Synthesis and Characterization of Zeolite NaY and its Glyphosate Adsorption Capacity with Varying Iron Content

Abstract

In this study, Fe loaded zeolite NaY with varying iron contents was prepared and used as glyphosate adsorbents. A hydrothermal method was used to synthesize the zeolite NaY from bagasse ash derived silica (Si-BA). Various Fe contents (1.75 - 7.66 %w/w) were impregnated onto the zeolite. Several techniques were used to examine the physicochemical properties of adsorbents, including X-ray diffraction (XRD), energy dispersive X-ray fluorescence (ED-XRF), N2 adsorption-desorption, field emission scanning electron microscopy (FE-SEM), pH drift method, and zeta potential. In a batch adsorption process with an initial glyphosate concentration of 50 mg/L at pH 4, the effect of contact time was investigated. The pseudo second order kinetic model fitted the experimental data well, indicating that chemisorption controlled the rate determining step for all adsorbents. The Fe loaded zeolite NaY outperformed the bare zeolite NaY in terms of adsorption capacity. The rate constant (K2) and adsorption capacity at equilibrium time (qe) increased when the adsorbents were used in the following order: 1.75 < 5.11 < 7.66 %Fe/NaY. Furthermore, the intra-particle diffusion model was fitted to the experimental data, with a correlation coefficient R2 greater than 0.95. The findings demonstrated that both internal and external diffusion contributed to the rate-determining step. The Langmuir and Freundlich adsorption isotherm models were used to depict the glyphosate adsorption mechanism by the adsorbents. The Freundlich adsorption isotherm best explained all of the data. Glyphosate was thus multilayer adsorbed on the heterogeneous surfaced adsorbents. The adsorption of glyphosate increased as the Fe content, which is primarily due to complexation between Fe and the glyphosate molecule. HIGHLIGHTS A novel Fe loaded zeolite NaY effectively improves the glyphosate adsorption as compared to the bare zeolite The faster adsorption kinetics, stronger adsorbate-adsorbent attraction and higher glyphosate adsorption capacity have been obtained from the adsorbents with a higher Fe content The main adsorption mechanisms are following of electrostatic interaction and Fe-complexation GRAPHICAL ABSTRACT