Karim Benhabib

Modeling the discharge of a powder fire extinguisher by mixed discrete element method and computational fluid dynamics

A model that combines the discrete element method (DEM) and computational fluid dynamics (CFD) was developed for investigating the discharge of a powder fire extinguisher. The mathematical model is based on the equations of k-ε turbulent models coupled with the equations of particle motion. The discrete element method is used for obtaining the contact forces and the movement of individual particles. The contact force is calculated from the concept of friction slider and the flow field of gas is predicted by the Navier-Stokes equation. This DEM-CFD model provides the information needed to evaluate fire extinguisher performance.

Evidence of colloidal transport of PAHs during column experiments run with contaminated soil samples

Brownfield soils may contain high levels of organic pollutants particularly polycyclic aromatic hydrocarbons (PAHs). It is essential to predict their migration and fate and to evaluate the risk of transfer to sensitive targets, such as water resources, ecosystems and human health. In this study, soil samples have been taken from an experimental contaminated site of former steel activities located at Homecourt (Lorraine, France). These samples have been lixiviated in laboratory column in water-saturated condition at room temperature. The effluent has been collected by fraction and analysed by a standard method giving total concentration of each of 16 PAHs. The breakthrough curves of 16 PAHs significantly evolve in the same way according to the volume of effluent and tend to vanish to 12–15 pore volumes. If several PAHs remain at a concentration below the solubility, others clearly exceed this threshold. Material balance sheets show that only a very small fraction of PAHs is mobilised. These results are interpreted by postulating that PAHs are transported by the solution not only in the dissolved state but also by associations with particulate or dissolved organic matter.

New Polyacrylamide [PAM] Material Formulations for the Coagulation/Flocculation/Decantation Process

A new copolymers, high molecular weight poly(acrylamide) [AM2A0.01W20] and [AM1A0.1W20] were synthesized by radical adiabatic copolymerization in aqueous solution. The [AM2A0.01W20] copolymer was hydrolysed in basic medium by using sodium hydroxide solution and leads to a new hydrolysed poly(acrylamide) [AM3A0.01W20-H]. The structure and composition of the copolymers were established by 1H NMR, IRTF and conductivity. The molecular weights are obtained by size exclusion chromatography [SEC] and by viscosity. The variation of the reduced viscosity of aqueous copolymer solutions with copolymer concentration revealed a strong viscosity values showing very high [PAM] molecular weights. In the present work, several copolymer formulations are tested by the process of Coagulation/Flocculation/Decantation with a Jar-test, using a 30xa0mgxa0L−1 clay suspension. The optimization process shows that the copolymers present different flocculation efficiencies. The copolymers with the best performances were tested on a semi-industrial experimental pilot for the Coagulation/Flocculation/Decantation process. Good Flocculation yield superior than 70xa0% are observed for the [AM3A0.01W20-H] with high molecular weight.

Comparative Study Between New Polyacrylamide Based Copolymer Poly(AM-4VP) and a Cationic Commercial Flocculant: Application in Turbidity Removal on Semi-Industrial Pilot

In the present work, adiabatic copolymerization allowed us to synthesize two poly(AM-4VP) (s) copolymers with various macromolecular weights as determined by viscosity measurement. The 1H-NMR was used for copolymer’s structure verification. UV–Visible was also used to determine the percentages of acrylamide (AM) and 4-vinylpyridine (4VP) monomers in each copolymer. Synthesized copolymers were tested in the aim to eliminate turbidity from bentonite suspension. A first study was realized on a conventional jar-test in order to determine the optimum parameters, such as time and the speed of stirring of different flocculants, during the flocculation process. Optimized parameters were then used on a semi-industrial pilot of coagulation/flocculation. Flocculation efficiency of the synthesized copolymers was compared with a commercial cationic flocculant FO4910 obtained from Sigma-Aldrich (France). The effect of macromolecular weight and 4VP amounts were also studied. The flocculation experiments results showed that a good turbidity removal superior to 80% was recorded using low copolymers concentrations of <5xa0mg/L.

Dynamic Solid Phase Microextraction (spme) of Atrazine at Pdms and Pa Coated Fibers

The accumulation rate and equilibrium partitioning behavior of the pesticide atrazine between water and two solid phase microextraction (SPME) fibers, polydimethylsiloxane (PDMS) and polyacrylate (PA), are presented. The more polar PA is found to accumulate atrazine to a greater extent than does PDMS. The solid phase-water partition coefficient, Ksw, for atrazine is 210 for PA and 55 for PDMS. The accumulation rate constant increases as the rate of solution stirring is increased. This result confirms that the rate of accumulation of atrazine in both PDMS and PA is limited by diffusion in the aqueous medium. Accordingly, these solid phases are useful for studying the speciation dynamics of atrazine in aqueous media.