High surface area biochar for the removal of naphthenic acids from environmental water and industrial wastewater.

This study reports the production of biochar adsorbents from two major crop residues (i.e., rice and wheat straw) to remove naphthenic acids from water. The alkali treatment approach was used for biochar activation that resulted in a tremendous increase in their surface area, i.e., up to 2252 and 2314 m2/g, respectively, for rice and wheat straw biochars. Benzoic acid was used as a model compound to optimize critical adsorption parameters. Its maximum monolayer adsorption capacity of 459.55 and 357.64 mg/g was achieved for activated rice and wheat straw biochars. The adsorption of benzoic acid was exothermic (∆H° = - 7.06 and - 3.89 kJ/mol) and identified possibly as physisorption (Gibbs free energy ranges 3.5-4.0 kJ/mol). The kinetic study suggested that adsorption follows pseudo-second-order kinetics with qe2 for rice straw and wheat straw-derived adsorbents at 200 and 194 mg/g, respectively. As adsorbent, the recyclability of activated biochars was noticed with no significant loss in their efficiency for up to ten successive regeneration cycles. The adsorption results were validated using a commercial naphthenic acid mixture-spiked river water and paper/pulp industrial effluent. The activated rice and wheat straw biochars exhibited excellent adsorption efficiency of 130.3 and 74.6 mg/g, respectively. The naphthenic acid adsorption on biochar surface was due to various interactions, i.e., weak van der Waal's, pore filling, π-π stacking, and ionic interactions. This study offers a cost-effective and eco-friendly approach to valorizing agricultural residues for pollutant removal from industrial wastewater, including petroleum refineries.

Cr- and Ga-Modified ZSM-5 Catalyst for the Production of Renewable BTX from Bioethanol.

Light aromatics (benzene, toluene, and xylene, collectively known as BTX) are essential commodity chemicals in the petrochemical industry. The present study examines the aromatization of bioethanol with Cr- and Ga-modified ZSM-5. Both Cr and Ga were incorporated by the ion-exchange method. Cr-modified ZSM-5 outperforms the Ga-modified ZSM-5 and H-ZSM-5 catalysts. Cr-H-ZSM-5 almost doubled the carbon yield of aromatics compared to H-ZSM-5 at an optimum reaction temperature of 450 °C. Cr-H-ZSM-5 produced aromatics with a yield of ~40 %. The effect of dilution in feed on BTX production is also studied. Cr-H-ZSM-5 was found to be more active than H-ZSM-5. Complete ethanol conversion was obtained with both pure and dilute bioethanol. The Bronsted-Lewis acid (BLA) pair formed after metal incorporation is responsible for dehydrogenation followed by aromatization, leading to increased aromatic production.

Food-grade xylitol production from corncob biomass with acute oral toxicity studies.

Xylitol, a sugar substitute, is widely used in various food formulations and finds a steady global market. In this study, xylitol crystals were produced from corncob by fermentation (as an alternative to the chemical catalytic process) by a GRAS yeast Pichia caribbica MTCC 5703 and characterized in detail for their purity and presence of any possible contaminant that may adversely affect mammalian cell growth and proliferation. The acute and chronic oral toxicity trials demonstrated no gross pathological changes with average weekly weight gain in female Wistar rats at high xylitol loading (LD50 > 10,000 mg/kg body weight). The clinical chemistry analysis supported the evidence of no dose-dependent effect by analyzing blood biochemical parameters. The finding suggests the possible application of the crystals (> 98% purity) as a food-grade ingredient for commercial manufacture pending human trials.

Heightened miR6024-NLR interactions facilitate necrotrophic pathogenesis in tomato.

KEY MESSAGE: miR6024 acts as a negative regulator of R genes, hence of Tomato plant immunity, and facilitates disease by the necrotrophic pathogen A. solani. Plant resistance genes or Nucleotide-binding leucine-rich repeat (NLR) genes, integral components of plant disease stress-signaling are targeted by variable groups of miRNAs. However, the significance of miRNA-mediated regulation of NLRs during a pathogen stress response, specifically for necrotrophic fungus, is poorly understood. A thorough examination of Tomato NLRs and miRNAs could map substantial interactions of which half the annotated NLRs were targets of Solanaceae-specific and conserved miRNAs, at the NB subdomain. The Solanaceae-specific miR6024 and its NLR targets analysed in different phytopathogenic stresses revealed differential and mutually antagonistic regulation. Interestingly, miR6024-targeted cleavage of a target NLR also triggered the generation of secondary phased siRNAs which could potentially amplify the defense signal. RNA-seq analysis of leaf tissues from miR6024 overexpressing Tomato plants evidenced a perturbation in the defense transcriptome with the transgenics showing unwarranted immune response-related genes' expression with or without infection with necrotrophic Alternaria solani, though no adverse effect could be observed in the growth and development of the transgenic plants. Transgenic plants exhibited constitutive downregulation of the target NLRs, aggravated disease phenotype with an enhanced lesion, greater ROS generation and hypersusceptibility to A. solani infection, thus establishing that miR6024 negatively impacts plant immune response during necrotrophic pathogenesis. Limited knowledge about the outcome of NLR-miRNA interaction during necrotrophic pathogenesis is a hindrance to the deployment of miRNAs in crop improvement programs. With the elucidation of the necrotrophic disease-synergistic role played by miR6024, it becomes a potent candidate for biotechnological manipulation for the rapid development of pathogen-tolerant solanaceous plants.

Application of laccase immobilized rice straw biochar for anthracene degradation.

The present study explores the immobilization of ligninolytic enzyme-laccase on the surface of rice straw biochar and evaluates its application for anthracene biodegradation. The rice straw biochar was acid-treated to generate carboxyl functionality on its surface, followed by detailed morphological and chemical characterization. The surface area of functionalized biochar displayed a two-fold increase compared to the untreated biochar. Laccase was immobilized on functionalized biochar, and an immobilization yield of 66% was obtained. The immobilized enzyme demonstrated operational stability up to six cycles while retaining 40% of the initial activity. Laccase immobilization was further investigated by performing adsorption and kinetic studies, which revealed the highest immobilization concentration of 500 U g-1 at 25 °C. The adsorption followed the Langmuir isotherm model at equilibrium, and the kinetic study confirmed pseudo-second-order kinetics. The equilibrium rate constant (K2) at 25 °C and 4 °C were 3.6 × 10-3 g U-1 min-1 and 4 × 10-3 g U-1 min-1 respectively for 100 U g-1 of enzyme loading. This immobilized system was applied for anthracene degradation in the aqueous batch mode, which resulted in complete degradation of 50 mg L-1 anthracene within 24 h of interaction exposure.

Alkylated graphene oxide and reduced graphene oxide: Grafting density, dispersion stability to enhancement of lubrication properties.

Alkylated graphene oxide (GO)/reduced graphene oxide (rGO) are prepared by covalent interaction with octadecyltrichlorosilane (OTCS) and octadecyltriethoxysilane (OTES). The variable oxygen functionalities in the GO/rGO and hydrolysis rate of octadecylsilanes having different leaving groups viz. trichloro and triethoxy found to govern the grafting density of octadecyl chains on the GO and rGO. FTIR, XPS, and TGA results revealed a higher grafting of octadecyl chains in the GO-OTCS, whereas the rGO-OTES exhibited minimum grafting. The van der Waals interaction between the octadecyl chain of alkylated GO/rGO and octadecenyl chains of polyol ester makes alkylated GO/rGO dispersible in the polyol lube base oil. The dispersion stability is collectively driven by grafting density of octadecyl chains and presence of oxygen functionalities in the GO/rGO. Tribological properties in terms of the coefficient of friction and wear scar diameter revealed a good correlation with the structure of alkylated GO/rGO and their dispersion stability in the polyol lube base oil. Raman analysis of the worn surface revealed the sheared-induced deposition of a graphene-based tribo-thin film, which reduced the friction and protected the tribo-interfaces against the wear.

Ionic-Liquid-Functionalized Copper Oxide Nanorods for Photocatalytic Splitting of Water.

Thin films of imidazolium (Im) ionic liquids with bis(salicylato)borate (BScB) and hexafluorophosphate (PF6 - ) anions were grafted onto copper oxide (CuO) nanorods. Chemical and structural features of ionic-liquid-functionalized CuO (CuO-IL) nanorods were examined by X-ray photoelectron spectroscopy, FTIR spectroscopy, XRD, and high-resolution TEM analyses. The CuO-IL nanorods were demonstrated to be efficient photocatalysts for the splitting of water under visible-light irradiation without using any sacrificial agent. The pristine CuO nanorods could not split water, whereas CuO-IL nanorods exhibited excellent photocatalytic activities and produced 1827 and 1082 µmol of hydrogen in 2 h with 20 mg of CuO-ImBScB and CuO-ImPF6 as photocatalysts, respectively. The photocatalytic activity of the CuO-IL nanorods was attributed to the synergistic effect of ionic-liquid thin films and CuO nanorods. The trapping of photoinduced charge carriers by ionic liquids inhibits the recombination process, and consequently, the CuO nanorods facilitate the water-splitting reaction. The CuO-IL photocatalysts were efficiently recycled without loss of catalytic activity, which revealed the stability of the ionic-liquid thin films grafted on the CuO nanorods.

Selective Oxidation of n-Hexane by Cu (II) Nanoclusters Supported on Nanocrystalline Zirconia Catalyst.

Cu (II) nanoclusters supported on nanocrystalline zirconia catalyst (with size ~15 nm), was prepared by using cationic surfactant cetyltrimethylammonium in a hydrothermal synthesis method. The catalyst was characterized by XRD, XPS, TGA, SEM, TEM, FTIR and ICP-AES. The catalyst was found to be efficient in selective oxidation of n-hexane to 2-hexanol. An n-hexane conversion of 55%, with a 2-hexanol selectivity of 70% was achieved over this catalyst in liquid phase, without the use of any solvent. The catalyst can be reused several times without any significant activity loss.

Molecular pillar supported graphene oxide framework: conformational heterogeneity and tunable d-spacing.

n-Alkylamines were grafted on the basal plane oxygen functionalities of graphene oxide (GO), yielding molecular pillar supported graphene oxide frameworks (GOFs) with tunable interlayer spacing. A major fraction of n-alkylamines was found to covalently interact with the basal plane epoxy groups via nucleophilic substitution reactions. The d-spacing in GOFs could be tailored between 10.5 and 28.9 Å by varying the chain length of the n-alkylamines. (13)C SSNMR explicitly showed the coexistence of both trans and gauche conformation modes. The relative populations of these modes control the conformational heterogeneity and orientation of n-alkylamines in the GOFs. A plausible bilayer structural model of the GOFs was demonstrated. The terminal methyl and methylene units of the n-alkylamines grafted on the GO basal plane were interdigitated with the counter layer and afforded a double-layer structure of alkyl chain supported GOFs.

Dual catalysis with magnetic chitosan: direct synthesis of cyclic carbonates from olefins with carbon dioxide using isobutyraldehyde as the sacrificial reductant.

Chitosan coated magnetic nanoparticles were synthesized and used as a support for the immobilization of the cobalt(II) acetylacetonate complex [Co(acac)2] and quaternary triphenylphosphonium bromide [P(+)Ph3Br(-)] targeting -NH2 and -OH moieties located on the surface of chitosan. The synthesized material was used as a catalyst for one pot direct synthesis of cyclic carbonates from olefins via an oxidative carboxylation approach with carbon dioxide using isobutyraldehyde as the sacrificial reductant and molecular oxygen as the oxidant. After the reaction, the catalyst was recovered by applying an external magnet and reused for several runs without significant loss in catalytic activity and no leaching was observed during this course.

Value addition to rice straw through pyrolysis in hydrogen and nitrogen environments.

Pyrolysis of rice straw has been carried out under hydrogen atmosphere at 300, 350, 400 and 450 °C and pressures of 1, 10, 20, 30 and 40 bar and in nitrogen atmosphere, experiments have been carried out at the same temperatures. It has been observed that the optimum process conditions for hydropyrolysis are 400 °C and 30 bar pressure and for slow pyrolysis, the optimum temperature is 400 °C. The bio-oil has been characterised using GC-MS, (1)H NMR and FT-IR and bio-char using FT-IR, SEM and XRD. The bio-oil yield under hydrogen pressure was observed to be 12.8 wt.% (400 °C and 30 bar) and yield under nitrogen atmosphere was found to be 31 wt.% (400 °C). From the product characterisation, it was found that the distribution of products is different for hydrogen and nitrogen environments due to differences in the decomposition reaction mechanism.

Corrosion behavior of titanium boride composite coating fabricated on commercially pure titanium in Ringer's solution for bioimplant applications.

The boriding of commercially pure titanium was performed at 850°C, 910°C, and 1050°C for varied soaking periods (1, 3 and 5h) to enhance the surface properties desirable for bioimplant applications. The coating developed was characterized for the evolution of phases, microstructure and morphology, microhardness, and consequent corrosion behavior in the Ringer's solution. Formation of the TiB2 layer at the outermost surface followed by the TiB whiskers across the borided CpTi is unveiled. Total thickness of the composite layer on the substrates borided at 850, 910, and 1050°C for 5h was found to be 19.1, 26.4, and 18.2µm respectively which includes <3µm thick TiB2 layer. The presence of TiB2 phase was attributed to the high hardness ~2968Hv15gf of the composite coating. The anodic polarization studies in the simulated body fluid unveiled a reduction in the pitting corrosion resistance after boriding the CpTi specimens. However, this value is >0.55VSCE (electrochemical potential in in-vivo physiological environment) and hence remains within the safe region. Both the untreated and borided CpTi specimens show two passive zones associated with different passivation current densities. Among the CpTi borided at various times and temperatures, a 3h treated shows better corrosion resistance. The corrosion of borided CpTi occurred through the dissolution of TiB2.

Grafting of a rhenium-oxo complex on Schiff base functionalized graphene oxide: an efficient catalyst for the oxidation of amines.

A rhenium-oxo complex such as methyltrioxorhenium (MTO) has been homogeneously immobilized on a Schiff base modified graphene oxide (GrO) support via covalent bonding. The loading of MTO on GrO nanosheets was monitored by FTIR, TG-DTA, and elemental analyses. The developed heterogeneous catalyst is found to be efficient for the oxidation of various amines to the corresponding N-oxides using hydrogen peroxide as an oxidant in high to excellent yields. At the end of the reaction, the catalyst is readily recovered by filtration and reused for subsequent runs. After the third run, the catalyst showed a marginal decrease in catalytic activity owing to the leaching of the MTO complex from the support.

Highly dispersed palladium nanoparticles grafted onto nanocrystalline starch for the oxidation of alcohols using molecular oxygen as an oxidant.

Highly dispersed Pd-nanoparticles grafted onto amino-functionalized nanocrystalline starch were found to be excellent heterogeneous catalysts for the aerobic oxidation of a variety of alcohols to their corresponding carbonyl compounds in excellent yields. The prepared catalyst was found to be selective for the oxidation of primary alcohols to aldehydes without giving over-oxidation products and was recycled several times without any leaching of the metal into the solution.

Electrochemical and mechanical behavior of laser processed Ti-6Al-4V surface in Ringer's physiological solution.

Laser surface modification of Ti-6Al-4V with an existing calcium phosphate coating has been conducted to enhance the surface properties. The electrochemical and mechanical behaviors of calcium phosphate deposited on a Ti-6Al-4V surface and remelted using a Nd:YAG laser at varying laser power densities (25-50 W/mm(2)) have been studied and the results are presented. The electrochemical properties of the modified surfaces in Ringer's physiological solution were evaluated by employing both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The potentiodynamic polarizations showed an increase in the passive current density of Ti-6Al-4V after laser modification at power densities up to 35 W/mm(2), after which it exhibited a decrease. A reduction in the passive current density (by more than an order) was observed with an increase in the laser power density from 25 to 50 W/mm(2). EIS studies at the open circuit potential (OCP) and in the passive region at 1.19 V showed that the polarization resistance increased from 8.274 × 10(3) to 4.38 × 10(5) Ω cm(2) with increasing laser power densities. However, the magnitudes remain lower than that of the untreated Ti-6Al-4V at OCP. The average hardness and modulus of the laser treated Ti-6Al-4V, evaluated by the nanoindentation method, were determined to be 5.4-6.5 GPa (with scatter <±0.976 GPa) and 124-155 GPa (with scatter <±13 GPa) respectively. The corresponding hardness and modulus of untreated Ti-6Al-4V were ~4.1 (±0.62) and ~148 (±7) GPa respectively. Laser processing at power densities >35 W/mm(2) enhanced the surface properties (as passive current density is reduced) so that the materials may be suitable for the biomedical applications.

Laser surface processing of Ti6Al4V in gaseous nitrogen: corrosion performance in physiological solution.

Laser surface processing was carried out in gaseous nitrogen atmosphere at ambient temperature. The laser scan speed was varied (50-150 cm/min) at constant power of 1500 watts and resulting changes such as microstructural evolution, hardness, and electrochemical response of modified surface in Ringer's physiological solution at varying pH were studied. Increase in laser scanning speed was found to reduce the thickness of alloyed zone from 258 to 87 microm. The microstructure of laser-modified surface contains dendrites grown perpendicular to the laser traverse direction, beneath which basket weave structure of acicular alpha (martensite) was prevalent. Hardness at the top surface of laser-processed at 50 cm/min was approximately 1137 kg/mm2 that reduced with increase in the laser scan speed (577 kg/mm2 at 150 cm/min). Laser surface processing shifted the corrosion potential of Ti6Al4V towards noble side as compared to untreated alloy; the maximum shift by approximately 494 mV was recorded in pH approximately 9 solution. Passivation after laser surface modification was improved as currents were at least 1/3 of the untreated Ti6Al4V in passive region. While the pitting potential of untreated material was found to increase from 1.84 V for 4.0 pH to >2.5 V for 9.0 pH, the pitting potential after laser treatment was observed to drop from maximum of 74% for 4.0 pH (at 100 cm/min) to maximum of 42% for 9.0 pH (at 150 cm/min).

Corrosion degradation and prevention by surface modification of biometallic materials.

Metals, in addition to ceramics and polymers, are important class of materials considered for replacement of non-functional parts in the body. Stainless steel 316, titanium and titanium alloys, Co-Cr, and nitinol shape memory alloys are the most frequently used metallic materials. These alloys are prone to corrosion in various extents. This review briefly discusses the important biomaterials, their properties, and the physiological environment to which these materials are exposed. Corrosion performance of currently used metallic materials has been assessed and threat to the biocompatibility from corrosion products/metal ions is discussed. The possible preventive measures to improve corrosion resistance by surface modification and to increase the bioactivity of the metallic surfaces have also been discussed. Importance of the formation of oxide layers on the metal surface, another aspect of corrosion process, has been correlated with the host response. The gap areas and future direction of research are also outlined in the paper.

Laser surface modification of Ti--6Al--4V: wear and corrosion characterization in simulated biofluid.

Laser surface melting (LSM) of Ti-6Al-4V is performed in argon to improve its properties, such as microstructure, corrosion, and wear for biomedical applications. Corrosion behavior is investigated by conducting electrochemical polarization experiments in simulated body fluid (Ringer's solution) at 37 C. Wear properties are evaluated in Ringer's solution using pin-on-disc apparatus at a slow speed. Untreated Ti-6Al-4V contains alpha+beta phase. After laser surface melting, it transforms to acicular alpha embedded in the prior beta matrix. Grain growth in the range of 65-89 microm with increase in laser power from 800 to 1500 W due to increase in associated temperature is observed. The hardness of as-laserprocessed Ti-6Al-4V alloy is more (275-297 HV) than that of the untreated alloy (254 HV). Passivation currents are significantly reduced to < 4.3 microA/cm2 after laser treatment compared to untreated Ti-6Al-4V (approximately 12 microA/cm2). The wear resistance of laser-treated Ti-6Al-4V in simulated body fluid is enhanced compared to that of the untreated one. It is the highest for the one that is processed at a laser power of 800 W. Typical micro-cutting features of abrasive wear is the prominent mechanism of wear in both untreated and as-laser-treated Ti-6Al-4V. Fragmentation of wear debris assisted by microcracking was responsible for mass loss during the wear of untreated Ti-6Al-4V in Ringer's solution.