Isabelle Baudin

Adsorption of trace organic compounds in CRISTAL® processes☆

A mathematical model for the removal of micropollutants in PAC/UF systems was successfully verified with experimental data. The model was based on a single set of equilibrium and kinetic parameters that were independently evaluated in bench-scale experiments. Laboratory-scale UF pilot plant experiments were conducted to determine the accuracy of model predictions for atrazine removal in the presence of natural organic matter. Good agreement was obtained between model predictions and experimental data. Greater mass of atrazine was adsorbed when all PAC was dosed at one time at the beginning of the membrane cycle as compared to PAC dosage at a constant rate throughout the membrane cycle. The model can be used to rapidly test different types of PAC and to optimize the process operating procedures for the removal of trace organic compounds in the presence of natural organic matter.

Adsorption of dextrans and pullulans at the silica—water interface; hydrodynamic layer thickness measurements; role in the fouling of ultrafiltration membranes

We studied the adsorption of a series of dextrans and pullulans at the silica-water interface. The system of dextran-precipitated silica was chosen as a model of solutes and mineral particles present in water to investigate the influence of the interactions between these two components on the fouling of membranes used for water treatment. Therefore, adsorption isotherms and hydrodynamic layer thicknesses were determined. Results show the importance of adsorption phenomena of polysaccharides on silica particles, particularly that of the high adsorbed layer thickness (δh), 4 < δh < 16 nm, which depends on molecular weight, 104 < Mw < 106. Thus, we suggest that a suspension covered by polymer must play a major role in the fouling process.

Adsorption of neutral polysaccharides at the silica-water interface role in the formation of a fouling cake at the filtration membrane surfaces used in water treatment

Abstract Membrane fouling is the main drawback of the ultrafiltration process used in water treatment, especially when mineral solids and polymer solutes are both present in the medium to be filtered. We are concerned with the role of the molecular interactions particles/solutes on the formation of a fouling cake. We used model components representative of natural system particles/macromolecular solutes. We worked with two polysaccharides (dextran and pullulan) and with spherical particles of silica. We simulated the fouling deposit accumulated at the membrane surface with a packed bed of silica particles and showed how the adsorption of the polysaccharides at the silica-water interface could induce a great increase of pressure through the bed. The pressure drop after adsorption makes it possible to obtain a hydrodynamic layer thickness of the macromolecules adsorbed on the silica. We compared these calculated values with the viscometric thicknesses determined in a previous study.