Effect of Natural and Artificial Light on Fe(III) Organic Complexes Photolysis: Case of Fe (III)-Malonate and Fe(III)-Malate

Abstract

The photolysis of iron(III) organic complexes in the presence of natural and simulated light was a concern for the role it plays within the environment in terms of producing hydroxyl radicals able to degrade organic products. In the present work, the study focused on two iron(III) organic complexes. The characterization of these complexes by spectrometry allowed to show their stability in environment with a stability constant equal to Log β = 13.13 for the complex Fe(III)-malonate, and Log β = 20.85 for the Fe(III)-malate complex. Photolysis of these complexes was carried out using a lamp at 365 nm at different pHs, and followed by several assay Fe(II), H2O2 and •OH. The complexes present different photo-reactivities, in the case of Fe(III)-malate, the photolysis is favored by the Fenton process and generates hydroxyl radicals, contrarily to Fe(III)-malonate photolysis which generates an oxidizing •CH2COOH radical without formation of H2O2 nor of •OH. The presence of oxygen and the addition of isopropanol and chloroform show different effects on the complex photolysis. Complexes mineralization at natural irradiation was also studied using chemical oxygen demand (COD).

Molecular investigation of the multi-phase photochemistry of Fe(iii)–citrate in aqueous solution

“…These absorption characteristics are very consistent with previous literature reports, 21,22,61,98,99 and are similar to optical characteristics exhibited by other Fe III –carboxylate complexes. 34,100–102 Spectral characteristics of Fe II –ligand species presented here and in the later text may be attributed to the λ max at ∼256 nm. A previous study 103 reported the UV-vis spectra of Fe II –tannic acid complexes at acidic pH absorbing closer to 260 nm, while Fe II –cationic complexes in aprotic solutions exhibit a unique and narrow λ max at 262 nm.…”

Iron(III) complexing ability of new ligands based on natural γ-pyrone maltol

“…[36] Consequently, we are expecting that Fe(III)/(3) solution had a spectral profile similar to other ferric complexes of -diketones. [37], [38], [39] In fact, at pH 4.5 Fe(III)/(3) solution showed the single symmetric peak of ligand at 263 nm and a shoulder band around 320 nm. Increasing pH, the absorbance of this lower wavelength peak increased till to pH > 8.5 when precipitation occurred.…”