Synthesis of magnetic borosilicate zeolite/graphene quantum dots nanocomposites for removal of nitrate and organic pollutants from water.

Natural and synthetic zeolites have been considered as capable candidates for removal of pollutants from water and wastewater due to their high surface area and porous structure. In this work, borosilicate zeolite (BZ) with ZSM-5 structure, graphene quantum dots (GQDs)/BZ and FeO/BZ as two component, and FeO-GQDs/BZ as three component nanocomposites were prepared using hydrothermal, solid state dispersion, and ultrasound-assisted co-precipitation methods. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray spectroscopy (EDX), N adsorption-desorption, and vibrating sample magnetometer (VSM) techniques. The synthesized composites were used for the removal of nitrate, methylene blue (MB), 4-nitrophenol (4-NPh), biological oxygen demand (BOD), and chemical oxygen demand (COD) from water and industrial wastewater. Among the studied adsorbents, the three-component nanocomposites demonstrated superior performance in removing nitrate and cationic and anionic dyes, achieving removal efficiencies of 85.5% for nitrate, 98.4% for MB, 91.0% for 4-NPh, 100.0% for BOD, and 60.0% for COD. The kinetics studies revealed that all adsorbents obey the pseudo-second-order kinetic model. The prepared new multifunctional magnetic nanocomposites composed of graphene quantum dots is expected to be promising adsorbents for the removal of pollutants from water and wastewater.