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The paper presents the rheological behavior study of castor oil mixed with different pyromellitic esters. The pyromellitic tetraesters used were obtained through the esterification of pyromellitic anhydride with a special alcohol of a complex alkyl-aryl structure (2-phenoxy-ethanol) in conjunction with a linear aliphatic alcohol with variable length (n-butanol, n-decanol). The influence of pyromellitic esters’ structure and concentration was determined, as well as that of temperature, on the rheological behavior, by setting the dependence between the shear stress τ and the shear rate γ. The analysis of dependence between τ and γ demonstrates that the studied solutions have Newtonian behavior. The evolution of samples' viscosity with temperature was characterized by Arrhenius type equations, being established the values of viscous flow activation energy, Ea. This constant can be correlated with the effect of reducing friction in the presence of additives. It was also realized a characterization of annulus fluids flow under the effect of rotational motion, calculating the values of Taylor-Reynolds number (TaRe).

In this work it was studied the removal of copper ions from wastewater by adsorption on oak wood ash and the effect of the ash resulting from adsorption process as a soil amendment. The process variables such as pH, contact time and adsorbent dose were optimized for maximum Cu2+ removal. It was establishing the mathematical correlation between this factors and the metal ions removal efficiency using specific 3D software. Adsorption process is described by Freundlich isotherm and pseudo-first order kinetic model. The effect of the wood ash, previously used as adsorbent, as soil amendment was studied using barley crop, Hordeum vulgare L. The values of the specific parameters: germination percent, plant average length, biomass and relative growth rate proving the beneficial effect of the use of wood ash (resulted from the adsorption process) on plant growth. [ABSTRACT FROM AUTHOR]

The aim of this paper was the synthesis of some citric esters with potential biodegradable properties and their use as plasticizers or PVC lubricants. Citric esters were obtained in a bubbling column-type esterification reactor, using citric acid as the acid component, and monoethylene glycol, n-butanol, t-butanol as the hydroxyl components. The esters were characterized by FT-IR spectrometry to reveal the existence of the esteric bonds. Esters present a good thermal stability. The TCS criterion shows a level of compatibility specific to secondary plasticizers. There is a similarity between the values of the tested compounds and the standard DOF regarding hardness. The breaking strength are better and the values of elongation at break are close to the considered standards. The esters prove a very good migration towards rubber and are comparable to tribological fluids. The four balls test showed that without additives and at a test level of 40 daN for 60 min time period, the diameters of the wear spot are generally very good, being in the range of 0.43-0.62 mm. By adding oils, their behavior improves. The welding load values are also good (200-220 daN). The synthesized citrus esters have clear characteristics of plasticizers and/or lubricants for PVC. [ABSTRACT FROM AUTHOR]

The paper presents the rheological characterization of a bio-ester with possible lubricant properties, obtained from soybean oil fatty acids. The rheological characterization was carried out under thermostatic conditions, using a Brookfield CAP2000+L viscometer in the characteristic domain of these fluids. The variation of the apparent viscosity ηa as a function of shear rate γ and the variation of the two indices (K and n) as a function of temperature were determined, as well as the flow activation energy, Ea from Arrhenius type equations. A rheological model was proposed. [ABSTRACT FROM AUTHOR]

In packed fractionation, the liquid phase can be forced to become continuous, and the vapor phase dispersed, realizing emulsification regime. The paper presents the efficiency comparing results of packed fractionation with respect to the fractionation in an empty flooded column, as well as the influence of the heat flux and of the temperature inside the column's jacket. Experiments for determining the boiling heat transfer of the different methanol - ethanol concentration mixtures were performed. The variation of the boiling heat transfer coefficient at different concentrations of methanol-ethanol mixtures has a minimum, corresponding to the maximum of the difference between concentrations of vapor phase in equilibrium with the liquid phase. [ABSTRACT FROM AUTHOR]

The paper presents the rheological behavior study of the mixtures of castor oil with two types of adipic esters. The influence of adipic esters' structure and concentration was determined, as well as that of temperature, on the rheological behavior, by setting the dependence between the shear stress t and the shear rateẏ. The analysis of the dependence between t and ẏ demonstrates that the studied solutions present Newtonian behavior. The evolution of samples' viscosity with temperature was characterized by Arrhenius type equations, being established the values of viscous flow activation energy, Ea. It was also realized a characterization of annulus fluids flow under the effect of rotational motion, calculating the values of dimensionless criterion Taylor-Reynolds (TaRe). [ABSTRACT FROM AUTHOR]

Present paper investigates the phytoremediation of cobalt from wastewaters using Elodea canadensis. Bioaccumulation tests were conducted at various concentrations of cobalt ranging from 1 to 15 mg/L. Final concentrations of cobalt in wastewaters, after phytoremediation, were less than 1 mg/L. E. canadensis’ hyperaccumulator character with regard to cobalt is emphasised by the amount of cobalt retained: 0.39% ± 0.02% of dry mass at an initial concentration in wastewater of 15 mg/L. After 14 days of exposure to contaminant, the biomass as well as the relative growth rate has increased with the amount of cobalt in wastewaters, the plant manifesting an excellent tolerance to cobalt exposure. Adsorption of cobalt ions by E. canadensis can be well described by the Langmuir adsorption isotherm and the pseudo-second-order model equation. [ABSTRACT FROM AUTHOR]

In this paper is described the synthesis and characterization of esters based on soybean oil fatty acids and an assessment of their potential use as plasticizers in wood, concrete or metal paints. Esters of fatty acids were obtained in a chemical reactor with microwave heating, using soybean oil fatty acids and n-butanol or isopentanol in acidic conditions. [ABSTRACT FROM AUTHOR]

In this paper are presented the experimental results obtained in assessing the degree of swelling of the leather by means of shrinkage temperature. The moisture content of the skin was determined in its various processing steps, correlated with the leather shrinkage value. [ABSTRACT FROM AUTHOR]

In this paper was studied the influence of some turbulence promoters (annular or spiral baffles), placed in the inner tube of a double pipe heat exchanger, on heat transfer intensification. These studies were performed in order to enhance heat transfer by convection of the fluid that moves through these spaces, flowing in transient or turbulent regime. The quantitative determination of heat transfer intensification in the presence of turbulence promoters was performed by calculating, from the energy balance data, the total or partial heat transfer coefficients and comparing these values to the values calculated in the absence of promoters. [ABSTRACT FROM AUTHOR]

The paper presents the rheological behavior study of castor oil additivated by different types of mixed pyromellitic esters. The influence of pyromellitic esters' structure and concentration was determined, as well as that of temperature, on the rheological behavior, by setting the dependence between the shear stress Τ and the shear rate ̇γ . The analysis of dependence Τ = f ̇γ) demonstrates that the solutions studied present Newtonian behavior. [ABSTRACT FROM AUTHOR]

In this paper was studied the influence of some turbulence promoters (annular or spiral baffles), placed in the inner tube of a double pipe heat exchanger, on the pressure losses of the fluid. These studies were conducted in conjunction with the intention to enhance heat transfer by convection of the fluid that moves through these spaces. [ABSTRACT FROM AUTHOR]

Powdered adsorbent obtained from bathurst burr biomass was tested for methylene blue removal from aqueous solutions. SEM and FTIR analyses were used to characterize the adsorbent before and after adsorption. The influence of contact time, adsorbent dose, pH, initial dye concentration, ionic strength and temperature on the process were investigated. Kinetic, equilibrium and thermodynamic studies were conducted to analyse the process. The Taguchi method was used to establish the most suitable conditions for the dye adsorption. The process is spontaneous, favourable, and exothermic and the Freundlich isotherm and pseudo-second order kinetic model best describe it. The Taguchi method indicate that the ionic strength is the factor with the greatest influence on the adsorption process. [ABSTRACT FROM AUTHOR]