Structure-property relationship of zeolite-Y/cubic ZnS nanohybrid material and its utilization for gaseous phase mercury removal

Abstract

Zinc acetate dihydrate and thiourea based metal sulfide was synthesized and used to develop zeolite-ZnS (ZY-ZnS) nanohybrid material by using sonication process, solvothermal method and heat treatment process. The sulfur atom in thiourea is involved in formation of metal sulfide and ethylene glycol was used as solvents in the solvothermal method. The structure of the nanohybrid material was analyzed by Raman spectroscopy, FTIR, XRD and XPS. Raman spectra confirmed the presence of 4, 6- membered rings of zeolite and polar modes A1 and E1 and nonpolar mode E2 of ZnS nanoparticles. The morphology of the nanohybrid material was analyzed by TEM and SEM analysis. The uniform distribution of ZnS in the zeolite matrix was observed in TEM and SEM morphology. The spherical aggregates ZnS crystals size between 100 and 200 nm were observed. Cubical morphology was observed in pure zeolite samples in the range of 400 nm−500 nm. The X-ray photoelectron spectroscopy analysis was used to confirm the metal-sulfide species in the hybrid material. Mercury adsorption (elemental (Hg°)) in the vapor phase follows both pseudo-first-order and pseudo-second-order kinetic models. Kinetic study shows that the mercury adsorption on the zeolite-ZnS nanohybrid adsorbent was mostly regulated by the chemisorption. Vapor phase mercury adsorption capacity of zeolite-Y (ZY) and zeolite-ZnS (ZY-ZnS), is 2295 and 3461 µg/g at 180 °C, respectively. In ZY and ZY-ZnS the intraparticle diffusion rates were 86.1 and 141.2 μg/gmin-1/2, respectively. The higher intraparticle diffusion rate observed in ZY-ZnS confirm the uniformly decorated ZnS nano particles in ZY-ZnS nanohybrid material.