Green synthesized Fe nanoparticles as heterogeneous Fenton catalysts for the degradation of textile dyes

A. FERRERO; J.M. MEICHTRY; G.E. DE SETA; F.E. GARCÍA; A. SENN; M.I. LITTER

Congreso; WCCE11- 11th world Congress of Chemical Engineering, Buenos Aires; 2023

The Fenton reaction is one of the Advanced Oxidation Processes (AOPs) that more attention has gained as a simple, low-cost, and easily scalable technology for the treatment of organic pollutants; however, there are still some drawbacks that hinder a wider implementation, like a narrow operational pH range, slow Fe(II) regeneration rate and the excess of sludge produced. Many alternatives have been studied to overcome these limitations, i.e., the combination of the Fenton process with electron-rich materials, UV-Vis or sonolytic irradiation, etc. The use of iron-based nanomaterials (FeNPs) in solid forms can be useful; among them, the nanoparticles produced by a green method using natural extracts and iron salts (gFeNPs) seem one of the simplest and cheapest options, as these compounds may avoid Fe(III) precipitation at circumneutral pH and enhance Fe(II) generation. The more than 200 publications regarding the use of gFeNPs in heterogenous Fenton processes (h-Fenton), mostly published recently (after 2019), indicate that this is a hot topic in the AOPs field. Compared with other FeNPs under similar conditions, gFeNPs offer similar efficiency parameters (dye degradation rates, dye degraded/H2O2 consumed ratio), being a low-cost and environmentally friendly material. In this work, preliminary results of the removal of a textile dye, reactive black 5 (RB5), using gFeNPs synthesized from aqueous extracts of yerba mate (Ilex paraguariensis) and FeCl3, in the absence and presence of H2O2 are presented; a comparison is made with literature reports of other FeNPs used in the degradation of dyes by h-Fenton.The synthesis of the gFeNPs using yerba mate was made as described in reference [3], with a molar ratio of Fe(III):polyphenols (as gallic acid) of 1:2.8. The structure of the material corresponds to a non-magnetic iron complex between the polyphenols and Fe(III). The experimental conditions for RB5 degradation were: [RB5]0 = 50 mg L-1, [gFeNPs]0 = 0.9 mM (as (Fe(III)), [H2O2]0 = 3.5 mM, pH0 7, [O2] ≥ 5 mg L-1. The experiments were performed in a 400 mL beaker with 250 mL of the RB solution together with the solid gFeNPs under magnetic stirring (100 rpm) at T = 25°C. The concentration of RB5 was followed by direct spectrophotometry at 600 nm. These preliminary results indicate that, in the absence of H2O2, gFeNPs synthesized from yerba mate can remove up to 50% of the initial RB5 concentration while, with the addition of H2O2, almost complete degradation can be achieved. The effect of different [H2O2]0, combination with UV-Vis or ultrasonic irradiation, etc., will be part of future studies. It can be concluded that gFeNPs are promising materials to be used as h-Fenton catalysts for the degradation of dyes.