Engineered silica nanoparticles as additives in lubricant oils

Silica nanoparticles (SiO₂ NPs) synthesized by the sol–gel approach were engineered for size and surface properties by grafting hydrophobic chains to prevent their aggregation and facilitate their contact with the phase boundary, thus improving their dispersibility in lubricant base oils. The surface modification was performed by covalent binding of long chain alkyl functionalities using lauric acid and decanoyl chloride to the SiO₂ NP surface. The hybrid SiO₂ NPs were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, simultaneous differential thermal analysis, nuclear magnetic resonance and dynamic light scattering, while their dispersion in two base oils was studied by static multiple light scattering at low (0.01% w/v) and high (0.50%w/v) concentrations. The nature of the functional layer and the functionalization degree seemed to be directly involved in the stability of the suspensions. The potential use of the functional SiO₂ NPs as lubricant additives in base oils, specially designed for being used in hydraulic circuits, has been outlined by analyzing the tribological properties of the dispersions. The dendritic structure of the external layer played a key role in the tribological characteristics of the material by reducing the friction coefficient and wear. These nanoparticles reduce drastically the waste of energy in friction processes and are more environmentally friendly than other additives.     

Diel variation of limnological parameters in a reservoir in northeastern Brazil (Boa Esperança, Maranhão/Piauí): Rainy period

The diel variation of limnological parameters, measured in Boa Esperança Reservoir, Brazil during the rainy period, exhibited small temperature gradients characterized by an increase in temperature by midday, followed by a partial homogenization of the water column in the night and the early morning. The result was an increase in the epilimnion to a depth of 17 m. The pH and dissolved oxygen concentrations showed higher values at the surface, with the occurrence of anomalies (concentrations higher than at the surface) of the latter variable in the epilimnion, probably as a result of the activity of primary producers and/or losses of oxygen to the atmosphere. The chemical forms of iron in the reservoir exhibited increasing concentrations with depth, as a result of an increase in the concentration of seston and/or accentuated reduction of the levels of oxygen in the bottom layers. The reduction of Fe³⁺ to Fe²⁺ in the bottom water layers in the reservoir, in addition to the primary production process in the epilimnion, could explain the increased phosphorus in the bottom water layer. The concentrations of nitrogen compounds did not exhibit relevant changes or a defined evolution profile, except for nitrate, which showed an outstanding increase in the bottom water layers, suggesting it could be an important nitrogen source for primary producers. Although not unequivocal, these data suggest that ecosystem instability in Boa Esperança Reservoir is the product of short diel thermal variations, and the reduced input of allochthonous materials and nutrients from local catchment. These conditions guarantee the oligotrophic status of Boa Esperança Reservoir for the present time.     

Synthesis,characterization and cation adsorption of p-aminobenzoic acid intercalated on calcium phosphate

Crystalline lamellar calcium phosphate retained 4-aminobenzoic acid inside its cavity without leaching. The intense infrared bands in the 1033 and 1010 cm^?1 interval confirmed the presence of the phosphonate groups attached to the inorganic layer, with sharp and intense peaks in X-ray diffraction patterns, which gave basal distances of 712 and 1578 pm for the original and the intercalated compounds, respectively. Solid-state ³¹P nuclear magnetic resonance spectra presented only one peak for the phosphate groups attached to the main inorganic polymeric structure near ?2.4 ppm. The adsorption isotherms from ethanol gave the maximum adsorption capacities of 6.44 and 3.34 mmol g^?1 for nickel and cobalt, respectively, which stability constant and distribution coefficient followed Co > Ni.     

Postharvest storage and cooking techniques affect the stability of glucosinolates and myrosinase activity of Andean mashua tubers (Tropaeolum tuberosum)

The identification and quantification of Glucosinolates (Gls) via UPLC^® MS-MS/PDA/qToF in ten mashua cultivars was carried out. Gls total contents were within the 4.9–54.2 μmol g⁻¹ dry matter range, of which 96–99% corresponded to glucoaubrietin. Other less abundant Gls were glucotropaeolin and tentatively two isomers of hydroxybenzyl Gls. Postharvest refrigeration and shade storage conditions increased the content of Gls up to day 6 in 39.7% and 51.5% respectively. Sun exposure increased the Gls content in 40% up to day 3 but from day 6 considerable losses were attained (92% at day 15). Low correlation levels (R²) between the Gls and myrosinase (MYR) activity of 0.57, 0.28 and 0.39 for the refrigeration, shade and sun exposure treatments were obtained. The cooking regimes tested, boiling, microwaving and baking totally inactivated MYR without affecting the Gls content.     

Screening,characterization, and biocatalytic capacity of lipases producing wild yeasts from Brazil biomes

The objective of this study was to develop a rice porridge containing perilla oil rich in α-linolenic acid which demonstrated anti-atherogenic effect in the previous study. Lipid lowering effect of emulsified perilla oil (EPO) was examined in apo E KO mice (n=18) and that for rice porridge containing EPO (RPEPO) was investigated in the pilot scale human study (n=20). Inhibitory effects of EPO on the plasma lipid levels and fatty streak lesion size in apo E KO mice were similar to those observed in mice fed perilla oil (PO), suggesting that EPO is applicable form of PO in manufacturing rice porridge product with PO’s health benefit properties. In human study with young adults aged between 20–35 years old, changes in plasma triglyceride concentration of subjects consumed RPEPO for 30 days as a breakfast was significantly lowered than those for subjects consumed rice porridge (p<0.05), of which calorie levels were the same (333 kcal/meal).     

Advanced performance evaluation of a reverse osmosis treatment for oilfield produced water aiming reuse

Technology advancements and the increasing need for fresh water resources have created the potential for desalination of oil field brine (produced water) to be a cost-effective fresh water resource for beneficial reuse. At the mature oil and gas production areas in the northeast of Brazil, the majority of wells produce a substantial amount of water in comparison with oil production (more than 90%). At these fields, the produced water has to be treated on site only for oil and solids removal aiming re-injection. The aim of this work is to assess the quality of the produced water stream after a reverse osmosis desalination process in terms of physicochemical characteristics influencing reuse of the water for irrigation or other beneficial uses.     

Free‐radical polymerization of urea,acrylic acid,and glycerol in aqueous solutions

The main objective of the present study is to produce copolymers of urea, acrylic acid, and glycerol through aqueous solution free‐radical polymerizations and analyze the structural, thermal, rheological, and release properties of the obtained materials. To do this, aqueous solution copolymerizations were performed in different reaction conditions and the obtained copolymers were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, rheological analyses, thermogravimetry, gel permeation chromatography, and rates of urea release in distilled water. The obtained results indicate that all constituents of the reacting mixture (potassium persulfate, glycerol, urea, and acrylic acid) affect the characteristics of the produced copolymers. In particular, it is shown that urea can be incorporated into the final copolymer through the proposed reaction scheme, that glycerol promotes crosslinking of polymer chains and that the obtained copolymer materials can be used in agricultural applications. POLYM. ENG. SCI., 55:1219–1229, 2015. © 2015 Society of Plastics Engineers     

A Screening Method to Evaluate Soybean Oil‐Based Biodiesel Oxidative Quality During Its Shelf Life

Biodiesel quality is negatively affected by oxidation, which occurs primarily during the storage and distribution steps. Therefore, the use of suitable analytical methods to assess the oxidation of this biofuel is a fundamental requirement. A direct ambient ionization mass spectrometric technique (EASI‐MS) was tested as a screening method to evaluate the oxidative quality of biodiesel during its shelf life. Using EASI‐MS, the relative abundance of the hydroperoxide ion of m/z 349 was monitored during the induction period (IP) in soybean and a blend of soybean/beef‐tallow (70/30) biodiesel samples. The peroxide value obtained by AOCS Cd 8b‐90 was used as a standard method to evaluate the EASI‐MS data by comparison. The results showed that the peroxide value and EASI‐MS data were highly correlated during the IP for both samples (r > 0.98). Relative abundances of the ion of m/z 349 below 72 % was also found to characterize biodiesel in an initial oxidation stage, whereas abundances exceeding 72 % indicated biodiesel samples nearing the end of their stability. EASI‐MS was therefore found to provide a simple and effective analytical protocol to evaluate the oxidative quality of biodiesel during the IP.     

Electrochemical recycling of cobalt from spent cathodes of lithium-ion batteries: its application as supercapacitor

The supercapacitive behavior of the metallic cobalt recycled from Li-ion batteries has been studied in this work. The reversibility of both redox process (Co^II/Co^III) and (Co^III/Co^IV) in KOH 6 mol L⁻¹ is very high and promising for capacitive applications in electrochemical devices. The specific capacitances calculated from cyclic voltammetry and electrochemical impedance spectroscopy show a good agreement, giving the value of 625 Fg⁻¹. The electrode morphology presents a high porosity, thus an electrical equivalent circuit composed of two parallel resistance and capacitance elements in series was proposed. The specific capacitance values calculated from charge/discharge curves at 0.23 and 2.3 mA/cm² are 601 and 384 Fg⁻¹, respectively. Thereby, it was observed that metallic cobalt recycled from ion-Li batteries is compatible with other supercapacitive materials. This shows that cobalt recycling from Li-ion batteries is economically and environmentally viable for application in supercapacitor devices.