Photocatalytic degradation of phenol under visible light irradiation by using ferrous oxalate synthesized from iron-rich mineral sands via a green hydrothermal route

Abstract

The development of efficient green-photocatalysts represents a promising alternative for eliminating organic contaminants found in water. In this work, the photocatalyst α-ferrous oxalate dihydrate (α-FOD) was synthesized using Ecuadorian black sands as an iron-rich precursor and was further used for phenol degradation for the first time. The synthesis was performed under hydrothermal conditions using aqueous oxalic acid at 135 °C and reaction times of 4 and 12 h. Also, ethanol and ethylene glycol were evaluated as co-solvents in the synthesis reaction. The characterization performed showed that synthesized photocatalysts were mainly composed of monoclinic FOD (crystallinity indexes between 75 and 87%) in the form of mesoporous particles with specific surface areas between 19.6 and 46.1 m2/g. The optical band gap energy was estimated in the range of 2.31–2.49 eV, which demonstrated visible light response. Indeed, under visible light irradiation, the photocatalytic activity of synthesized materials showed over 92% phenol removal within a short time (6 h) with a photocatalyst dose of 0.5 g/L. Also, stability and reusability of photocatalyst upon visible light was demonstrated. These results suggest that the photoactive green materials synthesized herein from a low-cost precursor can be used for degradation of organic contaminants under solar light irradiation.