Béatrice Biscans | Centre National de la Recherche Scientifique / French National Centre for Scientific Research (original) (raw)

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Papers by Béatrice Biscans

The Chemical Engineering Journal, 1992

ABSTRACT

Chemical Engineering Science, 1994

A modelling of a continuous fluidized-bed crystallizer is developed. The model is based on the de... more A modelling of a continuous fluidized-bed crystallizer is developed. The model is based on the description of the fltidized bed as a multistage crystallizer, in order to take into account the segregation and particles mixing within the bed. This model is compared to experimental data obtained during the laboratory-scale crystallization of tetrahydrate sodium perborate. It gives a better prediction of the mean size of the product than a usual model of suspended bed based on the assumption of perfect size classification. It can also predict the size distribution of the crystals along the column.

Journal of Crystal Growth, 2012

Starting from a mixture of enantiomers in solution, crystallization can generate different types ... more Starting from a mixture of enantiomers in solution, crystallization can generate different types of crystals. In order to determine which type of crystal is obtained in the case of acetyl leucine, an active pharmaceutical ingredient (API), analytical methods have been used to partially elucidate the binary and ternary phase diagrams of the system composed of the two enantiomers and water.The

Chemical Engineering Science, 2015

A dense MgO suspension is suitable as a precursor. The preparation of the suspension hydrates mor... more A dense MgO suspension is suitable as a precursor. The preparation of the suspension hydrates more than 99% of the initial MgO. The use of MgO is beneficial to the phosphorous recovery rate. Precipitation is highly influenced by the chemistry around the suspended particles. a b s t r a c t Phosphorous (P) is an essential element and plays a key role for life on Earth. It stiffens the bone structure, is a major component of DNA and is involved in the metabolism of living cells. One of the most widely known metabolic processes is photosynthesis, which, amongst many other things, fuels the growth of plants. Modern agriculture uses fertilizers to supply plants with additional phosphorous in order to support photosynthesis and maximize yields. Still today, the primary source for fertilizers is phosphate rock, the supply of which is finite and estimated to be depleted within in the next century. In recent years, several techniques were developed to recycle phosphorous and prevent future scarcity of this vital element. This study examines a method to recover P from nutrient-rich wastewater streams by crystallizing struvite (MgNH 4 PO 4 Á 6H 2 O). A low-grade magnesium oxide, a by-product of the magnesite industry, is added to the effluent to precipitate struvite. Precipitation was investigated in terms of the amount of magnesia added, and its influence on crystallization kinetics and the resulting particle morphologies and sizes. The amount of magnesia determines the supersaturation of the solution by fixing the pH and the chemical potential of magnesium ions in solution, thereby inducing crystallization. Here, the use of an MgO suspension couples the struvite precipitation to a prior MgO dissolution step. This step is controlled by surface reaction and it is assumed that the suspended particles facilitate heterogeneous nucleation. Apparently, the amount of magnesia solids has a strong influence and precipitation mainly occurs around the MgO particles.

International Journal of Chemical Reactor Engineering

In the last few years, the interest on nanomaterials and their applications have increased in a c... more In the last few years, the interest on nanomaterials and their applications have increased in a considerable way. Hence, the knowledge of the possible hazards on human health becomes necessary. Besides the description of the toxicological effects of nanomaterials, the exposure level on the worksites is one of the key data of the problem. The present work aims at studying the resuspension of ultrafine particles in the air during the falling of nanostructured powders. A numerical approach has been developed aiming at simulating the free falling of a powder cluster. The results show that a resuspension of particles occurs following the powder cluster deformation during the free fall of the particles in the air. Isolated particles remain suspended in the air for a long time.

In pharmaceutical industries, active pharmaceutical ingredients (API) are made of crystals whose ... more In pharmaceutical industries, active pharmaceutical ingredients (API) are made of crystals whose properties must be controlled because they influence the end-use properties of the drug. Even if crystal quality is mainly determined during the precipitation step, downstream processing also has an influence. In this study, the influence of washing on the crystal size and shape was analyzed. For the API being considered, different impurities have to be removed from the final suspension by filter cake washing. The efficiency of the washing steps was measured by different types of characterization on the solid phase (differential scanning calorimetry, scanning electron microscopy, and size distribution) and on the remaining filtrate (concentration of impurities). A second component also coprecipitates with the API. A specific study has been carried out on the withdrawal of this by-product and on its impact on the evolution of the crystalline form during washing steps. It was found that three filter cake washings allow us to remove all the impurities and to obtain a pure crystalline form.

Acta crystallographica. Section C, Structural chemistry, 2014

Calcium pyrophosphate hydrate (CPP, Ca(2)P(2)O(7) · nH2O) and calcium orthophosphate compounds (i... more Calcium pyrophosphate hydrate (CPP, Ca(2)P(2)O(7) · nH2O) and calcium orthophosphate compounds (including apatite, octacalcium phosphate etc.) are among the most prevalent pathological calcifications in joints. Even though only two dihydrated forms of CPP (CPPD) have been detected in vivo (monoclinic and triclinic CPPD), investigations of other hydrated forms such as tetrahydrated or amorphous CPP are relevant to a further understanding of the physicochemistry of those phases of biological interest. The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM; Ca(2)P(2)O(7) · H2O) by diffusion in silica gel at ambient temperature and the structural analysis of this phase are reported in this paper. Complementarily, data from synchrotron X-ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetrahydrated calcium pyrophosphate β phase (CPP...

Journal of Hazardous Materials, 2013

A sustainable way to recover phosphorus (P) in swine wastewater involves a preliminary step of P ... more A sustainable way to recover phosphorus (P) in swine wastewater involves a preliminary step of P dissolution followed by the separation of particulate organic matter. The next two steps are firstly the precipitation of struvite crystals done by adding a crystallization reagent (magnesia) and secondly the filtration of the crystals. A design of experiments with five process parameters was set up to optimize the size of the struvite crystals in a synthetic swine wastewater. More than 90% of P was recovered as large crystals of struvite in optimal conditions which were: low Mg:Ca ratio (2.25:1), the leading parameter, high N:P ratio (3:1), moderate stirring rate (between 45 and 90 rpm) and low temperature (below 20 °C).These results were obtained despite the presence of a large amount of calcium and using a cheap reactant (MgO). The composition of the precipitates was identified by Raman analysis and solid dissolution. Results showed that amorphous calcium phosphate (ACP) co-precipitated with struvite and that carbonates were incorporated with solid fractions.

Computers & Chemical Engineering, 1999

The modeling of batch crystallization involves a population balance to get the crystal size distr... more The modeling of batch crystallization involves a population balance to get the crystal size distribution which is one of the most important properties in this process. Thus, this model leads to a system of integral, partial differential and algebraic equations (IPDAE). This system can be easily solved by finite difference methods with uniform discretization. However to increase the calculation efficiency and the crystal size distribution accuracy, an adaptive finite difference method with a non-uniform discretization was developed. Results of both methods are compared in term of efficiency and are confronted to experimental data in term of accuracy.

Chemical Engineering Journal, 2011

This work addresses the problem of phosphorus recovery from wastewater by struvite precipitation,... more This work addresses the problem of phosphorus recovery from wastewater by struvite precipitation, which is chemically known as magnesium ammonium phosphate hexahydrate MgNH 4 PO 4 ·6H 2 O. The struvite solubility product values that are reported in the literature were found to vary significantly, from one solution to another and over the range of the experimental conditions as well. The various factors affecting the struvite solubility include pH, ionic strength and temperature. The struvite solubility product is yet a very important parameter to determine the supersaturation ratio.

Biochemical Engineering Journal, 2012

ABSTRACT Two granular sludge sequencing batch reactors (GSBR) with alternating anoxic/aerobic (R1... more ABSTRACT Two granular sludge sequencing batch reactors (GSBR) with alternating anoxic/aerobic (R1) and anaerobic/aerobic (R2) conditions were operated with a 4-carbon-source synthetic influent. The physical properties of the granular sludge were very good (SVI ≈ 20 mL g−1) and high solid concentrations (up to 35 g L−1) were obtained in the bioreactor operated with a pre-anoxic phase with additional nitrate (R1). In contrast, performance and granule settleability were lower in R2 due to the development of filamentous heterotrophic bacteria on the surface of granules. These disturbances were linked to the fact that a fraction of COD remained during the aerobic phase, which was not stored during the anaerobic period. To stabilize a GSBR with a mixture of organic carbon sources, it is thus necessary to maximize the amount of substrate used during the non-aerated, anaerobic or anoxic, phase. Comparable phosphate removal efficiency was observed in both systems; enhanced biological P removal being greater in anaerobic/aerobic conditions, while the contribution of precipitation (Ca–P) was more significant in anoxic/aerobic conditions.

Journal of Crystal Growth, 1990

id="ab1"&gt;Laboratoire de Genie Chimique (URA CNRS 192), ENSIGC, Chemi... more id="ab1"&gt;Laboratoire de Genie Chimique (URA CNRS 192), ENSIGC, Chemin de la Loge, F-31078 Toulouse Cedex, France Batch crystallization runs of D-xylose from aqueous solutions have been performed. Growth rate kinetics of xylose crystals have been evaluated from successive crystal size distribution records by means of a laser light scattering size analyser. The experiments have emphasized a broadening of the crystal