Aminated reduced graphene oxide-CuFe2O4 nanohybride adsorbent for efficient removal of imidacloprid pesticide

Abstract

To remove organic and inorganic agrochemicals from contaminated soil and water, adsorption has been regarded as a viable remediation approach. For the removal of organic pollutants, such as pesticides, cost-effective adsorbents have garnered a lot of interest. These include waste-derived materials, clay composites, metal-organic frameworks (MOFs), nanocomposites, and biochar-modified materials. In this study, copper ferrite (CuFe₂O₄) was prepared, characterized, and modified with aminated reduced graphene oxide (Am-rGO) to form a CuFe₂O₄/Am-rGO nanocomposite for the effective removal of imidacloprid (IMD) from water. The Langmuir isotherm model was used to determine the maximum adsorption capacity of the adsorbent (CuFe₂O₄/Am-rGO), which was estimated to be 13.1 (±1.5) mg g^-1. At 0.5 mg L^-1 IMD, the adsorbents were able to extract up to 97.8% of the IMD from the aqueous solution. The Freundlich model and the pseudo second-order model agreed well with the experimental data, proving that physisorption and chemosorption both played a role in the sorption process. CuFe₂O₄/Am-rGO nanocomposite offers high stability and improved reusability due to its improved removal efficiency. After five adsorption-desorption cycles, there was no appreciable reduction in elimination. Additionally, after adsorption tests, IMD can be easily removed after adsorption by an external magnetic field. These showed that Am-rGO had changed the surface of CuFe₂O₄ to make it easier for IMD to stick to it in aqueous solutions. When used adsorbent is co-processed with ethanol extraction and ultrasound cavitation, it can be regenerated and still work well as an adsorbent. Furthermore, CuFe₂O₄/Am-rGO demonstrated its environmental safety and ability to continue absorbing IMD across a variety of diverse matrices. As a result, this study demonstrates that CuFe₂O₄/Am-rGO is a long-lasting, easily prepared, and efficient adsorbent for the removal of IMD as one of the neonicotinoids.

Fig. 1. XRD pattern of both CuFe₂O₄ and CuFe₂O₄/Am-rGO nanocomposite.

Fig. 2. SEM images of (a) CuFe₂O₄ and (b) CuFe₂O₄/Am-rGO nanocomposite.

Fig. 3. EDAX analyses with the composition of the elements.

Fig. 4. N₂ adsorption–desorption isotherms of CuFe₂O₄ and CuFe₂O₄/Am-rGO nanocomposite.

Fig. 5. The pH point of zero charge of the synthesized CuFe₂O₄ nanoparticles and CuFe₂O₄/Am-rGO nanocomposite (a), and the effect of pH on IMD removal rate (b).

Fig. 6. Effect of adsorbent dose on IMD removal from aqueous solution [conditions: initial conc. of IMD solution = 0.5 mg L⁻¹, volume = 50 mL, contact time = 120 min, pH = 5.3].

Fig. 7. Effect of initial concentration of IMD solution on the adsorption capacity of IMD [conditions: adsorbent dose = 0.02 g, pH = 5.3, volume = 50 mL, contact time = 120].

Fig. 8. Impact of contact time on the removal of IMD [conditions: initial conc. of IMD solution = 0.5 mg L⁻¹, adsorbent dose = 0.02 g, pH = 5.3, volume = 50 mL].

Fig. 9. (A) Kinetic models of IMD adsorption onto CuFe₂O₄ and CuFe₂O₄/Am-rGO composite; (B) kinetics plot of pseudo first order; and (C) kinetics plot of pseudo second order [conditions: initial conc. of IMD solution = 5.0 mg L⁻¹, adsorbent dose = 0.02 g, pH = 5.3, volume = 50 mL].

Fig. 10. Adsorption isotherm for the adsorption of IMD onto (a) CuFe₂O₄ and (b) CuFe₂O₄/Am-rGO composites: (A) Langmuir, (B) Freundlich models and (C) C_evs. Q_e plot.

Fig. 11. Ethanol extraction and H₂O rinse result in a regeneration efficiency of CuFe₂O₄/Am-rGO.

Fig. 12. Schematic of IMD adsorption mechanism on CuFe₂O₄/Am-rGO composite, (A) a physical adsorption that occurs in the adsorbent's porosity or on the surface of the Am-rGO layer, and (B) adsorption via interactions between the IMD and the Am-rGO layer.