Ultrasonic Inspection of the Setting Mechanism of Glass Ionomer Cement

Russian Journal of Nondestructive Testing - Ultrasonic measurements were used to characterize the setting process of glass-ionomer dental cement (GIC) and to evaluate the effect of temperature on...     

PHOTOCATALYTIC DEGRADATION OF PATENT BLUE V BY SUPPORTED TiO2: KINETICS,MINERALIZATION, AND REACTION PATHWAY

The photocatalytic degradation of patent blue V (sodium salt of [4-(α-(4-diethylaminophenyl)-5-hydroxy-2, 4-disulfophenyl-methylidene)-2, 5-cyclohexadien-1-ylidene] diethylammonium hydroxide) in aqueous solutions has been investigated by using TiO₂-coated nonwoven fibers as the photocatalyst. Before the study began, adsorption in the dark was done, and the effect of the initial concentration of dye in the solution was determined. The mineralization was monitored by chemical oxygen demand (COD), and the HPLC-MS method was used to identify reaction intermediates. The experimental results show that adsorption is an important parameter, controlling the apparent kinetic constant of degradation. The rate of fading was favored by a high concentration of dye in the solution with respect to the Langmuir-Hinshelwood model. The COD abatement was slower than the discoloration of the solution; this indicates that the dye was not directly mineralized, but transformed to intermediate photoproducts. These intermediate photoproducts lead to other cycles of degradation, to the point of total mineralization. Several by-products were detected and identified by HPLC-MS. On the basis of these findings, we propose a probable degradation pathway as critical for assessing the suitability of detoxification procedures for the degradation of particular contaminant classes.     

Sol–gel synthesis of TiO2–SiO2 photocatalyst for β-naphthol photodegradation

Silica gel supported titanium dioxide particles (TiO₂–SiO₂) prepared by sol–gel method was as photocatalyst in the degradation of β-naphthol in water under UV-illumination. The prepared sample has been characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The supported catalyst had large surface area and good sedimentation ability. The photodegradation rate of β-naphthol under UV-irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The experiments were measured by high performance liquid chromatography (HPLC). The photodegradation rate of β-naphthol using 60% TiO₂–SiO₂ particles was faster than that using TiO₂ “Degussa P-25”, TiO₂ “PC-50” and TiO₂ “Aldrich” as photocatalyst by 2.7, 4 and 7.8 times, respectively. The kinetics of photocatalytic β-naphthol degradation was found to follow a pseudo-first-order rate law. The effect of the TiO₂ loading on the photoactivity of TiO₂–SiO₂ particles was also discussed. With good photocatalytic activity under UV-irradiation and the ability to be readily separated from the reaction system, this novel kind of catalyst exhibited the potential effective in the treatment of organic pollutants in aqueous systems.     

Theoretical and Experimental Studies of the Bone Damage Detection by the Ultrasonic Method

Russian Journal of Nondestructive Testing - The bones elastic characterization using the nondestructive technique based on the propagation of the ultrasonic waves well studied in this paper. The...     

Removal of textile dyes from aqueous solutions by natural phosphate as a new adsorbent

The objective of this study was to investigate the ability of natural phosphate (NP) to remove textile dyes from aqueous solutions. The adsorption of methylene blue (MB) as a reference molecule for the adsorption studies of organic molecules, basic yellow 28 (BY 28) and reactive yellow 125 (RY 125) representatives of two families of textile dyes was studied in a batch mode. The experimental results show that NP can totally remove MB and BY 28, whereas a low adsorption affinity was found in the case of RY 125. The adsorption rate data were analysed using the pseudo-first order kinetics of Lagergren and the pseudo second order model to determine adsorption rate constants. The isotherms of adsorption data were analyzed by various adsorption isotherm models. The adsorption was temperature- and pH-dependent with a high adsorption capacity of MB and BY 28 in the basic range and a high adsorption of RY125 in an acidic range.     

CFD investigation of the agitation in the desupersaturation during the wet-process phosphoric acid (WPPA) process

Desupersaturation is a complex cooling operation that involves hydrodynamic, thermal and mechanical phenomena. This process requires continuous agitation to avoid fouling problems and sludge deposition. The current work aims to investigate the well mixedness in the desupersaturation tank for optimal performance. For this purpose, a multi-fluid CFD study was conducted based on the Euler-Euler modeling approach, considering a multiphase flow involving a liquid phase (phosphoric acid) and a poly-dispersed solid phase, i.e. a sludge with three different sizes where each size is considered as a separate phase. First, the hydrodynamic behavior of the flow within the agitated desupersaturator is analyzed through the investigation of the velocity fields as well as the power and pumping numbers, to determine both the agitator capacity to pump the flow and its power consumption during the operation. Then, in order to assess the mixture homogeneity, we evaluated the solid suspension in the desupersaturation reactor following conventional methods and two new proposed methodologies: the first approach is to evaluate the suspension quality in the mixing system by compartment and the second consists on the assessment of the uniform convergence of the solid concentration. Furthermore, we calculated the time required to achieve a full suspension at different solid concentrations. On other hand, we conducted a detailed analysis of the solid distribution dependency on the impeller rotational speed at different solid volume fraction, which allows a good understanding of the parameters controlling the homogenization in the desupersaturator.     

CFD investigation of the agitation in the desupersaturation during the wet-process phosphoric acid(WPPA) process

Desupersaturation is a complex cooling operation that involves hydrodynamic, thermal and mechanical phenomena. This process requires continuous agitation to avoid fouling problems and sludge deposition. The current work aims to investigate the well mixedness in the desupersaturation tank for optimal performance. For this purpose, a multi-fluid CFD study was conducted based on the Euler–Euler modeling approach, considering a multiphase flow involving a liquid phase(phosphoric acid) and a poly-dispersed solid phase, i.e. a sludge with three different sizes where each size is considered as a separate phase. First, the hydrodynamic behavior of the flow within the agitated desupersaturator is analyzed through the investigation of the velocity fields as well as the power and pumping numbers, to determine both the agitator capacity to pump the flow and its power consumption during the operation. Then, in order to assess the mixture homogeneity, we evaluated the solid suspension in the desupersaturation reactor following conventional methods and two new proposed methodologies: the first approach is to evaluate the suspension quality in the mixing system by compartment and the second consists on the assessment of the uniform convergence of the solid concentration. Furthermore, we calculated the time required to achieve a full suspension at different solid concentrations. On other hand, we conducted a detailed analysis of the solid distribution dependency on the impeller rotational speed at different solid volume fraction,which allows a good understanding of the parameters controlling the homogenization in the desupersaturator.     

Photocatalytic degradation of indigo carmine in aqueous solution by TiO2-coated non-woven fibres

The photocatalytic degradation of indigo carmine has been investigated in aqueous solutions using TiO2 coated non-woven fibres as photocatalyst. The experiments were carried out to investigate the factors influencing the photocatalytic degradation, such as the previous adsorption in the dark, initial concentration of dye solution, temperature, and pH. The experimental results show that adsorption is an important parameter controlling the apparent kinetic constant of the degradation. The photocatalytic degradation rate was favoured by a high concentration of solution in respect to Langmuir-Hinshelwood model. The degradation rate was pH and temperature dependent with a high degradation rate at high temperature.