Selective Capture of Glyphosate from Aqueous Solution Via in Situ Growth of Mil-101-(Fe) on Modified Sugarcane Bagasse with Enhanced Adsorption Performance

Abstract

Glyphosate (GLY) is widely used with a global estimated total demand of over 700 kilotons per year. Due to its excessive application, freshwater resources including lakes and rivers are exposed to a great risk of eutrophication. Thus, a good adsorbent for capturing GLY from eutrophic water needs to be developed. In this study, MIL-101(Fe) was directly grown on pyromellitic dianhydride (PMDA)-modified sugarcane bagasse (SCB) using the grafting method, and the adsorption isotherms of the obtained adsorbent, MIL-101(Fe)/PMDA-SCB, were recorded at 288 K, 298 K, and 308 K, the kinetics at three GLY concentrations (25, 50, and 75 mg/L) were determined, and the effects of factors like solution pH, coexisting ions, and ionic strength on the GLY adsorption capability of the prepared material were investigated. Compared to MIL-101(Fe)/SCB and MIL-101(Fe), MIL-101(Fe)/PMDA-SCB exhibited a larger surface area and a higher adsorption capacity of 352.43 mg/g (within 150 min) at 298 K. Furthermore, the material maintained a high GLY adsorption capacity in the pH range of 3-10. Regarding the presence of coexisting ions, MIL-101(Fe)/PMDA-SCB exhibits notably lower adsorption energy and a high affinity and selectivity toward GLY according to density functional theory calculations. Based on Fourier transform infrared and X-ray photoelectron spectroscopy, electrostatic interaction and the formation of phosphonate and carboxylate motifs were identified as the main adsorption mechanisms. Furthermore, the prepared adsorbents could be reused in six adsorption-desorption cycles with high sorption amounts and applied in actual wastewater treatment, demonstrating the material to be an excellent candidate for GLY recovery in aqueous systems.

Keywords: MIL-101(Fe), Modified bagasse, Glyphosate, Adsorption