Abstract
A photo-Fenton process using a local iron oxide as a natural catalyst was compared to Fenton and UV/H2O2 advanced oxidation processes for degrading crystal violet (CV) dye in aqueous solutions. The catalyst was characterized by transmission electron microscopy (TEM), energy dispersive X-ray microanalysis (EDX), Fourier transform infrared spectroscopy (FT-IR), Raman spectrum, X-ray diffraction (XRD), UV-vis spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. The optical properties proved that the catalyst represents a good candidate for photocatalytic activity. The impact of different parameters (catalyst dose, initial CV concentration, initial H2O2 concentration, pH) on the photo-Fenton efficiency was evaluated. A photo-Fenton process operated under UVC light irradiation, at spontaneous pH, with 1.0 g/L of catalyst and 30 mg/L of H2O2 was the most effective process, resulting in 98% CV dye removal within 3 h. LC-MS and ion-chromatography techniques were used to identify demethylated organic intermediates during the process. Furthermore, a regeneration study of the catalyst showed its stability and reusability (after three treatment cycles, CV dye degradation decreased from 94% to 83%). Finally, the photo-Fenton process was tested in the treatment of real textile wastewater, and the effluent was found to be in compliance with standards for industrial wastewater disposal into sewerage.
Highlights
Dyes are organic compounds often utilized in the paper, plastic, pigment, cosmetic, and textile industries [1,2]
Fenton reaction based processes are effective for industrial wastewater treatment, to improve biodegradability before the biological process [10]
The catalyst was characterized by transmission electron microscopy (TEM), energy dispersive X-ray microanalysis (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses
Summary
Dyes are organic compounds often utilized in the paper, plastic, pigment, cosmetic, and textile industries [1,2]. Textile factories produce wastewater characterized by a very low biodegradability, high amounts of surfactants, high chemical oxygen demand (COD), toxicity, highly fluctuating temperature and pH, and a strong color [3,4] These textile effluents represent a serious problem for the environment, and even their degradation products may be toxic, threatening public health and aquatic organisms [5]. While effective in tertiary treatment of urban wastewater, the addition of chelating agents can be quite problematic when applied to remove organic pollutants in high concentrations, such as in industrial wastewater treatment [14] Another approach has been established with the utilization of solid phase (photo) catalysts (heterogeneous photo-Fenton). In the photocatalytic degradation of dyes, many iron oxides have been investigated in previous studies, regarding their impressive photocatalytic activity, structural stability, and narrow band gap, such as magnetite, goethite, and hematite [15]
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