Adsorção de íons metálicos utilizando zeólita 4A sintética: efeito das cinzas volantes do carvão como fonte de alumínio e silício

Abstract

Pollution on water bodies resulting from improper disposal of toxic metal contaminated effluents cause several problems for the environment. Several techniques can be used to remove these metal ions from the aquatic media, the adsorption process being the most efficient technique. In this process, a diversity of adsorbent materials is used, in which the use of zeolite 4A will be emphasized in this study. Thus, the present work aims to evaluate the efficiency of zeolite 4A as adsorbent material for the removal of metallic ions, Cu2+, Cd2+, Pb2+ e Zn2+, in aqueous media. For this, zeolite 4A was synthesized by the hydrothermal route starting from two sources of precursors, one from standard reagents (ZA-P) and the other from coal fly ash (ZA), a residue from a thermoelectric industry from state of Ceara. Both materials obtained were characterized by XRD, SEM, IV and CTC techniques. The materials were conducted to batch adsorption tests with multi-element synthetic solution of the metal ions (Pb2 +, Cu2 +, Zn2 +, Cd2 +). The parameters investigated in the adsorption experiments were the effect of dosage, contact time and adsorption equilibrium. It was used Flame Atomic Absorption Spectroscopy (FAAS) for initial and final metal ions quantification. The results revealed in the characterization that both materials presented mainly the crystalline phase corresponding to zeolite 4A. In the dosage test, the weight 0.10 g showed better results for both ZA-P and ZA, however ZA obtained better results than ZA-P for this test, and Pb2 + had the best removal percentage in both materials, 95% for ZA and 93% for ZA-P. In addition, at the time of contact, it was observed that ZA entered equilibrium faster (10 minutes) than ZA-P (50 minutes). In the adsorption equilibrium test the Langmuir model was able to model almost all results, only the Zn2 + cation for ZA was modeled by Freundlich expression. The affinity of metals for materials followed the order (Pb2+ > Cd2+ > Zn2 > Cu2+) for ZA-P and (Pb2+ > Cd2+ > Cu2+ > Zn2+) for ZA. Finally, it was identified for the studied materials have the potential for application as metal adsorbents Cu2+, Cd2+, Pb2+ e Zn2+ in aqueous solutions and the coal fly ash can be recycled to obtain zeolite.