The paper presents the rheological behaviour study of castor oil mixed with different pyromellitic esters. The pyromellitic tetra-esters used were obtained through the esterification of pyromellitic anhydride with a special alcohol with a complex alkyl-aryl structure (2-phenoxy-ethanol) in conjunction with linear aliphatic alcohols with variable length (n-butanol, n-decanol). The influences of the structure and concentration of the pyromellitic esters as well as that of temperature, on the rheological behaviour were determined from the dependence between the shear stress τ and the shear rate γ . An analysis of the dependence between τ and γ demonstrated that the studied solutions exhibited Newtonian behaviour. The evolution of the viscosity of the samples with temperature was characterized by Arrhenius type equations, the values of activation energy of viscous flow, E a , were established. This constant can be correlated with the effect of friction reduction in the presence of additives. Characterization of the annulus of fluids flow under the effect of rotational motion was also realized by the calculation of the values of the Taylor--Reynolds number (Ta Re ).
The dye industry is one of the largest water consuming industries, and at the same time generates large quantities of wastewaters. The resulting wastewaters require proper treatment before discharge, because the dye contents have a negative effect on the water body and organisms present in it. The most efficient treatment method for water containing dyes is represented by adsorption processes. The challenge with these adsorption processes is to develop new, efficient, viable, and economic adsorbent materials. Therefore, in the present paper, the performance of Zn2Al-layered double hydroxide, prepared from an industrial waste (zinc ash) as a zinc source, was investigated in the Orange II dye adsorption process. The Zn2Al-layered double hydroxide prepared from secondary sources presents similar morphological and structural characteristics as those prepared from analytical grade reagents. The influence of initial dye concentration, adsorption time, solid:liquid ratio, pH, and temperature was evaluated in order to confirm the benefit of this waste valorization. A comparison with the reference Zn2Al-layered double hydroxide prepared from analytical grade reagents was performed and the results show that due to the small presence of impurities, the material prepared from zinc ash shows better adsorption capacities (qmax,exp = 42.5 mg/g at 293 K) than the material prepared from reagents (qmax,exp = 36.9 mg/g at 293 K), justifying the utilization of secondary sources for layered double hydroxides preparation. The proposed treatment process presents advantages from both economic and environmental protection point of view.
In this paper, a comparative study of the physico-chemical properties and composition of walnuts and peanuts oils obtained by cold pressing or Soxhlet extraction in hexane was performed. The physical properties (color, density, refractive index, acidity, saponification, iodine and peroxide values, rheological behavior), the distribution of the major fatty acids in oils (through gas-chromatographic analysis) and the metal content were determined.
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.
In this paper is being studied the behaviour of structured packing subjected to certain chemical, thermal or electrochemical treatments, in specified conditions (temperature and exposure time). The wettability of the materials used has a direct effect on the liquid layer, being influenced by the density, viscosity and surface tension of the liquid as well as the surface condition, which has allowed the comparison of the thickness experimental values with those determined analytically. The treatments applied had in view the possibility of improving or regenerating the packing efficiency as a result of the changes that occur on the contact surface. The characterization was done after each treatment. Also, it was established the number of equilibrium stages related to one packing element used in the separation process.
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