Arsenic Adsorption on Nanoscale Zerovalent Iron Immobilized on Reduced Graphene Oxide (nZVI/rGO): Experimental and Theoretical Approaches

CAIO VINÍCIUS DE LIMA; JULIAN JUAN; RICARDO FACCIO; ESTELA A. GONZÁLEZ; CAROLINA PISTONESI; MARCELO F PISTONESI; JULIO S. REBOUÇAS

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Lugar: Washington; Año: 2022

1932-7447

Arsenic contamination of water and foodstuffs have motivated the development of methods to sense, quantify and/or remediate arsenic contamination in such samples. Nanoscale Zero-Valent Iron (nZVI) particles have recently emerged as a suitable material for adsorbing arsenic. In order to enhance its performance, these nanoparticles were assembled into reduced graphene oxide (rGO) sheets via a direct iron reduction to yield nZVI/rGO materials. Transmission electron microscopy (TEM) images showed that nZVI of 7 nm mean particle size were well dispersed over the rGO sheets. Zeta potential was measured in a pH range from 2 to 12 and showed a point of zero charge at pHpzc 6.5. The arsenic adsorption onto nZVI/rGO materials, using 15 ppm arsenic solutions of pH ranging from 3.6 to 7.9, showed that adsorption is better in acidic pH, reaching approximately 80% of arsenic adsorption in 10 min. DFT calculations were carried out to evaluate the arsenic adsorption over nZVI/rGO, by using simplified models of magnetite nanoparticles supported on graphene. Arsenic bonds to surface oxygen atoms and adsorption is greatly favorable near lattice defects, with adsorption energies between –6.61 and –6.44 eV. After adsorption, arsenic transfers electron density to the surface, resulting in a positive charge of +3.