Concentration Of Functional Groups Research Articles

Morphology, functional groups, and CO2 adsorption performance of Cu2(OH)PO4: Effects of synthesis conditions

Global warming, primarily driven by emissions of greenhouse gases, particularly carbon dioxide, has emerged as a widely acknowledged concern. Hence, the development of novel carbon capture materials with high capacity and low cost holds substantial practical significance. This study investigates the influence of aging time, pH, and copper salt on the synthesis of Cu2(OH)PO4 and its CO2 adsorption performance. Cu2(OH)PO4 adsorbents were synthesized under various aging time, pH, and copper salt conditions, and their morphology and surface functional groups were characterized. Experimental findings indicate that excessively prolonged or abbreviated aging times adversely affect the formation of distinct, discernible lamellar structures within the material. Different pH levels influence the stacking configuration of the lamellae, impacting both their thickness and size. Under acidic conditions, lamellae exhibit dispersed three-dimensional stacking; under neutral conditions, lamellae notably enlarge and demonstrate two-dimensional stacking; at pH 9, lamellae stack three-dimensionally and aggregate. Additionally, the CO2 adsorption performance of Cu2(OH)PO4 adsorbents synthesized with different copper salts varies. By examining the relationship between surface functional group content and CO2 adsorption capacity, we deduced the mechanism by which various synthesis conditions affect both surface functional groups and adsorption capacity. Cu2(OH)PO4 synthesized with a 24 h aging time, pH 7, and CuSO4 as the copper salt exhibits the highest CO2 adsorption capacity, achieving 1.006 mmol/g.

Enhanced Adsorption of Aqueous Pb(II) by Acidic Group-Modified Biochar Derived from Peanut Shells

Using peanut shells, a sustainable agricultural waste product, as its raw material, the acid group-modified biochar (AMBC) was prepared through phosphoric acid activation, partial carbonization, and concentrated sulfuric acid sulfonation for efficient removal of lead ion from aqueous solutions. Characterization techniques such as N2 isothermal adsorption–desorption, SEM, XRD, FT-IR, TG-DTA, and acid–base titration were utilized to fully understand the properties of the AMBC. It was found that there were high densities of acidic oxygen-containing functional groups (-SO3H, -COOH, Ph-OH) on the surface of the AMBC. The optimal adsorption performance of the AMBC for Pb(II) in water occurred when the initial concentration of Pb(II) was 100 mg/L, the pH was 5, the dosage of the adsorbent was 0.5 g/L, and the contact time was 120 min. Under the optimal conditions, the removal ratio of Pb(II) was 76.0%, with an adsorption capacity of 148.6 mg/g. This performance far surpassed that of its activated carbon precursor, which achieved a removal ratio of 39.7% and an adsorption capacity of 83.1 mg/g. The superior adsorption performance of AMBC can be caused by the high content of acidic oxygen-containing functional groups on its surface. These functional groups facilitate the strong binding between AMBC and Pb(II), enabling effective removal from water solutions.

Optimization of Cellulose Nanofibers and Castor Oil in the Synthesis of Starch-carrageenan-polyvinyl Alcohol Biothermoplastic Film

The improvement of the properties of starch, carrageenan, and polyvinyl alcohol (SCPVA) biothermoplastics film is necessary be used as packaging materials that comply with SNI 7818:2014 and international standards. The aim of this research is to optimize the concentration of cellulose nanofiber and castor oil in the synthesis of SCPVA bio-thermoplastic film; so that, the best characteristics are obtained and SNI 7818:2014 and international standards are met. Optimization was carried out using the Response Surface Methodology (RSM) application with the independent variable (input control variable) concentration of cellulose nanofiber and castor oil with the dependent variable (response variable) tensile strength, elongation at break, and Young Modulus. SCPVA bio-thermoplastic film with an optimal concentration of cellulose nanofiber and castor oil was observed for swelling, WVTR, surface profile, functional group content, thermal stability, and crystallinity by reviewing X-ray diffraction intensity. The research results showed that the optimum concentrations of cellulose nanofiber and castor oil in the synthesis of SCPVA biothermoplastic film are 6.05% and 0.96%, respectively. The tensile strength, elongation at break and Young's modulus values of the resulting optimum treatment are 37.21 MPa, 4.347% and 1041.86 MPa, respectively. Hence, with optimization, the SCPVA bio-thermoplastic film has the highest tensile strength and Young's modulus values but the lowest elongation at break values. The physical and mechanical characteristics of SCPVA bio-thermoplastic film have met SNI 7818:2014 and most of ASTM 5336, therefore, it can be used as packaging.

STUDY OF NON-FUEL APPLICATION OF BROWN COAL DERIVATIVES IN THE PRODUCTION OF MEMBRANES BASED ON HYBRID BIODEGRADABLE MATERIALS

The article shows research into the non-fuel use of brown coal derivatives in the production of membranes based on hybrid biodegradable materials. The work used polylactide brand Terramac TP-4000, humic substances obtained from brown coals. Membranes for water purification from heavy metals were obtained from hybrid biopolymer materials based on pol- ylactide and humic substances in the form of polymer porous films with a pore size of 20 microns and a working surface area of the membrane of 28.26∙10-4 m2 with a circle diameter of 6 cm. Used in our The work of humic substances belonged to the group of well-hummified, more aromatic with a high content of acidic functional groups, which leads to their high com- plexing ability to form stable metal-humic complexes. The developed hybrid biodegradable materials based on polylactide and humic substances were used as highly effective sorption membrane materials to reduce the content of heavy metals in aqueous solutions. Obtaining membranes of hybrid biodegradable materials based on polylactide and humic substances have maximum selectivity for the extraction of metal ions in relation to Cu2+ – 95 % and Pb2+ – 94 %; and for metals such as Cd2+, Hg2+, Zn2+ and Co2+, it ranges from 82 to 89 %. Comparing the percentage of metal ions adsorbed, it can be seen that the easiest adsorbed metal was lead, copper and zinc adsorbed similarly, with cadmium showing the lowest percentage, but its adsorption was slightly worse than in the case of copper and zinc. The highest value was obtained for single adsorption of Cu2+ ions; in the case of adsorption from a mixture, this metal also had the highest distribution coefficient, and strong adsorption was also found for Pb2+. On the other hand, the adsorption of Zn2+ was, according to the “partition coefficient,” relatively weak. Strong and residual phases were highest for copper and lead, these two metals were largely bound into strong complexes by humic substances and only a very small amount could be washed out under normal conditions. It was found that the leaching of metal ions from mem- brane hybrid biodegradable materials based on polylactide and humic substances into water was very low, in most cases it was about 10 % and did not exceed 20 %. Most of the metal ions (≥60 %) were very tightly bound and were partially leached out under strongly acidic conditions. The obtained results of adsorption resistance vary significantly and correlate well with the age and degree of humification of humic substances.

Research on the Interaction Mechanisms between ScCO2 and Low-Rank/High-Rank Coal with the ReaxFF-MD Force Field.

CO2 geological sequestration in coal seams can be carried out to achieve the dual objectives of CO2 emission reduction and enhanced coalbed methane production, making it a highly promising carbon capture and storage technology. However, the injection of CO2 into coal reservoirs in the form of supercritical fluid (ScCO2) leads to complex physicochemical reactions with the coal seam, altering the properties of the coal reservoir and impacting the effectiveness of CO2 sequestration and methane production enhancement. In this paper, theoretical calculations based on ReaxFF-MD were conducted to study the interaction mechanism between ScCO2 and the macromolecular structures of both low-rank and high-rank coal, to address the limitations of experimental methods. The reaction of ScCO2 with low-rank coal and high-rank coal exhibited significant differences. At the swelling stage, the low-rank coal experienced a decrease in aromatic structure and aliphatic structure, and high-rank coal showed an increase in aromatic structure and a decrease in aliphatic structure, while the swelling phenomenon was more pronounced in high-rank coal. At the dissolution stage, low-rank coal was initially decomposed into two secondary molecular fragments, and then these recombined to form a new molecular structure; the aromatic structure increased and the aliphatic structure decreased. In contrast, high-rank coal showed the occurrence of stretches-breakage-movement-reconnection, a reduction in aromatic structure, and an increase in aliphatic structure. The primary reasons for these variations lie in the distinct molecular structure compositions and the properties of ScCO2, leading to different reaction pathways of the functional group and aromatic structure. The reaction pathways of functional groups and aromatic structures in coal can be summarized as follows: the breakage of the O-H bond in hydroxyl groups, the breakage of the C-OH bond in carboxyl groups, the transformation of aliphatic structures into smaller hydrocarbon compounds or the formation of long-chain alkenes, and various pathways involving the breakage, rearrangement, and recombination of aromatic structures. In low-rank coal, there is a higher abundance of oxygen-containing functional groups and aliphatic structures. The breakage of O-H and C-OH chemical bonds results in the formation of free radical ions, while some aliphatic structures detach to produce hydrocarbons. Additionally, some of these aliphatic structures combine with carbonyl groups and free radical ions to generate new aromatic structures. Conversely, in high-rank coal, a lower content of oxygen-containing functional groups and aliphatic structures, along with stronger intramolecular forces, results in fewer chemical bond breakages and makes it less conducive to the formation of new aromatic structures. These results elucidate the specific deformations of different chemical groups, offering a molecular-level understanding of the interaction between CO2 and coal.

Construct functional PEGDA/CSMA/CuII photosensitive ink for SLA 3D printing of blood contact appliance

Stereolithography (SLA) is an emerging technology in three-dimensional printing that has garnered significant attention in the biomedical field due to its high printing fidelity, good biocompatibility, and high spatial resolution. Polyethylene glycol diacrylate (PEGDA) is commonly used as a photosensitive printing ink in SLA, and it possesses excellent biocompatibility, photosensitivity, processability, water solubility, and biomechanical tunability. Additionally, PEGDA exhibits unique anti-protein, platelet, and cell adhesion possibilities, making it a promising material for blood contact applications. However, cross-linking PEGDA using chain growth photopolymerization results in a high concentration of reactive functional groups, leading to high print volume shrinkage, decreased precision of the finished product, warping, deformation, and cracking. This study introduces a chemically modified methacryloylated chitosan (CSMA) as a cross-linking agent into the PEGDA ink. This strategy effectively reduces the volume shrinkage of the ink and imparts antimicrobial properties to the final product. The dual anticoagulation properties of PEGDA were achieved by loading divalent copper ion (CuII) into the ink, which better addresses the antimicrobial and anticoagulant needs in the physiological environment of blood. The results show that SLA printable inks based on PEGDA/CSMA/CuII have low swelling, high print fidelity, high stability, and good cell compatibility. Furthermore, by verifying the functionality of PEGDA/CSMA/CuII, the research shows that the bioprinting ink exhibits excellent antibacterial and anticoagulant properties, making it a promising material candidate for SLA 3D printing of blood purification, central venous catheter, and other semi-implanted blood materials. This study provides new ideas for developing multifunctional photosensitive inks in biomedical engineering.

Hyaluronic Acid/Chondroitin Sulfate-Based Dynamic Thiol-Aldehyde Addition Hydrogel: An Injectable, Self-Healing, On-Demand Dissolution Wound Dressing.

Frequent removal and reapplication of wound dressings can cause mechanical disruption to the healing process and significant physical discomfort for patients. In response to this challenge, a dynamic covalent hydrogel has been developed to advance wound care strategies. This system comprises aldehyde functionalized chondroitin sulfate (CS-CHO) and thiolated hyaluronic acid (HA-SH), with the distinct ability to form in situ via thiol-aldehyde addition and dissolve on-demand via the thiol-hemithioacetal exchange reaction. Although rarely reported, the dynamic covalent reaction of thiol-aldehyde addition holds great promise for the preparation of dynamic hydrogels due to its rapid reaction kinetics and easy reversible dissociation. The thiol-aldehyde addition chemistry provides the hydrogel system with highly desirable characteristics of rapid gelation (within seconds), self-healing, and on-demand dissolution (within 30 min). The mechanical and dissolution properties of the hydrogel can be easily tuned by utilizing CS-CHO materials of different aldehyde functional group contents. The chemical structure, rheology, self-healing, swelling profile, degradation rate, and cell biocompatibility of the hydrogels are characterized. The hydrogel possesses excellent biocompatibility and proves to be significant in promoting cell proliferation in vitro when compared to a commercial hydrogel (HyStem® Cell Culture Scaffold Kit). This study introduces the simple fabrication of a new dynamic hydrogel system that can serve as an ideal platform for biomedical applications, particularly in wound care treatments as an on-demand dissolvable wound dressing.

Biomass derived hard carbon materials for sodium ion battery anodes: Exploring the influence of carbon source on structure and sodium storage performance

Compared to the scarce resources of lithium-ion batteries, sodium ion batteries have gradually become an ideal carrier for large-scale energy storage systems due to their abundant raw material resources. In recent years, hard carbon as an anode material for sodium ion batteries has attracted much attention. Biomass materials have become an ideal hard carbon precursor due to their natural and renewable advantages. This article evaluates the effect of hard carbon derived from three types of biomass waste (peanut shell, coffee grounds, and sugarcane bagasse) on the electrochemical performance of sodium ion batteries through pre carbonization pyrolysis method. The three materials exhibit different structures and surface functional group contents. Compared with coffee grounds and sugarcane bagasse, peanut shell-derived hard carbon has lower structural ordering and smaller specific surface area, and exhibits a higher initial Coulombic efficiency of 53.84 %. The initial reversible capacity of the HC-P electrode is 203.6 mAh/g, and the Coulombic efficiency of the electrode is close to 100 % with a reversible capacity of 127.1 mAh/g and a capacity retention of 81.4 % after cycling 100 at 1C current. The excellent electrochemical properties of HC-P can be attributed to its higher C=O bond content, larger layer spacing and lamellar structure.

Microbial etch: A novel construction method of functionalized biochar for enhanced uranium extraction in radioactive wastewater

Nuclear energy is playing an increasingly important role on the earth, but the nuclear plants leaves a legacy of radioactive waste pollution, especially uranium-containing pollution. Straw biochar with wide sources, large output, low cost, and easy availability, has emerged as a promising material for uranium extraction from radioactive wastewater, but the natural biomass with suboptimal structure and low content of functional groups limits the efficiency. In this work, microbial etch was first came up to regulate the biochar's structure and function. The surface of the biochar becomes rougher and more microporous, and the mineral contents (Ca, P) indirectly increased by microbial etch. The biochar was modified by calcium phosphate and exhibited a remarkable uranium extraction capacity of 590.8 mg g−1 (fitted value). This work provides a cost-effective and sustainable method for preparing functionalized biochar via microbial etch, which has potential for application to uranium extraction from radioactive wastewater.

Synthesis of linear polyesters bearing amino groups via lipase-catalyzed polymerization of N-protected monomer and deprotection

Linear biodegradable polyesters with a controlled number of side chains of amino groups have been synthesized. Such polyesters with a large number of amino side groups can be conjugated with a wide variety of functional molecules to obtain multi-functional biodegradable polyesters. In this study, poly(1,3-propylene-co-2-amino-1,3-propylene) adipate) (P(P-co-AP)A) was synthesized by enzymatic polymerization of divinyl adipate, 1,3-propanediol, and N-Boc-2-amino-1,3-propanediol (BocAPDO), and subsequent deprotection under strong acidic conditions. The mild reaction conditions and the specificity of the enzymatic polymerization could effectively inhibit side reactions, while the protecting groups of the monomers prevented polymer branching from the amino groups. It was found that the introduction rates of BocAPDO in the polymers could be well-controlled as the feeding rates changed from 0 to 100 mol%. After the deprotection and desalting, the ester groups in the main chain gradually converted into amide groups by intramolecular ester aminolysis at room temperature for a few days due to nucleophilic free amino groups. It was also found that the synthesized functional copolymers were all amorphous, since the random component of amino groups disrupted the crystallinity of poly(1,3-propylene adipate) (PPA). The glass transition temperature gradually increased with the increase in the content of 2-amino-1,3-propylene adipate (APA), eventually reaching −0.4 °C at the APA content of 100 mol% due to the intermolecular hydrogen bonding. Moreover, P(P-co-AP)A shows high hygroscopicity, where 3.9 wt% and 8.1 wt% of water were absorbed in the polymers with the APA contents of 50 and 100 mol%, respectively, when left in air at 60–70 % humidity for 6 h. Thus, the hydrophilicity dramatically improved with the increase in the APA content, eventually resulting in the acquisition of water solubility. The model post-polymerization modification using butyric acid was also conducted, and it was confirmed that carboxylic acids could be conjugated to the polymers by simple condensation reaction. Since polymerization of functional monomers is generally susceptible to the polarity of metal catalysts, the mild and selective reaction employed in this study could realize a higher content of various functional groups in the side chains of polyesters leading to a newly designed multi-functional polyester.

Iron anchored carbon–nitrogen catalyst for enhanced activation performance of peroxymonosulfate: Synergy of 1O2 and high-valent iron

Herein, Iron anchored in carbon–nitrogen nanosheets (Fe-CNx) catalysts were synthesized successfully through one-step in situ pyrolysis for activating peroxymonosulfate (PMS) to degrade sulfachloropyridazine (SCP). Fe-CN800/PMS could realized the complete removal SCP in 20 min (kobs = 0.644 min−1). Its reaction rates were 214.7 times higher than that in PMS system. Additionally, Fe-CN800 could effectively activate PMS in a wide range of pH (3–10.6). The relationship between the content of Fe-CNx functional groups and the catalytic performance indicated that C = O and Fe-N4 were the main active sites. The structural–functional association between active sites and reactive oxygen species (ROS) was revealed by regression analysis and Density Functional Theory calculations, indicating that C = O stimulated 1O2 production, while HV-Fe was derived from C = O and Fe-N4. Moreover, the PMS activation was enhanced via electron transfer between Fe(II) and Fe(III). Based on LC-MS and Fukui index, the action of ROS during SCP decomposition was analyzed, and proposed three probable pathways for SCP degradation. The transformation pattern of the structure and toxicity of the intermediates was revealed via T.E.S.T. analysis, and plant growth experiments showed that the effect of the treated SCP solution on Brassica napus significantly decreased. Finally, Fe-CN800 exhibited excellent stability, with SCP removal remaining above 95 % in five cycles and Fe leaching concentrations lower than ones which have been reported catalysts. This work provided new insights for the precise design of more efficient PMS catalysts. It will provide a fundamental basis for the practical application in wastewater treatment based on PMS-AOPs.

Interfacial effects on photooxidative aging of silica-filled polypropylene composites

The nature of the functional groups on the filler surface is one of the key influences on the interfacial interaction in the aging of polymer composites. However, the characteristics of this interfacial effect and its relation with functional groups remain unclear. In this study, we investigated the effects of interfacial interactions on the photooxidative aging of silica-filled polypropylene (PP) composites in which the interfaces comprise functional groups possessing different photooxidative properties. Results showed that the effects of interfacial interactions on the photooxidative aging of the silica-filled PP composites were closely related to the composition of the interfacial functional groups. Since the effect of interfacial interactions on the PP oxidation rate was correlated with the concentration of the interfacial functional groups, an aging kinetic model of interfacial effects could be constructed for determining the role of interfacial functional groups in the photooxidative aging of PP composites. This study will provide new ideas for developing interfacial antioxidant strategies for polymer composites.

Effect of Ti on the properties of diamond microcrystals synthesized in C–O–H supercritical fluid at high pressure and high temperature

Diamond micropowders 1–10 μm were synthesized at 7.5 GPa, 1300–1500 °C, and 3–6 s. Detonation nanodiamonds and pentaerythritol (C5H8(OH)4) with the addition of Ti were used as the reaction medium. The total nitrogen concentration, determined by electron paramagnetic resonance (EPR) and infrared (IR) spectroscopies, in diamonds synthesized without the addition of Ti was 1700 ppm. In diamonds synthesized with the addition of Ti, there are no 2N (A-center) and N3VH0 centers as well as oxygen-related functional groups, and the total concentration of nitrogen centers is reduced to 640 ppm. The addition of Ti leads to an increase in the synthesis temperature by 100–200 °C.Thermodynamics model calculations of the equilibrium compositions of the reaction medium at a pressure of 7.5. GPa and temperatures of 500, 1000 and 1500 °C were performed. The Gibbs free energy of possible reactions between the components of the reaction medium was calculated. It has been shown that under equilibrium conditions and a reaction medium corresponding to the synthesis conditions, the formation of TiN is thermodynamically possible. This leads to a decrease in the nitrogen concentration in diamonds. However, the formation of TiO2 is a competing reaction that can lead to a decrease in the concentration of oxygen-related functional groups.

Study on the effects of inorganic salts and ionic surfactants on the wettability of coal based on the experimental and molecular dynamics investigations

Through the evaluation and preparation of a novel inorganic salt composite solution consisting of sodium dodecyl benzene sulfonate (SDBS), the nonionic surfactants polyethylene glycol pisooctyl phenyl ether (Triton X-100), and inorganic salt Na2SO4, based on surface tension, contact angle, settling time, wetting rate, and changes in the surface microstructure and functional groups of coal, this study analyzed the wetting behavior of the solution on coal dust and its adsorption capacity on the surface of coal particles. The results demonstrate that the composite solution of inorganic salts can significantly enhance the wettability of coal samples, reducing the contact angle to 21.54° and lowering the surface tension to 26.10 mN/m. After treatment with the solution, the relative content of oxygen-containing functional groups in the microscopic structure of the coal sample increased to 59.6 % and pores more prominent than 25 nm increased to 34.63 %. Molecular dynamics (MD) simulations of the water-inorganic salt composite solution-coal system are conducted using Materials Studio software, revealing that after the addition of the composite solution, the self-diffusion coefficient (D) of water molecules is 6.3 × 10-9 m2/s, the starting point of the composite solution is 15 Å, and the system's interaction energy increase to 14000 kcal/mol. It further elucidated the modification of the surface molecular structure of coal dust by the inorganic salt composite solution, increasing hydrogen bonds, enhancing wetting, and demonstrating a solid adsorption capability of the inorganic salt composite solution on the surface of coal dust.

Exploring chitosan-plant extract bilayer coatings: Advancements in active food packaging via polypropylene modification

UV-ozone activated polypropylene (PP) food films were subjected to a novel bilayer coating process involving primary or quaternary chitosan (CH/QCH) as the first layer and natural extracts from juniper needles (Juniperus oxycedrus; JUN) or blackberry leaves (Rubus fruticosus; BBL) as the second layer. This innovative approach aims to redefine active packaging (AP) development. Through a detailed analysis by surface characterization and bioactivity assessments (i.e., antioxidant and antimicrobial functionalities), we evaluated different coating combinations. Furthermore, we investigated the stability and barrier characteristics inherent in these coatings. The confirmed deposition, coupled with a comprehensive characterization of their composition and morphology, underscored the efficacy of the coatings. Our investigation included wettability assessment via contact angle (CA) measurements, X-ray photoelectron spectroscopy (XPS), and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), which revealed substantial enhancements in surface concentrations of elements and functional groups of CH, QCH, JUN, and BBL. Scanning electron microscopy (SEM) unveiled the coatings' heterogeneity, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) and CA profiling showed moderately compact bilayers on PP, providing active species on the hydrophilic surface, respectively. The coatings significantly reduced the oxygen permeability. Additionally, single-layer depositions of CH and QCH remained below the overall migration limit (OML). Remarkably, the coatings exhibited robust antioxidative properties due to plant extracts and exceptional antimicrobial activity against S. aureus, attributed to QCH. These findings underscore the pivotal role of film surface properties in governing bioactive characteristics and offer a promising pathway for enhancing food packaging functionality.

Carbon nanostructures synthesis by catalyst-free atmospheric pressure plasma jet

In this study, carbon nanostructures were synthesized utilizing a warm plasma jet at atmospheric pressure in a continuous and catalyst-free process. The procedure and apparatus were designed and constructed in our laboratory. Plasma was generated with 600 W of electrical energy, using a high-voltage, high-frequency alternating current power source. The working gas utilized was a propane/butane mixture, with a concentration ratio of 60:40, respectively. A production rate of 300 mg min−1 of powdered material was achieved, with a particle size between 20 and 100 nm. The product was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, x-ray diffraction, and transmission electron microscopy. Results show the formation of multilayer carbon nanostructures with a low content of functional groups; the obtained material presented structural defects and amorphous carbon. This work demonstrates that, with adequate control, warm plasma jet discharges can be employed for the synthesis of carbon nanostructures. The process is scalable and can be utilized for hydrocarbon reforming and hydrogen production. However, further studies are needed to improve the quality of the nanostructures and process efficiency. The synthesized material can potentially be used in gas adsorption or in the manufacture of polymeric nanocomposites with enhanced thermal, electrical, and mechanical properties.

Experimental study on the mechanism of coal spontaneous combustion inhibition by degradation of white-rot fungus

To investigate the mechanism of inhibition of spontaneous combustion of coal by degradation of white-rot fungus, the changes of macroscopic oxidizing characteristics and microstructure of the degraded coal were investigated by the programmed temperature-raising test and the in situ Fourier-transform infrared spectroscopy experiments. The difference in gas production between the degraded coal and the blank samples indicated that the degradation inhibited the oxidation process of coal, and the intensity of the inhibition effect was different at different oxidation stages. The strongest inhibition effect was found in the accelerated oxidation stage, i.e. 80–140 °C. To further analyze the micro-mechanism of the degradation of Phanerochaete chrysosporium affecting the spontaneous combustion of coal, the relative contents of active functional groups in coal samples were compared. The results showed that the degradation affected the relative contents of hydroxyl, aliphatic hydrocarbon, and oxygenated functional groups in coal. Among them, the most significant changes of –OH and –CO- were observed at 80–140 °C. Thus, it was analyzed that Phanerochaete chrysosporium could degrade the macromolecular structure of coal by generating biological enzymes to reduce the number of oxidizable functional groups such as –OH, –CH2, –CH3, –CO-, and so on, thus reducing the risk of spontaneous combustion of coal.

A promotion strategy of enhancing the mercury removal in Shewanella oneidensis MR-1 based on the mercury absorption and electronic consumption via mer operon

Shewanella oneidensis (S. oneidensis) bacteria have bioremediation capabilities for various heavy metals, however, their repertoire of mercury-removal proteins is limited, restricting their effectiveness in mercury remediation. In this study, the integration of an exogenous mer operon into S. oneidensis expanded the range of mercury-removal proteins, significantly boosting both mercury tolerance and removal efficiency. The engineering bacteria (MR-mer) exhibited growth in a 180 mg/L Hg2+ solution, showing a 40% increase in tolerance over S. oneidensis. In a liquid medium with 50 mg/L Hg2+, the MR-mer strain achieved 73% mercury removal efficiency, outperforming the original strain by 50%, and facilitated Hg0 formation on the cell membrane. Extensive analysis of transmembrane structures and Fourier analysis revealed that mer operon proteins might target the cell membrane, modifying its functional group contents to enhance mercury adsorption. Additionally, the absence of the key protein OmcA in the electron transport chain led to a 30% reduction in Hg2+ removal capacity. This suggests that S. oneidensis transfers electrons to the cell surface through this chain, providing electrons for Hg2+ reduction. In conclusion, the mer operon, targeting the cell membrane in MR-mer strain, synergizes with the electron transport chain to markedly elevate Hg2+ removal capability. This approach not only augments Shewanella's mercury biodegradation capacity, but also offers novel perspectives for microbial heavy metal pollutant removal.

Surface state modulation of carbon dots for efficient generation of hydrogen peroxide

Electrocatalytic dual electron oxygen reduction to hydrogen peroxide (2e ORR) is considered a special and sustainable method for on-site continuous production of hydrogen peroxide. Oxygen doped carbon based materials have demonstrated their superiority in the generation of H2O2. However, there is still a lack of direct experimental evidence to determine the true active site on complex carbon surfaces. In this work, we introduce only carboxyl functional groups on the surface of carbon dots by a mild and simple synthesis method to study the specific COOH functional groups on the generation of H2O2. The H2O2 selectivity was correlated with the contents of COOH functional groups. In alkaline environments, the citric acid modified CDs (CA-OCDs) own excellent catalytic ability for 2e ORR, showing a maximum starting potential of 0.829 V (vs. RHE) and a high selectivity of 89.7 % over a wide potential range of 0.2–0.7 V (vs. RHE). In actual H2O2 production, the Faraday efficiency (FE) of CA-OCDs can be up to 97 %, and the yield achieves 838 mmol gcatalyst−1 h−1. This work provides an effective and simple strategy for designing efficient carbon-based catalysts for sustainable H2O2 electrosynthesis.

Cocoa husk as precursor of carbonaceous materials for supercapacitors electrodes

Activated carbon materials are widely used as high-performance electrodes for supercapacitors because they allow improving the electrochemical performance of these devices. The development of high surface areas and high porosity contributes to the energy storage by double electric layer, whereas the content of different functional groups on their surface to the pseudocapacitive storage. In addition, they can be obtained from lignocellulosic wastes providing a novel and economic perspective for the development of carbon-based electrodes. In this work, activated carbons were synthesized from cocoa husks using KOH as activating agent. The materials were obtained at three impregnation ratios (1:1, 3:1, 5:1) and three carbonization temperatures (500, 650, and 800 °C), optimizing the best conditions to obtain materials with high surface areas and porosity together with surface functional groups to improve energy storage. The results show that the 800 °C synthesized material with 3:1 impregnation ratio presents a capacitance of 120 F/g at 1 A/g, with a retention capacity of 93 % after 12,000 cycles, being the best electrochemical behavior among the carbons prepared. This is attributed to the adequate micro-mesoporosity, content of surface oxygenated functional groups and high surface area (1444 m2/g).