gradually improved, but there is still a lack of research on the inhibition characteristics at specific release temperatures and the mechanism of inhibiting coal spontaneous combustion. Based on this, In this study, the inhibition characteristics of adding inhibitor to coal under critical temperature (R70) are studied in depth. In the experiment, lignite was selected as the research object, and four different types of inhibitors, MgCl2, triphenyl phosphite (TPPI), Phytic acid (PA), and melatonin, were applied to coal samples at room temperature and 70 °C, respectively. The temperature-programmed-gas chromatography test and Fourier infrared spectroscopy experiment were carried out, and the oxidation kinetic parameters were calculated to study the oxidation characteristics and micromechanism of the coal samples in the process of spontaneous combustion. The experimental results show that the amount of CO gas release and oxygen consumption rate are lower, and the inhibition rate and apparent activation energy are higher when the inhibitor is added under R70 than at room temperature. Under R70, the content of oxygen-containing functional group -COOH with higher activity of inhibitor is reduced, the generation of active sites is inhibited, the concentration of active center is reduced, the path of mutual transformation between active sites and oxygen-containing functional groups is blocked, and the active groups are promoted to form a relatively stable inert oxygen-containing ether bond, which reduces the spontaneous combustion tendency of coal.

On the discrepancy between nominal and effective charge density of polyamide reverse osmosis membranes

Quantitative and reliable information on the ionization of functional groups in polyamide (PA) active layers of thin film composite membranes is of vital importance for understanding and modeling of ion transport. Independent measurements using Ag+ ion-probing with RBS, XPS, or ICP-MS, indicate a nominal charge density in the order of 0.5 M. Conversely, model fitting to salt rejection experiments suggests an effective membrane charge at least three orders of magnitude lower for brackish water (BWRO) and seawater (SWRO) membranes. In this study we show that the original interpretation of the ion-probe experiments is inconsistent with the principles of ion partitioning used in ion transport models. We provide an alternative interpretation of ion-probe experiments in the literature, explaining the results through binding of silver ions to the carboxylic groups. By using this interpretation, the discrepancy between nominal and effective charge can be resolved: the Ag measured in the ion-probe experiments is mostly bound to the membrane (-COOAg, not –COO−/Ag+), while the membrane is virtually uncharged. Consequently, the ion-probe experiments can quantify the concentration of functional groups, but not theirpKa. We propose that confinement affecting membrane ionization, should be explicitly included in ion-transport modeling.

Sulfuric acid-assisted ball milling for the preparation of Si-O-enriched straw biochar: removal efficiency of rhodamine B and adsorption mechanism.

Traditional pyrolysis biochar has been widely employed to treat dye wastewater. However, there are some problems in the pyrolysis process, such as the generation of harmful gases and the low content of silico-oxygen functional groups to promote adsorption. Straw biochar (Ac-BCbm) was prepared by sulfuric acid co-ball milling method. The adsorption performance and adsorption mechanism of rhodamine B (RhB) under different preparation conditions and factors were investigated. The results showed that the adsorption rate of Ac-BCbm on RhB was up to 94.9%, which was 60.5% and 55.8% higher than that of ball-milling straw (STbm) and biochar prepared by pyrolysis (STBC600), respectively. The Ac-BCbm had better adaptability under different pH and common interfering ions for remove RhB. Characterization and DFT simulation analysis revealed that the sulfuric acid co-ball milling process promoted the formation of Si-OH and Si-O-CH3 oxygen-containing functional groups of Si component in straw, which enhanced the hydrogen bonding interactions and effectively improved the adsorption efficiency. This study investigated a new strategy for biochar preparation by sulfuric acid co-ball milling, which provides an additional development direction for the efficient resource utilization of straw.

Soybean-Based Bio-Adhesives: Role of Diamine on the Adhesive Properties.

One possible approach to achieving sustainable development in the materials sector is to produce polymers from plant oils (POs), which are renewable and environmentally beneficial. Polymers with a high concentration of functional groups can be used as cross-linking agents to enhance the properties of epoxidized POs (epoxidation of plant oil)-based polymers. In this work, a unique resin with novel properties and potential uses was produced by cross-linking epoxidized soybean oil (ESO) with branched and flexible polyamines by ring-opening and amidation polymerizations. This approach is straightforward and ecologically benign. After curing, melamine pentane diamine (MPD) polymer maintained its position as the strongest structural adhesive among the synthesized resins, with a bonding strength of almost 2000 kPa for stainless steel; irrespective of the temperature, stainless steel consistently outperforms melamine ethylene diamine-ESO resin in strength comparisons. At 100 °C, stainless steel has a lap shear strength of about 300 kPa, which is far higher than copper and aluminum; at 180 °C, this value increases by another 750 kPa. While MPD-ESO resin has a shear strength of 1996 kPa at 180 °C, melamine butane diamine-ESO resin has a shear strength of only 1220 kPa.

Machine-learning-aided prediction and engineering of nitrogen-containing functional groups of biochar derived from biomass pyrolysis

Biochar, derived through biomass pyrolysis, is an emerging carbonaceous material with significant potential in various applications. The performance of biochar in applications depends heavily on its surface characteristics, including its content of N-containing functional groups. In this study, machine learning (ML) was used for the prediction and engineering of biochar N-containing functional groups, specifically amine-N (N-A), pyrrolic-N (N-5), and pyridinic-N (N-6). The single-target random forest model accurately predicted N recovery in biochar (char-N yield) and N-A, N-5, and N-6 contents, achieving test R2 of 0.91–0.97. Model interpretations revealed that pyrolysis temperature was the most influential factor in predicting char-N yield, N-A, N-5, and N-6. The multi-target random forest model achieved an average test R2 of 0.93, and it was used to optimize pyrolysis parameters for designing biochar N-functional groups. This process was followed by experimental verification. Relative errors for the three N-containing functional groups were mostly within 15% (18.4% on average). The favorable results obtained from experimental verification demonstrate the significant potential of ML in biochar engineering.

Enhanced green leaching of spent lithium-ion batteries: Pyrolysis pretreatment combined with eco-friendly citric acid and ascorbic acid

The presence of polyvinyl fluoride (PVDF) between electrode particles is a potentially critical factor to reduce the leaching rate of the electrode materials in spent lithium-ion batteries (LIBs). Pyrolysis method was proposed to remove the PVDF to improve the leaching behavior. The pyrolysis characteristics of electrode materials, PVDF and pure LiCoO2 were analyzed to determine the pyrolysis temperature. The content of functional groups representing PVDF in the pyrolyzed and un-pyrolyzed electrode material was measured by XPS to evaluate the pyrolysis effect. Subsequently, eco-friendly citric acid and ascorbic acid was used to leach pyrolyzed and un-pyrolyzed electrode materials. Meanwhile, leaching behavior of pure LiCoO2 was also verified to evaluate the leaching effect of waste LiCoO2, the leaching behavior of pyrolyzed and un-pyrolyzed electrode materials was analyzed to evaluate the enhancement effect of pyrolysis. The morphology of the leaching residue was analyzed by SEM to verify the leaching effect. Results show that pyrolysis at 500 °C can fully remove PVDF and enhance the leaching rate of electrode materials. Further, citric acid and ascorbic acid can achieve efficient and green leaching of electrode materials. The leaching rate of Li and Co in un-pyrolyzed electrode materials is 58.51 % and 58.88 %, while it is 92.01 % and 90.87 % in the pyrolyzed electrode materials. The XPS analysis of pyrolyzed electrode materials and SEM analysis of the leaching residue also verified that the pyrolysis achieved full removal of PVDF.

Probing the molecular interaction between photoaged polystyrene microplastics and fulvic acid

As emerging contaminants, microplastics (MPs) are becoming a matter of global concern, and they have complex interactions with dissolved organic matter (DOM) widely present in aqueous environments. Here, we investigate the molecular interactions between aged polystyrene microplastics (PS-MPs) and fulvic acid (FA) under neutral conditions using a series of analytical techniques. The structural changes of FA and the binding interactions of PS-MPs with FA at a molecular level were explored by fluorescence and FT-IR combined with two-dimensional correlation spectroscopy (2D-COS). Results showed that photoaging of PS-MPs changed the sequence of structural variations with FA. Atomic force microscopy-infrared spectroscopy (AFM-IR) strongly demonstrated that the surface roughness of both pristine and aged PS-MPs greatly increased after FA addition. Meanwhile, AFM-IR and Raman spectroscopy revealed a stronger interaction between aged PS-MPs and FA. The content of oxygen-containing functional groups in PS-MPs increased after aging and after binding with FA, and surface distribution of these functional groups also changed. XPS analyses indicated that the oxygen content in PS-MPs increased after the interaction with FA and the increase in oxygen content was even greater in aged PS-MPs. Overall, these research findings are useful to understand the environmental impacts of DOM-MPs interactions and to address the uncertainty of MPs aging effect on their environmental behavior in aquatic ecosystems.

Comparing Ammonium and Tetraaminophosphonium Anion-Exchange Membranes Derived from Vinyl-Addition Polynorbornene Copolymers.

Herein, we systematically examined how composition influenced the properties of vinyl addition polynorbornene anion exchange membranes (AEMs) prepared from 5-n-hexyl-2-norbornene and 5-(4-bromobutyl)-2-norbornene. Copolymerization kinetics revealed that 5-n-hexyl-2-norbornene is consumed faster than 5-(4-bromobutyl)-2-norbornene, leading to a portion of the chain being richer in bromoalkyl groups. The alkyl halide pendants can then be converted to either trimethylammonium or tetrakis(dialkylamino)phosphonium cations through straightforward substitution with trimethylamine or a tris(dialkylamino)phosphazene. A series of cationic ammonium polymers were synthesized first, where conductivity and water uptake increased as a function of increasing ionic content in the polymer. The optimized copolymer had a hydroxide conductivity of 95 ± 6 mS/cm at 80 °C. The living polymerization of the two monomers catalyzed by a cationic tert-butylphosphine palladium catalyst also enabled precise changes in the molecular weight while keeping the functional group concentration constant. Molecular weight did not have a significant impact on hydroxide conductivity over the range of ∼60-190 kg/mol (Mn). The optimized tetraaminophosphonium AEM had the highest conductivity for any tetraaminophosphonium polymer to date (70 ± 3 mS/cm at 80 °C). Clear phase separation and larger domains were observed for the phosphonium-based AEM compared to the ammonium at an identical composition, which is attributed to the larger occupied volume of the phosphorus cation. Fuel cell studies with the two membranes resulted in peak power densities of 1.59 and 0.79 W/cm2 for the ammonium and tetraaminophosphonium membrane electrode assemblies, respectively. The ammonium-based membrane was more water permeable as evidenced by water limiting current studies, which likely contributed to the improved performance.

Comparative Analysis of Electrokinetic Properties of Periodate- and TEMPO-Oxidized Regenerated Cellulose Fabric Functionalized with Chitosan

The electrokinetic properties of materials give useful insight into the behavior of surfaces in contact with liquids and other compounds and their quantification is a powerful tool to predict their behavior during further processing and application, especially in textile materials. In this work, we perform a comparative analysis of influence of the two most common selective oxidative protocols for viscose (regenerated cellulose) fabrics on subsequent functionalization with chitosan, and cellulose fabrics’ electrokinetic properties, zeta potential in a pH range of approx. 3–10, and isoelectric point (IEP). For oxidation before deposition of chitosan, sodium periodate and 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) were used. The content of functional groups in oxidized cellulose fabric (carboxyl and carbonyl groups) was determined by titration methods, while amino functional groups’ availability in samples with chitosan was determined using the CI acid orange 7 dye absorption method. This study reveals that the periodate oxidation (PO) of cellulose is more effective for binding chitosan onto material, which gave rise to higher availability of amino groups onto cellulose/chitosan material, which also influenced the shift in zeta potential curve towards positive values at a pH below 5. Analysis of a relationship between zeta potential increase at pH 4.4 and amino groups’ amount measured using absorption of CI acid orange 7 dye at pH 4.4 revealed dependency that can be fitted linearly or exponentially, with the latter providing the better fit (R2 = 0.75).

Highly efficient capture of E. coli using amidoximated polyacrylonitrile nanofiber membrane immobilized with reactive green 19 dye/polyhexamethylene biguanide: Antibacterial and cytotoxicity studies

In this study, we synthesized an amidoximated polyacrylonitrile nanofiber membrane (P-Oxime). Subsequently, we grafted reactive green 19 (RG19) dye onto its surface, resulting in the formation of the P-Oxime-RG19 membrane. Further enhancement was achieved by physically attaching poly(hexamethylene biguanide) hydrochloride (PHMB) to the P-Oxime-RG19 membrane, leading to the formation of the P-Oxime-RG19-PHMB membrane. Extensive characterization of the nanofiber membranes was conducted, focusing on crucial physical and mechanical properties such as functional group content, morphology, and thermostability. The optimization of various modification conditions, including initial dye and PHMB concentrations, duration, temperature, and nitrile group conversion to oxime concentrations, played a pivotal role in achieving superior antibacterial performance in P-Oxime-RG19-PHMB nanofiber membranes. In-depth analyses involved the application of kinetic and equilibrium thermodynamic models to unravel the modification processes of RG19 dye and PHMB in the nanofiber membranes. Under the carefully tuned optimal modification conditions, the P-Oxime-RG19-PHMB nanofiber membrane exhibited remarkable antibacterial efficacy, achieving nearly 100% disinfection of E. coli. In addition to exploring its antimicrobial capabilities, we thoroughly examined the repeatability and biocompatibility of the nanofiber membranes. The results indicated not only the P-Oxime-RG19-PHMB nanofiber membrane was a highly promising antibacterial material but also highlighted its potential for diverse applications, particularly in food and textile fabrication, owing to its exceptional performance and suitability.

Effects of rock water with different acidity on microstructure and reburning ability of residual coal in goaf

To explore the influences of rock water acidity (PH = 4,5,7) over the microstructure and reburning behaviors of oxidized residual coal in the overlying goaf, the pore morphology, coal surface, functional group content and activity of pre-oxidized coal (O0) and water-immersed oxidized coal (OI) were analyzed by Low-temperature nitrogen adsorption and In-situ diffuse reflection experiments, combining with fractal dimension theory and functional group oxidation kinetics. The oxidation and reburning ability of coal samples has been analyzed by Thermogravimetric-Differential thermal analysis experiment. The results are as follows: Part of the type-III pores of pre-oxidized coal become type-II pores when immersed. The acidic solution has stronger corrosivity to O0 than distilled water, playing a role in smoothing coal and improving the uniformity of pore structure. The order of reburning ability of samples is OI7>OI4>O0>OI5 according to the ignition and stage average mass loss rate (RM). The reactivity of –OH may affect the reburning ability of coal more than its initial content. Soaking is beneficial to the decrease of activation energy of aliphatic groups, and the activity of –C=O- and -C-O- in acid-soaked coal molecules is stronger, so that they can take part in coal-oxygen composite reactions at low temperature.

The effect of co-pyrolysis of bamboo waste and polypropylene on biomass deoxygenation and carbonization processes

While numerous research studies have delved into the co-pyrolysis of biomass and plastic waste, limited attention has been devoted to comprehending the interaction mechanism that impacts biomass deoxygenation and carbonization. Therefore, this study explores the co-effect of temperature and polypropylene blending ratio on co-pyrolysis reaction kinetics, distribution of oxygenates/hydrocarbons, as well as the evolution of biochar structure. At a blending ratio of 0.5, the co-pyrolysis exhibits the lowest activation energy (146 kJ/mol), approximately 25.1 % lower than that required for individual pyrolysis. The interaction between bamboo waste with polypropylene increases the O-abstraction process, resulting in the creation of O-containing free radicals and hydrocarbon compounds. The peak proportion of aromatic compounds, reaching approximately 69.5 %, is observed at 700 °C when the blending ratio is 0.5. The H-abstraction process converts large-molecular alkanes into H free radicals and tiny-molecular unsaturated hydrocarbons. The aliphatic functional group content diminishes as the polypropylene ratio increases. The maximum specific surface area (7.70 m2/g) and pore volume (21.7 mm3/g) are achieved at a blending ratio of 0.75. Notably, polypropylene exerts minimal influence on the graphite crystallite size and graphitization degree of biochar. This research significantly contributes to advancing our understanding of the interaction mechanisms between biomass and plastic waste.

Efficient degradation of sulfamethoxazole by a peroxymonosulfate system activated by g-C3N4@polyethylene glycol-derived carbon-nitrogen nanosheets: The key roles of N and O groups

A simultaneous thermal polymerization reaction was performed with graphitic carbon nitride and polyethylene glycol to synthesize a novel metal-free carbon–nitrogen (CN) material, and the prepared material was applied to activate a peroxymonosulfate (PMS) system. Sulfamethoxazole (SMX) removal by CN7/PMS reached 93.75 % in 10 min, which was 39.86 times higher than that achieved by PMS systems alone. Material characterization showed that the pyrolysis temperature could be adjusted to modulate the N atom and functional group contents. As determined by experimental validation and DFT calculations, C = O/C-N, graphitic N and defects were the main active sites. This finding indicates that CN7 activated PMS to produce hydroxyl radicals (•OH), sulfate radicals (SO4•-) and singlet oxygen (1O2) through electrostatic interactions, nucleophilic addition, electron transfer and other pathways. Moreover, 1O2 was dominant, with a 91.58 % contribution. In addition, the materials maintained high catalytic stability in different water matrices and multiple cycling experiments. The present study innovatively illustrated the mechanism by which nitrogen-doped carbon materials activated PMS, providing a new insight into the development of highly active metal-free catalysts applied in PMS systems.

Application potential of modified waste-lignin as microbial immobilization carriers for improve soil fertility

The immobilized microorganism technology is used to load the functional microorganism on a suitable carrier to maintain its biological activity, resist the impact of adverse environment. In this study, chemical modification of lignin side chain phenolic hydroxyl groups was carried out to increase the content of amide functional groups and enhance their adsorption and fixation effects on microorganisms due to the numerous active sites in the structure of discarded lignin, and studied its impact on microbial activity and crop growth. The results show that the modified lignin could be effectively combined with functional microorganisms, and the proposed bio-composite material was an effective method for cell protection. In addition, it was shown that functional microorganisms maintained high biological activity by immobilization of modified lignin, which was 34.3–41.0% higher than that of CK. Moreover, the technology could increase the total nitrogen content and available phosphorus content in soil by 70.8% and 64.4%, respectively, compared with CK. Therefore, it could increase eventually wheat growth indices and biomass. The completed research opens new perspectives for the effective immobilization of microorganisms and utilization of wasted lignin of significant economic importance.