Low-cost iron nanoparticles for remediation of agricultural pollution: adsorption of herbicides bromoxynil and paraquat

Low-cost and highly efficient organic herbicides find extensive use in commercial, agricultural, and residential applications. Concerns about widespread occurrence, bioaccumulation, and chronic toxicity have led to calls for their eradication from surface and groundwater due to potential environmental impacts. Crystalline zero-valent iron nanoparticles (ZVI-NPs) synthesized using a green route were assessed for their potential as adsorbents for the herbicides bromoxynil (C7H3Br2NO) and paraquat (C12H14Cl2N2). ZVI-NPs, with a crystal size of 10 +/- 0.2 nm, are capped and stabilized by biomolecules from plant extract. The study assessed the impact of contact time (0-60 min) and nano-adsorbent concentrations (0.1-0.4 mg) on herbicide adsorption, revealing enhanced interaction due to active sites on the nanomaterial surfaces. In 50 minutes, at an initial concentration of 0.1 mg ZVI-NPs, the herbicide removal efficiency reached 90-99.9%. The adsorption data for both herbicides was best fitted by a second-order kinetics with regression values of 0.90 to 0.99. Incorporating ZVI-NPs into cellulose membranes increases the adsorptive efficiency to 99.9 to 100% within 18 to 25 minutes, significantly reducing fouling. This study indicated that the synthesized ZVI-NPs have potential as an efficient herbicide adsorbent, ideally embedded into a matrix or membrane device. Green synthesis of 10 nm zero-valent iron nanoparticles (ZVI-NPs) and incorporation into a polymer membrane offers a promising solution for removal of herbicides, bromoxynil and paraquat. 100% removal was achieved in 18-25 mins with 0.1 mg ZVI-NPs.