Chitosan/Ni-ZIF composite beads as regenerable adsorbents for glyphosate removal from agricultural wastewater

The removal of glyphosate (GLY) from aqueous effluents has attracted increasing attention due to the widespread use of this herbicide and its environmental and toxicological implications. Among available adsorbents, zeolitic imidazolate frameworks (ZIFs) have gained prominence because of their high surface area, porosity, and thermal and chemical stability. However, their small particle size limits their application in dynamics systems, regeneration processes, and large-scale industrial operations. To overcome these limitations, the incorporation of ZIFs into polymeric matrices has been widely investigated. In this work, chitosan beads were modified with Ni-based ZIF (NiZIF) and used as adsorbents for glyphosate removal. The results demonstrated superior adsorption performance of the composite beads compared to unmodified chitosan beads. The adsorption process was characterized as spontaneous and endothermic, occurring through combined chemical and physical mechanisms. Kinetic and isothermal data were well described by the Elovich and Redlich-Peterson models, respectively, yielding a maximum adsorption capacity (Q_max) of 23 mg g^-1 at 60 °C, and pH 4 after 24 h according to Langmuir Model. Regeneration tests showed that the beads could be reused for up to four adsorption cycles, with only a 10% loss in efficiency after successively washing steps with an alkaline solution. These findings indicate that chitosan/NiZIF composites are promising, regenerable, and environmentally friendly adsorbents for the remediation of glyphosate - contaminated effluents.