On the efficient removal, regeneration and reuse of quaternary chitosan magnetite nanosorbents for glyphosate herbicide in water

In this study, magnetic nanosorbents consisting of magnetite (Fe3O4) cores coated with trimethyl chitosan (TMC)-silica hybrid shells were synthesized using a one-step coating procedure, and their application in the adsorptive removal of glyphosate (GLY) from artificial (ultra-pure) and real water (wastewater) samples was investigated. In synthetic laboratory samples, the magnetic nanosorbents decreased realistic environmental concentrations of GLY to values that are below the maximum permissible value (0.1 mu g/L) defined by the European Directive of Drinking Water. In spiked wastewater samples, the nanosorbents at a dose of 2.5 mg/mL removed 76.8% of the GLY (initial concentration of 3.0 mu g/L), demonstrating the potential application of these nanosorbents in aqueous matrices of complex nature. The adsorption performance towards GLY was assessed by varying the operational conditions in ultra-pure water, including initial GLY concentration, pH, contact time and sorbent dose. The magnetic nanosorbent showed fast adsorption of GLY, with the maximum adsorption being reached within 60 min contact time attaining a maximum of 97% removal for the GLY concentrations tested. The kinetic data were consistent with the pseudo-first-order model. The equilibrium sorption data was better described by Sips model, with a maximum adsorption capacity of 3.04 mg/g. The magnetic nanosorbents could be reused after regeneration and the removal of GLY remained above 80% after 4 adsorption-desorption cycles. Our results indicate that assisted magnetic water remediation using recyclable TMC surface-modified nanosorbents is an efficient process for the elimination of glyphosate from ultra-pure water and real wastewater to meet water quality standards.