Green synthesis of carbon nanotubes impregnated with metallic nanoparticles: Characterization and application in glyphosate adsorption

Abstract

In the present work, multi-walled carbon nanotubes (MWCNTs) were used as support material for the impregnation of metallic nanoparticles (MNPs) produced by green synthesis. The influences of the plant extracts (pomegranate (Punica Granatum), Eucalyptus, and pecan (Carya illinoinensis, leaves), metal species (copper and iron), metallic concentrations, and type of functionalization (OH and COOH) on the characteristics of the obtained materials were studied. The precursor and impregnated MWCNTs were characterized through X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, point of charge, N2 adsorption/desorption isotherms and, X-ray photoelectron spectroscopy. All the synthesized materials were tested as adsorbents to remove glyphosate (GLY) in an aqueous medium. The MWCNTs were resistant to withstand the synthesis process, preserving its structure and morphological characteristics. The copper and iron on the surface of MWCNTS confirm the successful synthesis and impregnation of the MNPs. The MWCNTs impregnated with high metallic concentrations showed favorable adsorption of GLY. The adsorption capacity and percentage of removal were 21.17 mg g−1 and 84.08%, respectively, for the MWCNTs impregnated with iron MNPs using the pecan leaves as a reducing agent. The results indicated that an advanced adsorbent for GLY could be obtained by green synthesis, using MWCNTs as precursors and pecan leaves as a reducing agent.

New insights into glyphosate adsorption on modified carbon nanotubes via green synthesis: Statistical physical modeling and steric and energetic interpretations

“…Nutshells (Carya illinoinensis) were used as a natural reducing agent, and iron sulfate (FeSO 4 ⋅7H 2 O, CAS: 7782-63-0, 99.99%, Neon) was used as a metal salt for reduction. The preparation and characterization of the modified material, labeled MWCNT/MPNs-Fe, were described in detail in the reported reference [39,44].…”

“…The modified material MWCNT/MPNs-Fe was used as an adsorbent in the removal of GLY (C 3 H 8 NO 5 P, molecular weight: 169.073 g mol − 1 , CAS: 1071-83-6, purity: 98%, Sigma-Aldrich) in the aqueous matrix and the adsorption results obtained (pH study, kinetic and equilibrium modeling, thermodynamic behavior, simulated effluent, and material regeneration) are included in the same reference [39,44]. Ninhydrin (C 9 H 6 O 4 , CAS: 485-47-2, Sigma-Aldrich) and sodium molybdate (MoNa 2 O 4 , CAS: 7631-95-0, purity: 98%, Sigma-Aldrich) were used for colorimetric complexation reaction [45], allowing the quantification of the pesticide in a UV-Vis spectrophotometer (Shimadzu, model: UV-2600, Japan), at 570 nm.…”

“…It is necessary to improve their potential by increasing their selectivity and adsorptive capacity by adding functional groups, such as OH and COOH, and modifying their surface [38]. In the case of GLY, the modification of CNTs by impregnating metallic nanoparticles (MNPs) through a green synthesis route proved to be a viable alternative to increase the intensity of interaction with the surface of the adsorbent introducing adsorption sites [39].…”

“…The authors carried out previous studies aiming to modify MWCNTs via green synthesis, the characterization of the synthesized material, and the performance of adsorption tests for the removal of GLY in the aqueous matrix [39]. However, so far, there are no reports of analysis and modeling of the adsorption of this herbicide from the perspective of statistical physics.…”

Removal of glyphosate from aqueous solution by CuO coated MIL‐101(Fe)

“…[10] It is vital that the selected adsorbent should have high capacity and selectivity for the objective pollutant. Adsorbents, such as activated carbons and biochar, [11] carbon nanotubes, [12] composites, [13,14] resin, [8] and metal organic frameworks (MOFs), [15][16][17] are frequently used to capture glyphosate from aqueous solutions.…”