Nitrogen-containing Groups Research Articles

Charge Density Modulation of Pyrene-Related Small Molecules by Nitrogen Heteroatoms Precisely Regulates Photocatalytic Generation of Hydrogen.

Organic semiconductor materials hold promising applications in photocatalytic hydrogen evolution due to their high modifiability and wide range of light absorption capability. In this study, we present an effective strategy for promoting the separation of photoexcited electrons from organic conjugated centers to active sites by modifying different nitrogen-containing groups on pyrene molecules. Building on this foundation, the well-designed catalyst Py-m-2N has demonstrated good performance by achieving a photocatalytic hydrogen evolution rate of 48.86 mmol g-1 h-1, even in the absence of the precious metal platinum cocatalyst. This achievement places the pyrene-based photocatalyst ahead of the majority of its organic counterparts. Our comprehensive characterization and density functional theory calculations reveal that the nitrogen atom not only serves as an active site for hydrogen production but also plays a pivotal role in efficiently accumulating bulk-phase electrons. This electron enrichment process enhances the transport of photoexcited electrons from the light-absorbing pyrene units to the active nitrogen sites. This work provides inspiration for the future design of effective nitrogen-atom-modified organic semiconductor photocatalysts at the molecular level.

The role of chitosan in enhancing the solubility and antibacterial activity of emodin against drug-resistant bacteria

Similar to most anthraquinone compounds, the pharmacological properties of emodin are limited because of its low water solubility. In this study, the formulation of chitosan and emodin (EMD/CS) was prepared by a bottom-up method with precipitation and sonication steps in order to enhance the solubility of emodin. Thanks to the interactions of oxygen-and nitrogen-containing groups in chitosan with emodin molecules, the solubility of emodin in the formulation was remarkably increased to 0.5 mg/mL. The EMD/CS particles were well dispersed and distributed in a range of sub-micrometer with an average particle size of 342 nm. The EMD/CS formulation exhibited synergic antibacterial activity of emodin and chitosan, against drug-resistant bacterial strains, namely Methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli O157:H7 (E. coli O157:H7). When the compositions of emodin and chitosan increased, the antibacterial effectiveness of the EMD/CS formulation increased. The EMD/CS formulation with compositions of 0.5 mg/mL of emodin and 9.0 mg/mL of chitosan could significantly inhibit the proliferation of E. coli O157:H7. Meanwhile, the EMD/CS formulation with a lower concentration of emodin (0.4 mg/mL) and chitosan (7.2 mg/mL) could cause an extermination effect on MRSA. The enhanced solubility of EMD/CS formulation suggests that this formulation can be a potential candidate for the treatment of infectious diseases caused by drug-resistant bacterial pathogens.

Enhanced adsorption complexation of biochar by nitrogen-containing functional groups

Biochar has abundant oxygen-containing functional groups and a unique surface structure, which endow it with properties that are desirable for various environmental protection applications. However, to our knowledge, the potential applicability of biochar comprising non–‍oxygen-containing functional groups has not yet been systematically studied. This work comprehensively investigated the adsorption capacity of grafted biochars modified with various N-, O-, and S-containing functional groups. We also analyzed the mechanisms governing, pollutant removal processes, and their recycling properties of biochars. The degree of adsorption of the biochars increased with the increasing electron-withdrawing ability of the grafted functional groups (i.e., -NO2 > -NH2 > -CN > -SO3H > -OH), and the optimal temperature for preparing biochars with grafting modifications was 300 °C. The -NO2 group was successfully grafted onto the cellulose of bagasse-based biochar. The maximum adsorption capacity of -NO2 grafted biochar (NBC300) was 158.73 mg/g, and the desorption rate was 88.35% for 0.1 M HCl. Nitro grafting modifications of internal molecular compositions led to biochars with good stability and regeneration properties in acidic, alkaline, and oxidizing environments. Thermodynamic studies suggested that Cd(II) could be effectively removed by NBC300 at low temperatures through a spontaneous and feasible process. Spectroscopic analysis and batch adsorption experiments showed that the modified biochar removed Cd(II) via a mechanism involving strong adsorption-complexation of the π-conjugated system on the -NO2 groups. The present study supports biochar applications for the recycling and reuse of agricultural waste and describes a novel technology for addressing the key issue of metal pollution.

Ignition of Small Molecule Inhibitors in Friedreich's Ataxia with Explainable Artificial Intelligence

Iron (Fe) chelating medicines and Histone deacetylase (HDAC) inhibitors are two therapy options for hereditary Friedreich's Ataxia that have been shown to improve clinical results (FA). Fe chelation molecules can minimize the quantity of stored Fe, and HDAC inhibitors can boost the expression of the Frataxin (FXN) gene in enhancing FA. A complete quantitative structure-activity relationship (QSAR) search of inhibitors from the ChEMBL database is reported in this paper, which includes 437 compounds for Fe chelation and 1,354 compounds for HDAC inhibitors. For further investigation, the IC50 was chosen as the unit of bioactivity, and following data refinement, a final dataset of 436 and 1,163 compounds for Fe chelation and HDAC inhibition, respectively, was produced. The Random Forest (RF) technique was used to generate models (train R2 score, 0.701 and 0.892; test R2 score 0.572 and 0.460, for Fe and HDAC, respectively). The models created using the PubChem fingerprint were the strongest of the 12 fingerprint kinds; hence that feature was chosen for interpretation. The results showed the importance of properties related to nitrogen-containing functional groups (SHAP value of PubchemFP656 is -0.29) and aromatic rings (SHAP value of PubchemFP12 is -0.16). As a result, we explained the effect of the molecular fingerprints on the models and the impact on possible drugs that can be developed for FA with artificial intelligence (XAI), which can be explained through SHAP (Shapley Additive Explanations) values. Model scripts and fingerprinting methods are also available at https://github.com/tissueandcells/XAI.

Insights into the nitrogen-rich pyrolysis of cellulose in the presence of alkali and alkaline earth metals: Structural transformation of target products

Here, cellulose loaded with Ca and K was subjected to nitrogen-rich pyrolysis to investigate how alkali and alkaline earth metals affected its properties and the structural transformation of target products, especially the nitrogen transformation mechanism. Ca significantly reduced the activation energy of nitrogen-rich pyrolysis. The effect of Ca on the component distribution of bio-oil was significantly stronger than that of K. At Ca-0.5, the bio-oil had the highest content of nitrogen-containing compounds (77.98%), and the content of nitrogenous heterocyclic compounds (37.98%) was significantly higher than that of Ca-K-0 (27.75%). Ca and K promoted the production of pyridines. K acted on pyrroles and pyrazoles, while Ca acted on pyrazines. As Ca and K increased, both nitrogen-containing functional groups and nitrogen were enriched in biochar. Ca enhanced the H/C value of biochar and accelerated the conversion of char-N to tar-N. K tended to produce nitrogen-rich biochar with higher graphitization degree and stability.

SORPTION OF RARE-EARTH ELEMENTS BY ORGANIC MATTER FROM AQUEOUS SOLUTIONS ACCORDING TO EXPERIMENTAL DATA

Laboratory model experiments have shown that peat, brown coal and its constituent organomineral components, as well as microscopic fungi isolated from brown coal, are characterized by a high potential for the extraction of all lanthanides from aqueous solutions. The processes of sorption of rare-earth elements by the components of organic matter proceed through the mechanisms of physical sorption, ion-exchange reactions involving carboxyl and hydroxyl groups, and complex formation involving –OH, –CO, and –COOH groups. SEM-EDS analysis revealed REE-containing mineral phases on fungal biomass, which are formed due to interaction with phosphorus- and nitrogen-containing functional groups of cell wall proteins. This indicates the participation of the biotic component in the formation of rare earth mineralization in brown coal deposits.

Improved electrochemical detection of copper ions in nitrogen doped ta-C films for marine corrosive monitoring

The corrosion of copper-based alloy in the harsh marine environment threatens the reliable operation and service life of marine engineering equipment. In this work, the nitrogen modified tetrahedral amorphous carbon (ta-C:N) film electrodes were prepared for marine-oriented copper ions detection. The relationship between structural evolution and electrochemical performance of ta-C:N film electrode tailored by N2 flux was evaluated. The sp2 cluster and the content of sp2-bonded carbon in ta-C:N film were promoted with the increase of N2 flux. XPS results indicated that the variation of N2 flux modified the nitrogen-containing groups of the ta-C:N film electrodes. The optimized ta-C:N film electrode deposited at N2 flux of 3 sccm showed a quasi-reversible electrode behaviors. Moreover, the ta-C:N film electrode exhibited a linear range from 8 × 10−3 mM to 5 mΜ, a detection limit of 8 × 10−3 mM, and good repeatability and reproducibility for Cu2+ detection in 3.5 wt% NaCl solution. The improved Cu2+ sensing properties were ascribed to the enhanced sp2 cluster and the introduction of multiple nitrogen-containing functional groups, especially the pyrrolic nitrogen and graphitic nitrogen. DFT computation and wavefunction analysis revealed that the pyrrolic nitrogen possessed the strongest interaction for copper ions among different nitrogen configurations.

Enhanced low-frequency microwave absorption of N-doped biomass derived carbon

Hierarchical porous undoped and N-doped carbon derived from the natural spinach roots was prepared by a facile carbonization process at 600–800 ℃ respectively. The electromagnetic properties were carefully investigated in the range of 1–18 GHz in order to study the effect of the tunable permittivity on the microwave absorbing and shielding performance by modulating the intrinsic polarization of the biomass carbon. Compared with the other samples, the undoped one sintered at 650 ℃ shows the minimum reflection loss (RL) of − 42.93 dB at 16.72 GHz with a thickness of 2.0 mm, while the effective absorbing bandwidth achieves 6.46 GHz at 2.4 mm. With the N-doping, the permittivity is obviously affected by the nitrogen-containing groups and compounds induced dipolar and interfacial polarization. The RLmin of the N-doped carbon sample sintered at 700 ℃ has arrived at − 49.96 dB at 15.88 GHz with a very thin thickness of 1.5 mm. Besides, the impedance matching bandwidth can cover the L-C band in the N-doped carbon with the excellent RL of − 43.195 dB at d= 8.4 mm and f= 2.4 GHz. The competitive and tunable mechanism of the dielectric property are also studied for the tunable impedance and microwave absorption.

In vitro and in vivo toxicity of carbon dots with different chemical compositions

Carbon dots (CDs) are easy-obtained nanoparticles with wide range of biological activity; however, their toxicity after prolonged exposure is poorly investigated. So, in vitro and in vivo toxicity of CDs with the surfaces enriched with hydroxylated hydrocarbon chains and methylene groups (CD_GE), carboxyl and phenol groups accompanied with nitrogen (CD_3011), trifluoromethyl (CDF19) or toluidine and aniline groups (CDN19) were aimed to be discovered. CDs’ in vitro toxicity was assessed on A549 cells (real-time cell analysis of impedance, fluorescence microscopy) after 24 h of incubation, and we observed no changes in cell viability and morphology. CDs’ in vivo toxicity was assessed on C57Bl6 mice after multiple dosages (5 mg/kg subcutaneously) for 14 days. Lethality (up to 50%) was observed in CDN19 and CD_3011 groups on different days of dosing, accompanied by toxicity signs in case of CD_3011. There were no changes in serum biochemical parameters except Urea (increased in CDF19 and CD_3011 groups), nor substantial kidney, liver, and spleen injuries. The most impactful for all organs were also CD_3011 and CDF19, causing renal tubule injury and liver blood supply violation. Thus, CDs with a surface enriched with oxygen- and nitrogen-containing functional groups might be toxic after multiple everyday dosing, without, however, significant damages of internal organs in survived animals.

Boosting anionic dyes removal performance of polyacrylonitrile nanofibers by incorporating nitrogen-rich conjugated polymer

In this study, poly(1,5-diaminonaphthalene) (PDAN) as nitrogen-rich conjugated polymer was successfully synthesized and incorporated into polyacrylonitrile nanofibers (PAN NFs) by one-step-electrospinning technique. The fabricated poly(1,5-diaminonaphthalene)/polyacrylonitrile nanofiber composite (PDAN/PAN NFs) was characterized using various techniques. The modification of PAN NFs caused their surface to become rich in nitrogen-containing functional groups and conjugated CC bonds. Morphological characterization confirmed that the incorporation of PDAN into PAN NFs made their surface rougher and increased their average diameters from 197 ± 46–214 ± 46 nm. The incorporation of PDAN into PAN NFs boosted the adsorption capacity for the removal of anionic Amido Black 10B dye (AB10B) by 140 times (from 1 mg/g to 140 mg/g). The uptake of the AB10B dye from aqueous solutions by the PDAN/PAN NFs was investigated as a function of the pH value, the initial dye solution, temperature and contact period. The Dubbin-Radushkevich isotherm model was found to fit well with the equilibrium adsorption isotherm data, and the maximum adsorption capacity was determined to be 240.53 mg/g at pH 3 and 35 °C. The pseudo-second-order was a reliable kinetic model for predicting the adsorption of AB10B dye onto the PDAN/PAN NFs composite. The efficient and selective adsorption of the designed adsorbent is due to the nitrogen-rich functional groups and the π-conjugated system of PDAN. This study will pave the way for the boosting adsorption capacity and selectivity of membrane-type nanoadsorbent for the treatment of more toxic organic dyes.

High energy density pouch-type supercapacitor achieved by MOFs derived 3D hollow N-doped carbon with Fe2O3 and hierarchical CuCo2S4@NiFe-LDH core-shell nanostructures

The multicomponent rational control and distinctive architectural design of electrode materials remain critical factors for enhancing the energy density of supercapacitors. Herein, metal-organic framework (MOF)-derived three-dimensional (3D) hollow nitrogen-doped carbon (NHCs) with Fe2O3 core-shell composite negative electrode materials (NHCs@Fe2O3) were developed. In this framework, 1) the high specific surface area caused by the distinctive core-shell structure facilitated the electrolyte infiltration in the hollow skeleton, which shortened the ion transport path and enabled fast electron transfer; and 2) the synergistic effect of the nitrogen-containing groups of the hollow carbon and the reversible Faraday reaction of metal oxides increased the ratio of the pseudocapacitance. These phenomena were the primary reasons for the enhanced capacity of the core-shell electrode. Additionally, hierarchical CuCo2S4@layered double hydroxide (NiFe-LDH) nanobelt core-shell heterostructure arrays integrated on the nickel foam were used for the positive electrode materials. The asymmetric pouch-type supercapacitor assembled with NHCs@Fe2O3 (negative electrode) and CuCo2S4@NiFe-LDH (positive electrode) exhibited a high energy density of 68.6 W h kg–1 at a power density of 828.9 W kg–1. This work offers an effective strategy for fabricating multicomponent core-shell materials and optimizing the interactions between the components to enhance the electrochemical performance in energy storage applications.

Acid–base bifunctional ZnNbCl/eg-C3N4 materials towards catalytic synthesis of dimethyl carbonate via transesterification of ethylene carbonate

The catalytic transesterification reaction between ethylene carbonate (EC) with methanol is a sustainable approach for the production of dimethyl carbonate (DMC). In this work, exfoliated carbon nitride (eg-C3N4) was supported with ZnCl2 and NbCl5. The synthesized materials (ZnNbCl/eg-C3N4) were analyzed by XRD, N2 adsorption–desorption, FT-IR, XPS, SEM, TG, CO2-TPD, and NH3-TPD. The eg-C3N4 could disperse well Zn2+ and Nb5+ species via nitrogen-containing groups. The combined Zn2+ and Nb5+ components enhanced the alkaline strength of eg-C3N4 and introduced acidic sites, enabling ZnNbCl/eg-C3N4 as solid-base bifunctional catalysts. As heterogeneous catalysts, ZnNbCl/eg-C3N4 exhibited superior activity to ZnCl2/eg-C3N4 or NbCl5/eg-C3N4 in the transesterification of EC. At 140 °C of reaction temperature, EC conversion and DMC selectivity reached 80.1% and 100%, respectively. The catalysts showed good recycling performance and were also compared with other recently reported heterogeneous catalysts.

Investigating the mechanism behind the synergistic ultraviolet photooxidation degradation of gaseous benzene through modified ACF

The effects of relative humidity were studied on the direct conversion efficiency, mineralization rate and components of waste gas from benzene photooxidation degradation. The adsorption energies, adsorption types, and molecular interaction forces of activated carbon fiber (ACF) modified with nitrogen and oxygen-containing functional groups were calculated using quantum chemical density functional theory (DFT) calculations and wave function analysis. Five polar intermediate products including acetone, acetol, hexanal, benzaldehyde, and acetophenone generated from benzene photooxidation degradation were selected as the computational object. The independent gradient model method based on Hirshfeld partition was used to study the weak interactions among the five equilibrium molecular adsorption configurations. The results demonstrated that the direct conversion efficiency of benzene increased first and then decreased with increasing relative humidity. The maximum direct conversion efficiency was 82% observed at a relative humidity of 50%. The mineralization rate decreased significantly at higher relative humidity, and the lowest value was 2%. The overall adsorption effect of nitrogen-containing functional groups on the modified ACF surface is higher than that of oxygen-containing functional groups. The functional groups with the best adsorption effect are ACF modified by pyridone, amino and carboxyl groups. Combined with electron localization function (ELF) analysis and Mayer bond-level calculation, it was found that all the modified ACF surfaces do not form chemical bonds for the equilibrium molecular adsorption configurations of the five organic compounds, which belong to physical adsorption. The adsorption of five intermediate products by modified ACF mainly depended on hydrogen bonds or van der Waals forces. The existence of hydrogen bonds greatly improved the adsorption capacity of modified ACF to organic molecules.

A computational investigation on the roles of binding affinity and pore size on CO2/N2 overall adsorption process performance of MOFs through modifying MIL-101 structure

To develop an appropriate metal-organic framework to capture CO2 from dry flue gas, understanding the roles of structural modifications, location of primary adsorption sites and underlying adsorption mechanisms is crucial. Herein, effects of type, position and concentration of nitrogen-containing functional groups and C/N-substituted ligands are investigated on overall CO2/N2 adsorption process performance and mechanism of pristine and metal-substituted MIL-101 MOFs. In this investigation, density functional theory computations, grand-canonical Monte-Carlo, and molecular dynamics simulations are applied. Taguchi-based overall evaluation criteria objective function is also used to assess the overall adsorption performances of these MIL-101 MOFs in terms of CO2 uptake capacity, CO2/N2 selectivity, isosteric heat of adsorption and mass transfer resistance. The PBE/DZVP computations resulted in the CO2-framework binding energies ranging from −3.85 to −21.01 kJ/mol implying an acid-base type of physisorption. A correlation is introduced to estimate the CO2 uptake capacity from binding affinity and pore diameter of these MIL-101 MOFs. Mechanistic investigations show that to enhance CO2 uptake capacity and CO2/N2 selectivity, functionalization of the linker ligands is more successful than functionalization of the open metal sites having strong interactions with CO2 molecules. Results also showed that the best possible scenario to improve the overall adsorption process performance of MIL-101 is to substitute the C atom(s) of the BDC ligands with the N atom(s), regardless of the central metal atom type. The comprehensive molecular design approach introduced in this work can be used as a methodology by scientists for the development of new MOFs for practical CO2 capture applications.

Optimization of hydrogen sulfide adsorption performance by tar based porous carbon prepared by template method

This study provides a method of preparation of tar based porous carbon (TPC) for H2S adsorption by high-temperature carbonization with tar as precursor and zinc chloride (ZnCl2) as template. Response surface methodology (RSM) was used to systematically investigate the effects of carbonization temperature, mass percentage of template and carbonization time on the cumulative adsorption (CAC) of H2S. The adsorption kinetics and isotherms, thermodynamics, and TPC’s properties were explored to obtain its adsorption mechanism on H2S. The results demonstrate that TPC was a microporous material with a rich surface functional group structure. The specific surface area and pore volume of the optimal sample (TPC-750-66-90) could reach 890.08 m2/g and 0.440 cm3/g, respectively, accompanied by a CAC of 34.01 mg/g. FTIR and XPS analysis results indicate that there were abundant oxygen- and nitrogen-containing groups on the surface of TPC, which helped to promote the chemisorption on H2S. The adsorption kinetics and isotherms fitting and thermodynamic calculation of H2S adsorption demonstrate that both physisorption and chemisorption played important roles, and the adsorption was a spontaneous, exothermic, random, and monolayer process. According to the regeneration tests, TPC could maintain at least 70% of its initial capacity after three rounds of regeneration. All the above results demonstrated that porous carbon preparation through high-temperature carbonization is a promising method for tar utilization, and the prepared porous carbon as adsorbent for gas pollutants like H2S has wide application potential in areas including kitchen trash, sewage treatment facilities, and biogas purification.

Molecular simulation of CH4 adsorption characteristics in bituminous coal after different functional group fractures

To explore the effect of different functional group fractures in coal on the adsorption characteristics of CH4, molecular models of bituminous coal (Wiser) with fractured oxygen-containing functional groups (W–O5), sulfur-containing functional groups (W–S5), and nitrogen-containing functional groups (W–N5) were constructed. The microscopic mechanism by which the fracture of different functional groups in bituminous coal molecules affects CH4 adsorption was analyzed using Density Functional Theory (DFT), Molecular Dynamics (MD), and Grand Canonical Monte Carlo (GCMC) methods. The results show that functional groups facilitated the polarization of CH4 during the adsorption process, with the following influence relationship: oxygen-containing functional groups > sulfur-containing functional groups > nitrogen-containing functional groups; Fracturing functional groups in bituminous coal molecules weakened the adsorption capacity and reduced adsorption sites of CH4, the sequence of CH4 adsorption was Wiser > W–N5 > W–S5 > W–O5. High temperature reduced the effect of nitrogen-containing functional group fractures on CH4 adsorption, but had no obvious effect on sulfur-containing and oxygen-containing functional groups. The interaction between CH4 and the coal molecule decreased after functional group fractures, causing the enhanced diffusion of CH4 on bituminous coal molecules, and the order was W–O5 > W–S5 > W–N5 > Wiser. Additionally, the fracture of functional groups decreased the pore size of the bituminous coal molecules, which inhibited CH4 adsorption but facilitated its diffusion. The research provides theoretical support for enhancing CH4 desorption and improving the recovery rate of coalbed CH4.

In situ formation of partially carbonized polyvinylpyrrolidone as a green binder for high-voltage Li-ion battery cathode with improved electrochemical performance

We propose the in situ formation of partially carbonized polyvinylpyrrolidone (PC-PVP) as a green binder for high-voltage LiNi0.5Mn1.5O4 (LNMO) cathodes. A mixture of water and ethanol with an equal volume ratio is shown to enable a more uniform dispersion of LNMO particles in the active material matrix with fewer crevices rather than pure water or pure ethanol. Conformal coverage of LNMO with PC-PVP can be achieved through a stepwise thermal process, which not only enhances the electrical conductance of the cathode material but also protects the electrode surface from overreaction with the electrolyte at high voltages. This can be attributed to the coral reef-like structure of the PC-PVP coating layer, which offers abundant electrical contact without sacrificing ion transport pathways. In addition, the specific nitrogen-containing groups of PC-PVP promote ion transport within the electrode. Furthermore, a carbon paper (CP) substrate is introduced as a current collector to support the PC-PVP/LNMO material layer and to establish a good interconnection. Owing to these features, the PC-PVP/LNMO/CP electrode outperforms the PVDF/LNMO/Al counterpart in terms of high-voltage cycling stability and rate capability. The improved electrode performance is supported by the reduced cathode–electrolyte interphase (CEI) resistance, which corresponds to mitigated electrolyte decomposition and stable CEI formation.

Concurrent photochemical whitening and darkening of ambient brown carbon

Abstract. The light-absorbing organic aerosol (OA), known as brown carbon (BrC), has important radiative impacts; however, its sources and evolution after emission remain to be elucidated. In this study, the light absorption at multiple wavelengths, mass spectra of OA and microphysical properties of black carbon (BC) were characterized at a typical suburban environment in Beijing. The absorption of BC is constrained by its size distribution and mixing state, and the BrC absorption is obtained by subtracting the BC absorption from the total aerosol absorption. Aerosol absorption was further apportioned to BC, primary BrC and secondary BrC by applying the least correlation between secondary BrC and BC. The multilinear regression analysis on the factorized OA mass spectra indicated that the OA from traffic and biomass burning emission contributed to primary BrC. Importantly, the moderately oxygenated OA (O / C = 0.62) was revealed to highly correlate with secondary BrC. These OA had higher nitrogen content, in line with the nitrogen-containing functional groups detected by the Fourier transform infrared spectrometer. The photochemical processes were found to reduce the mass absorption cross section (MAC) of primary OA, reducing its contribution to total absorption by 20 %, at the same time increasing MAC for secondary OA, which showed a 30 % enhancement in contribution to total absorbance, implying the concurrent whitening and darkening of BrC. This provides field evidence that the photochemically produced secondary nitrogen-containing OA can considerably compensate for some bleaching effect on the primary BrC, hereby causing radiative impacts.

Production of artificial humic acid from corn straw acid hydrolysis residue with biogas slurry impregnation for fertilizer application

This study investigated hydrothermal humification of corn straw acid hydrolysis residue with biogas slurry impregnation, aiming at producing water-soluble artificial humic acid fertilizer for fertilizer application and soil remediation. Hydrothermal humification parameters, including potassium hydroxide concentration (1–3 mol/L), retention time (2–6 h), and temperature (140–180 °C), were investigated using water as the liquid phase. The selected hydrothermal humification condition was 1.5 mol/L potassium hydroxide at 180 °C for 4 h. Moreover, biogas slurry impregnation (0–30 days) was evaluated to improve humic acid yield without introducing additional chemicals or energy input. Biogas slurry as the liquid phase increased the humic acid production by 73.24% with 5 days of impregnation compared to the control due to the alkalinity. The humic acid concentration was sufficient for China's national standard of water-soluble humic acid fertilizers in such conditions. The organic components in biogas slurry were involved in artificial humification as a precursor, forming C–N bonds with humic acid. The product with fortified nitrogen-containing functional groups enhanced the nutrient slow-release characteristics and water retention capabilities. The pot experiment further confirmed that artificial humic acid prepared in this study not only promoted the growth of plants but also achieved soil remediation.

Sustainable preparation of hierarchical porous carbon from discarded shells of crustaceans for efficient CO2 capture

The improved CO2 adsorption capacity and selectivity is the focus of research on the carbon-based CO2 adsorbent, while nitrogen-containing groups on the surface of adsorbent have an important effect on the CO2 adsorption. In this study, nitrogen self-doped hierarchical porous carbon was prepared from three kinds of crustacean shells, namely, hairy crab shell, crayfish shell and greasyback shrimp shell. It revealed that the pore structure of porous carbon can be regulated well with the varied activation temperature and the amount of KOH. With the favorable activation temperature of 800℃ and the mass ratio of activator to carbon (A/C) of 1:1, the obtained porous carbon with different carbon precursors exhibited relatively high specific surface area (1430.63–1734.64 m2/g), large pore volume (0.70–1.48 cm3/g) and developed pore-size distribution. Consequently, among the three kinds of hierarchical porous carbon tested, that prepared form greasyback shrimp displayed the excellent CO2 adsorption of 5.144 and 4.325 mmol/g at 1 bar, 273 K and 298 K and the highest CO2/N2 selectivity was observed of 32.32, attributed to the volume of mesopore and micropore and the type of nitrogen-containing groups. The effects of nitrogen-containing groups in porous carbon on the CO2 adsorption and CO2/N2 selectivity were analyzed, and it revealed that the CO2/N2 selectivity of porous carbon was positively correlated with pyrrolic N. In conclusion, the porous structures and nitrogen-containing groups of porous carbons both contribute to the CO2 adsorption and selectivity. The porous carbon with well recycling performance in this study presented a practical application prospect.