Est-Il possible d'utiliser la pulpe de betterave pour depollure des eaux chargees en metaux lourds? Can sugar-beet pulp be used to treate waters contaminated by heavy metals?

摘要

Binding of divalent metal cations (Ca~(2+), Co~(2+), Cu~(2+), Ni~(2+), pb~(2+) and An~(2+)) by native and modified sugar-beet pulp was studied to evaluate the potentiality of this waste material from the sugar-industry as an ion-exchanger to treate waters contaminated by heavy metals. Native sugar-beet pulp possessed a cation-exchange capacity of 0.55 mecq/g and high hydration capacities. Improvement of retention capacities in terms of volume of hydrated pulp was attempted. Alkaline treatment doubled the number of anionic sites but hydration capacities were still high and similar to those of the native pulp (swelling: 32 mug at pH-7 in the presence of O.1 mol/L NAN0_3). Native and alkalitreated pulp were cross-linked chemically with either formaldehyde or epichlorohydrin in order to limit swelling and to improve binding performances of the hydrated pulp. Epichlorohydrin gave better results than formaldehyde and markedly reduced swelling and water-retention capacity; in addition, the hydration properties became independant of solvent conditions. Such modifications increase the cost of the material though the enhanced mechanical properties would make the modified beet-pulp suitable as a re-usable ion-exchanger. On the contrary, metal-contaminated native pulp could be incinerated once pressed allowing a massive use of pulp.