Application of Ferrocene for the Treatment of Winery Wastewater in a Heterogeneous Photo-Fenton Process

The winery wastewater (WW) is a major concern for the winery industry due to the high volume generated, high organic carbon content and toxicity associated to the polyphenols. To treat these WW, it can be applied advanced oxidation processes (AOPs), such as heterogeneous photo-Fenton. In this work, it was studied a nanocomposite, ferrocene (Fc), which is a compound formed by nanotubes (2 pentanes with iron inside). Considering that Fc was never used before in the treatment of WW, the aim of this work was (1) to characterize Fc by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), (2) optimize heterogenous photo-Fenton catalyzed by Fc and (3) study the kinetic rate and regeneration of Fc catalyst. The FTIR analysis showed main bands at 3093 cm^-1 associated to C-H stretching and an Fe peak at 476 cm^-1, and SEM images showed that Fc has adsorption capacity. The heterogeneous photo-Fenton was optimized by variation of the pH (3.0 – 7.0), single vs multiple H₂O₂ addition, variation of H₂O₂ concentration (97 – 291 mM) and Fc concentration (0.25 – 1.0 g/L). Results showed that under the best operational conditions, as follows: [Fc] = 0.50 g/L, [H₂O₂] = 194 mM, pH = 3.0, agitation = 350 rpm, radiation UV-C, t = 240 min, it was achieved a total organic carbon (TOC) removal of 82.7%. Fermi’s kinetic model was applied, and it was observed a k_TOC = 4.770x10^-2 min^-1. The Fc catalyst was recuperated, and it was performed 3 consecutive cycles, with a TOC removal of 82.7, 76.2 and 63.9%, respectively, for 1^st, 2^nd and 3^rd cycles. In conclusion, Fc catalyst provides an efficient TOC removal through heterogeneous photo-Fenton process and demonstrates a high potential for WW treatment.