Microporous activated carbons from ammoxidised anthracite and their capacitance behaviours

The paper presents results of a study on obtaining N-enriched active carbons from anthracite mined in Siberia, and on its use as electrode material in supercapacitors. The anthracite was carbonised, activated with KOH and ammoxidised by a mixture of ammonia and air at the ratio 1:3 at 300 or 350 °C, at each stage of the activate production. The products were microporous N-enriched active carbon samples of well-developed surface area reaching from 1255 m²/g to 2011 m²/g and containing from 0.3 to 5.4 wt% of nitrogen. Capacity curves characteristics of the ammoxidised active carbon samples were determined by the galvanostatic and potentiodynamic methods, and by impedance spectroscopy for acidic and basic electrolyte solutions. The best capacity parameters in an acidic medium were obtained for the coal samples ammoxidised at the precursor stage (191 F/g), containing about 0.4 wt% of nitrogen, while in a basic medium—for the coal samples ammoxidised at the stage of active carbon (200 F/g), containing 4.0 wt% of nitrogen.     

The microstructure and properties of energetically deposited carbon nitride films

The intrinsic stress, film density and nitrogen content of carbon nitride (CN_x) films deposited from a filtered cathodic vacuum arc were determined as a function of substrate bias, substrate temperature and nitrogen process pressure. Contour plots of the measurements show the deposition conditions required to produce the main structural forms of CN_x including N-doped tetrahedral amorphous carbon (ta-C:N) and a variety of nitrogen containing graphitic carbons. The film with maximum nitrogen content (~ 30%) was deposited at room temperature with 1.0 mTorr N₂ pressure and using an intermediate bias of − 400 V. Higher nitrogen pressure, higher bias and/or higher temperature promoted layering with substitutional nitrogen bonded into graphite-like sheets. As the deposition temperature exceeded 500 °C, the nitrogen content diminished regardless of nitrogen pressure, showing the meta-stability of the carbon–nitrogen bonding in the films. Hardness and ductility measurements revealed a diverse range of mechanical properties in the films, varying from hard ta-C:N (~ 50 GPa) to softer and highly ductile CN_x which contained tangled graphite-like sheets. Through-film current–voltage characteristics showed that the conductance of the carbon nitride films increased with nitrogen content and substrate bias, consistent with the transition to more graphite-like films.     

The production of hypocrellin colorants by submerged cultivation of the medicinal fungus Shiraia bambusicola

Hypocrellin production using submerged cultivation of the medicinal fungus Shiraia bambusicola revealed that both glucose and (NH₄)₂SO₄ were optimal carbon and nitrogen sources. Hypocrellin production increased with increasing initial glucose concentration within the range of 10–50 g l^?1 and (NH₄)₂SO₄ concentration in the range of 1–2 g l^?1. The effects of carbon and nitrogen concentration were optimized using central composite experimental design and response surface analysis; maximum hypocrellin production (196.94 ± 6.93 mg l^?1) was achieved using 45.7 g l^?1 glucose and 1.93 g l^?1 (NH₄)₂SO₄.     

Efficient biocatalytic hydrolysis of 2-chloronicotinamide for production of 2-chloronicotinic acid by recombinant amidase

For efficient production of 2-chloronicotinic acid from 2-chloronicotinamide, an amidase gene was synthesized by codon-optimized and expressed. The optimum pH and temperature for the biocatalytic process were 7.5 and 45–50 °C, respectively. The recombinant E. coli whole cells exhibited tolerance against a high substrate concentration of up to 180 mM. It could also be repeatedly used in the biotransformation and the residual activity after 10 batches was still over 50% of the initial activity. These results indicated this recombinant amidase is of great potential for the practical production of 2-chloronicotinic acid.     

Screening of lactic acid bacteria for fermentation of minced wastes of Argentinean hake (Merluccius hubbsi)

Sixteen strains of lactic acid bacteria were evaluated for their capacity of acidification of Merluccius hubbsi fish wastes obtained from a processing factory. Only three lactobacilli (Lactobacillus buchneri B-1837, Lactobacillus arizonensis B-14768 and Lactobacillus plantarum B-4496) were able to reduce the pH value to 4.0 or below when using glucose or sucrose as carbon source. Either with only 25 g l^?1 of glucose or sucrose, L. arizonensis B-14768 reduced the pH to 3.8 ± 0.2 within 24 h of fermentation. The acid tolerance test (pH 3.0 at 37 °C) for the strains presented D_pH3-values of 192, 383 and 767 min for L. buchneri, L. plantarum and L. arizonensis, respectively. However, at a lower pH value (pH 2.0) only L. arizonensis was significantly recovered after 45 min of exposure (D_pH2 68 min). Considering together the acidification capacity, the tolerance to other stresses (heat and bile salts) and the lower optimum temperature for the process, L. arizonensis is described as a suitable strain for M. hubbsi silage; constituting a promissory alternative for fish fermentation at location with temperate or cold climes.     

The effects of the surface oxidation of activated carbon,the solution pH and the temperature on adsorption of ibuprofen

A commercial microporous–mesoporous granular activated carbon was modified by oxidation with either H₂O₂ in the presence or absence of ultrasonic irradiation, or NaOCl or by a thermal treatment under nitrogen flow. Raw and modified materials were characterized by N₂ adsorption–desorption measurements at 77 K, Boehm titrations, pH measurements and X-ray photoelectron spectroscopy. Ibuprofen adsorption kinetic and isotherm studies were carried out at pH 3 and 7 on raw and modified materials. The thermodynamic parameters of adsorption were calculated from the isotherms obtained at 298, 313 and 328 K. The pore size distribution of carbon loaded with ibuprofen brought out that adsorption occurred preferentially into the ultramicropores. The adsorption of ibuprofen on pristine activated carbon was found endothermic, spontaneous (ΔG° = −1.1 kJ mol⁻¹), and promoted at acidic pH through dispersive interactions. All explored oxidative treatments led mainly to the formation of carbonyl groups and in a less extent to lactonic and carboxylic groups. This then helped to enhance the adsorption uptake while decreasing adsorption Gibbs energy (notably −7.3 kJ mol⁻¹ after sonication in H₂O₂). The decrease of the adsorption capacity after bleaching was attributed to the presence of phenolic groups.     

Cosolvent effect on the phase behavior for the poly(benzyl acrylate) and poly(benzyl methacrylate) in supercritical carbon dioxide and dimethyl ether

Experimental cloud-point data up to 433.2 K and 193.0 MPa are reported for binary and ternary mixtures of poly(benzyl methacrylate) [poly(BzMA)] + carbon dioxide + benzyl methacrylate (BzMA) and poly(benzyl acrylate) [Poly(BzA)] + carbon dioxide + benzyl acrylate (BzA) systems. High-pressure cloud-point data are also reported for Poly(BzMA) + carbon dioxide and Poly(BzA) + carbon dioxide in supercritical dimethyl ether (DME). Cloud-point behavior for the Poly(BzMA) + carbon dioxide + BzMA system was measured in changes of the pressure–temperature (p–T) slope, and with BzMA weight fraction of 50.6, 61.0, 67.2 and 95.0 wt.%. The Poly(BzA) + carbon dioxide + 30.4, 40.7 and 49.4 wt.% BzA systems change the (p–T) curve from upper critical solution temperature region (UCST) to lower critical solution temperature (LCST) region as the BzA concentration increases. With 52.3 wt.% BzA to the Poly(BzA) + carbon dioxide solution, the cloud-point curves are taken on the appearance of a typical lower critical solution temperature boundary. Also, the impact by cosolvent (BzMA and BzA) concentrations for the Poly(BzMA) + DME and Poly(BzA) + DME systems is measured at temperature to 453.2 K and pressure range of 24.6–61.3 MPa.     

Phase behavior of catalytic deactivated compounds and water with 1-ethyl-3-methylimidazolium acetate [EMIM][OAc] ionic liquid at T = 298.15–323.15 K and p = 1 bar

Density, surface tension and refractive index of the binary mixture of catalytic deactivated compounds with 1-ethyl-3-methylimidazolium acetate {[EMIM][OAc]} ionic liquid were measured at temperature of 298.15–323.15 K from which the derived thermodynamic properties including excess molar volume and deviation of surface tension and refractive index were calculated. The derived thermodynamic properties could be explained well by the interaction between similar and dissimilar aromatic structure of the molecules over the entire mole fraction of ILs. It was observed that all the catalytic deactivated compounds and water molecules have significant structural interaction with [EMIM][OAc] via CH?π bond interaction, π?π stacking and n?π interaction over the entire mole fraction of IL at T = 298.15 K. Further the composition of ionic liquid have significant influence on the interaction between dissimilar aromatic structure of molecules like pyridine, indoline and quinoline in liquid phase as compared to temperature. The surface tension increases in the order of: hiophene > pyridine > quinoline > pyrrole > indoline > water; while the refractive index increases in the order: pyridine < water < pyrrole < thiophene < indoline < quinoline. The deviation of surface tension was found to be inversely proportional to the deviation of refractive index at T = 298.15 K. From these results it was concluded that the structure of the ionic liquids is very important for extraction processes on catalytic deactivated compounds, especially for pyridine, indoline and quinoline as compared to water molecules.     

Phase behavior for the poly[2-(2-ethoxyethoxy)ethyl acrylate] and 2-(2-ethoxyethoxy)ethyl acrylate in supercritical solvents

Pressure-composition (p, x) isotherms were obtained for the carbon dioxide + 2-(2-ethoxyethoxy)ethyl acrylate [2-(2-EE)EA] system at five temperatures (313.2 K, 333.2 K, 353.2 K, 373.2 K, and 393.2 K) and pressure up to 22.86 MPa. The carbon dioxide + 2-(2-EE)EA system exhibits type-I phase behavior with a continuous mixture critical curve. The experimental results for carbon dioxide + 2-(2-EE)EA mixtures are correlated using the Peng–Robinson equation of state (PR-EOS) using mixing rule including two adjustable parameters. The critical property of 2-(2-EE)EA is estimated with the Joback–Lyderson method.Experimental data up to 485 K and 206.6 MPa are reported for binary and ternary mixtures of poly(2-(2-ethoxyethoxy)ethyl acrylate) [P(2-(2-EE)EA)] + carbon dioxide + 2-(2-EE)EA, P(2-(2-EE)EA) + carbon dioxide + dimethyl ether (DME), P(2-(2-EE)EA) + carbon dioxide + propylene and P(2-(2-EE)EA) + carbon dioxide + 1-butene systems. High-pressure cloud-point data are also reported for P(2-(2-EE)EA) in supercritical carbon dioxide, propane, propylene, butane, 1-butene, and DME at temperature to 474 K and a pressure range of (8.45–206.6) MPa. Cloud-point behavior for the P(2-(2-EE)EA) + carbon dioxide + 2-(2-EE)EA system were measured in changes of the pressure–temperature (p, T) slope and with 2-(2-EE)EA mass fraction of 0.0 wt%, 5.9 wt%, 14.9 wt%, 30.3 wt% and 60.2 wt%. With 0.650 2-(2-EE)EA to the P(2-(2-EE)EA) + carbon dioxide solution, the cloud point curves take on the appearance of a typical lower critical solution temperature boundary. The P(2-(2-EE)EA) + carbon dioxide + (0.0–46.6) wt% DME systems change the (p, T) curve from upper critical solution temperature region to lower critical solution temperature region as the DME mass fraction increases. Also, the impact by propylene and 1-butene mass fraction for the P(2-(2-EE)EA) + carbon dioxide + propylene and 1-butene system is measured at temperatures to 454 K and a pressure range of (75.7 to 119.6) MPa.     

Effects of emulsification variables on fuel properties of two- and three-phase biodiesel emulsions

Biodiesel has attractive fuel properties such as excellent biodegradability and lubricity, almost no emissions of sulfur oxides, PAH and n-PAH, reduced CO₂, PM and CO emission, superior combustion efficiency, etc. However, burning of biodiesel generally produces higher levels of NO_x emissions, primarily due to its high oxygen content. In this study, the emulsification technology has been considered to reduce the NO_x emission level of fossil fuel. Biodiesel, produced by means of transesterification reaction accompanied with a peroxidation process, was emulsified to form two-phase W/O and three-phase O/W/O emulsions. The effects of the emulsification variables such as hydrophilic lipophilic balance (HLB), and water content on the fuel properties and emulsion characteristics of W/O and O/W/O emulsions were investigated in this study. The experimental results show that the surfactant mixture with HLB = 13 produced the highest emulsification stability while HLB = 6 produced the lowest emulsification stability and the most significant extent of water–oil separation among the various HLB values for O/W/O biodiesel emulsion. The kinematic viscosity, specific gravity and carbon residual of the biodiesel emulsions were larger than those of the neat biodiesel. In addition, the W/O biodiesel emulsion was found to have a smaller mean droplet size, lower volumetric fraction of the dispersed phase than the O/W/O biodiesel emulsion, and the highest heating value among the test fuels, if the water content is deducted from the calculation of the heating value.     

Solid-state production of esterase using fish processing wastes by Bacillus altitudinis AP-MSU

The bacterium Bacillus altitudinis AP-MSU, able to produce esterase was isolated from the gut of marine fish Sardinella longiceps. The esterase production was investigated in solid-state fermentation experiment using various fish processing waste meal. Among the tested fish processing wastes, red grouper waste emerged as the best source for higher esterase production. The suitable surfactant and triglyceride identified to increase the lipase production was neem oil. Effect of individual carbon and nitrogen sources supplementation on esterase production revealed that fructose and peptone aided the higher esterase production than the other tested carbon and nitrogen sources. The suitable concentration of sodium chloride for higher esterase production was at 5%. Effect of surfactants and trace elements on esterase production showed that Tween 20 and zinc sulphate, respectively produced maximum amount of esterase. The effect of physical parameters on lipase production revealed that 50 °C temperature and pH 7–8 were optimum for higher esterase production. Statistical optimization with Plackett–Burman design showed that neem oil, NaCl and fructose were found to be the most predictive factors for esterase production by this strain.     

Phase equilibria for the binary mixture of n-vinyl pyrrolidone and N,N-dimethylacrylamide in supercritical carbon dioxide

High pressure phase equilibria for the (carbon dioxide + n-vinyl pyrrolidone) and (carbon dioxide + N,N-dimethylacrylamide) systems are measured in a static apparatus at five temperatures of 313.2, 333.2, 353.2, 373.2 and 393.2 K and pressures up to 24.66 MPa. These two systems exhibit maximums in pressure at temperatures between the critical temperatures of carbon dioxide and n-vinyl pyrrolidone or N,N-dimethylacrylamide. The solubility of n-vinyl pyrrolidone and N,N-dimethylacrylamide for the carbon dioxide + n-vinyl pyrrolidone and carbon dioxide + N,N-dimethylacrylamide systems increases as the temperature increases at a fixed pressure. The carbon dioxide + n-vinyl pyrrolidone and carbon dioxide + N,N-dimethylacrylamide systems exhibit type-I phase behavior. The experimental results for the carbon dioxide + n-vinyl pyrrolidone and carbon dioxide + N,N-dimethylacrylamide systems are correlated with the Peng–Robinson equation of state using a mixing rule including binary interaction parameters (k_ij and η_ij).     

Efficient production of l-lactic acid from chicken feather protein hydrolysate and sugar beet molasses by the newly isolated Rhizopus oryzae TS-61

The aim of this study was to investigate production of l-lactic acid from molasses and chicken feather protein hydrolysate (CFP) by the newly isolated Rhizopus oryzae TS-61. R. oryzae TS-61 was capable of utilizing molasses sucrose and CFP as carbon and nitrogen sources, respectively. In contrast to yeast extract and ammonium sulfate, CFP had potential not only to prevent excessive pH changes and foaming but also to provide smaller uniform pellet formation in during fermentation. Thanks to these properties, it was concluded that CFP might have resulted in higher l-lactic acid production than the other two nitrogen sources (yeast extract and ammonium sulfate). At the end of 42-h optimal cultivation period, the highest (38.5 g/L) and lowest (28.8 g/L) concentrations of l-lactic acid were obtained with CFP and ammonium sulfate, respectively. This is the first report on use of waste chicken feather as a lactic acid production substrate. In addition, a new R. oryzae strain, being capable of using molasses sucrose as carbon source in order to produce l-lactic acid, was isolated.     

Extraction,purification and application of thermostable and halostable alkaline protease from Bacillus alveayuensis CAS 5 using marine wastes

A marine bacterium Bacillus alveayuensis CAS 5 produced protease when grown at 55 °C for 60 h in 100 ml of basal medium containing 1% SSP (w/v) and purified to 7.77 fold with specific activity of 518.78 U/mg. The optimum temperature, pH and NaCl for enzyme activity were 50 °C, 9 and 35% respectively. The enzyme was highly stable even at 80 °C, pH 12, 35% NaCl and presence of ionic, non-ionic and commercial detergents. The protease was investigated for its application as cleansing additive in blood stain removal. The preset study emphasized that marine wastes can be utilized to generate high value-added products and hidden potential in the production of functional foods.     

Selective low temperature synthesis of carbon nanospheres via the catalytic decomposition of trichloroethylene

The catalytic growth of structured carbon from a C₂H₄ and C₂HCl₃ feed promoted by Ni/SiO₂ in the presence of H₂ over the temperature range 673 K ≤ T ≤ 1023 K has been examined. The supported Ni phase exhibited an exclusive cubic symmetry (XRD analysis) with a range of Ni particle sizes (TEM analysis) and a net shift in the distribution to larger particles with increasing reduction temperature (from 20 to 36 nm), accompanied by a decrease in H₂ chemisorption. Conversion of C₂H₄ generated hydrogenation (C₂H₆), hydrogenolysis (CH₄) and decomposition (C + H₂) products. Ethane formation was favoured at lower temperatures with C formation increasingly preferred at higher temperatures so that C₂H₄ decomposition was the predominant process at T > 723 K; significant CH₄ production was only observed at T > 900 K. Carbon yield from C₂H₄ passed through a maximum at 773 K and took the form of high aspect ratio graphitic nanofibres with a central hollow core and diameters in the range 5–180 nm. The carbonaceous product has been characterized by a combination of TEM-EDX, SEM, XRD, BET area and temperature programmed oxidation (TPO). Carbon formation from C₂HCl₃ exceeded (by a factor of up to an order of magnitude) that generated via the decomposition of C₂H₄ at the same inlet C:Ni ratio to deliver essentially a carbon yield invariance (9.1 ± 0.3 g_C g_Ni^?1) where 898 K ≤ T ≤ 1023 K, which represents a carbon efficiency (fraction of carbon in the inlet feed that is converted to a solid carbon product) in excess of 96%. Ni/SiO₂ promoted a composite dehydrochlorination/decomposition of C₂HCl₃ to HCl + C. The nature of the carbon product generated from C₂HCl₃ is strongly temperature dependent with a shift from a pseudo-fibrous product at 773 K to a predominant nanosphere formation at 923 K. These nanospheres exhibit a wide diameter range (40–700 nm), a significant Cl content (1.1–2.6%, w/w) and a conglomeration or clustering to give a less ordered carbonaceous product than that generated at the lower temperature (773 K). A tentative carbon growth rationale is presented to account for the observed dependence of carbon structure on carbon-containing precursor and reaction temperature.     

Monodisperse biopolymer nanoparticles by Continuous Supercritical Emulsion Extraction

In this work Continuous Supercritical Emulsions Extraction (SEE-C) has been tested to produce monodisperse biopolymer nanoparticles. The SEE-C technology allows an improved control of particle size distribution by reducing the emulsion processing times and preventing any droplet/particle aggregation. Biopolymers as, poly-lactic acid (PLA), poly-caprolactone (PCL) and poly-lactic-co-glycolic acid (PLGA) in different emulsion formulations were tested using acetone as oily-phase solvent. Emulsion formulation parameters, such as surfactant and/or polymer concentration and emulsification techniques (ultrasound or high speed emulsification) were analyzed in connection to SEE-C, to produce monodisperse nanoparticles. Operating at 38 °C and 80 bar, with an L/G ratio of 0.1, particles of PLA, PCL and PLGA with mean size of 233 nm, 342 nm and 212 nm, respectively, were produced. Poly-dispersity indexes lower to 0.1 nm were also obtained, confirming the possibility to obtain sharp distributions with monodisperse characteristics. Solvent residues as low as 500 ppm were also observed.     

A novel agricultural waste based adsorbent for the removal of Pb(II) from aqueous solution: Kinetics,equilibrium and thermodynamic studies

Fig sawdust was used as a precursor for the production of activated carbon by chemical activation with H₃PO₄. The developed Fig sawdust activated carbon (FSAC) was used as a biosorbent for the removal of Pb(II) from aqueous solution. Highest adsorption of Pb(II) (95.8%) was found at pH 4. Equilibrium data fitted very well with the Langmuir isotherm model. Maximum adsorption capacity was determined 80.645 mg g⁻¹ at pH 4. Kinetic studies demonstrated that the adsorption followed a pseudo second order kinetics model. The negative value of ΔG° confirmed the feasibility and spontaneity of FSAC for Pb(II) adsorption.     

Adsorption of sulfur and nitrogen compounds on hydrophobic bentonite

The successful synthesis of hydrophobic magnetic composites formed by carbon filaments on bentonite surface has been obtained via chemical vapor deposition of ethanol and studied by electron microscopy, XRD, Mössbauer spectroscopy, Raman, and thermal analysis measurements. Bentonite clay was impregnated with different concentrations of iron salt and subjected to a chemical vapor deposition using ethanol as carbon source. The results suggest the reaction of iron on the surface of bentonite with ethanol leading to the formation of reduced iron phases and carbon. The carbon deposited is present as graphite, amorphous and filaments and the resulting materials show hydrophobic behavior besides magnetic properties conferred by the iron phases. This magnetic property is very interesting and allows the materials to be easily removed from the system. The hydrophobic bentonite was used as adsorbent of sulfur and nitrogen compounds, important contaminants in fuels, showing adsorption capacity of 38.7 mg g^− 1 and 54.5 mg g^− 1 for nitrogen and sulfur compounds respectively, a very high adsorption capacity compared with other materials with carbon presented in the literature.     

Hydrothermal synthesis and activation of graphene-incorporated nitrogen-rich carbon composite for high-performance supercapacitors

Graphene-incorporated nitrogen-rich carbon composite with nitrogen content of ca. 10 wt.% has been synthesized by an effective yet simple hydrothermal reaction of glucosamine in the presence of graphene oxide (GO). The nitrogen content of carbon composite is nearly twice as high as that of hydrothermal carbon without graphene. GO is favorable for the high nitrogen doping in the carbon composite by the reaction between the glucosamine-released ammonia and GO. The hydrothermal carbon composite is further activated by KOH, and graphene in the activated carbon composite demonstrates a positive effect of increasing specific surface area, pore volume and electrical conductivity, resulting in superior electrochemical performance. The activated carbon composite with higher specific surface area and micropore volume possesses higher specific capacitance with a value of 300 F g⁻¹ at 0.1 A g⁻¹ in 6 M KOH aqueous solution in the two electrode cell. Larger mesopore volume and higher conductivity of the activated carbon composite will provide fast ion and electron transfer, thus leading to higher rate capacity with a capacitance retention of 76% at 8 A g⁻¹ in comparison to the activated hydrothermal carbon without graphene.