Utilisation de ligno-celluloses cationiques pour la dépollution des eaux (application à la sorption de surfactants et des oxy-anions du chrome)

Des ligno-celluloses de diverses origines ont été modifiées par greffage de groupes ammonium quaternaire en vue de leur utilisation comme adsorbant pour des polluants présentant un caractère anionique. Les capacités d'adsorption Ca sont modulables selon les conditions expérimentales et varient de 0,3 à 1,32 millimole de sites ammonium par gramme de support. Des surfactants anioniques, le dodécyl sulfate de sodium et le dodécyl benzène sulfonate de sodium, et l'anion oléate sont rapidement adsorbés et solidement retenus sur ces supports grâce à une interaction ionique forte. Les quantités de chaque polluant adsorbées Qa dépendent de la valeur de Ca, mais quel que soit le support utilisé, le rapport Qa/Ca correspond à une stoechiométrie 1/1. D'autres polluants très toxiques, les oxy-anions du chrome VI, ont un comportement très semblable, mais avec Qa/Ca égal à 1/1 pour l'ion chromate et 1/2 pour l'ion dichromate. Dans le cas des molécules à propriétés tensio-actives, cette première fixation d'anions sur les sites cationiques peut entraîner l'agrégation d'autres surfactants, identiques ou différents, voire zwitterioniques, grâce aux interactions entre les chaînes hydrophobes, à condition de maintenir le milieu au repos. La valeur de Qa/Ca atteint alors 1,8-2,5. L'ensemble des résultats obtenus a été traité par les modèles de Langmuir, Freundlich et Jossens. Seul ce dernier rend bien compte du processus d'adsorption sur tout le domaine de concentration utilisé. En raison de la forte interaction ionique, la désorption des polluants, une fois le support saturé, est difficile à réaliser, il faut utiliser des solutions salines de force ionique élevée et opérer bien au-dessus de la température ambiante.LYON1-BU.Sciences (692662101) / SudocSudocFranceF

Cationized Lignocelluloses as Scavengers for Anionic Surfactants. II. Hydrophobic Interactions

As reported in Part I of this study, anionic surfactants are rapidly adsorbed and strongly retained on cationized lignocellulosic materials as a result of ionic interactions. Consequently, the initially hydrophilic surface of the sorbent is strongly modified by the adsorbed surfactant molecules. Hydrophobic interactions with this modified surface allow a second layer of surfactant molecules to be adsorbed via their alkyl chains. Many combinations are possible with different kinds of surfactants, with the highest adsorption capacity being obtained when zwitterionic surfactants are involved in the second step

Adsorption of Oleate Anions on to Cationized Lignocelluloses

Oleic acid and its salts are present among the toxic pollutants in olive oil mill wastewaters. Four lignocellulosic materials modified by grafting quaternary ammonium groups have been tested for the adsorption of the oleate anion from aqueous solutions, viz. cotton fibres, viscose fabric, wood sawdust and maize cob powder. As a result of their strong ionic interactions, the carboxylate moities were entrapped at a rate equivalent to the ammonium content of the support. Furthermore, when this charged support was left in contact with the polluted solution without agitation, an additional quantity of pollutant was adsorbed due to associations by the hydrophobic tails of the oleate moities. Partial desorption was achieved in 1 M HCl solution

Cationized Lignocelluloses as Scavengers for Anionic Surfactants. I. Ionic Interactions

Various cationized lignocelluloses were used for the adsorption of anionic surfactants from wastewaters. The number of cationic sites anchored per g support governed the quantities of pollutant adsorbed. A rapid adsorption led to saturation of all the cationic sites and gave type I adsorption isotherms. Some parameters such as the pH or the temperature had a limited effect. Due to the strong ionic interaction, only partial desorption was observed under severe conditions, viz. when high ionic strength solutions were used at 60–80°C

Cationization of Cellulose by Using N-Oxiranylmethyl-N-Methylmorpholinium Chloride and 2-Oxiranylpyridine as Etherification Agents

Cationization of cellulose under aqueous alkaline conditions was studied. Two new epoxy reagents, N-oxiranylmethyl-N-methylmorpolinitim chloride and 2-oxiranylpyridine, were used for preparation of cationic cellulose ethers. Using the first agent, cationic ethers were obtained in one step, whereas the latter one yielded a reactive intermediate used as a precursor for two different cationizations. Etherification with the commonly used 2,3-epoxypropyltrimethylammonium chloride was also performed and used as a reference reaction. By changing water content in the reaction mixture two groups cellulose ethers with different degrees of cationization were prepared. As expected, reducing the water content resulted in a higher degree of etherification and hence a more pronounced cationic character of the obtained ethers. Characterization by FTIR, elemental- and gravimetric analysis confirmed the formation of the desired ethers. Their ability to interact with water and adsorb the acid dye, methyl orange, was also studied, confirming further introduction of the cationic substituents and revealing different reactivities of the used epoxy reagents. From characterization, it could be concluded that N-oxiranylmethyl-N-methylmorpholinium chloride exhibits higher reactivity toward cellulose than both the reference compounds and 2-oxiranylpyridine. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 1449-1456, 200