Degradation of salicylic acid coordinated to Fe3O4 nanoparticles by H2O2

Abstract

Salicylic acid (SA) has strong tendency to form complexes with iron (III). Depending upon the concentrations of SA, the complexes formed are FeR⁺, ${\mathrm{FeR}}_2^{+}$, ${\mathrm{FeR}}_3^{2+}$where R represents salicylate ion (^-OC₆H₄COO^-). Fe₃O₄ nanoparticles binds with the salicylate ions through the sites having Fe³⁺ and at the site containing Fe₂⁺ reacts with H₂O₂ to produces OH* radicals. The OH* radicals oxidise the salicylic acid attached to Fe₃O₄ nanoparticles. Thus, the degradation occurs through the formation of SA-Fe₃O₄ nanoparticles complexes and then followed by the reaction with H₂O₂ at the nanoparticle site. FT-IR, TGA were used to confirm the synthesis of Fe₃O₄ nanoparticles as well as to investigate SA-Fe₃O₄ nanoparticles complex formation and the degradation of the complex by H₂O₂. Spectrophotometric studies were employed for the monitoring of the degradation of SA at the surface. Here, the nanoparticles act as platform to which both the reactants SA and H₂O₂ get activated and the degradation reaction occurs. The concentrations of SA, H₂O₂, nanoparticle dosage, surfactants and polymers were changed and the % degradation were noted. It has been observed that the degradation percentage decreased with the increase in nanoparticle dosage, [surfactant] and [polymers]. The [H₂O₂] and [HClO₄] gave peaked-like curve for the degradation of SA for the plot of % degradation versus concentrations of H₂O₂ and HClO₄. Degradation of SA was observed maximum at [H₂O₂](= 8.0 × 10⁻⁴ mol dm⁻³) and at [HClO₄] (= 1.0 × 10⁻² mol dm⁻³).