Aplicabilidade de resíduos à base de ferro como catalisadores Fenton para degradação de fenol

Abstract

Contamination of water bodies by organic compounds has been a matter of great concern due to its impacts on the human health and the environment. Phenol is a highly toxic compound commonly found in industrial effluents due to its high use in several segments. Advanced Oxidative Processes (AOP), which encompass a wide range of techniques for generating reactive radicals, have shown satisfactory efficiencies in the degradation of recalcitrant organic compounds. The heterogeneous Fenton reaction is a type of AOP that employs hydrogen peroxide and solid catalysts containing iron for generating reactive species. This study aimed to investigate the potential application of two industrial waste materials as alternative catalysts in the Fenton reaction for the degradation of phenol in water: coal bottom ash from a thermoelectric power plant and amethyst mining residue (AMR). The materials were characterized using different techniques, such as X-ray diffraction, X-ray fluorescence, scanning electron microscopy coupled with energy dispersive spectroscopy, Fourier transform infrared spectroscopy and textural analysis. Bottom ash was applied in the Fenton reaction, while AMR was used in the photo-Fenton system. The effects of different operational parameters, including solution pH, catalyst dosage, and H2O2 concentration, were investigated. The characterization results indicated that both materials have mesoporous structures with well-distributed active iron species. Regarding the bottom ash, under optimal conditions, which involve the use of 1,0 g L-1 of catalyst, 6 mM H2O2 and pH = 3, a phenol degradation efficiency of 98.7% was observed after 60 min of reaction, along with 71.6% organic carbon removal after 150 min. The photo- Fenton reaction using AMR exhibited 96.5% degradation under optimal conditions (0.75 g L-1 of catalyst, 7.5 mM H2O2 and pH = 3) after 180 min, removing 42.3% of the organic carbon after 240 min. Through tests with the addition of isopropanol, it was verified that the hydroxyl radical is the main oxidizing agent involved in the cleavage of the phenol molecule for the two studied systems. Regarding the reuse tests, both catalysts showed stability and satisfactory catalytic activity through four consecutive cycles. Therefore, the obtained results demonstrate that the two waste materials display potential activity for application in Fenton reactions for degrading phenol.