Oxygen Functional Groups Research Articles

Insight into the effect of structural differences among pitch fractions on sodium storage performance of pitch-derived hard carbons

Pitch is an excellent precursor of hard carbons (HCs) with low-cost and high carbon content, enabling its commercial-scale application in sodium-ion batteries. Pre-oxidation is the key to obtaining pitch-derived HCs with disordered microstructures. However, pitch is a mixture of fractions with different molecular weights and structures. With the introduction of oxygen, the cross-linked structure established by each fraction could be different, the effect of which on the microstructure and sodium storage performance of HCs remains unclear. Here, we separate pitch into three fractions and further pre-oxidize and carbonize to produce HCs, in order to systematically investigate the effects of structural differences among pitch fractions on the cross-linking mechanism and microstructure of as-obtained HCs. It is found that tetrahydrofuran-insoluble (THFI) enables the enrichment of polar oxygen functional groups, thus enhancing its oxidative activity to obtain more oxygen for the construction of abundant three-dimensional cross-linked structure. It is conducive to preventing the rearrangement of carbon layers and promoting the development of micropores during high-temperature carbonization process, which facilitates the storage of sodium ions in the low-voltage plateau region. The resulting hard carbon (THFI-1400) has significantly improved overall sodium storage performances. This work provides a new strategy to prepare low-cost and high-performance HCs.

Achieving unprecedented cyclability of flowless zinc-bromine battery by nitrogen-doped mesoporous carbon on thick graphite felt electrode

The flowless zinc-bromine battery (FLZBB) is non-flammable as it is based on an aqueous electrolyte and is considered an alternative to redox flow batteries because of its cost-effectiveness using a simple cell platform. However, it faces challenges related to self-discharge caused by the crossover of bromine (Br2) and polybromide anions (Brn+2-) formed at the positive electrode during the charging process. The self-discharge reaction consumes the charging active materials, thereby decreasing battery performance and lifespan. To address the critical issues, this study introduces the development of a revolutionary positive electrode: a nitrogen-doped mesoporous carbon-coated thick graphite felt (NMC/GF). This positive electrode effectively suppresses the crossover of active materials and prevents the self-discharge reaction. The mesopores, strategically embedded with nitrogen sites, serve as a stronghold, capturing and immobilizing bromine and polybromide anions, significantly reducing their undesirable effects. Furthermore, we enhanced the electrochemical performance of the NMC/GF electrode by modifying it to be ultrahydrophilic. Abundant oxygen and nitrogen functional groups were incorporated onto the electrode, resulting in an amplified affinity with the aqueous electrolyte. This modification led to improved bromine redox reaction kinetics. Demonstrating an excellent Coulombic efficiency surpassing 96 % and an energy efficiency of over 76 % at a current density of 20 mA cm−2 with a high-rate areal capacity of 2 mAh cm−2, this novel positive electrode achieves a previously unattained milestone; cyclability unprecedentedly extended to 10,000 cycles. The development of NMC/GF positive electrodes further advances the FLZBB system, and large-area scale-up research of these carbon electrodes makes looking forward to practical uses in energy storage systems.

The Research Progress of Biochar for Heavy Metal Soil Remediation was Briefly Discussed

Due to its structural advantages, biochar has developed pore structure, large porosity, surface potential energy, and more oxygen and nitrogen functional groups on the surface, which can adsorb and solidified heavy metals and organic pollutants in contaminated soil to achieve the purpose of repairing contaminated soil. At the same time, adding an appropriate amount of biochar to the soil can also enhance soil nutrition and improve water retention performance, and promote the good development of microbial systems. At present, it has become a research hotspot of contaminated soil remediation. In this paper, the preparation technology of biochar, the remediation mechanism of biochar and heavy metal pollutants, as well as the development prospect and precautions are described, in order to provide theoretical reference for the study of biochar in soil remediation.

ZIF-8/balsa wood derived N-doped porous carbon as self-supporting electro-Fenton cathode for efficient antibiotics degradation

Efficient electrochemical advanced oxidation processes (EAOPs) based on carbon catalysts are highly promising candidates for green environmental remediation technologies. Wood derived N-doped porous carbon (WNPC) was prepared the balsa wood with in-situ growth of zeolitic imidazolate framework-8 (ZIF-8) was used as precursor. WNPC acted as self-supporting electric Fenton cathode with high yield and selectivity (96 %) of in-situ H2O2 generation, which effectively avoided the use binder for powder material. Owing to abundant N-doping and oxygen functional groups, the H2O2 yield of WNPC was three times that of balsa wood derived carbon (WC) in electro-Fenton system. The graphite-N promoted the electron transfer, while the pyridinic-N could enhance the selectivity of the 2e-ORR for H2O2 generation. Furthermore, the specific surface area of WNPC was 10 times of WC, with improved hydrophilicity and accelerated electron transfer. The removal efficiency of tetracycline hydrochloride (TC) achieved 91 % within 120 min in electro-Fenton system with WNPC and Fe2+, which was much higher than that with WC (63 %). Free radical scavenging and electron paramagnetic resonance experiments confirmed that ·OH and O2–· were the main active substances for TC degradation in electro-Fenton system. In addition, WNPC has good stability, reusability, and comparable degradation performance of various organic pollutants, and also had efficient degradation performance with actual water. This research proposed a novel strategy to construct efficient electro-Fenton catalyst with wood as precursor, which provides an advancing electrocatalytic methods to achieve efficient and environmentally conscious water purification.

Photochemically induced aging of polystyrene nanoplastics and its impact on norfloxacin adsorption behavior

The co-occurrence of nanoplastics (NPs) and antibiotics in the environment is a growing concern for ecological safety. As NPs age in natural environments, their surface properties and morphology may change, potentially affecting their interactions with co-contaminants such as antibiotics. It is crucial to understand the effect of aging on NPs adsorption of antibiotics, but detailed studies on this topic are still scarce. The study utilized the photo-Fenton-like reaction to hasten the aging of polystyrene nanoplastics (PS-NPs). The impact of aging on the adsorption behavior of norfloxacin (NOR) was then systematically examined. The results showed a time-dependent rise in surface oxygen content and functional groups in aged PS-NPs. These modifications led to noticeable physical changes, including increased surface roughness, decreased particle size, and improved specific surface area. The physicochemical changes significantly increased the adsorption capacity of aged PS-NPs for norfloxacin. Aged PS-NPs showed 5.03 times higher adsorption compared to virgin PS-NPs. The adsorption mechanism analysis revealed that in addition to the electrostatic interactions, van der Waals force, hydrogen bonding, π-π* interactions and hydrophobic interactions observed with virgin PS-NPs, aged PS-NPs played a significant role in polar interactions and pore-filling mechanisms. The study highlights the potential for aging to worsen antibiotic risk in contaminated environments. This study not only enhances the comprehension of the environmental behavior of aged NPs but also provides a valuable basis for developing risk management strategies for contaminated areas.

Treatment of carbon electrodes with Ti3C2Tx MXene coating and thermal method for vanadium redox flow batteries: a comparative study.

One of the significant challenges of vanadium redox flow batteries is connected to the negative electrode where the main reaction of V(ii)/V(iii) and the side reaction of hydrogen evolution compete. To address this issue, we used titanium carbide (Ti3C2Tx) MXene coating via drop-casting to introduce oxygen functional groups and metals on the carbon electrode surface. Characterization through scanning electron microscopy and X-ray photoelectron spectroscopy confirmed the even distribution of Ti3C2Tx MXene on the electrodes and the presence of titanium and termination groups (-O, -Cl, and -F). The cyclic voltammetry analysis of MXene-coated electrodes showed more sharp electrochemical peaks for the V(ii)/V(iii) reaction than thermal-treated electrodes, even at relatively high scan rates. Notably, a relatively high reaction rate of 5.61 × 10-4 cm s-1 was achieved for the V(ii)/V(iii) reaction on MXene-coated electrodes, which shows the competitiveness of the method compared to thermal treatment (4.17 × 10-4 cm s-1). The flow battery tests, at a current density of 130 mA cm-2, using MXene-coated electrodes showed pretty stable discharge capacity for over 100 cycles. In addition, the voltage and energy efficiency were significantly higher than those of the system using untreated electrodes. Overall, this work highlights the potential application of MXene coating in carbon electrode treatment for vanadium redox flow batteries due to remarkable electrocatalytic activity and battery performance, providing a competitive method for thermal treatment.

Molecular structure characterization of coal with different coalification degrees: a combined study from FT-IR, Raman, 13C NMR spectroscopy and modelling

While extensive research has been conducted on the evolution of coal's molecular structure during coalification, the heterogeneity and complexity of coal continue to impede the accurate and precise quantitative characterization of its structural evolution mechanism. In this study, the organic matter source, coal quality, carbon skeleton structure, and functional group occurrence of coal at different coalification stages have been determined using maceral identification, vitrinite reflectance, industrial quality, elemental analysis, and spectral analysis. Four molecular models have been created through computer-aided molecular design. The results indicate that the hydrogen atoms in the benzene ring structure reduce as coalification increases. The content of aliphatic compounds gradually decreases, while the length of aliphatic side chains first decreases (Ro,max<1.81%) and then increases (Ro,max>1.81%). Moreover, the chemical structure of coal tends to mature and stabilize, as the degree of coal crystallization increases, and the oxygen-containing groups gradually decrease. Therefore, aromatization increases with the condensation reaction dominating in the late stage of coalification. After intensive attempts to determine the chemical bond mode between aromatic carbon, aliphatic side chain, and oxygen functional group, the final molecular structure models are presented as C188H165O13N3 (F-1), C182H161O9N5 (J-1), C195H153O10N3 (T-1), and C193H129O7N3 (W-1). Furthermore, the mechanism of coalification is discussed based on the variation of the side chains and chemical bonds. According to the adsorption heat of functional groups, the methane adsorption capacity increases as the degree of coalification increases. The inflection point of methane adsorption capacity is at Ro,max>1.80%. This study provides a theoretical framework to understand the molecular structure evolution of coals at varying degrees of metamorphism. Additionally, it proposes a reliable method for characterizing coal molecular structures with high accuracy.

Hydrochar Derived from Sewage Sludge and Water Hyacinth and Its Characterization

Population and urbanization increase the sewage generation. Sewage treatment plant (STP) generates the sewage sludge. Agricultural runoff and sewage water discharge into water bodies proliferates the growth of water hyacinth and creates environmental issues. Managing the sewage sludge and water hyacinth are difficult task because of high water content, environmental concerns, regulatory measures and high operational cost. Hydrothermal carbonization (HTC) converts the wet biomass into condensed solid product called hydrochar at moderate temperature range of 180 – 250°C under auto generated pressure. Through HTC process, the sewage sludge and water hyacinth were mixed and converted into hydrochar @ temperature of 200℃ and 4h resident time with L/S ratio of 9:1. The produced hydrochar showed desired functional groups viz., CH – methyl groups, C-O-C – alcohol groups, esters, ethers and Oxygenic functional groups (-C=O, -OH, -CO-O, C-O-C) with particle size of 494.8 nm, BET surface area of 369.70 m2 g-1, Zeta Potential of -27.9 mV. The hydrochar recorded slightly acidic pH (5.8) with appreciable levels of C (24.4%), N (2.51%), P (0.44%), K (0.98%), Ca (1.24%), Mg (0.68%). These properties of sewage sludge and water hyacinth derived hydrochar exhibits its potential use in agricultural and environmental applications.

Feasibility study of Aesculus turbinata fruit shell-derived biochar for ammonia removal in wastewater and its subsequent use as nitrogen fertilizer

In the face of increasing nitrogen demand for crop cultivation driven by population growth, this study presents a sustainable solution to address both the heightened demand and the energy-intensive process of nitrogen removal from wastewater. Our approach involves the removal of nitrogen from wastewater and its subsequent return to the soil as a fertilizer. Using biochar derived from Aesculus turbinata fruit shells (ATFS), a by-product of post-medical use, we investigated the effect of pyrolysis temperature on the NH4–N adsorption capacity of ATFS biochar (ATFS-BC). Notably, the ATFS-BC pyrolyzed at 300 °C (ATFS-BC300) exhibited the highest NH4–N adsorption capacity of 15.61 mg/g. The superior performance of ATFS-BC300 was attributed to its higher number of oxygen functional groups and more negatively charged surface, which contributed to the enhanced NH4–N adsorption. The removal of NH4–N by ATFS-BC300 involved both physical diffusion and chemisorption, with NH4–N forming a robust multilayer adsorption on the biochar. Alkaline conditions favored NH4–N adsorption by ATFS-BC300; however, the presence of trivalent and divalent ions hindered this process. Rice plants were cultivated to assess the potential of NH4–N adsorbed ATFS-BC300 (NH4-ATFS-BC300) as a nitrogen fertilizer. Remarkably, medium doses of NH4-ATFS-BC300 (594.5 kg/ha) exhibited key agronomic traits similar to those of the commercial nitrogen fertilizer in rice seedlings. Furthermore, high doses of NH4-ATFS-BC300 demonstrated superior agronomic traits compared to the commercial fertilizer. This study establishes the viability of utilizing ATFS-BC300 as a dual-purpose solution for wastewater treatment and nitrogen fertilizer supply, presenting a promising avenue for addressing environmental challenges.

Resorcinol/formaldehyde resin-derived carbon conductive network for superior fluorinated graphite based lithium primary batteries

The high energy density of fluorinated graphite (CFx) based lithium primary battery has aroused tremendous attention. However, the nonconductive CFx always induces high interface impedance and low power density. Herein, the carbon conductive network is generated by thermal treatment of resorcinol/formaldehyde (RF) resin on CFx and RF resin spheres (RF RSs), a conductive carbon layer coats on CFx surface, the electrical conductivity of CFx is improved. The oxygen functional groups in incomplete carbonized RF RSs also dedicate to the electrochemical performance of CFx. When different mass ratios of CFx/RF RSs are employed, the cathodes exhibit improved rate performance and voltage plateaus, and the initial voltage delays observed in CFx are significantly reduced. Notably, CFx/RF RSs−13 cathode delivers an impressive discharge capacity of 843.8 mAh g−1 with a voltage plateau of 2.68 V at 10 mA g−1. This leads to the maximum energy density of 2174.9 Wh kg−1 and a peak power density of 18600 W kg−1. Additionally, CFx/RF RSs−13 cathode demonstrates commendable electrochemical stability across a wide temperature spectrum (−20–70 °C). Given these superior electrochemical attributes, the CFx/RF RSs combination holds significant promise for deployment in high-power devices and for standard operations under extreme temperature conditions.

Effects of molecular structure on the grafting of diaminobenzene sulfonic acid onto graphene oxide

Molecular grafting is an effective technique for introducing sulfo groups into materials such as graphene oxide (GO). Existing studies on the grafting molecules with sulfo groups onto GO have been empirical, and the analytical elucidation of this process remains insufficient. In this study, we experimentally and numerically investigated the adsorption and reduction reactions between GO and two types of diaminobenzene sulfonic acids (DBSAs), namely 2,4- and 2,5-DBSAs, that possess an equal number of functional groups but different coordination numbers. Composite films of GO and DBSA were prepared from a GO/DBSA solution using centrifugation and filtration. Initially, X-ray diffractometry was employed to confirm the intercalation of DBSAs between GO layers in GO/DBSA composite films. Subsequently, X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy were performed; the results indicated that the bonding in GO to the oxygen functional group was replaced by the bonding to the amino group of DBSA; moreover, 2,5-DBSA was more reactive towards GO than 2,4-DBSA. To further investigate the reactivity differences, density functional theory calculations were performed. The decrease in enthalpy after the reaction of 2,5-DBSA was found to be higher than that of 2,4-DBSA, suggesting higher reactivity for 2,5-DBSA.

Spiro-Bifluorene-Cored Dopant-Free Conjugated Polymeric Hole-Transporting Materials Containing Passivation Parts for Inverted Perovskite Solar Cells.

Two spiro-bifluorene-based dopant-free HTMs (X22 and X23) have been synthesized by facilely condensing spiro-bifluorene diamine with 3,4-ethylenedioxythiophene (EDOT)-5,7-dicarbonyl dichloride and 2,3,5,6-tetrafluoro-terephthaloyl dichloride, respectively. In the X22 molecule, lone pairs of electrons on the sulfur (S) and oxygen (O) functional groups interact with the perovskite materials. The hole mobility (μh) of X22 (3.9 × 10-4 cm2 V-1 S1-) is more than twice that of X23 (1.4 × 10-4 cm2 V-1 S1-). The conductivity (σ0) of X22 is 2.73 × 10-4 S cm-1, which is also higher than that of X23 (2.39 × 10-4 S cm-1). The EDOT moiety benefits the contact angle of CH3NH3PbI3 precursor solutions on HTMs as low as 24°. The X22-based device with an indium-doped tin oxide/hole transport material (HTM)/CH3NH3PbI3/phenyl-C61-butyric acid methyl ester (PC61BM)/bathocuproine/Ag structure achieves a power conversion efficiency (PCE) of 19.18%. The PCE of the device based on X23 containing fluorine is 18.70%, and the contact angle between HTM and the perovskite precursor solution is 32°. The X22- and X23-based devices at ambient temperature (≈25 °C) in N2 retain 86% and 79% of the initial PCE after 150 days. The effect of S, O, and F heteroatoms plays an important role in the side chain modification of HTMs, improving defect passivation in HTM/CH3NH3PbI3 interfaces by multiple functional groups.

Resembling Graphene/Polymer Aerogel Morphology for Advancing the CO2/N2 Selectivity of the Postcombustion CO2 Capture Process.

The separation of CO2 from N2 remains a highly challenging task in postcombustion CO2 capture processes, primarily due to the relatively low CO2 content (3-15%) compared to that of N2 (70%). This challenge is particularly prominent for carbon-based adsorbents that exhibit relatively low selectivity. In this study, we present a successfully implemented strategy to enhance the selectivity of composite aerogels made of reduced graphene oxide (rGO) and functionalized polymer particles. Considering that the CO2/N2 selectivity of the aerogels is affected on the one hand by the surface chemistry (offering more sites for CO2 capture) and fine-tuned microporosity (offering molecular sieve effect), both of these parameters were affected in situ during the synthesis process. The resulting aerogels exhibit improved CO2 adsorption capacity and a significant reduction in N2 adsorption at a temperature of 25 °C and 1 atm, leading to a more than 10-fold increase in selectivity compared to the reference material. This achievement represents the highest selectivity reported thus far for carbon-based adsorbents. Detailed characterization of the aerogel surfaces has revealed an increase in the quantity of surface oxygen functional groups, as well as an augmentation in the fractions of micropores (<2 nm) and small mesopores (<5 nm) as a result of the modified synthesis methodology. Additionally, it was found that the surface morphology of the aerogels has undergone important changes. The reference materials feature a surface rich in curved wrinkles with an approximate diameter of 100 nm, resulting in a selectivity range of 50-100. In contrast, the novel aerogels exhibit a higher degree of oxidation, rendering them stiffer and less elastic, resembling crumpled paper morphology. This transformation, along with the improved functionalization and augmented microporosity in the altered aerogels, has rendered the aerogels almost completely N2-phobic, with selectivity values ranging from 470 to 621. This finding provides experimental evidence for the theoretically predicted relationship between the elasticity of graphene-based adsorbents and their CO2/N2 selectivity performance. It introduces a new perspective on the issue of N2-phobicity. The outstanding performance achieved, including a CO2 adsorption capacity of nearly 2 mmol/g and the highest selectivity of 620, positions these composites as highly promising materials in the field of carbon capture and sequestration (CCS) postcombustion technology.

Activation of polyimide by oxygen plasma for atomic layer deposition of highly compact titanium oxide coating

Titanium oxide (TiO2) coated polyimide has broad application prospects under extreme conditions. In order to obtain a high-quality ultra-thin TiO2 coating on polyimide by atomic layer deposition (ALD), the polyimide was activated by in situ oxygen plasma. It was found that a large number of polar oxygen functional groups, such as carboxyl, were generated on the surface of the activated polyimide, which can significantly promote the preparation of TiO2 coating by ALD. The nucleation and growth of TiO2 were studied by x-ray photoelectron spectroscopy monitoring and scanning electron microscopy observation. On the polyimide activated by oxygen plasma, the size of TiO2 nuclei decreased and the quantity of TiO2 nuclei increased, resulting in the growth of a highly uniform and dense TiO2 coating. This coating exhibited excellent resistance to atomic oxygen. When exposed to 3.5 × 1021 atom cm−2 atomic oxygen flux, the erosion yield of the polyimide coated with 100 ALD cycles of TiO2 was as low as 3.0 × 10−25 cm3/atom, which is one order less than that of the standard POLYIMIDE-ref Kapton® film.

Co-pyrolysis behaviors of biomass and polymer plastics by using reactive molecular dynamics simulation

Co-pyrolysis of oxygen-rich biomass and hydrogen-rich plastic polymer is a promising approach for waste management, which has been investigated by using reactive molecular dynamics simulation (ReaxFF MD) in this work. The blend models containing multicomponent mixtures of polymer (polyethylene, polypropylene, polystyrene) and biomass (cellulose, hemicellulose and lignin) were constructed for the first time, which is close to the real utilization of waste materials. The simulation results show that the degree of positive synergistic effect between biomass and polymer increases with temperature, where the polymer promotes biomass pyrolysis and delays its recombination. Co-pyrolysis greatly affects the product yields through cross reactions of hydrogen and hydroxyl transfer, leading to more oxygen-containing bio-oils produced with the aid of polymers providing hydrogen. Produced from heavy tar at first and light char at late pyrolysis period, char precursors are generated more and faster in the co-pyrolysis system with more biomass because oxygen functional groups provide the initial cross-linking sites. As compared to pyrolysis of only binary components, the observed qualitative synergistic results in co-pyrolysis of biomass-polymer mixtures provide important insights into the detailed reactions for co-pyrolysis process, which can complement experimental observations to modulate the nature and yield of the desired bio-oils and bio-chars.

Enhancing Graphene Nanoplatelet Reactivity through Low-Temperature Plasma Modification.

Graphene-based materials have great potential for applications in many fields, but their poor dispersion in polar solvents and chemical inertness require improvements. Low-temperature plasma allows the precise modification of materials, improving the physicochemical properties of the surface and thus creating the possibility of their potential use. Plasma treatment offers the possibility of introducing oxygen functional groups simply, rapidly, and in a controlled way. In this work, a systematic investigation of the effect of plasma modification on graphene nanoplatelets has been carried out to determine the optimal plasma parameters, especially the exposure time, for introducing the highest amount of oxygen functional groups on a surface. Different gases (O2, CO2, air, Ar, and C2H4) were used for this purpose. The chemical nature of the introduced oxygen-containing functionalities was characterized by X-ray photoelectron spectroscopy, and the structural properties of the materials were studied by Raman spectroscopy. The plasma-induced changes have been shown to evolve as the surface functionalities observed after plasma treatment are unstable. The immersion of the materials in liquids was carried out to check the reactivity of carbons in postplasma reactions. Stabilization of the material's surface after plasma treatment using CH3COOH was the most effective for introducing oxygen functional groups.

Properties of Carbon Fibers as Supercapacitor Electrodes via Electrospinning Using a Blending Solution of Polyacrylonitrile and Bisphenol A

Supercapacitors have attracted attention as efficient energy storage systems owing to their high power density and cycling stability. The use of appropriate electrode materials is important for high-performance supercapacitors, and various carbon materials have been studied as supercapacitor electrodes. In this study, carbon nanofibers with high specific surface areas were fabricated via a simple electrospinning process. Carbon nanofibers were fabricated by adjusting the ratio of polyacrylonitrile (PAN) to bisphenol A (BPA) and evaluated as electrode materials for supercapacitors. With the addition of BPA, improved specific surface area and oxygen functional groups were observed compared with nanofibers using only PAN. Therefore, BPA3, which had the highest specific surface area, exhibited a 28% improvement in capacitance (162 F/g) compared with BPA0 fabricated using only PAN. Carbon nanofibers fabricated by adjusting the ratio of BPA to PAN are promising electrodes for supercapacitors owing to their high capacitance and stability.

Growing ZIF-L seeds in graphene oxide interlayers towards synthesizing efficient cation sieving membranes

Designing and synthesizing membranes with fast and selective cation transport remains extremely challenging. Herein, ZGO membranes are conceived via a two-dimensional zeolitic imidazolate framework (ZIF-L) in situ grown on graphene oxide (GO), with ZIF-L as an interlayer that increases both vertical interlayer spacing and lateral tortuous path spacing of GO, thus improving the stability, selectivity, and ion permeation of the ZGO lamellar membrane. Structural analyses reveal that GO surfaces with abundant oxygen functional groups favored the formation of ZIF-L with 316 crystal planes and offered a high ion-accessible surface area. More importantly, the ZGO membrane delivers an excellent K+ permeability of 86.9 mmol m−2 h−1 and K+/Mg2+ selectivity up to 266, outperforming state-of-the-art GO-based membranes. Furthermore, molecular simulations confirm that the hydrogen bonding between hydrated cations and polar functional groups of ZGO membranes substantially restricted the dynamical transport of bivalent cation, and thus led to excellent cation selectivity. These results open a pathway to developing membranes for fast and highly selective ion separations in the future.

Study of conduction mechanism in swift heavy ion irradiated reduced graphene oxide samples and its applications towards low level detection of SO2 at room temperature

The reduced graphene oxide (rGO) sample is synthesized by the reduction of hydrazine hydrate. The prepared samples further reduced with swift heavy ion irradiation beam of silver (Ag8+) ions of 100 MeV energies. Ion beam irradiation causes defect in the rGO samples which is explained on the basis of Raman study. The removal of oxygen functional groups are explained on the basis of FTIR study. Ion irradiation has increased dc electrical conductivity on reduction. The room temperature dc conductivity of sample S4 is increases from 2.5 × 10−2 to 1.94 S/cm during reduction. The conduction mechanism is accounted by Mott's formulation of 3D variable range hopping model in the temperature range of 77 to 400 K. Along with it, the prepared samples are also tested for gas sensing abilities towards SO2 gas at 5 ppm. The sample exhibits good sensing properties towards analytes at room temperature.

Preparation of highly adsorptive biochar by sequential iron impregnation under refluxing and pyrolysis at low temperature for removal of tetracycline

Iron-doping modification is a prevailing approach for improving adsorption capability of biochar with environmental friendliness, but usually requires high temperature and suffers from iron aggregation. Herein, a highly adsorptive biochar was manufactured via sequential disperse impregnation of iron by refluxing and pyrolysis at low temperature for eliminating tetracycline (TC) from aqueous solution. Iron oxides and hydroxides were impregnated and stably dispersed on the carbon matrix as pyrolyzed at 200 °C, meanwhile abundant oxygen and nitrogen functional groups were generated on surface. The iron-doped biochar exhibited up to 891.37 mg/g adsorption capacity at pH 5, and could be recycled with high adsorption capability. The adsorption of TC should be mostly contributed to the hydrogen bonding of N/O functional groups and the hydrogen bonding/coordination of iron oxides/hydroxides. This would provide a valuable guide for dispersedly doping iron and conserving functional groups on biochar, and a super iron-doped biochar was prepared with superior recyclability.