Synthesis of NaY zeolite from coal gangue and its characterization for lead removal from aqueous solution

This work presents a method for synthesizing NaY zeolite from quartz abundant coal gangue through alkali fusion and hydrothermal processes. The synthesized zeolite was systematically characterized using X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), selected area electron diffraction (SAED), Fourier-transform infrared (FTIR), and X-ray Photoelectron spectroscopy (XPS). Molar ratios of Na2O/SiO2 = 2.0, H2O/Na2O = 30, crystallization temperature 80 °C, and crystallization time 10–12 h were identified as the optimum synthesis parameters for producing well crystalized NaY zeolite from quartz abundant coal gangue. A total specific surface area, pore volume, and average pore diameter of the synthesized NaY were found to be 759.008 m2 g−1, 0.318 cm3 g−1, and 6.450 nm, respectively. The synthesized NaY presented high adsorption capacity for lead (Pb2+) removal from its contaminated water. Pb2+ removal efficiency of the original synthesized NaY zeolite was as high as 100% and more than 63.71% even after five adsorption/desorption cycles. The experimental adsorption data were well described by Langmuir isotherm and kinetics models. Adsorption and desorption rate constants were derived to be 6.18×10-3 L mg−1 min−1 and 2.89×10-3 min−1, respectively. Our experimental results revealed that ion exchange is the predominant mechanism for Pb2+ adsorption onto the NaY zeolite.