Phenol decomposition in water cathode of DC atmospheric pressure discharge in air

We studied phenol decomposition in aqueous solution under the action of DC discharge at atmospheric pressure in air. The decomposition efficiency was 0.017 molecules per 100 eV. When the kinetics of forming destruction products was studied in detail, the peculiarities of air plasma action were revealed for the first time. Plasma action not only results in the formation of oxygen-containing products, which are usually formed under oxygen plasma action (hydroxyhenols, carboxylic acids, aldehydes), but also the formation of nitro phenols. The treatment is accompanied by hydrogen peroxide formation, a pH decrease, and nitric and nitrous acids formation. We also discussed the possible mechanism of the processes and the role of some active species in chemical transformations after determining some parameters of the discharge.     

Kinetic study of liquid lipase-catalyzed glycerolysis of olive oil using Lipozyme TL 100L

Monoacylglycerol (MAG) and diacylglycerol (DAG) are two natural components found in most edible oils and fats. Conventional synthesis of MAG and DAG is usually conducted by glycerolysis of triacylglycerol (TAG) at high temperatures (above 200°C) in the presence of an alkaline catalyst. In this work, the synthesis of MAG and DAG using enzymatic glycerolysis of olive oil was investigated using Tween 80 as surfactant, n-butanol as co-surfactant and the novel lipase in free/liquid formulation Lipozyme TL 100L as catalyst. Experimental design was used to evaluate the effect of enzyme load and reaction temperature on the feedstock conversion. Enzyme load and system temperature were significant variables in the statistical design and the best condition was found at 35°C, 7.5 vol% of Lipozyme TL 100L and glycerol to oil volumetric ratio of 2:1 with conversion of TAG at approximately 98% after 2 h of process. A mathematical model based on the Ping-Pong Bi-Bi mechanism was used to describe the reaction kinetics. The model adequately described the behavior of the system and can be a useful tool for the design of reactors in larger scales.     

Effect of Acidic Peptization on Formation of Highly Photoactive TiO2 Films Prepared without Heat Treatment

Nowadays, it is a great challenge to synthesize crystalline TiO₂ nanostructures using low‐temperature methods without annealing stage. Such an approach allows to perform functional and structural modification in the formed crystalline phase by thermally unstable compounds, such as biomaterials, MOFs, dye sets in situ, which was previously considered impossible. In this work, we have developed and analyzed the effect of acidic peptization on formation of highly photoactive titania crystallites in an aqueous solution using titanium tetraisopropylate as a precursor. Acids with different dissociation degrees in water were used as peptizing mediators to determine the effect of protonation on sol formation. The dip‐coating films were obtained with consequent drying of the sols via evaporation of the solvent. The as‐prepared catalysts were characterized by X‐ray diffraction, AFM microscopy, UV–V is spectroscopy, Brunauer–Emmett–Teller surface area. The aggregate size of TiO₂ in the colloidal suspension solution was measured by dynamic light scattering. Photocatalytic activity of films was studied by decomposition of Rhodamine B dye. It is found that the size of colloids in an aqueous solution is proportional to the protonation degree of the surface of particles and does not depend on the [Ti⁴⁺]/[H⁺] ratio, and peptization under weakly acidic conditions leads to anisotropic rod‐like nanoparticles. The highest photocatalytic activity was exhibited by the TiO₂–HCl‐based coatings, ~3.5 times higher than that of the Acet.‐prepared sample.     

Inventory pinch based,multiscale models for integrated planning and scheduling‐part II: Gasoline blend scheduling

Integration of planning and scheduling optimizes simultaneous decisions at both levels, thereby leading to more efficient operation. A three‐level discrete‐time algorithm which uses nonlinear models and integrates planning and detailed scheduling is introduced: first level optimizes nonlinear blend models via multiperiod nonlinear programming (NLP), where period boundaries are initially determined by the inventory pinch points; second level uses fixed recipes (from the first level) in a multiperiod mixed‐integer linear program to determine first an optimal production plan and then to optimize an approximate schedule which minimizes the total number of switches in blenders and swing tanks; third level computes detailed schedules that adhere to inventory constraints computed in the approximate schedule. If inventory infeasibilities appear at the second or the third level, the first‐level periods are subdivided and blend recipes are reoptimized. Algorithm finds the same or better solutions and is substantially faster than previously published full‐space continuous‐time model. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2475–2497, 2014     

Nanocrystalline Barium Strontium Titanate Ceramics Synthesized via the “Organosol” Route and Spark Plasma Sintering

Dense nanocrystalline barium strontium titanate Ba_0.6Sr_0.4TiO₃ (BST) ceramics with an average grain size around 40 nm and very small dispersion were obtained by spark plasma sintering at 950°C and 1050°C starting from nonagglomerated nanopowders (~20 nm). The powders were synthesized by a modified “Organosol” process. X‐ray diffraction (XRD) and dielectric measurements in the temperature range 173–313 K were used to investigate the evolution of crystal structure and the ferroelectric to paraelectric phase transformation behavior for the sintered BST ceramics with different grain sizes. The Curie temperature T_C decreases, whereas the phase transition becomes diffuse for the particle size decreasing from about 190 to 40 nm with matching XRD and permittivity data. Even the ceramics with an average grain size as small as 40 nm show the transition into the ferroelectric state. The dielectric permittivity ε shows relatively good thermal stability over a wide temperature range. The dielectric losses are smaller than 2%–4% in the frequency range of 100 Hz–1 MHz and temperature interval 160–320 K. A decrease in the dielectric permittivity in nanocrystalline ceramics was observed compared to submicrometer‐sized ceramics.     

Interpolyelectrolyte complexes of maleic acid copolymers and chitosan for stabilization and functionalization of magnetite nano‐ and microparticles

A facile method of preparation of stabilized and functionalized nano‐ and microparticles of magnetite by successive application of oppositely charged polymers with a regular structure of macromolecular chains (chitosan and maleic acid copolymers) onto Fe₃O₄ core are developed. This approach makes it possible to create two types of magnetite interpolyelectrolyte shells, containing carboxylic or amino groups in outer layer of shell. Composition and magnetic properties of composite particles depend on nature of the copolymer of maleic acid, reaction conditions and size of obtained particles. The carboxylic groups of copolymer in outer layer of interpolyelectrolyte shell were converted into reactive anhydride groups by heating. Thermal treatment also leads to covalent crosslinking of shell and improves stability of composites both in acidic and alkaline media. Horseradish peroxidase was successfully immobilized onto covalently crosslinked and activated microparticles of Fe₃O₄ in aqueous medium without of condensing agents. The proposed reproducible and low‐cost technique does not use toxic reagents or solvents at all stages, including preparation of Fe₃O₄, formation, activation and crosslinking, of magnetite shell, modification of activated surface of composite particles. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39663.     

Electroactive behavior assessment of poly(acrylic acid)‐graphene oxide composite hydrogel in the detection of cadmium

Super absorbent polymers of acrylic acid‐graphene oxide (PAA‐GO) were synthesized with different percentage of chemical neutralization (0, 10, and 20%) of the acrylic acid monomer before its polymerization. The influence of their swelling and adsorption/desorption capacity of cadmium ions in aqueous solutions were studied and revealed that the GO enables greater mechanical stability in the materials. The PAA hydrogels, with the same degrees of neutralization, were also prepared without GO to compare with the composites. Additionally, carbon paste electrodes (CPE) modified with the composites PAA‐GO were used to asses and compare their adsorption properties with cadmium(II). The anodic stripping voltammetry (ASV) peak, in the differential pulse voltammetry mode, for cadmium oxidation was found to be influenced by the presence of GO into the polymer, and also by their percentage of neutralization. The accumulation of cadmium(II) on the surface of the modified CPEs was performed under open‐circuit conditions taking an account the preconcentration time of the metal cation. The presence of GO enhances the electrical signal of the electrodes in short times of immersion in cadmium(II) solutions. This property contributed to get linear responses of the CPEs modified with the composites, which were influenced by their degrees of neutralization. The PAA‐GO 10N electrode with 10% of neutralization combined the influence of GO and the degree of neutralization in the same matrix, and also showed good performance in terms of its mechanical stability, it was chosen for preliminary studies on the selectivity of the electrode toward Zn(II) and Cu(II). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40846.     

Dielectric and thermal studies of segmental dynamics in silica/PDMS and silica/titania/PDMS nanocomposites

Effects of silica and silica/titania nanoparticles on glass transition and segmental dynamics of poly(dimethylsiloxane) (PDMS) were studied for composites of a core–shell type using differential scanning calorimetry, thermally stimulated depolarization current, and dielectric relaxation spectroscopy techniques. Strong interactions between the filler and the polymer suppress crystallinity (T_c, X_c) and affect significantly the evolution of the glass transition in the nanocomposites. The segmental relaxation associated with the glass transition consists of three contributions, arising, in the order of decreasing mobility, from the bulk (unaffected) amorphous polymer fraction (α relaxation), from polymer chains restricted between condensed crystal regions (α_c relaxation), and from the semi‐bound polymers in an interfacial layer with strongly reduced mobility due to interactions with surface hydroxyls of silica and silica/titania nanoparticles (α′ relaxation). The evolution of surface affected CH₃ groups, as well as the degree of interaction of PDMS molecules with surface hydroxyl groups as a function of treatment temperature, was assessed by Fourier transform infrared spectroscopy, thermogravimetry and differential thermal analysis. The effectiveness of silica/PDMS and silica/titania/PDMS nanocomposites as hydrophobic coatings was investigated by static contact angle measurements. It was shown that the presence of titania nanoparticles and adsorbed PDMS promotes the hydrophobic properties of the PDMS coating after treatment in the 80–650°C range. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41154.     

Possibilities of the Computer-Controlled Detonation Spraying method: A chemistry viewpoint

This article is aimed to discuss the chemical aspects of detonation spraying of powder materials. In this method of coating deposition, ceramic, metallic or composite powders are injected into the barrel of a detonation gun filled with an explosive gaseous mixture. When the latter is ignited, the powders are heated and accelerated toward the substrate. Subjected to high temperatures, the powders are prone to chemical reactions, the reaction products possibly becoming the major phase constituents of the coatings. What types of reactions are possible? Can these reactions be carried out in a controlled manner? We answer these questions considering the interactions of the sprayed powders with the gaseous environment of the barrel as well as those between the phases of a composite feedstock powder. In Computer-Controlled Detonation Spraying (CCDS), the explosive charge and stoichiometry of the fuel-oxygen mixtures are precisely measured and can be flexibly changed. Our studies demonstrate that with the introduction of a highly flexible process of CCDS, detonation spraying has entered a new development stage, at which it can be considered as a powerful method of composition and microstructure tailoring of thermally sprayed coatings. During CCDS of TiO₂-containing powders, chemical reduction of titanium dioxide can be carried out to different levels to form either oxygen-deficient TiO_2−x or Ti₃O₅ suboxide. CCDS of Ti₃Al can produce titanium oxide coatings when oxidation by the detonation products dominates or titanium nitride-titanium aluminide coatings when oxidation is hindered but the interaction of the powders with nitrogen—a carrier gas component—is favored. During detonation spraying of Ti₃SiC₂–Cu composites, the Ti₃SiC₂ phase is preserved only in cold conditions; otherwise, Si de-intercalates from the Ti₃SiC₂ phase and dissolves in Cu resulting in the formation of the TiC_x–Cu(Si) composite coatings.     

Design of Porous Alginate Hydrogels by Sacrificial CaCO3 Templates: Pore Formation Mechanism

Fabrication of porous alginate hydrogels with a well‐controlled architecture useful for tissue engineering is still a challenge. Here, CaCO₃‐based templating is utilized to design stable alginate gels with controlled pore dimensions in the range of 5–50 μm. The mechanism of pore formation is studied considering two factors affecting the pore size: i) osmotic pressure generated during the dissolution of sacrificial CaCO₃ templates and ii) alginate gel network density. Osmotic pressure can achieve an upper limit of 100 MPa but does not affect the gel porosity. Additional osmotic pressure (range of kPa) induced by dextrans pre‐encapsulated into CaCO₃ vaterite is also insufficient for pore enlargement. Pore stability depends merely on the gel network density and on the number of crosslinking calcium ions provided locally per unit time; pores are collapsed when template dissolution is too slow or if there is insufficient alginate concentration (below 2%). Young's modulus indicates the soft nature of the prepared hydrogels (tens of kPa) applicable as soft porous scaffolds with a tuned internal structure.