Valorisation d’un sous-produit de l’industrie sucrière : mise en œuvre dans un procédé de traitement d’eaux usées industrielles

International audienceSugar beet pulp generated by sugar refining factories is a very cheap and available by-product. The aim of the present work is to develop a new dynamic process involving this low cost biosorbent in order to remove metal ions from aqueous solutions. As a preliminary step, a complete characterization of the polysaccharide has shown that sugar beet pulp contained about 20% galacturonic acid and 0.466 mmol.g-1 as carboxylic groups. The total cation exchange capacity (0.575 mmol.g-1) suggests good metal binding capacities. Then, batch adsorption studies were performed for several metal ions, namely Pb2+, Cu2+, Zn2+, Cd2+ and Ni2+ cations. For 8 10-4 M initial metal concentration, the initial sorption rates ranged from 0.063 mmol.g-1.min-1 for Pb2+ to 0.275 mmol.g-1.min-1 for Ni2+ ions. The equilibrium data fitted well with the Langmuir model and the maximum adsorption capacities ranged from 0.202 to 0.356 mmol.g-1 with the following affinity order: Pb2+ > Cu2+ > Zn2+ > Cd2+ > Ni2+. Ion exchange with Ca2+ ions neutralizing the carboxyl groups of the polysaccharide was found to be the predominant mechanism, added with complexation for Pb2+, Cu2+ and Zn2+ metal ions. The dynamic studies of Pb2+ and Cd2+ fixation onto the natural polysaccharide involve an adsorption reactor coupled with a microfiltration membrane in order to confine the particles. Due to their lower affinity for the biosorbent, Cd2+ ions were found to break through the process faster than Pb2+ cations. A mass balance model based on the Langmuir equilibrium isotherm was used to describe the adsorption process in transitory regime. This model successfully simulated the entire breakthrough curves whatever the operating conditions used. It provides a useful tool for process simulation and optimisation. Based on these results, it is demonstrated that the biosorbent studied represents an interesting low-cost solution for the treatment of metal polluted waters.L’objectif général de cette étude vise à valoriser un sous-produit de l’industrie sucrière dans le traitement des effluents chargés en ions métalliques. La pulpe de betterave est un polysaccharide naturel abondant, dont les fonctions de surface (CEC = 575 meq.g1) développent des propriétés de fixation intéressante vis-à-vis des ions métalliques en solution : les capacités maximales de fixation, déduites du modèle de Langmuir, s’échelonnent de 0,36 mmol.g1 pour le plomb à 0,22 mmol.g1 pour le cadmium. Tous les cations métalliques étudiés se fixent très rapidement sur la pulpe puisque l’équilibre, en réacteur discontinu parfaitement agité, est atteint après une heure de mise en contact entre le support et les ions en solution. Un procédé couplant un réacteur parfaitement agité à une séparation par membrane a été mis au point et un modèle de transfert de matière a été établi à partir des données obtenues en réacteur discontinu. Ce modèle a permis de décrire correctement les courbes de percée expérimentales, en prenant en compte les capacités de fixation différentes de chaque ion, leur concentration et la quantité d’adsorbant dans le réacteur. L’ensemble de ces résultats confirme la possibilité d’utiliser la pulpe de betterave comme adsorbant pour éliminer les ions métalliques présents dans les eaux usées

Removal of metal ions from aqueous solution on low cost natural polysaccharides. Sorption mecanism approach

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Cross-Linked Chitosan-Based Hydrogels for Dye Removal

International audienceSynthetic dyes are a major class of recalcitrant organic compounds, often occurring in the environment as a result of their wide industrial use. More than 100,000 dyes are commercially available. Synthetic dyes are common contaminants, many of them being toxic or carcinogenic. Colored effluents from industrial plant are also perceived by the public as an indication of the presence of a dangerous pollution. Even at very low concentrations, dyes are both highly visible, inducing an esthetic pollution, and impacting the aquatic life and food chain, as a chemical pollution. Dye contamination of water is a major problem worldwide and the treatment of wastewaters before their discharge into the environment is a priority. Dyes are difficult to treat due to their complex aromatic structure and synthetic origin. In general, a combination of different physical, chemical and biological processes is often used to obtain the desired water quality. However, there is a need to develop new removal strategies and decolorization methods that are more effective, acceptable in industrial use, and ecofriendly. Currently, there is an increasing interes

Fundamentals and Applications of Chitosan

International audienceChitosan is a biopolymer obtained from chitin, one of the most abundant and renewable material on Earth. Chitin is a primary component of cell walls in fungi, the exoskeletons of arthropods, such as crustaceans, e.g. crabs, lobsters and shrimps, and insects, the radulae of molluscs, cephalopod beaks, and the scales of fish and lissamphibians. The discovery of chitin in 1811 is attributed to Henri Braconnot while the history of chitosan dates back to 1859 with the work of Charles Rouget. The name of chitosan was, however, introduced in 1894 by Felix Hoppe-Seyler. Because of its particular macromolecular structure, biocompatibility, biode-gradability and other intrinsic functional properties, chitosan has attracted major scientific and industrial interests from the late 1970s. Chitosan and its derivatives have practical applications in food industry, agriculture, pharmacy, medicine, cos-metology, textile and paper industries, and chemistry. In the last two decades, chito-san has also received much attention in numerous other fields such as dentistry, ophthalmology, biomedicine and bio-imaging, hygiene and personal care, veterinary medicine, packaging industry, agrochemistry, aquaculture, functional textiles and cosmetotextiles, catalysis, chromatography, beverage industry, photography, wastewater treatment and sludge dewatering, and biotechnology. Nutraceuticals and cosmeceuticals are actually growing markets, and therapeutic and biomedical products should be the next markets in the development of chitosan. Chitosan is also the N. Morin-Crini (*) · Laboratoire Chrono-environnement, UMR 6249, UFR Sciences et Techniques