REMOVAL OF CHROMIUM (VI) FROM AQUEOUS SOLUTION BY Opuntia Ficus-indica BIOMASS - Juan F. Cárdenas-González*1, Itzel Alcaraz-Vázquez1, María de Guadalupe Moctezuma-Zarate1, Adriana Rodríguez-Pérez1, Víctor M. Martínez-Juárez2 e Ismael Acosta Rodríguez1 (2016)