Synthesis and characterization of zeolites prepared from industrial fly ash (original) (raw)

2014, Environmental Monitoring and Assessment

In this paper, we present the possibility of using fly ash to produce synthetic zeolites. The synthesis class F fly ash from the Stalowa Wola SA heat and power plant was subjected to 24 h hydrothermal reaction with sodium hydroxide. Depending on the reaction conditions, three types of synthetic zeolites were formed: Na-X (20 g fly ash, 0.5 dm 3 of 3 mol•dm −3 NaOH, 75°C), Na-P1 (20 g fly ash, 0.5 dm 3 of 3 mol•dm −3 NaOH, 95°C), and sodalite (20 g fly ash, 0.8 dm 3 of 5 mol•dm −3 NaOH+0.4 dm 3 of 3 mol•dm −3 NaCl, 95°C). As synthesized materials were characterized to obtain mineral composition (X-ray diffractometry, Scanning electron microscopy-energy dispersive spectrometry), adsorption properties (Brunauer-Emmett-Teller surface area, N 2 isotherm adsorption/ desorption), and ion exchange capacity. The most effective reaction for zeolite preparation was when sodalite was formed and the quantitative content of zeolite from X-ray diffractometry was 90 wt%, compared with 70 wt% for the Na-X and 75 wt% for the Na-P1. Residues from each synthesis reaction were the following: mullite, quartz, and the remains of amorphous aluminosilicate glass. The best zeolitic material as characterized by highest specific surface area was Na-X at almost 166 m 2 •g −1 , while for the Na-P1 and sodalite it was 71 and 33 m 2 •g −1 , respectively. The ion exchange capacity decreased in the following order: Na-X at 1.8 meq•g −1 , Na-P1 at 0.72 meq•g −1 , and sodalite at 0.56 meq•g −1. The resulting zeolites are competitive for commercially available materials and are used as ion exchangers in industrial wastewater and soil decontamination.