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Zwitterionic functionalization of the polysaccharide present in Opuntia ficus índica and its possible application in ion uptake of polluted water
Cactaceae is a plant family distributed along of the American Continent and Mexico possess more than half of the total species. Here one of the most popular cacti used for different purposes is a paddle cactus with spines called nopal (Opuntia cacti) either as ingredient of traditional medicine and cosmetology or in the Mexican cuisine dishes (prepared raw or cooked). Therefore, Mexico is considered the main supplier of nopal worldwide. Although its cultivation brings important benefits principally like nourishment, also generates wastes mostly resulted from its pruning and from the liquors obtained after the cooking process. In this thermal treatment of nopal, boiling water extracts a viscous substance known as mucilage composed of a branched polysaccharide which normally after cooking this solution is discarded. The chemical composition of this mucilage has been previously reported as well as the uses as natural glue and flocculant to remove the turbidity in rivers and ponds. This las point demonstrates the capability of ion association of the polysaccharide. However, these ion interactions can be also enhanced by chemical functionalization with ion moieties including mechanical properties by crosslinking. Thus, the present work proposes the preparation of an ionic hydrogel by chemical modification of the polysaccharide obtained from Opuntia ficus indica mucilage with zwitterion groups. The resulted material could be tested in environmental applications such as to remove industrial dyes or heavy metal ions from water streams.