CeO 2 /TiO 2 -doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2 -20Al 2 ... more CeO 2 /TiO 2 -doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2 -20Al 2 O 3 -10CaO-25CaF 2 were synthesized and irradiated by gamma ray. The effects of CeO 2 /TiO 2 on the structure and optical properties of the samples before and after irradiation were investigated. Doping with CeO 2 causes network depolymerization and conversion of [AlO 6 ] to [AlO 4 ], enlarging the percolation region and promoting CaF 2 crystallization. Co-doping with CeO 2 /TiO 2 helps reduce the intrinsic coloring of transparent glass ceramics containing only CeO 2 , and the addition of TiO 2 enhances network interconnectivity, suppressing CaF 2 crystallization. Doping with CeO 2 and/or TiO 2 improves the structural stability of transparent glass ceramics upon irradiation and maintains the optical band gap and Urbach energy constant due to the defect saturation over the irradiation dose. Doping solely with CeO 2 allows for a lower radiation-induced absorption coefficient than co-doping CeO 2 /TiO 2 because of the enhanced crystallization induced by CeO 2 and balanceable light absorption of polyvalent cerium ions.
Estimation and knowledge of transport properties of fluids are essential for heat and mass flow. ... more Estimation and knowledge of transport properties of fluids are essential for heat and mass flow. Viscosity is one of the important properties which are affected by temperature and pressure. In the present work, based on the use of econometric and statistical techniques for parametric and non-parametric regression analysis and statistical correlation tests, we propose an equation modeling the relationship between the two parameters of viscosity Arrhenius-type equation, such as the Arrhenius energy (E a) or the pre-exponential factor (A s). In addition, we introduce a third interesting parameter called Arrhenius temperature (T A), to enrich the discussion. Empirical validation using 48 data set of pure solvents from the literature and studied at different temperature ranges gives excellent statistical results which allow us to redefine the Arrhenius equation using a single parameter instead of two ones. In addition, the proposed model is very useful for engineering data and permits to estimate one non-available parameter when the second one is available. 2014 Elsevier B.V. All rights reserved.
The aim of the present work is to study the disinfection of a mobile object by UVGI lamps. Two di... more The aim of the present work is to study the disinfection of a mobile object by UVGI lamps. Two different disinfection processes are examined: the stationary and dynamic disinfection. In the stationary process, the infected object moves and takes its place under the lamp during a stationary exposure time, t es. However, in the dynamic process the object is in motion with a velocity, v, during a dynamic exposure time t ed. For the stationary disinfection process, the expressions of irradiance lamp and the received dose are established by taking into account the non-uniformity of the light emission into the object surface. In the dynamic disinfection process, novel expressions of the lamp irradiance and the received dose are established by considering the velocity of the object, the non-uniformity of the light emission and so explicit expressions equations depending on dynamic exposure time are reported. The last developments are used to study the disinfection of a mobile object by an airline check-in luggage according to the two disinfection processes. The number of the required lamps to kill different varieties of Coronaviruses is calculated. For the same exposure time, 10 s, the dynamic disinfection process is found to be more efficient than the stationary disinfection process and the number of the required lamps is reduced from 20 to 50%.
Journal of Radioanalytical and Nuclear Chemistry, Oct 1, 2019
CeO 2 /TiO 2-doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2-20Al 2 O ... more CeO 2 /TiO 2-doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2-20Al 2 O 3-10CaO-25CaF 2 were synthesized and irradiated by gamma ray. The effects of CeO 2 /TiO 2 on the structure and optical properties of the samples before and after irradiation were investigated. Doping with CeO 2 causes network depolymerization and conversion of [AlO 6 ] to [AlO 4 ], enlarging the percolation region and promoting CaF 2 crystallization. Co-doping with CeO 2 /TiO 2 helps reduce the intrinsic coloring of transparent glass ceramics containing only CeO 2 , and the addition of TiO 2 enhances network interconnectivity, suppressing CaF 2 crystallization. Doping with CeO 2 and/or TiO 2 improves the structural stability of transparent glass ceramics upon irradiation and maintains the optical band gap and Urbach energy constant due to the defect saturation over the irradiation dose. Doping solely with CeO 2 allows for a lower radiation-induced absorption coefficient than co-doping CeO 2 /TiO 2 because of the enhanced crystallization induced by CeO 2 and balanceable light absorption of polyvalent cerium ions.
Journal of Macromolecular Science, Part B, Feb 28, 2017
The 1 H NMR technique was used to study the behaviour of poly(ethylene oxide) chains grafted chem... more The 1 H NMR technique was used to study the behaviour of poly(ethylene oxide) chains grafted chemically on silica. A noticeable influence of the nature of the surface and solvent on the conformation of the grafted macromolecules was observed. For precipitated silica the chains adopted a disordered conformation whereas for pyrogenic silica they formed a more uniform layer. The grafting ratio and the solvent can both modify the conformations of the chains. The
Journal of Macromolecular Science, Part B, Jul 20, 2011
ABSTRACT The aim of the present work was to determine first the behavior of a neutral polymer, po... more ABSTRACT The aim of the present work was to determine first the behavior of a neutral polymer, polyvinylpyrrolidone (Mw = 3,6 105 g/mol), in the dilute and semidilute regimes in water by a rotational concentric cylinder viscometer and then to deduce the Flory exponent. The absolute viscosity of the samples was directly determined from the shear stress–shear rate rheograms over a temperature range of 20°C–40°C and a polymer concentration range of 0.114–1.438 g/dl. The rheological nature of the polymer solutions was systematically analyzed, showing Newtonian behavior. Then, the intrinsic viscosity [η] was determined according to the Schultz–Blaschke equation. The overlapping concentration C* was determined by plotting the double logarithmic plots of reduced viscosity ηr versus polymer concentration C, yielding . The Flory exponents, ν, were deduced from viscosity measurements in the semidilute regime (ν = 0.544). In addition, the hydrodynamic radius, RH, was measured for different polymer molar mass (Mw (g/mol) = 10,000, 40,000, 50,000, and 360,000) by a dynamic light scattering technique at 25°C, yielding a Flory exponent at this temperature of 0.521. The obtained value was thus in agreement with that obtained by the rheological method in the semidilute regime with a relative deviation close to 4.5%.
The aim of the present paper was to study the interaction between polyvinylpyrrolidone (PVP) and ... more The aim of the present paper was to study the interaction between polyvinylpyrrolidone (PVP) and sodium bis(2ethylhexyl) sulfoccinate (AOT), as an anionic surfactant, over a temperature range of 25-60°C by viscosity and electrical conductivity measurements. A coil-to-globule transition of PVP in water was observed. The critical micellar concentration (CMC) was determined by conductivity at 25 and 50°C. The formation of the complex PVP-AOT in water was studied by conductivity and viscometry at 25 and 50°C, where the polymer chain adopts respectively coil and globule conformations, and the obtained curves show two break points corresponding to the critical aggregation concentration (CAC) and the polymer saturation point (PSP). The viscometric behavior of PVP-AOT system was studied by using three selected AOT concentrations: C AOT,1 , C AOT,2 , and C AOT,3 with C AOT,1 < CAC < C AOT,2 < PSP < C AOT,3. For C AOT,1 , the system behaves as a neutral polymer. A pseudopolyelectrolyte behavior was observed for the surfactant concentration (C AOT,2). Above the PSP, and for the C AOT,3 concentration, a screening effect appears due to the increase of the free AOT micelles concentrations. In presence of surfactants, the polymer chains swell especially when the PVP is in globular state.
The Journal of Chemical Thermodynamics, Apr 1, 2016
Abstract We have studied the viscosity behaviour of water/AOT/isooctane micro-emulsions as a func... more Abstract We have studied the viscosity behaviour of water/AOT/isooctane micro-emulsions as a function of the volume fraction of the dispersed phase over a temperature range from the (298.15 to 328.15) K. For all the studied temperature range, a sharp increase of the viscosities is observed when the droplets concentration was varied. Several equations based on hard sphere model were examined to explain the behaviours of micro-emulsions under temperature and concentration effects. According to these equations, the shape factor and the inter-particle interaction parameters were found to be dependent on temperature which is in contradiction with experimental results reported in the literature. A modified Vand equation, taking into account the inter-particle collision time, is used to interpret the results obtained. This deviation is attributed to the aggregation of the droplets which becomes important by increasing temperature. The maximum packaging volume fraction of particles Φ dm and the intrinsic viscosity [ η ] were determined according to the Krieger and Dougherty equation through the temperature range studied. These two parameters were shown to be dependent on temperature but their product was found to be constant and close to 2 as reported in theory.
Brazilian Journal of Chemical Engineering, Sep 1, 2013
The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on... more The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on the interaction between water and methanol. First, the dynamic viscosities were measured for polymer solutions by a rotational concentric cylinder at 25 °C and for the polymer concentration range from 0.1 to 0.6 g/dl. The results show a polynomial dependence of the viscosity on polymer concentration. On the hypothesis of a quasi-binary system, a pseudo Grumberg-Nissan constant, ' p d , was introduced to quantify the interaction between unlike molecules in the presence of polymer. The interaction between unlike molecules due to the presence of the polymer was quantified by the deviation of the Grumberg-Nissan constant, ' ' p p p d d d δ = −. Generally, this constant is negative which means that the interactions between water and methanol decrease in the presence of polyvinylpyrrolidone at 25 °C. The presence of the polymer induces a perturbation of the dynamic equilibrium between free and complexed molecules.
The aim of the current study is to investigate the spread of the COVID-19 pandemic as a multiphas... more The aim of the current study is to investigate the spread of the COVID-19 pandemic as a multiphase percolation process. Mathematical equations have been developed to describe the time dependence of the number of cumulative infected individuals, I (t), and the velocity of the pandemic, V p (t), as well as to calculate epidemiological characteristics. The study focuses on the use of sigmoidal growth models to investigate multiwave COVID-19. Hill, logistic dose response and sigmoid Boltzmann models fitted successfully a pandemic wave. The sigmoid Boltzmann model and the dose response model were found to be effective in fitting the cumulative number of COVID-19 cases over time 2 waves spread (N 2). However, for multiwave spread (N > 2), the dose response model was found to be more suitable due to its ability to overcome convergence issues. The spread of N successive waves has also been described as multiphase percolation with a period of pandemic relaxation between two successive waves.
Since 2019, the spread of the Coronavirus pandemic becomes the global health crisis. To fight the... more Since 2019, the spread of the Coronavirus pandemic becomes the global health crisis. To fight the pandemic, several measures were adopted such as: Hygiene measure, massive test, social distancing, quarantine and distancing. Disinfection is an important operation in the fight against the spread of Corona virus pandemic. The disinfection methods are of chemical and physical type. In this work, we focused our interest to the physical methods. These methods are classified in three principal categories: irradiation techniques, heat treatment and mechanical techniques. All the different aspect of techniques are exposed in this chapter. The efficiency of the used techniques is also discussed.
The main aim of this paper is the analysis of micellar collisions and polymer confinement effects... more The main aim of this paper is the analysis of micellar collisions and polymer confinement effects on the electrical conductivity percolative behavior of water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles. Firstly, we have performed conductance measurements of the system for three AOT to isooctane volume ratio, and 0.1, 0.15 m 0.2 to examine the influence of micellar collisions on the percolation parameters. All the measurements were carried out over the 298.15 K to 333.15 K temperature range at a fixed water to AOT molar ratio,. We have assessed that the rise of micellar collisions 0 45 W frequency enhances the conductance percolation. Secondly, the confinement effect of a watersoluble polymer, polyvinylpyrrolidone (PVP), on the reverse micelles conductance behavior was investigated. Temperature-induced percolation, , have shown a dependence on the p T polymer concentration,. It was also observed that for various PVP concentrations, the PVP C activation energy of percolation decreases. Finally, the values of the critical exponents determined in the presence and absence of PVP prove that the polymer affects the dynamic of percolation.
Journal of Macromolecular Science, Part B, Apr 27, 2010
ABSTRACT The aim of the present work was to purpose a simple model to study the behavior of a pol... more ABSTRACT The aim of the present work was to purpose a simple model to study the behavior of a polar polymer in a mixture of two polar solvents where the mixed solvents are considered as an effective solvent. This effective solvent interacts with the polymer. The ternary system polymer/solvent1/solvent2 is described by an effective solvent interacting with polymer model (E.S.I.P. model). We propose to calculate the polymer-mixed-solvents interaction parameter on the basis of the solubility parameter concept. New expressions for the second virial coefficient and the preferential adsorption coefficient are given. The proposed model is used to explain the structural transition observed in the system of polyvinylpyrrolidone (PVP)/water/methanol mixture at 25°C and to calculate the preferential adsorption parameter. The enthalpy contribution to the PVP/water interaction parameter was found to dominate the PVP/water interaction parameter. Thus, we consider the dominance of the enthalpy contribution to the polymer-solvent interaction parameter as a fundamental hypothesis when polymer and solvent interact. In addition, according to this hypothesis, the calculated PVP/methanol interaction parameter shows that methanol is a good solvent for PVP at 25°C, as reported in the literature. The E.S.I.P model and the dominance of the enthalpy contribution to the polymer-interaction parameter are used to calculate the polymer-mixed-solvents interaction parameter. Then, the second virial coefficient of the PVP in mixed solvents is deduced, showing a change in the solvent quality in agreement with our previous experimental studies. Finally, the variation of the preferential adsorption parameter versus methanol molar fraction XA is calculated showing different behavior of the polymer versus the mixture composition. The obtained results are in agreement with previous studies by light scattering and rheoviscosimetry of the ternary system PVP/water/methanol at 25°C.
The present paper aims to study the proprieties of water confined in water/AOT/ isooctane reverse... more The present paper aims to study the proprieties of water confined in water/AOT/ isooctane reverse micelles from their refractive indices at 298.5 K. The refractive indices of the microemulsions were investigated at increasing water concentration and at different micellar volume fractions, U d. The refractive index of micellar water was deduced for a large water to AOT molar ratio, W 0. The refractive index of interfacial water was also calculated. Then, the molar faction of interfacial water, a, was deduced for different W 0 values and compared with those measured by NMR as reported in the literature. The results show qualitative agreement. Finally, the average aggregation number, n agg , the area per surfactant headgroup, r, as well as the interfacial thickness, d i , of the reverse micelles were determined for the W 0 values studied. The values of these structural parameters also show good qualitative agreement with NMR and small angle X-ray scattering data reported in the literature. Thus, the refractive index method can be a cheap and fast alternative for these two methods.
Effect of ion exchange in NaAOT surfactant on droplet size and location of dye within Rhodamine B... more Effect of ion exchange in NaAOT surfactant on droplet size and location of dye within Rhodamine B (RhB)-containing microemulsion at low dye concentration
The aim of this paper is to study the temperature effect and ethanol (non-solvent) addition on th... more The aim of this paper is to study the temperature effect and ethanol (non-solvent) addition on the electrical conductivity of a polyelectrolyte aqueous solution. In fact, the electrical conductivity of poly(soudim-4-styrenesulfonate) (Mw = 70.000 gmol−1) in water/ethanol (non-solvent) mixture was measured over the temperature range from 298.15 to 323.15 K in dilute regime concentration. The obtained data were analyzed on the basis of an Arrhenius equation type. The equivalent conductivity was deduced from the experimental values and calculated according to the Manning’s theory. A large deviation was detected between those quantities over the studied temperature range and polyelectrolyte concentration. A novel semi-empirical equation, based on the Manning equation, was proposed for the electrical conductivity of polyelectrolyte solution in dilute regime concentration.
Journal of Macromolecular Science, Part B, Nov 3, 2016
The effect of temperature and a non-solvent, ethanol, addition on the specific volume of poly (so... more The effect of temperature and a non-solvent, ethanol, addition on the specific volume of poly (sodium 4-styrene sulfonate) in water was investigated. The refractive indices of the studied solutions were measured over the 298.15 K to 323.15 K temperature range. Then the specific volumes of the polyelectrolyte were calculated according to the Lorentz-Lorenz and Gladstone-Dale equations. The relative deviations of the specific volumes between measured and calculated according to these equations didn't exceed 2.5%. Several empirical equations were deduced to describe the variations of the refractive index increment and the specific volume versus the temperature and the mixture composition.
The effect of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) addition on the structure of polyvin... more The effect of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) addition on the structure of polyvinylpyrrolidone (PVP) aqueous solution, in dilute and semi-dilute regimes, has been investigated at 25°C. The intrinsic viscosity, Huggins constant, Flory exponent and the Mark-Houwink-Sakurada coefficient were deduced by viscosimetry. The structure of PVP (M W = 40.000 g/mol) aqueous solution in semi-dilute regime was described according the blob model. The monomer size, the density of monomer, the correlation length and the number of monomer in each blob were determined. The PVP-AOT interaction in water was studied in dilute and semi-dilute concentration regime of the polymer by electrical conductivity. A complexation occurs between polymer and surfactant independently on the concentration regime, where the complex nature depends on surfactant concentration. The overlapping concentration of PVP-AOT aqueous solution increases with increasing AOT concentration from 0 to 0.6 g/dl. The Flory exponent decreases from 0.545 to 0.509 and the Mark-Houwink-Sakurada coefficient decreases from 0.636 to 0.528 g/dl. The effect of AOT complexation with PVP in water was also discussed according the blob model. At the overlapping concentration, the density of monomers and the correlation length decrease with increasing surfactant concentration. The density of monomers increases from its value at the overlapping concentration as the polymer concentration increases at the semi-dilute regime. However, the monomer size, the correlation length and the number of monomer in each blob decrease from their values at the overlapping concentration as the polymer concentration increases.
CeO 2 /TiO 2 -doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2 -20Al 2 ... more CeO 2 /TiO 2 -doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2 -20Al 2 O 3 -10CaO-25CaF 2 were synthesized and irradiated by gamma ray. The effects of CeO 2 /TiO 2 on the structure and optical properties of the samples before and after irradiation were investigated. Doping with CeO 2 causes network depolymerization and conversion of [AlO 6 ] to [AlO 4 ], enlarging the percolation region and promoting CaF 2 crystallization. Co-doping with CeO 2 /TiO 2 helps reduce the intrinsic coloring of transparent glass ceramics containing only CeO 2 , and the addition of TiO 2 enhances network interconnectivity, suppressing CaF 2 crystallization. Doping with CeO 2 and/or TiO 2 improves the structural stability of transparent glass ceramics upon irradiation and maintains the optical band gap and Urbach energy constant due to the defect saturation over the irradiation dose. Doping solely with CeO 2 allows for a lower radiation-induced absorption coefficient than co-doping CeO 2 /TiO 2 because of the enhanced crystallization induced by CeO 2 and balanceable light absorption of polyvalent cerium ions.
Estimation and knowledge of transport properties of fluids are essential for heat and mass flow. ... more Estimation and knowledge of transport properties of fluids are essential for heat and mass flow. Viscosity is one of the important properties which are affected by temperature and pressure. In the present work, based on the use of econometric and statistical techniques for parametric and non-parametric regression analysis and statistical correlation tests, we propose an equation modeling the relationship between the two parameters of viscosity Arrhenius-type equation, such as the Arrhenius energy (E a) or the pre-exponential factor (A s). In addition, we introduce a third interesting parameter called Arrhenius temperature (T A), to enrich the discussion. Empirical validation using 48 data set of pure solvents from the literature and studied at different temperature ranges gives excellent statistical results which allow us to redefine the Arrhenius equation using a single parameter instead of two ones. In addition, the proposed model is very useful for engineering data and permits to estimate one non-available parameter when the second one is available. 2014 Elsevier B.V. All rights reserved.
The aim of the present work is to study the disinfection of a mobile object by UVGI lamps. Two di... more The aim of the present work is to study the disinfection of a mobile object by UVGI lamps. Two different disinfection processes are examined: the stationary and dynamic disinfection. In the stationary process, the infected object moves and takes its place under the lamp during a stationary exposure time, t es. However, in the dynamic process the object is in motion with a velocity, v, during a dynamic exposure time t ed. For the stationary disinfection process, the expressions of irradiance lamp and the received dose are established by taking into account the non-uniformity of the light emission into the object surface. In the dynamic disinfection process, novel expressions of the lamp irradiance and the received dose are established by considering the velocity of the object, the non-uniformity of the light emission and so explicit expressions equations depending on dynamic exposure time are reported. The last developments are used to study the disinfection of a mobile object by an airline check-in luggage according to the two disinfection processes. The number of the required lamps to kill different varieties of Coronaviruses is calculated. For the same exposure time, 10 s, the dynamic disinfection process is found to be more efficient than the stationary disinfection process and the number of the required lamps is reduced from 20 to 50%.
Journal of Radioanalytical and Nuclear Chemistry, Oct 1, 2019
CeO 2 /TiO 2-doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2-20Al 2 O ... more CeO 2 /TiO 2-doped oxyfluoride transparent glass ceramics with a composition of 45SiO 2-20Al 2 O 3-10CaO-25CaF 2 were synthesized and irradiated by gamma ray. The effects of CeO 2 /TiO 2 on the structure and optical properties of the samples before and after irradiation were investigated. Doping with CeO 2 causes network depolymerization and conversion of [AlO 6 ] to [AlO 4 ], enlarging the percolation region and promoting CaF 2 crystallization. Co-doping with CeO 2 /TiO 2 helps reduce the intrinsic coloring of transparent glass ceramics containing only CeO 2 , and the addition of TiO 2 enhances network interconnectivity, suppressing CaF 2 crystallization. Doping with CeO 2 and/or TiO 2 improves the structural stability of transparent glass ceramics upon irradiation and maintains the optical band gap and Urbach energy constant due to the defect saturation over the irradiation dose. Doping solely with CeO 2 allows for a lower radiation-induced absorption coefficient than co-doping CeO 2 /TiO 2 because of the enhanced crystallization induced by CeO 2 and balanceable light absorption of polyvalent cerium ions.
Journal of Macromolecular Science, Part B, Feb 28, 2017
The 1 H NMR technique was used to study the behaviour of poly(ethylene oxide) chains grafted chem... more The 1 H NMR technique was used to study the behaviour of poly(ethylene oxide) chains grafted chemically on silica. A noticeable influence of the nature of the surface and solvent on the conformation of the grafted macromolecules was observed. For precipitated silica the chains adopted a disordered conformation whereas for pyrogenic silica they formed a more uniform layer. The grafting ratio and the solvent can both modify the conformations of the chains. The
Journal of Macromolecular Science, Part B, Jul 20, 2011
ABSTRACT The aim of the present work was to determine first the behavior of a neutral polymer, po... more ABSTRACT The aim of the present work was to determine first the behavior of a neutral polymer, polyvinylpyrrolidone (Mw = 3,6 105 g/mol), in the dilute and semidilute regimes in water by a rotational concentric cylinder viscometer and then to deduce the Flory exponent. The absolute viscosity of the samples was directly determined from the shear stress–shear rate rheograms over a temperature range of 20°C–40°C and a polymer concentration range of 0.114–1.438 g/dl. The rheological nature of the polymer solutions was systematically analyzed, showing Newtonian behavior. Then, the intrinsic viscosity [η] was determined according to the Schultz–Blaschke equation. The overlapping concentration C* was determined by plotting the double logarithmic plots of reduced viscosity ηr versus polymer concentration C, yielding . The Flory exponents, ν, were deduced from viscosity measurements in the semidilute regime (ν = 0.544). In addition, the hydrodynamic radius, RH, was measured for different polymer molar mass (Mw (g/mol) = 10,000, 40,000, 50,000, and 360,000) by a dynamic light scattering technique at 25°C, yielding a Flory exponent at this temperature of 0.521. The obtained value was thus in agreement with that obtained by the rheological method in the semidilute regime with a relative deviation close to 4.5%.
The aim of the present paper was to study the interaction between polyvinylpyrrolidone (PVP) and ... more The aim of the present paper was to study the interaction between polyvinylpyrrolidone (PVP) and sodium bis(2ethylhexyl) sulfoccinate (AOT), as an anionic surfactant, over a temperature range of 25-60°C by viscosity and electrical conductivity measurements. A coil-to-globule transition of PVP in water was observed. The critical micellar concentration (CMC) was determined by conductivity at 25 and 50°C. The formation of the complex PVP-AOT in water was studied by conductivity and viscometry at 25 and 50°C, where the polymer chain adopts respectively coil and globule conformations, and the obtained curves show two break points corresponding to the critical aggregation concentration (CAC) and the polymer saturation point (PSP). The viscometric behavior of PVP-AOT system was studied by using three selected AOT concentrations: C AOT,1 , C AOT,2 , and C AOT,3 with C AOT,1 < CAC < C AOT,2 < PSP < C AOT,3. For C AOT,1 , the system behaves as a neutral polymer. A pseudopolyelectrolyte behavior was observed for the surfactant concentration (C AOT,2). Above the PSP, and for the C AOT,3 concentration, a screening effect appears due to the increase of the free AOT micelles concentrations. In presence of surfactants, the polymer chains swell especially when the PVP is in globular state.
The Journal of Chemical Thermodynamics, Apr 1, 2016
Abstract We have studied the viscosity behaviour of water/AOT/isooctane micro-emulsions as a func... more Abstract We have studied the viscosity behaviour of water/AOT/isooctane micro-emulsions as a function of the volume fraction of the dispersed phase over a temperature range from the (298.15 to 328.15) K. For all the studied temperature range, a sharp increase of the viscosities is observed when the droplets concentration was varied. Several equations based on hard sphere model were examined to explain the behaviours of micro-emulsions under temperature and concentration effects. According to these equations, the shape factor and the inter-particle interaction parameters were found to be dependent on temperature which is in contradiction with experimental results reported in the literature. A modified Vand equation, taking into account the inter-particle collision time, is used to interpret the results obtained. This deviation is attributed to the aggregation of the droplets which becomes important by increasing temperature. The maximum packaging volume fraction of particles Φ dm and the intrinsic viscosity [ η ] were determined according to the Krieger and Dougherty equation through the temperature range studied. These two parameters were shown to be dependent on temperature but their product was found to be constant and close to 2 as reported in theory.
Brazilian Journal of Chemical Engineering, Sep 1, 2013
The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on... more The present work aims to determine the influence of a dissolved polymer, polyvinylpyrrolidone, on the interaction between water and methanol. First, the dynamic viscosities were measured for polymer solutions by a rotational concentric cylinder at 25 °C and for the polymer concentration range from 0.1 to 0.6 g/dl. The results show a polynomial dependence of the viscosity on polymer concentration. On the hypothesis of a quasi-binary system, a pseudo Grumberg-Nissan constant, ' p d , was introduced to quantify the interaction between unlike molecules in the presence of polymer. The interaction between unlike molecules due to the presence of the polymer was quantified by the deviation of the Grumberg-Nissan constant, ' ' p p p d d d δ = −. Generally, this constant is negative which means that the interactions between water and methanol decrease in the presence of polyvinylpyrrolidone at 25 °C. The presence of the polymer induces a perturbation of the dynamic equilibrium between free and complexed molecules.
The aim of the current study is to investigate the spread of the COVID-19 pandemic as a multiphas... more The aim of the current study is to investigate the spread of the COVID-19 pandemic as a multiphase percolation process. Mathematical equations have been developed to describe the time dependence of the number of cumulative infected individuals, I (t), and the velocity of the pandemic, V p (t), as well as to calculate epidemiological characteristics. The study focuses on the use of sigmoidal growth models to investigate multiwave COVID-19. Hill, logistic dose response and sigmoid Boltzmann models fitted successfully a pandemic wave. The sigmoid Boltzmann model and the dose response model were found to be effective in fitting the cumulative number of COVID-19 cases over time 2 waves spread (N 2). However, for multiwave spread (N > 2), the dose response model was found to be more suitable due to its ability to overcome convergence issues. The spread of N successive waves has also been described as multiphase percolation with a period of pandemic relaxation between two successive waves.
Since 2019, the spread of the Coronavirus pandemic becomes the global health crisis. To fight the... more Since 2019, the spread of the Coronavirus pandemic becomes the global health crisis. To fight the pandemic, several measures were adopted such as: Hygiene measure, massive test, social distancing, quarantine and distancing. Disinfection is an important operation in the fight against the spread of Corona virus pandemic. The disinfection methods are of chemical and physical type. In this work, we focused our interest to the physical methods. These methods are classified in three principal categories: irradiation techniques, heat treatment and mechanical techniques. All the different aspect of techniques are exposed in this chapter. The efficiency of the used techniques is also discussed.
The main aim of this paper is the analysis of micellar collisions and polymer confinement effects... more The main aim of this paper is the analysis of micellar collisions and polymer confinement effects on the electrical conductivity percolative behavior of water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles. Firstly, we have performed conductance measurements of the system for three AOT to isooctane volume ratio, and 0.1, 0.15 m 0.2 to examine the influence of micellar collisions on the percolation parameters. All the measurements were carried out over the 298.15 K to 333.15 K temperature range at a fixed water to AOT molar ratio,. We have assessed that the rise of micellar collisions 0 45 W frequency enhances the conductance percolation. Secondly, the confinement effect of a watersoluble polymer, polyvinylpyrrolidone (PVP), on the reverse micelles conductance behavior was investigated. Temperature-induced percolation, , have shown a dependence on the p T polymer concentration,. It was also observed that for various PVP concentrations, the PVP C activation energy of percolation decreases. Finally, the values of the critical exponents determined in the presence and absence of PVP prove that the polymer affects the dynamic of percolation.
Journal of Macromolecular Science, Part B, Apr 27, 2010
ABSTRACT The aim of the present work was to purpose a simple model to study the behavior of a pol... more ABSTRACT The aim of the present work was to purpose a simple model to study the behavior of a polar polymer in a mixture of two polar solvents where the mixed solvents are considered as an effective solvent. This effective solvent interacts with the polymer. The ternary system polymer/solvent1/solvent2 is described by an effective solvent interacting with polymer model (E.S.I.P. model). We propose to calculate the polymer-mixed-solvents interaction parameter on the basis of the solubility parameter concept. New expressions for the second virial coefficient and the preferential adsorption coefficient are given. The proposed model is used to explain the structural transition observed in the system of polyvinylpyrrolidone (PVP)/water/methanol mixture at 25°C and to calculate the preferential adsorption parameter. The enthalpy contribution to the PVP/water interaction parameter was found to dominate the PVP/water interaction parameter. Thus, we consider the dominance of the enthalpy contribution to the polymer-solvent interaction parameter as a fundamental hypothesis when polymer and solvent interact. In addition, according to this hypothesis, the calculated PVP/methanol interaction parameter shows that methanol is a good solvent for PVP at 25°C, as reported in the literature. The E.S.I.P model and the dominance of the enthalpy contribution to the polymer-interaction parameter are used to calculate the polymer-mixed-solvents interaction parameter. Then, the second virial coefficient of the PVP in mixed solvents is deduced, showing a change in the solvent quality in agreement with our previous experimental studies. Finally, the variation of the preferential adsorption parameter versus methanol molar fraction XA is calculated showing different behavior of the polymer versus the mixture composition. The obtained results are in agreement with previous studies by light scattering and rheoviscosimetry of the ternary system PVP/water/methanol at 25°C.
The present paper aims to study the proprieties of water confined in water/AOT/ isooctane reverse... more The present paper aims to study the proprieties of water confined in water/AOT/ isooctane reverse micelles from their refractive indices at 298.5 K. The refractive indices of the microemulsions were investigated at increasing water concentration and at different micellar volume fractions, U d. The refractive index of micellar water was deduced for a large water to AOT molar ratio, W 0. The refractive index of interfacial water was also calculated. Then, the molar faction of interfacial water, a, was deduced for different W 0 values and compared with those measured by NMR as reported in the literature. The results show qualitative agreement. Finally, the average aggregation number, n agg , the area per surfactant headgroup, r, as well as the interfacial thickness, d i , of the reverse micelles were determined for the W 0 values studied. The values of these structural parameters also show good qualitative agreement with NMR and small angle X-ray scattering data reported in the literature. Thus, the refractive index method can be a cheap and fast alternative for these two methods.
Effect of ion exchange in NaAOT surfactant on droplet size and location of dye within Rhodamine B... more Effect of ion exchange in NaAOT surfactant on droplet size and location of dye within Rhodamine B (RhB)-containing microemulsion at low dye concentration
The aim of this paper is to study the temperature effect and ethanol (non-solvent) addition on th... more The aim of this paper is to study the temperature effect and ethanol (non-solvent) addition on the electrical conductivity of a polyelectrolyte aqueous solution. In fact, the electrical conductivity of poly(soudim-4-styrenesulfonate) (Mw = 70.000 gmol−1) in water/ethanol (non-solvent) mixture was measured over the temperature range from 298.15 to 323.15 K in dilute regime concentration. The obtained data were analyzed on the basis of an Arrhenius equation type. The equivalent conductivity was deduced from the experimental values and calculated according to the Manning’s theory. A large deviation was detected between those quantities over the studied temperature range and polyelectrolyte concentration. A novel semi-empirical equation, based on the Manning equation, was proposed for the electrical conductivity of polyelectrolyte solution in dilute regime concentration.
Journal of Macromolecular Science, Part B, Nov 3, 2016
The effect of temperature and a non-solvent, ethanol, addition on the specific volume of poly (so... more The effect of temperature and a non-solvent, ethanol, addition on the specific volume of poly (sodium 4-styrene sulfonate) in water was investigated. The refractive indices of the studied solutions were measured over the 298.15 K to 323.15 K temperature range. Then the specific volumes of the polyelectrolyte were calculated according to the Lorentz-Lorenz and Gladstone-Dale equations. The relative deviations of the specific volumes between measured and calculated according to these equations didn't exceed 2.5%. Several empirical equations were deduced to describe the variations of the refractive index increment and the specific volume versus the temperature and the mixture composition.
The effect of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) addition on the structure of polyvin... more The effect of sodium bis (2-ethylhexyl) sulfosuccinate (AOT) addition on the structure of polyvinylpyrrolidone (PVP) aqueous solution, in dilute and semi-dilute regimes, has been investigated at 25°C. The intrinsic viscosity, Huggins constant, Flory exponent and the Mark-Houwink-Sakurada coefficient were deduced by viscosimetry. The structure of PVP (M W = 40.000 g/mol) aqueous solution in semi-dilute regime was described according the blob model. The monomer size, the density of monomer, the correlation length and the number of monomer in each blob were determined. The PVP-AOT interaction in water was studied in dilute and semi-dilute concentration regime of the polymer by electrical conductivity. A complexation occurs between polymer and surfactant independently on the concentration regime, where the complex nature depends on surfactant concentration. The overlapping concentration of PVP-AOT aqueous solution increases with increasing AOT concentration from 0 to 0.6 g/dl. The Flory exponent decreases from 0.545 to 0.509 and the Mark-Houwink-Sakurada coefficient decreases from 0.636 to 0.528 g/dl. The effect of AOT complexation with PVP in water was also discussed according the blob model. At the overlapping concentration, the density of monomers and the correlation length decrease with increasing surfactant concentration. The density of monomers increases from its value at the overlapping concentration as the polymer concentration increases at the semi-dilute regime. However, the monomer size, the correlation length and the number of monomer in each blob decrease from their values at the overlapping concentration as the polymer concentration increases.
Uploads
Papers by Moez Guettari