Effect of Chemical Modification of Stilbite Zeolite on Removing Lead from Wastewaters

摘要

Stilbite is a natural zeolite that allows both reversible ion exchange and ion adsorption. These properties are due to the size and the charge of the hydrated cation and to the distribution of exchange sites in the zeolite. The suitability of Brazilian natural zeolite for wastewater treatment is still not known. Two kind of treatments were carried out with original Stilbite to convert it into a homoionic state: in treatment 1, the zeolite was mixed with a 2N NaCl solution; and in treatment 2, the solution was exchanged for a 0.5N NaOH. These procedures improved significantly the zeolite cationic exchange capacity (CEC). Comparatively, CEC values increase from 0.92 meq/g (original Stilbite) to 2.97 and 2.56 meq/g (treatment 1 and 2, respectively). The increase on lead removal efficiency ranges from 45.94% for natural zeolite (original) to 79.59 and to 99.97% for treatment 1 and 2, respectively.