Oxygen-based Functional Groups Research Articles

Evaluation of the aqueous Fe (II) ion sorption capacity of functionalized microcrystalline cellulose

The absence of relevant functional groups, especially the oxygen-based groups, have been reported to strongly limit the metal binding capacity of native cellulose. Therefore, this study successfully introduced substantive oxygenous functional groups (C˭O, –OH, C–O, etc.) onto microcrystalline cellulose via functionalization with 1,2,3,4-Butanetetracarboxylic acid. The synthesized adsorbent (‘FM-cell’) was further utilized for aqueous iron (II) ion uptake. The adsorbent’s instrumental characterization (scanning electron microscopy, SEM; Energy dispersion X-ray, EDX; X-ray diffraction, XRD and Fourier-transform infrared spectroscopy, FTIR) result confirmed the presence of the oxygen-based functional groups and their relative structural crystallinity. Similarly, the effect of the process variable on the ‘FM-cell’ adsorption capacity was elucidated via batch mode. The Dubinin-Radushkevich and intraparticle diffusion models satisfactorily predicted the isotherm and kinetic data, respectively. The sorption mechanism postulated strong adsorbent-adsorbate electrostatic interaction occasioned by the large coordination number of Fe (II) ions. Thus, the surface oxygenous functional groups abundance significantly enhanced the metal binding capacity of ‘FM-cell’.

Tuning the Oxygen Content of Reduced Graphene Oxide and Effects on Its Properties.

The need to recover the graphene properties in terms of electrical and thermal conductivity calls for the application of reduction processes leading to the removal of oxygen atoms from the graphene oxide sheet surface. The recombination of carbon–carbon double bonds causes a partial recovery of the original graphene properties mainly limited by the presence of residual oxygen atoms and lattice defects. However, the loss of polar oxygen-based functional groups renders the material dispersibility rather complicated. In addition, oxygen-containing functional groups are reaction sites useful to further bind active molecules to engineer the reduced graphene sheets. For these reasons, a variety of chemical processes are described in the literature to reduce the graphene oxide. However, it is greatly important to select a chemical process enabling a thin modulation of the residual oxygen content thus tuning the properties of the final product. In this work, we will present a chemical-processing technique based on the hydroiodic acid to carefully control the degree of residual oxidation. Graphene oxides were reduced using hydroiodic acid with concentrations from 0.06 to 0.95 mol L–1. Their properties were characterized in detail and tested, and the results showed that their oxygen content was finely tuned from 33.6 to 10.7 atom %. This allows carefully tailoring the material properties with respect to the desired application, which is exemplified by the variation of the bulk resistance from 92 Ω to 14.8 MΩ of the film from the obtained rGO.

Fe-Mn co-embed carbon spheres for aqueous divalent Cd removal

In this study, Fe-Mn co-embed sodium alginate carbon spheres (Fe-Mn/SA-C) were prepared as a cost-effective adsorbent for aqueous Cd(II) removal by a facile pyrolysis method. The morphology and chemical composition of Fe-Mn/SA-C were explored with various characterized techniques. The results indicate that Fe-Mn/SA-C possess porous structures and abundant oxide-based functional groups. Fe-Mn/SA-C exhibits excellent adsorption properties for aqueous Cd(II) and the adsorption process is pH-dependent. The adsorption data could fit pseudo second-order and Langmuir models well, suggesting that chemisorption is a dominant adsorption mechanism and the maximum adsorption capacity is 280.11 mg−1. Thermodynamic analysis demonstrates that the adsorption is spontaneous and endothermic. The adsorption mechanisms of Cd(II) include the complexation of Cd(II) with oxygen-based functional groups, precipitation, and ion exchange. Finally, the granulated and magnetic Fe-Mn/SA-C is an efficient and practical adsorbent for cadmium-containing wastewater treatment.

The effect of ambient air plasma generated by coplanar and volume dielectric barrier discharge on the surface characteristics of polyamide foils

This study targeted wettability and adhesion enhancement of polyamide (PA) foil surface by plasma treatment at atmospheric pressure. Volume dielectric barrier discharge (VDBD) and diffuse coplanar surface barrier discharge (DCSBD) were applied in ambient air using exposure times 0.25–2 s. Water contact angle (WCA) measurements proved that both plasma sources achieved significant wettability improvement of PA 6 foil surface immediately after treatment. However, the durability of this hydrophilic effect was much more pronounced with the DCSBD, compared to the VDBD. The lowest registered drop of WCA after DCSBD treatment was from the initial 65° to 28°, which even after one month of storage recovered only to 44°. In contrast, the VDBD treatment at similar parameters resulted in the WCA increase from 45° to 54° already after the first day of ageing. The XPS analysis of oxygen-based polar functional groups incorporated onto the treated PA 6 surface proved higher efficiency of DCSBD plasma. Moreover, the degree of surface oxidation was raised by increasing DCSBD's input power. Tape peel test revealed adhesion improvement achieved only with DCSBD, which had a growing tendency with increasing exposure time and input power. SEM did not show any noticeable damage of surface after the applied plasma treatments.

Hard carbon derived from coconut shells, walnut shells, and corn silk biomass waste exhibiting high capacity for Na-ion batteries

Hard carbons derived from renewable biomass were explored as anodes for Na-ion batteries and delivered a high reversible capacity (315 mAh g −1 ) and capacity retention (93%). An “adsorption-intercalation” mechanism is proposed to explain the observed performances. In recent years, hard carbon materials have gained significant interest as anode materials for Na-ion batteries. Biomass waste is considered one of the most interesting, renewable, available, and cost-effective precursor to obtain hard carbon (HC); however, HC properties must be finely tuned to achieve performance comparable to those provided by Li-ion batteries. In this work, three biomass wastes (coconut shells, walnut shells, and corn silk) were evaluated as potential precursors for HC preparation involving a pyrolysis process and subsequent acid washing to remove the inorganic impurities. All obtained materials exhibited low and similar specific surface areas (<10 m 2 ⋅g −1 ), but they presented different structures and surface functionalities. The walnut shell HC possessed a lower amount of inorganic impurities and oxygen-based functional groups compared to the coconut shell and corn silk HCs, leading to higher initial coulombic efficiency (iCE). The structural organization was higher in the case of the walnut shell HC, while the corn silk HC revealed a heterogeneous structure combining both highly disordered carbon and localized graphitized domains. All HCs delivered high initial reversible capacities between 293 and 315 mAh g −1 at 50 mA g −1 current rate, which remained rather stable during long-term cycling. The best capacity (293 mAh g −1 after 100 charge/discharge cycles) and highest capacity retention (93%) was achieved in walnut HCs in half-cells, which could be associated with its higher sp 2 C content, better organized structure, and fewer impurities. An “adsorption-insertion” Na storage mechanism is suggested based on several techniques. The walnut HCs exhibited an attractive energy density of 279 Wh/kg when tested in full cells.

Plasma Treatment of Polypropylene-Based Wood-Plastic Composites (WPC): Influences of Working Gas.

In this study, a polypropylene (PP)-based wood–plastic composite with maleic anhydride-grafted polypropylene (MAPP) as a coupling agent and a wood content of 60% was extruded and specimens were injection molded. The samples were plasma treated utilizing a dielectric barrier discharge (DBD) setup with three different working gases: Ar/O2 (90%/10%), Ar/N2 (90%/10%), and synthetic air. This process aims to improve the coating and gluing properties of the otherwise challenging apolar surface of PP based wood–plastic composites (WPC). Chemical analysis with X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) showed the formation of oxygen-based functional groups on the surface, independently from the working gas used for the treatment. Laser scanning microscopy (LSM) examined the surface roughness and revealed that the two argon-containing working gases roughened the surface more than synthetic air. However, the contact angle for water was reduced significantly after treatment, revealing measurement artifacts for water and diiodomethane due to the severe changes in surface morphology. The adhesion of acrylic dispersion coating was significantly increased, resulting in a pull-off strength of approximately 4 N/mm2, and cross-cut tests assigned the best adhesion class (0), on a scale from 0 to 5, after plasma treatment with any working gas.

Properties and adsorption mechanism of magnetic biochar modified with molybdenum disulfide for cadmium in aqueous solution

In this paper, we present the preparation of MoS2-modified magnetic biochar (MoS2@MBC) as a novel adsorbent by a simple hydrothermal method. MoS2@MBC contains abundant S-containing functional groups that facilitate efficient Cd(II) removal from aqueous systems. We employed various characterization techniques to explore the morphology, surface area, and chemical composition of MoS2@MBC; these included Brunauer–Emmett–Teller analysis scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction,. The results indicated the successful decoration of the surface of MoS2@MBC with iron and MoS2, and a higher surface area of MoS2@MBC than that of unmodified biochar. Moreover, adsorption properties including thermodynamics and kinetics were investigated along with the effects of pH, humic acid, and ionic strength on the Cd(II) adsorption onto MoS2@MBC. The O-, C-, S-, and Fe-containing functional groups on the surface of MoS2@MBC led to an electrostatic attraction of Cd(II) and strong Cd–S complexation. The Langmuir and pseudo second-order models fitted best for the batch adsorption experiments results. The adsorption capacity of MoS2@MBC (139 mg g−1 on the basis of the Langmuir model) was 7.81 times higher than that of pristine biochar. The adsorption process was found to be pH-dependent. The experimental results indicated that MoS2@MBC is an effective adsorbent for removing Cd(II) from water solutions. Further, the adsorption process involved the complexation of Cd(II) with oxygen-based functional groups, ion exchange, electrostatic attraction, Cd(II)–π interactions, metal–sulfur complexation, and inner-surface complexation. This work provides new insights into the Cd(II) ions removal from water via adsorption. It also demonstrates that MoS2@MBC is an efficient and economic adsorbent to treat Cd(II)-contaminated water.

CHARACTERIZATION OF UNTREATED AND COMPOSTED BIOCHAR DERIVED FROM ORANGE AND PINEAPPLE PEELS

Biochar production is a waste management option for agro-businesses and it is widely used to sequester carbon and to improve soil fertility. The preferred feedstock to produce biochar has been lignin and cellulose rich materials, or a mixture of industrial or animal residues. However, residues rich in soluble sugars, pectin and polysaccharides, such as fruit wastes, have been rarely used and are widely available. Furthermore, the release of toxic compounds has been reported when untreated biochars are used as soil amendments. Here we test if composting is able to eliminate toxicants and to improve biochar characteristics. We produced biochar out of orange and pineapple peels by pyrolysis, and characterized the physical and chemical properties of untreated and composted biochars. The analyses show that the untreated biochar has a high soluble salt and C content, an alkaline nature and high porosity. The composting process increased the pH, micronutrients, exchangeable cations, oxygen-based functional groups and the labile carbon, and reduced the PAHs and dioxins. Our results reveal that orange and pineapple peels are suitable raw materials for producing biochar but should be composted before using them as soil amendments.

Hybrid Plasma-Liquid Treatment of Carbon Nanotubes for Application in Direct Absorption Solar Thermal Collectors

Awareness of the environmental pollution caused by fossil fuels and the ever-increasing demand for energy has driven research focussed on zero-carbon renewable energy sources. Conscious of this, direct absorption solar thermal collectors are gaining prominence, both for domestic heating and steam generation. Carbon nanotubes (CNTs) have been investigated as an additive to take advantage of the near blackbody absorption and high thermal conductivity to improve system efficiency. Critical to the success of the additive nanoparticles is the stability in the fluid, however, due to their high surface energy CNTs tend to agglomerate which can limit the efficacy of their integration into real-world products. Covalent functionalization of the CNT sidewalls with oxygen-based or nitrogen-based functional groups is one of the most popular techniques to modify the surface energy of the CNTs.1 As an alternative to the harsh chemicals used by traditional chemical functionalisation, plasma-based surface treatments can be used with great efficacy and reduced reaction times.In this work, macroscopic ribbon-like assemblies of carbon nanotubes are functionalized using a simple direct current-based plasma-liquid system. This system utilizes the plasma-generated species in a fluid of 10 %vol ethanol in water, with or without a nitrogen precursor, for the oxygen and/or nitrogen functionalisation of the carbon nanotube assembly. For this treatment, a ribbon-like piece of CNT was used as the anode and a helium plasma discharge triggered by applying 10 mA and 1 - 1.6 kV to act as the cathode. The plasma-generated species are then expected to migrate towards the CNTs and functionalisation the sidewalls.The oxygen content is shown to be increased by between 50 % and 200 % when the treatment solution of 10 %vol ethanol is used in the ribbon electrode configuration. When ethylenediamine is added as a nitrogen precursor, the atomic concentration of nitrogen reaches 23 % in the ribbon electrode configuration, with amine groups, pyrrolic groups and graphitic nitrogen observed in the x-ray photoelectron spectra. This nitrogen content is unmatched in quantity when compared to either a simple soaking procedure or an electrolysis process with a platinum foil replacing the plasma as the counter-electrode. This demonstrates that the plasma either directly or indirectly, by means of plasma-generated species, facilitates and enhances the availability of nitrogen from the ethylenediamine precursor. The potential plasma-induced chemical pathways which lead to the functionalization of the CNTs are also investigated and discussed.In the application of a DASC system, it is found that the covalent functionalisation provided by the plasma-liquid system enhances the stability of the CNT-EG nanofluid, with the oxygen-functionalized samples producing the most stable nanofluids. This functionalization method generates interest for a broader range of applications including mechanically superior advanced composites,2 more sensitive gas sensors,3 enhanced energy storage materials4 or ultra-conductive fibres.5 References (1) Mallakpour, S.; Soltanian, S. Surface Functionalization of Carbon Nanotubes: Fabrication and Applications. RSC Adv. 2016, 6 (111), 109916–109935.(2) Williams, J.; Broughton, W.; Koukoulas, T.; Rahatekar, S. S. Plasma Treatment as a Method for Functionalising and Improving Dispersion of Carbon Nanotubes in Epoxy Resins. J. Mater. Sci. 2013, 48 (3), 1005–1013.(3) Ham, S. W.; Hong, H. P.; Kim, J. H.; Min, S. J.; Min, N. K. Effect of Oxygen Plasma Treatment on Carbon Nanotube-Based Sensors. J. Nanosci. Nanotechnol. 2014, 14 (11), 8476–8481.(4) Hulicova-Jurcakova, D.; Seredych, M.; Lu, G. Q.; Bandosz, T. J. Combined Effect of Nitrogen- and Oxygen-Containing Functional Groups of Microporous Activated Carbon on Its Electrochemical Performance in Supercapacitors. Adv. Funct. Mater. 2009, 19 (3), 438–447.(5) Li, L.; Liu, E.; Shen, H.; Yang, Y.; Huang, Z.; Xiang, X.; Tian, Y. Charge Storage Performance of Doped Carbons Prepared from Polyaniline for Supercapacitors. J. Solid State Electrochem. 2011, 15 (1), 175–182. Figure 1

Effects of air-based nonequilibrium atmospheric pressure plasma jet treatment on characteristics of polypropylene film surfaces

Polypropylene (PP) film surfaces were treated using air-based nonequilibrium atmospheric pressure plasma jets generated with a twisted wires-cylindrical electrode configuration. For comparison, PP samples were also processed with Ar plasma jets. The flux of charged particles imparted to the polymer surface by the air plasma jet greatly increased with decreases in both the gas flow rate and nozzle-to-sample distance, which was not the case for the Ar plasma jet. Reducing the gas flow rate and the nozzle-to-sample distance greatly enhanced the extent to which the surface was rendered hydrophilic by the air plasma within a short treatment time of 1 min. This enhanced effect is believed to originate from a high concentration of oxygen-based functional polar groups (FPGs) containing CO/COH and CO/COOH bonds grafted onto the surface. The hydrophilic surfaces resulting from this process also exhibited nanopore structures. The large number of oxygen-based FPGs produced by the air plasma can be attributed primarily to oxygen radical ions impinging from the air plasma on the surface. This can further be attributed secondarily to heat-induced oxidation rather than the sticking of oxygen radicals and UV-induced oxidation from the plasma. The nanoporous structure can also be ascribed to oxidation from UV photogenerated holes.

Room-Temperature Sustainable Synthesis of Selected Platinum Group Metal (PGM = Ir, Rh, and Ru) Nanocatalysts Well-Dispersed on Porous Carbon for Efficient Hydrogen Evolution and Oxidation.

Electroless deposition via a spontaneous redox reaction between the metal precursor and support is believed to be a promising approach for the syntheses of supported metal nanoparticles (SMNPs). However, its widespread applications are significantly prohibited by the low reductivity and high cost of support. To overcome these shortcomings, a porous carbon (PC) is herein developed as a promising matrix for the electroless deposition of metal NPs. Benefiting from abundant oxygen-based surface functional groups, the PC shows stronger reducibility (low redox potential) than conventional carbon substrate such as carbon nanotubes or graphene oxide, enabling a facile electroless deposition of Ir, Rh, and Ru NPs on its surface. These SMNPs exhibit an impressive electrocatalytic activity for the hydrogen evolution reaction (HER) or hydrogen oxidation reaction (HOR). For example, the Rh NP/PC can deliver an HER current density of 10 mA cm-2 with a small overpotential of 21 mV in 0.5 m H2 SO4 , while the Ru NP/PC exhibits excellent HOR activity in 0.1 m KOH in terms of high mass and surface specific exchange current density of 263 A g-1 Ru and 0.227 mA cm-2 Ru . The present strategy may open up opportunities for mass production of efficient supported NPs for diverse applications.

Biochar-Mediated Anaerobic Oxidation of Methane.

Biochar was recently identified as an effective soil amendment for CH4 capture. Corresponding mechanisms are currently recognized to be from physical properties of biochar, providing a favorable growth environment for aerobic methanotrophs which perform aerobic methane (CH4) oxidation. However, our study shows that the chemical reactivity of biochar can also stimulate anaerobic oxidation of CH4 (AOM) by anaerobic methanotrophic archaea (ANME) of ANME-2d, which proposes another plausible mechanism for CH4 mitigation by biochar amendment in anaerobic environments. It was found that, by adding biochar as the sole electron acceptor in an anaerobic environment, CH4 was biologically oxidized, with CO2 production of 106.3 ± 5.1 μmol g-1 biochar. In contrast, limited CO2 production was observed with chemically reduced biochar amendment. This biological nature of the process was confirmed by mcr gene transcript abundance as well as sustained dominance of ANME-2d in the microbial community during microbial incubations with active biochar amendment. Combined FTIR and XPS analyses demonstrated that the redox activity of biochar is related to its oxygen-based functional groups. On the basis of microbial community evolution as well as intermediate production during incubation, different pathways in terms of direct or indirect interactions between ANME-2d and biochar were proposed for biochar-mediated AOM.

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices.

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Polyethylene/Graphene Nanoplatelet Nanocomposite-Based Insulating Materials for Effective Reduction of Space Charge Accumulation in High-Voltage Direct-Current Cables

We have demonstrated a straightforward hydrophobic surface modification of graphene nanoplatelets (GNPs) through a defect-healing process to fabricate well-dispersed insulating low-density polyethylene (LDPE)/GNP nanocomposites and have confirmed their effective suppression of space charge accumulation. Without any organic modifiers, GNPs containing oxygen-based functional groups at the edges were successfully reduced at optimal high-temperature defect-healing condition and modified to have hydrophobic surface properties similar to those of the LDPE matrix. The degree of dispersion and the reproducibility of the mechanically melt-mixed LDPE/GNP nanocomposites were immediately analyzed by thickness-normalized optical absorption measurement. In the LDPE matrix, below the percolation threshold concentration, well-dispersed GNP fillers effectively acted as trapping sites under high electric fields, resulting in the successful suppression of packet-like space charge accumulation (field enhancement factor=1.04 @ 0.1 wt% LDPE/GNP nanocomposite).

Platinum nanoparticles decorated graphene nanoribbon with eco-friendly unzipping process for electrochemical sensors

Abstract In this study, an innovative large-scale synthesis of graphene nanoribbons (GNRs) with the eco-friendly unzipping process (only 0.1 mL H2SO4 acid solution for 1.0 mg carbon nanotube) was proposed. Nearly 100% yields of carbon nanotube derived GNRs was achieved by the proposed procedure. Through the longitudinal unzipping method, abundant oxygen-based functional groups were formed at the edges of GNRs, thus offering tremendous advantages for material synthesis and design. Furthermore, the reduction of platinum precursor to form platinum nanoparticles (PtNPs) can be facilitated by the functional groups on GNR surface for specific sensing. In fact, PtNPs played a role in connecting nodes to synergize the synthesized composite. The composite of PtNPs/GNRs could be further utilized as non-enzymatic biosensing materials against either oxidative or reductive analyte. Two essential biomarkers, namely hydrogen peroxide (H2O2) and β-nicotinamide adenine dinucleotide (NADH), were chosen to prove the feasibility of the proposed biosensors. From the experimental results of the amperometric analysis, sensitivities of the modified PtNPs/GNRs electrode toward H2O2 (378.5 µA/mM/cm–2) and NADH (724.3 µA/mM/cm–2) were obtained. The composite of PtNPs/GNRs has been verified to be a potential material for electrochemical biosensing with attractive sensitivity, selectivity, and stability.

Binding of calcium cations with three different types of oxygen-based functional groups of superplasticizers studied by atomistic simulations.

This work investigated interactions between calcium cations (Ca2+) and three common types of oxygen-based functional groups of concrete superplasticizers using density functional theory (DFT) calculations and all-atom molecular dynamics (MD) simulations. The three common types of oxygen-based functional groups were modeled as three hypothetical, low-molecular-weight organic molecules, each containing a methyl-terminated oxyethylene dimer and an adsorbing head of two oxygen-based functional groups, and are referred to as carboxylate, sulfonate, and phosphate groups, respectively, following the usual terminology in the field of concrete admixtures. Our DFT results show that the binding strength of the three groups with calcium cations follows (from high to low) phosphate>carboxylate>sulfonate, and both the electrophilic attack and the chemical reactivity of the three groups contribute significantly to the binding strength. The MD simulation results indicate that the adsorption of the three small molecules on the calcite (1 0 4) surface in aqueous solution shares a similar pattern in the sense that just two oxygen atoms of two adjacent anchor groups adsorb on the calcium atoms on the top layer of the crystal. The adsorption strength among the three types of functional groups follows the same order as the binding strength obtained from DFT calculations; both results corroborate a similar rule-of-thumb established by experiments. Furthermore, interactions of the three types of groups with water molecules suggest that strong hydrogen-bonding interactions exist in those systems. Graphical abstract Binding of calcium cations with three different types of oxygen-based functional groups of superplasticizersᅟ.

One-Pot Transformation of Technical Lignins into Humic-Like Plant Stimulants through Fenton-Based Advanced Oxidation: Accelerating Natural Fungus-Driven Humification.

Commercial humic acids mainly obtained from leonardite are in increasing demand in agronomy, and their market size is growing rapidly because these materials act as soil conditioners and direct stimulators of plant growth and development. In nature, fungus-driven nonspecific oxidations are believed to be a key to catabolizing recalcitrant plant lignins, resulting in lignin humification. Here we demonstrated the effective transformation of technical lignins derived from the Kraft processing of woody biomass into humic-like plant fertilizers through one-pot Fenton oxidations (i.e., artificially accelerated fungus reactions). The lignin variants resulting from the Fenton reaction, and manufactured using a few different ratios of FeSO4 to H2O2, successfully accelerated the germination of Arabidopsis thaliana seeds and increased the tolerance of this plant to NaCl-induced abiotic stress; moreover, the extent of the stimulation of the growth of this plant by these manufactured lignin variants was comparable or superior to that induced by commercial humic acids. The results of high-resolution (15 T) Fourier transform-ion cyclotron resonance mass spectrometry, electrostatic force microscopy, Fourier transform-infrared spectroscopy, and elemental analyses strongly indicated that oxygen-based functional groups were incorporated into the lignins. Moreover, analyses of the total phenolic contents of the lignins and their sedimentation kinetics in water media together with scanning electron microscopy- and Brunauer–Emmett–Teller-based surface characterizations further suggested that polymer fragmentation followed by modification of the phenolic groups on the lignin surfaces was crucial for the humic-like activity of the lignins. A high similarity between the lignin variants and commercial humic acids also resulted from autonomous deposition of iron species into lignin particles during the Fenton oxidation, although their short-term effects of plant stimulations were maintained whether the iron species were present or absent. Finally, we showed that lignins produced from an industrial-scale acid-induced hydrolysis of wood chips were transformed with the similar enhancements of the plant effects, indicating that our fungus-mimicking processes could be a universal way for achieving effective lignin humification.

Synthesis of Multi-walled Carbon Nanotubes Modified with Silver Nanoparticles and Evaluation of Their Antibacterial Activities and Cytotoxic Properties.

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver MWCNTs were prepared by the reductive deposition of silver from an aqueous solution of AgNO3 on the oxidized MWCNTs. Given the unique color of the CNTs, it was not possible to apply them to the minimum inhibitory concentration or mitochondrial toxicity assays to evaluate the toxicity and antibacterial properties, since they would interfere with the assays. The inhibition zone and minimum bactericidal concentration for the Ag-MWCNTs were measured and Live/Dead and Trypan Blue assays were used to measure the toxicity and antibacterial properties without interfering with the color of the CNTs.

Adsorption characteristics of Cd(ii) in aqueous solutions using spent mushroom substrate biochars produced at different pyrolysis temperatures.

To effectively remove Cd from water, biochars were produced by pyrolyzing surplus agricultural wastes of spent mushroom substrate (SMS) at 300, 500, and 700 °C. The biochars were characterized, and their Cd(ii) removal ratios and adsorption capacities in aqueous solutions were evaluated. The physical and chemical properties of the biochars were significantly affected by increasing the pyrolysis temperature; the data indicated that the ash content, pH and specific surface area of the biochars increased, whereas the yield and contents of carbon, hydrogen, nitrogen and oxygen decreased. In addition, the molar ratios of H/C, O/C and (O + N)/C decreased, which implied that the biochars became more aromatic and carbonaceous with a lower polarity and fewer oxygen-based functional groups. The pseudo-second-order kinetics model and Langmuir and Temkin isotherm models described the Cd(ii) adsorption better than the other tested models. The biochars derived at higher pyrolysis temperatures had higher adsorption capacities, and the maximum adsorption capacities for PC700 and SC700 were 71.49 and 46.87 mg g−1, respectively. The Qm values in our study were equivalent to or even higher than those for other modified biochars. This result shows that the biochars in this study are effective adsorbents for Cd(ii) removal from wastewater.

Thermal properties of polyethylene glycol/carbon microsphere composite as a novel phase change material

Polyethylene glycol (PEG) as phase change materials has been extensively studied. However, it is difficult to uniformly disperse the PEG in the unmodified matrix material owing to the impregnation problem. It is therefore challenging to overcome the shortcoming of low thermal conductivity. In order to solve this problem, carbon microspheres (CMPs) prepared by the hydrothermal method is firstly proposed as the supporting matrix for preparation of PEG composite. The PEG/CMPs composite is prepared via a mutual diffusion methodology in a high-temperature environment. The test result shows the CMPs nano-material has rich oxygen-based functional groups and can be uniformly dispersed in the PEG phase. As the carbon content increases, the CMPs become gradually connected in the PEG/CMPs composite, which can result in a network with good thermal conductivity. Compared with the thermal conductivity of pure PEG, the thermal conductivity of the composite is increased by 65.07%. Owing to the existence of hydrogen bonds in the composite, the crystallinity fraction of the PEG is in the range of 102–105%. It means that the test result is higher than the theoretical value of latent heat for the composite. Finally, its cycling performance was measured. After 500 thermal cycles, the phase transition temperature of the composite remains almost constant, and the latent heat values of the melting and freezing decrease by 1.05 and 1.45%, respectively. The PEG/CMPs composite would be a promising material for thermal energy storage applications and can be used in various engineering disciplines.